Adding upstream version 2.4.1.upstream/2.4.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 5844 insertions, 0 deletions

diff --git a/src/share/database/scripts/mysql/dhcpdb_create.mysql b/src/share/database/scripts/mysql/dhcpdb_create.mysql
new file mode 100644
index 0000000..d05ccae
--- /dev/null
+++ b/src/share/database/scripts/mysql/dhcpdb_create.mysql
@@ -0,0 +1,5844 @@
+# Copyright (C) 2012-2023 Internet Systems Consortium, Inc. ("ISC")
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# This is the Kea schema specification for MySQL.
+#
+# The schema is reasonably portable (with the exception of the engine
+# specification, which is MySQL-specific).  Minor changes might be needed for
+# other databases.
+
+# To create the schema, either type the command:
+#
+# mysql -u <user> -p <password> <database> < dhcpdb_create.mysql
+# # ... at the command prompt, or log in to the MySQL database and at the 'mysql>'
+# prompt, issue the command:
+#
+# source dhcpdb_create.mysql
+#
+# This script is also called from kea-admin, see kea-admin db-init mysql
+#
+# Over time, Kea database schema will evolve. Each version is marked with
+# major.minor version. This file is organized sequentially, i.e. database
+# is initialized to 1.0, then upgraded to 2.0 etc. This may be somewhat
+# sub-optimal, but it ensues consistency with upgrade scripts. (It is much
+# easier to maintain init and upgrade scripts if they look the same).
+# Since initialization is done only once, it's performance is not an issue.
+
+# This line starts database initialization to 1.0.
+
+# Holds the IPv4 leases.
+CREATE TABLE lease4 (
+    address INT UNSIGNED PRIMARY KEY NOT NULL,  # IPv4 address
+    hwaddr VARBINARY(20),                       # Hardware address
+    client_id VARBINARY(128),                   # Client ID
+    valid_lifetime INT UNSIGNED,                # Length of the lease (seconds)
+    expire TIMESTAMP,                           # Expiration time of the lease
+    subnet_id INT UNSIGNED,                     # Subnet identification
+    fqdn_fwd BOOL,                              # Has forward DNS update been performed by a server
+    fqdn_rev BOOL,                              # Has reverse DNS update been performed by a server
+    hostname VARCHAR(255)                       # The FQDN of the client
+    ) ENGINE = INNODB;
+
+# Create search indexes for lease4 table
+# index by hwaddr and subnet_id
+CREATE INDEX lease4_by_hwaddr_subnet_id ON lease4 (hwaddr, subnet_id);
+
+# index by client_id and subnet_id
+CREATE INDEX lease4_by_client_id_subnet_id ON lease4 (client_id, subnet_id);
+
+# Holds the IPv6 leases.
+# N.B. The use of a VARCHAR for the address is temporary for development:
+# it will eventually be replaced by BINARY(16).
+CREATE TABLE lease6 (
+    address VARCHAR(39) PRIMARY KEY NOT NULL,   # IPv6 address
+    duid VARBINARY(128),                        # DUID
+    valid_lifetime INT UNSIGNED,                # Length of the lease (seconds)
+    expire TIMESTAMP,                           # Expiration time of the lease
+    subnet_id INT UNSIGNED,                     # Subnet identification
+    pref_lifetime INT UNSIGNED,                 # Preferred lifetime
+    lease_type TINYINT,                         # Lease type (see lease6_types
+                                                #    table for possible values)
+    iaid INT UNSIGNED,                          # See Section 12 of RFC 8415
+    prefix_len TINYINT UNSIGNED,                # For IA_PD only
+    fqdn_fwd BOOL,                              # Has forward DNS update been performed by a server
+    fqdn_rev BOOL,                              # Has reverse DNS update been performed by a server
+    hostname VARCHAR(255)                       # The FQDN of the client
+
+    ) ENGINE = INNODB;
+
+# Create search indexes for lease6 table
+# index by iaid, subnet_id, and duid
+CREATE INDEX lease6_by_iaid_subnet_id_duid ON lease6 (iaid, subnet_id, duid);
+
+# ... and a definition of lease6 types.  This table is a convenience for
+# users of the database - if they want to view the lease table and use the
+# type names, they can join this table with the lease6 table.
+# Make sure those values match Lease6::LeaseType enum (see src/bin/dhcpsrv/
+# lease_mgr.h)
+CREATE TABLE lease6_types (
+    lease_type TINYINT PRIMARY KEY NOT NULL,    # Lease type code.
+    name VARCHAR(5)                             # Name of the lease type
+    ) ENGINE = INNODB;
+
+START TRANSACTION;
+INSERT INTO lease6_types VALUES (0, 'IA_NA');   # Non-temporary v6 addresses
+INSERT INTO lease6_types VALUES (1, 'IA_TA');   # Temporary v6 addresses
+INSERT INTO lease6_types VALUES (2, 'IA_PD');   # Prefix delegations
+COMMIT;
+
+# Finally, the version of the schema.  We start at 1.0 during development.
+# This table is only modified during schema upgrades.  For historical reasons
+# (related to the names of the columns in the BIND 10 DNS database file), the
+# first column is called 'version' and not 'major'.
+CREATE TABLE schema_version (
+    version INT PRIMARY KEY NOT NULL,       # Major version number
+    minor INT                               # Minor version number
+    ) ENGINE = INNODB;
+START TRANSACTION;
+INSERT INTO schema_version VALUES (1, 0);
+COMMIT;
+
+# This line concludes the schema initialization to version 1.0.
+
+# This line starts the schema upgrade to version 2.0.
+ALTER TABLE lease6
+    ADD COLUMN hwaddr varbinary(20), # Hardware/MAC address, typically only 6
+                                     # bytes is used, but some hardware (e.g.
+                                     # Infiniband) use up to 20.
+    ADD COLUMN hwtype smallint unsigned, # hardware type (16 bits)
+    ADD COLUMN hwaddr_source int unsigned; # Hardware source. See description
+                                     # of lease_hwaddr_source below.
+
+# Kea keeps track of the hardware/MAC address source, i.e. how the address
+# was obtained. Depending on the technique and your network topology, it may
+# be more or less trustworthy. This table is a convenience for
+# users of the database - if they want to view the lease table and use the
+# type names, they can join this table with the lease6 table. For details,
+# see constants defined in src/lib/dhcp/dhcp/pkt.h for detailed explanation.
+CREATE TABLE lease_hwaddr_source (
+    hwaddr_source INT PRIMARY KEY NOT NULL,
+    name VARCHAR(40)
+) ENGINE = INNODB;
+
+# Hardware address obtained from raw sockets
+INSERT INTO lease_hwaddr_source VALUES (1, 'HWADDR_SOURCE_RAW');
+
+# Hardware address converted from IPv6 link-local address with EUI-64
+INSERT INTO lease_hwaddr_source VALUES (2, 'HWADDR_SOURCE_IPV6_LINK_LOCAL');
+
+# Hardware address extracted from client-id (duid)
+INSERT INTO lease_hwaddr_source VALUES (4, 'HWADDR_SOURCE_DUID');
+
+# Hardware address extracted from client address relay option (RFC6939)
+INSERT INTO lease_hwaddr_source VALUES (8, 'HWADDR_SOURCE_CLIENT_ADDR_RELAY_OPTION');
+
+# Hardware address extracted from remote-id option (RFC4649)
+INSERT INTO lease_hwaddr_source VALUES (16, 'HWADDR_SOURCE_REMOTE_ID');
+
+# Hardware address extracted from subscriber-id option (RFC4580)
+INSERT INTO lease_hwaddr_source VALUES (32, 'HWADDR_SOURCE_SUBSCRIBER_ID');
+
+# Hardware address extracted from docsis options
+INSERT INTO lease_hwaddr_source VALUES (64, 'HWADDR_SOURCE_DOCSIS');
+
+# Update the schema version number.
+UPDATE schema_version
+    SET version = '2', minor = '0';
+
+# This line concludes the schema upgrade to version 2.0.
+
+# This line starts the schema upgrade to version 3.0.
+
+# Upgrade extending MySQL schema with the ability to store hosts.
+
+CREATE TABLE IF NOT EXISTS hosts (
+    host_id INT UNSIGNED NOT NULL AUTO_INCREMENT,
+    dhcp_identifier VARBINARY(128) NOT NULL,
+    dhcp_identifier_type TINYINT NOT NULL,
+    dhcp4_subnet_id INT UNSIGNED NULL,
+    dhcp6_subnet_id INT UNSIGNED NULL,
+    ipv4_address INT UNSIGNED NULL,
+    hostname VARCHAR(255) NULL,
+    dhcp4_client_classes VARCHAR(255) NULL,
+    dhcp6_client_classes VARCHAR(255) NULL,
+    PRIMARY KEY (host_id),
+    INDEX key_dhcp4_identifier_subnet_id (dhcp_identifier ASC , dhcp_identifier_type ASC),
+    INDEX key_dhcp6_identifier_subnet_id (dhcp_identifier ASC , dhcp_identifier_type ASC , dhcp6_subnet_id ASC)
+)  ENGINE=INNODB;
+-- -----------------------------------------------------
+-- Table `ipv6_reservations`
+-- -----------------------------------------------------
+CREATE TABLE IF NOT EXISTS ipv6_reservations (
+    reservation_id INT NOT NULL AUTO_INCREMENT,
+    address VARCHAR(39) NOT NULL,
+    prefix_len TINYINT(3) UNSIGNED NOT NULL DEFAULT 128,
+    type TINYINT(4) UNSIGNED NOT NULL DEFAULT 0,
+    dhcp6_iaid INT UNSIGNED NULL,
+    host_id INT UNSIGNED NOT NULL,
+    PRIMARY KEY (reservation_id),
+    INDEX fk_ipv6_reservations_host_idx (host_id ASC),
+    CONSTRAINT fk_ipv6_reservations_Host FOREIGN KEY (host_id)
+        REFERENCES hosts (host_id)
+        ON DELETE NO ACTION ON UPDATE NO ACTION
+)  ENGINE=INNODB;
+-- -----------------------------------------------------
+-- Table `dhcp4_options`
+-- -----------------------------------------------------
+CREATE TABLE IF NOT EXISTS dhcp4_options (
+    option_id INT UNSIGNED NOT NULL AUTO_INCREMENT,
+    code TINYINT UNSIGNED NOT NULL,
+    value BLOB NULL,
+    formatted_value TEXT NULL,
+    space VARCHAR(128) NULL,
+    persistent TINYINT(1) NOT NULL DEFAULT 0,
+    dhcp_client_class VARCHAR(128) NULL,
+    dhcp4_subnet_id INT NULL,
+    host_id INT UNSIGNED NULL,
+    PRIMARY KEY (option_id),
+    UNIQUE INDEX option_id_UNIQUE (option_id ASC),
+    INDEX fk_options_host1_idx (host_id ASC),
+    CONSTRAINT fk_options_host1 FOREIGN KEY (host_id)
+        REFERENCES hosts (host_id)
+        ON DELETE NO ACTION ON UPDATE NO ACTION
+)  ENGINE=INNODB;
+-- -----------------------------------------------------
+-- Table `dhcp6_options`
+-- -----------------------------------------------------
+CREATE TABLE IF NOT EXISTS dhcp6_options (
+    option_id INT UNSIGNED NOT NULL AUTO_INCREMENT,
+    code INT UNSIGNED NOT NULL,
+    value BLOB NULL,
+    formatted_value TEXT NULL,
+    space VARCHAR(128) NULL,
+    persistent TINYINT(1) NOT NULL DEFAULT 0,
+    dhcp_client_class VARCHAR(128) NULL,
+    dhcp6_subnet_id INT NULL,
+    host_id INT UNSIGNED NULL,
+    PRIMARY KEY (option_id),
+    UNIQUE INDEX option_id_UNIQUE (option_id ASC),
+    INDEX fk_options_host1_idx (host_id ASC),
+    CONSTRAINT fk_options_host10 FOREIGN KEY (host_id)
+        REFERENCES hosts (host_id)
+        ON DELETE NO ACTION ON UPDATE NO ACTION
+)  ENGINE=INNODB;
+
+DELIMITER $$
+CREATE TRIGGER host_BDEL BEFORE DELETE ON hosts FOR EACH ROW
+-- Edit trigger body code below this line. Do not edit lines above this one
+BEGIN
+DELETE FROM ipv6_reservations WHERE ipv6_reservations.host_id = OLD.host_id;
+END
+$$
+DELIMITER ;
+
+# Update the schema version number.
+UPDATE schema_version
+    SET version = '3', minor = '0';
+
+# This line concludes the schema upgrade to version 3.0.
+
+# This line starts the schema upgrade to version 4.0.
+
+# Upgrade extending MySQL schema with the state columns for lease tables.
+
+# Add state column to the lease4 table.
+ALTER TABLE lease4
+    ADD COLUMN state INT UNSIGNED DEFAULT 0;
+
+# Add state column to the lease6 table.
+ALTER TABLE lease6
+    ADD COLUMN state INT UNSIGNED DEFAULT 0;
+
+# Create indexes for querying leases in a given state and segregated
+# by the expiration time. One of the applications is to retrieve all
+# expired leases. However, these indexes can be also used to retrieve
+# leases in a given state regardless of the expiration time.
+CREATE INDEX lease4_by_state_expire ON lease4 (state ASC, expire ASC);
+CREATE INDEX lease6_by_state_expire ON lease6 (state ASC, expire ASC);
+
+# Create table holding mapping of the lease states to their names.
+# This is not used in queries from the DHCP server but rather in
+# direct queries from the lease database management tools.
+CREATE TABLE IF NOT EXISTS lease_state (
+  state INT UNSIGNED PRIMARY KEY NOT NULL,
+  name VARCHAR(64) NOT NULL
+) ENGINE=INNODB;
+
+# Insert currently defined state names.
+INSERT INTO lease_state VALUES (0, 'default');
+INSERT INTO lease_state VALUES (1, 'declined');
+INSERT INTO lease_state VALUES (2, 'expired-reclaimed');
+
+# Add a constraint that any state value added to the lease4 must
+# map to a value in the lease_state table.
+ALTER TABLE lease4
+    ADD CONSTRAINT fk_lease4_state FOREIGN KEY (state)
+    REFERENCES lease_state (state);
+
+# Add a constraint that any state value added to the lease6 must
+# map to a value in the lease_state table.
+ALTER TABLE lease6
+    ADD CONSTRAINT fk_lease6_state FOREIGN KEY (state)
+    REFERENCES lease_state (state);
+
+# Add a constraint that lease type in the lease6 table must map
+# to a lease type defined in the lease6_types table.
+ALTER TABLE lease6
+    ADD CONSTRAINT fk_lease6_type FOREIGN KEY (lease_type)
+    REFERENCES lease6_types (lease_type);
+
+# Modify the name of one of the HW address sources, and add a new one.
+UPDATE lease_hwaddr_source
+    SET name = 'HWADDR_SOURCE_DOCSIS_CMTS'
+    WHERE hwaddr_source = 64;
+
+INSERT INTO lease_hwaddr_source VALUES (128, 'HWADDR_SOURCE_DOCSIS_MODEM');
+
+# Add UNSIGNED to match with the lease6.
+ALTER TABLE lease_hwaddr_source
+    MODIFY COLUMN hwaddr_source INT UNSIGNED NOT NULL;
+
+# Add a constraint that non-null hwaddr_source in the lease6 table
+# must map to an entry in the lease_hwaddr_source.
+ALTER TABLE lease6
+    ADD CONSTRAINT fk_lease6_hwaddr_source FOREIGN KEY (hwaddr_source)
+    REFERENCES lease_hwaddr_source (hwaddr_source);
+
+# Procedure that returns a result set containing the column names for lease4 dumps
+DROP PROCEDURE IF EXISTS lease4DumpHeader;
+DELIMITER $$
+CREATE PROCEDURE lease4DumpHeader()
+BEGIN
+SELECT 'address,hwaddr,client_id,valid_lifetime,expire,subnet_id,fqdn_fwd,fqdn_rev,hostname,state';
+END $$
+DELIMITER ;
+
+# Procedure that returns a result set containing the data for lease4 dumps
+DROP PROCEDURE IF EXISTS lease4DumpData;
+DELIMITER $$
+CREATE PROCEDURE lease4DumpData()
+BEGIN
+SELECT
+    INET_NTOA(l.address),
+    IFNULL(HEX(l.hwaddr), ''),
+    IFNULL(HEX(l.client_id), ''),
+    l.valid_lifetime,
+    l.expire,
+    l.subnet_id,
+    l.fqdn_fwd,
+    l.fqdn_rev,
+    l.hostname,
+    s.name
+FROM
+    lease4 l
+    LEFT OUTER JOIN lease_state s on (l.state = s.state)
+ORDER BY l.address;
+END $$
+DELIMITER ;
+
+# Procedure that returns a result set containing the column names for lease6 dumps
+DROP PROCEDURE IF EXISTS lease6DumpHeader;
+DELIMITER $$
+CREATE PROCEDURE lease6DumpHeader()
+BEGIN
+SELECT 'address,duid,valid_lifetime,expire,subnet_id,pref_lifetime,lease_type,iaid,prefix_len,fqdn_fwd,fqdn_rev,hostname,hwaddr,hwtype,hwaddr_source,state';
+END $$
+DELIMITER ;
+
+# Procedure that returns a result set containing the data for lease6 dumps
+DROP PROCEDURE IF EXISTS lease6DumpData;
+DELIMITER $$
+CREATE PROCEDURE lease6DumpData()
+BEGIN
+SELECT
+    l.address,
+    IFNULL(HEX(l.duid), ''),
+    l.valid_lifetime,
+    l.expire,
+    l.subnet_id,
+    l.pref_lifetime,
+    IFNULL(t.name, ''),
+    l.iaid,
+    l.prefix_len,
+    l.fqdn_fwd,
+    l.fqdn_rev,
+    l.hostname,
+    IFNULL(HEX(l.hwaddr), ''),
+    IFNULL(l.hwtype, ''),
+    IFNULL(h.name, ''),
+    IFNULL(s.name, '')
+FROM lease6 l
+    left outer join lease6_types t on (l.lease_type = t.lease_type)
+    left outer join lease_state s on (l.state = s.state)
+    left outer join lease_hwaddr_source h on (l.hwaddr_source = h.hwaddr_source)
+ORDER BY l.address;
+END $$
+DELIMITER ;
+
+# Update the schema version number.
+UPDATE schema_version
+    SET version = '4', minor = '0';
+
+# This line concludes the schema upgrade to version 4.0.
+
+# This line starts the schema upgrade to version 4.1.
+
+# In the event hardware address cannot be determined, we need to satisfy
+# foreign key constraint between lease6 and lease_hardware_source
+INSERT INTO lease_hwaddr_source VALUES (0, 'HWADDR_SOURCE_UNKNOWN');
+
+# Update the schema version number.
+UPDATE schema_version
+    SET version = '4', minor = '1';
+
+# This line concludes the schema upgrade to version 4.1.
+
+# This line starts the schema upgrade to version 5.0.
+
+# Update index used for searching DHCPv4 reservations by identifier and subnet id.
+# This index is now unique (to prevent duplicates) and includes DHCPv4 subnet
+# identifier.
+DROP INDEX key_dhcp4_identifier_subnet_id ON hosts;
+CREATE UNIQUE INDEX key_dhcp4_identifier_subnet_id ON hosts (dhcp_identifier ASC , dhcp_identifier_type ASC , dhcp4_subnet_id ASC);
+
+# Update index used for searching DHCPv6 reservations by identifier and subnet id.
+# This index is now unique to prevent duplicates.
+DROP INDEX key_dhcp6_identifier_subnet_id ON hosts;
+CREATE UNIQUE INDEX key_dhcp6_identifier_subnet_id ON hosts (dhcp_identifier ASC , dhcp_identifier_type ASC , dhcp6_subnet_id ASC);
+
+# Create index to search for reservations using IP address and subnet id.
+# This unique index guarantees that there is only one occurrence of the
+# particular IPv4 address for a given subnet.
+CREATE UNIQUE INDEX key_dhcp4_ipv4_address_subnet_id ON hosts (ipv4_address ASC , dhcp4_subnet_id ASC);
+
+# Create index to search for reservations using address/prefix and prefix
+# length.
+CREATE UNIQUE INDEX key_dhcp6_address_prefix_len ON ipv6_reservations (address ASC , prefix_len ASC);
+
+# Create a table mapping host identifiers to their names. Values in this
+# table are used as a foreign key in hosts table to guarantee that only
+# identifiers present in host_identifier_type table are used in hosts
+# table.
+CREATE TABLE IF NOT EXISTS host_identifier_type (
+    type TINYINT PRIMARY KEY NOT NULL,   # Lease type code.
+    name VARCHAR(32)                     # Name of the lease type
+) ENGINE = INNODB;
+
+START TRANSACTION;
+INSERT INTO host_identifier_type VALUES (0, 'hw-address');
+INSERT INTO host_identifier_type VALUES (1, 'duid');
+INSERT INTO host_identifier_type VALUES (2, 'circuit-id');
+COMMIT;
+
+# Add a constraint that any identifier type value added to the hosts
+# must map to a value in the host_identifier_type table.
+ALTER TABLE hosts
+    ADD CONSTRAINT fk_host_identifier_type FOREIGN KEY (dhcp_identifier_type)
+    REFERENCES host_identifier_type (type);
+
+# Store DHCPv6 option code as 16-bit unsigned integer.
+ALTER TABLE dhcp6_options MODIFY code SMALLINT UNSIGNED NOT NULL;
+
+# Subnet identifier is unsigned.
+ALTER TABLE dhcp4_options MODIFY dhcp4_subnet_id INT UNSIGNED NULL;
+ALTER TABLE dhcp6_options MODIFY dhcp6_subnet_id INT UNSIGNED NULL;
+
+# Scopes associate DHCP options stored in dhcp4_options and
+# dhcp6_options tables with hosts, subnets, classes or indicate
+# that they are global options.
+CREATE TABLE IF NOT EXISTS dhcp_option_scope (
+    scope_id TINYINT UNSIGNED PRIMARY KEY NOT NULL,
+    scope_name VARCHAR(32)
+) ENGINE = INNODB;
+
+START TRANSACTION;
+INSERT INTO dhcp_option_scope VALUES (0, 'global');
+INSERT INTO dhcp_option_scope VALUES (1, 'subnet');
+INSERT INTO dhcp_option_scope VALUES (2, 'client-class');
+INSERT INTO dhcp_option_scope VALUES (3, 'host');
+COMMIT;
+
+# Add scopes into table holding DHCPv4 options
+ALTER TABLE dhcp4_options ADD COLUMN scope_id TINYINT UNSIGNED NOT NULL;
+ALTER TABLE dhcp4_options
+    ADD CONSTRAINT fk_dhcp4_option_scope FOREIGN KEY (scope_id)
+    REFERENCES dhcp_option_scope (scope_id);
+
+# Add scopes into table holding DHCPv6 options
+ALTER TABLE dhcp6_options ADD COLUMN scope_id TINYINT UNSIGNED NOT NULL;
+ALTER TABLE dhcp6_options
+    ADD CONSTRAINT fk_dhcp6_option_scope FOREIGN KEY (scope_id)
+    REFERENCES dhcp_option_scope (scope_id);
+
+# Add UNSIGNED to reservation_id
+ALTER TABLE ipv6_reservations
+    MODIFY reservation_id INT UNSIGNED NOT NULL AUTO_INCREMENT;
+
+# Add columns holding reservations for siaddr, sname and file fields
+# carried within DHCPv4 message.
+ALTER TABLE hosts ADD COLUMN dhcp4_next_server INT UNSIGNED NULL;
+ALTER TABLE hosts ADD COLUMN dhcp4_server_hostname VARCHAR(64) NULL;
+ALTER TABLE hosts ADD COLUMN dhcp4_boot_file_name VARCHAR(128) NULL;
+
+# Update the schema version number.
+UPDATE schema_version
+    SET version = '5', minor = '0';
+
+# This line concludes the schema upgrade to version 5.0.
+
+# This line starts the schema upgrade to version 5.1.
+
+# Add missing 'client-id' and new 'flex-id' host identifier types.
+INSERT INTO host_identifier_type VALUES (3, 'client-id');
+INSERT INTO host_identifier_type VALUES (4, 'flex-id');
+
+# Recreate the trigger removing dependent host entries.
+DROP TRIGGER host_BDEL;
+
+DELIMITER $$
+CREATE TRIGGER host_BDEL BEFORE DELETE ON hosts FOR EACH ROW
+-- Edit trigger body code below this line. Do not edit lines above this one
+BEGIN
+DELETE FROM ipv6_reservations WHERE ipv6_reservations.host_id = OLD.host_id;
+DELETE FROM dhcp4_options WHERE dhcp4_options.host_id = OLD.host_id;
+DELETE FROM dhcp6_options WHERE dhcp6_options.host_id = OLD.host_id;
+END
+$$
+DELIMITER ;
+
+# Update the schema version number.
+UPDATE schema_version
+    SET version = '5', minor = '1';
+
+# This line concludes the schema upgrade to version 5.1.
+
+# This line starts the schema upgrade to version 5.2.
+
+# Make subnet_id column types consistent with lease table columns
+ALTER TABLE dhcp4_options MODIFY dhcp4_subnet_id INT UNSIGNED;
+ALTER TABLE dhcp6_options MODIFY dhcp6_subnet_id INT UNSIGNED;
+
+# Update the schema version number.
+UPDATE schema_version
+    SET version = '5', minor = '2';
+
+# This line concludes the schema upgrade to version 5.2.
+
+# This line starts the schema upgrade to version 6.0.
+
+# Add user context into table holding hosts
+ALTER TABLE hosts ADD COLUMN user_context TEXT NULL;
+
+# Add user contexts into tables holding DHCP options
+ALTER TABLE dhcp4_options ADD COLUMN user_context TEXT NULL;
+ALTER TABLE dhcp6_options ADD COLUMN user_context TEXT NULL;
+
+# Create index for searching leases by subnet identifier.
+CREATE INDEX lease4_by_subnet_id ON lease4 (subnet_id);
+
+# Create for searching leases by subnet identifier and lease type.
+CREATE INDEX lease6_by_subnet_id_lease_type ON lease6 (subnet_id, lease_type);
+
+# The index by iaid_subnet_id_duid is not the best choice because there are
+# cases when we don't specify subnet identifier while searching leases. The
+# index will be universal if the subnet_id is the right most column in the
+# index.
+DROP INDEX lease6_by_iaid_subnet_id_duid on lease6;
+CREATE INDEX lease6_by_duid_iaid_subnet_id ON lease6 (duid, iaid, subnet_id);
+
+# Create lease4_stat table
+CREATE TABLE lease4_stat (
+    subnet_id INT UNSIGNED NOT NULL,
+    state INT UNSIGNED NOT NULL,
+    leases BIGINT,
+    PRIMARY KEY (subnet_id, state)
+) ENGINE = INNODB;
+
+# Create stat_lease4_insert trigger
+DELIMITER $$
+CREATE TRIGGER stat_lease4_insert AFTER INSERT ON lease4
+    FOR EACH ROW
+    BEGIN
+        IF NEW.state = 0 OR NEW.state = 1 THEN
+            # Update the state count if it exists
+            UPDATE lease4_stat SET leases = leases + 1
+            WHERE subnet_id = NEW.subnet_id AND state = NEW.state;
+
+            # Insert the state count record if it does not exist
+            IF ROW_COUNT() <= 0 THEN
+                INSERT INTO lease4_stat VALUES (NEW.subnet_id, NEW.state, 1);
+            END IF;
+        END IF;
+    END $$
+DELIMITER ;
+
+# Create stat_lease4_update trigger
+DELIMITER $$
+CREATE TRIGGER stat_lease4_update AFTER UPDATE ON lease4
+    FOR EACH ROW
+    BEGIN
+        IF OLD.state != NEW.state THEN
+            IF OLD.state = 0 OR OLD.state = 1 THEN
+                # Decrement the old state count if record exists
+                UPDATE lease4_stat SET leases = leases - 1
+                WHERE subnet_id = OLD.subnet_id AND state = OLD.state;
+            END IF;
+
+            IF NEW.state = 0 OR NEW.state = 1 THEN
+                # Increment the new state count if record exists
+                UPDATE lease4_stat SET leases = leases + 1
+                WHERE subnet_id = NEW.subnet_id AND state = NEW.state;
+
+                # Insert new state record if it does not exist
+                IF ROW_COUNT() <= 0 THEN
+                    INSERT INTO lease4_stat VALUES (NEW.subnet_id, NEW.state, 1);
+                END IF;
+            END IF;
+        END IF;
+    END $$
+DELIMITER ;
+
+# Create stat_lease4_delete trigger
+DELIMITER $$
+CREATE TRIGGER stat_lease4_delete AFTER DELETE ON lease4
+    FOR EACH ROW
+    BEGIN
+        IF OLD.state = 0 OR OLD.state = 1 THEN
+            # Decrement the state count if record exists
+            UPDATE lease4_stat SET leases = leases - 1
+            WHERE subnet_id = OLD.subnet_id AND OLD.state = state;
+        END IF;
+    END $$
+DELIMITER ;
+
+# Create lease6_stat table
+CREATE TABLE lease6_stat (
+    subnet_id INT UNSIGNED NOT NULL,
+    lease_type INT UNSIGNED NOT NULL,
+    state INT UNSIGNED NOT NULL,
+    leases BIGINT,
+    PRIMARY KEY (subnet_id, lease_type, state)
+) ENGINE = INNODB;
+
+# Create stat_lease6_insert trigger
+DELIMITER $$
+CREATE TRIGGER stat_lease6_insert AFTER INSERT ON lease6
+    FOR EACH ROW
+    BEGIN
+        IF NEW.state = 0 OR NEW.state = 1 THEN
+            # Update the state count if it exists
+            UPDATE lease6_stat SET leases = leases + 1
+            WHERE
+                subnet_id = NEW.subnet_id AND lease_type = NEW.lease_type
+                AND state = NEW.state;
+
+            # Insert the state count record if it does not exist
+            IF ROW_COUNT() <= 0 THEN
+                INSERT INTO lease6_stat
+                VALUES (NEW.subnet_id, NEW.lease_type, NEW.state, 1);
+            END IF;
+        END IF;
+    END $$
+DELIMITER ;
+
+# Create stat_lease6_update trigger
+DELIMITER $$
+CREATE TRIGGER stat_lease6_update AFTER UPDATE ON lease6
+    FOR EACH ROW
+    BEGIN
+        IF OLD.state != NEW.state THEN
+            IF OLD.state = 0 OR OLD.state = 1 THEN
+                # Decrement the old state count if record exists
+                UPDATE lease6_stat SET leases = leases - 1
+                WHERE subnet_id = OLD.subnet_id AND lease_type = OLD.lease_type
+                AND state = OLD.state;
+            END IF;
+
+            IF NEW.state = 0 OR NEW.state = 1 THEN
+                # Increment the new state count if record exists
+                UPDATE lease6_stat SET leases = leases + 1
+                WHERE subnet_id = NEW.subnet_id AND lease_type = NEW.lease_type
+                AND state = NEW.state;
+
+                # Insert new state record if it does not exist
+                IF ROW_COUNT() <= 0 THEN
+                    INSERT INTO lease6_stat
+                    VALUES (NEW.subnet_id, NEW.lease_type, NEW.state, 1);
+                END IF;
+            END IF;
+        END IF;
+    END $$
+DELIMITER ;
+
+# Create stat_lease6_delete trigger
+DELIMITER $$
+CREATE TRIGGER stat_lease6_delete AFTER DELETE ON lease6
+    FOR EACH ROW
+    BEGIN
+        IF OLD.state = 0 OR OLD.state = 1 THEN
+            # Decrement the state count if record exists
+            UPDATE lease6_stat SET leases = leases - 1
+            WHERE subnet_id = OLD.subnet_id AND lease_type = OLD.lease_type
+            AND state = OLD.state;
+        END IF;
+    END $$
+DELIMITER ;
+
+# Update the schema version number.
+UPDATE schema_version
+    SET version = '6', minor = '0';
+
+# This line concludes the schema upgrade to version 6.0.
+
+# This line starts the schema upgrade to version 7.0.
+
+# Add user context into tables holding leases
+ALTER TABLE lease4 ADD COLUMN user_context TEXT NULL;
+ALTER TABLE lease6 ADD COLUMN user_context TEXT NULL;
+
+DROP PROCEDURE IF EXISTS lease4DumpHeader;
+DELIMITER $$
+CREATE PROCEDURE lease4DumpHeader()
+BEGIN
+SELECT 'address,hwaddr,client_id,valid_lifetime,expire,subnet_id,fqdn_fwd,fqdn_rev,hostname,state,user_context';
+END $$
+DELIMITER ;
+
+# Procedure that returns a result set containing the data for lease4 dumps
+DROP PROCEDURE IF EXISTS lease4DumpData;
+DELIMITER $$
+CREATE PROCEDURE lease4DumpData()
+BEGIN
+SELECT
+    INET_NTOA(l.address),
+    IFNULL(HEX(l.hwaddr), ''),
+    IFNULL(HEX(l.client_id), ''),
+    l.valid_lifetime,
+    l.expire,
+    l.subnet_id,
+    l.fqdn_fwd,
+    l.fqdn_rev,
+    l.hostname,
+    s.name,
+    IFNULL(l.user_context, '')
+FROM
+    lease4 l
+    LEFT OUTER JOIN lease_state s on (l.state = s.state)
+ORDER BY l.address;
+END $$
+DELIMITER ;
+
+DROP PROCEDURE IF EXISTS lease6DumpHeader;
+DELIMITER $$
+CREATE PROCEDURE lease6DumpHeader()
+BEGIN
+SELECT 'address,duid,valid_lifetime,expire,subnet_id,pref_lifetime,lease_type,iaid,prefix_len,fqdn_fwd,fqdn_rev,hostname,hwaddr,hwtype,hwaddr_source,state,user_context';
+END $$
+DELIMITER ;
+
+# Procedure that returns a result set containing the data for lease6 dumps
+DROP PROCEDURE IF EXISTS lease6DumpData;
+DELIMITER $$
+CREATE PROCEDURE lease6DumpData()
+BEGIN
+SELECT
+    l.address,
+    IFNULL(HEX(l.duid), ''),
+    l.valid_lifetime,
+    l.expire,
+    l.subnet_id,
+    l.pref_lifetime,
+    IFNULL(t.name, ''),
+    l.iaid,
+    l.prefix_len,
+    l.fqdn_fwd,
+    l.fqdn_rev,
+    l.hostname,
+    IFNULL(HEX(l.hwaddr), ''),
+    IFNULL(l.hwtype, ''),
+    IFNULL(h.name, ''),
+    IFNULL(s.name, ''),
+    IFNULL(l.user_context, '')
+FROM lease6 l
+    left outer join lease6_types t on (l.lease_type = t.lease_type)
+    left outer join lease_state s on (l.state = s.state)
+    left outer join lease_hwaddr_source h on (l.hwaddr_source = h.hwaddr_source)
+ORDER BY l.address;
+END $$
+DELIMITER ;
+
+# Create logs table (logs table is used by forensic logging hook library)
+CREATE TABLE logs (
+    timestamp TIMESTAMP DEFAULT CURRENT_TIMESTAMP,  # creation timestamp
+    address VARCHAR(43) NULL,                       # address or prefix
+    log TEXT NOT NULL                               # the log itself
+    ) ENGINE = INNODB;
+
+# Create search index
+CREATE INDEX timestamp_index ON logs (timestamp);
+
+#add auth key for reconfiguration
+ALTER TABLE hosts
+    ADD COLUMN auth_key VARCHAR(16) NULL;
+
+# Add scope for shared network specific options.
+INSERT INTO dhcp_option_scope (scope_id, scope_name)
+    VALUES(4, "shared-network");
+
+# Add scope for pool specific options.
+INSERT INTO dhcp_option_scope (scope_id, scope_name)
+    VALUES(5, "pool");
+
+# Add scope for PD pool specific options.
+INSERT INTO dhcp_option_scope (scope_id, scope_name)
+    VALUES(6, "pd-pool");
+
+-- -----------------------------------------------------
+-- Table `modification`
+-- -----------------------------------------------------
+CREATE TABLE IF NOT EXISTS modification (
+  id TINYINT(3) NOT NULL,
+  modification_type VARCHAR(32) NOT NULL,
+  PRIMARY KEY (id)
+) ENGINE=InnoDB;
+
+INSERT INTO modification(id, modification_type)
+    VALUES(0, "create");
+
+INSERT INTO modification(id, modification_type)
+    VALUES(1, "update");
+
+INSERT INTO modification(id, modification_type)
+    VALUES(2, "delete");
+
+-- -----------------------------------------------------
+-- Table `dhcp4_server`
+-- -----------------------------------------------------
+CREATE TABLE IF NOT EXISTS dhcp4_server (
+    id BIGINT(20) UNSIGNED NOT NULL AUTO_INCREMENT,
+    tag VARCHAR(64) NOT NULL,
+    description TEXT,
+    modification_ts TIMESTAMP NOT NULL,
+    PRIMARY KEY (id),
+    UNIQUE KEY dhcp4_server_tag_UNIQUE (tag),
+    KEY key_dhcp4_server_modification_ts (modification_ts)
+) ENGINE=InnoDB;
+
+# Special server entry meaning "all servers". This refers to
+# the configuration entries owned by all servers.
+INSERT INTO dhcp4_server(id, tag, description, modification_ts)
+    VALUES(1, "all", "special type: all servers", NOW());
+
+-- -----------------------------------------------------
+-- Table `dhcp4_audit`
+-- -----------------------------------------------------
+CREATE TABLE IF NOT EXISTS dhcp4_audit (
+    id BIGINT(20) UNSIGNED NOT NULL AUTO_INCREMENT,
+    object_type VARCHAR(256) NOT NULL,
+    object_id BIGINT(20) UNSIGNED NOT NULL,
+    modification_type TINYINT(1) NOT NULL,
+    modification_ts TIMESTAMP NOT NULL,
+    log_message TEXT,
+    PRIMARY KEY (id),
+    KEY key_dhcp4_audit_by_modification_ts (modification_ts),
+    KEY fk_dhcp4_audit_modification_type (modification_type),
+    CONSTRAINT fk_dhcp4_audit_modification_type FOREIGN KEY (modification_type)
+        REFERENCES modification (id)
+        ON DELETE NO ACTION ON UPDATE NO ACTION
+) ENGINE=InnoDB;
+
+-- -----------------------------------------------------
+-- Table `dhcp4_global_parameter`
+-- -----------------------------------------------------
+CREATE TABLE IF NOT EXISTS dhcp4_global_parameter (
+    id BIGINT(20) UNSIGNED NOT NULL AUTO_INCREMENT,
+    name VARCHAR(128) NOT NULL,
+    value LONGTEXT NOT NULL,
+    modification_ts timestamp NOT NULL,
+    PRIMARY KEY (id),
+    KEY key_dhcp4_global_parameter_modification_ts (modification_ts),
+    KEY key_dhcp4_global_parameter_name (name)
+) ENGINE=InnoDB;
+
+-- -----------------------------------------------------
+-- Table `dhcp4_global_parameter_server`
+-- M-to-M cross-reference between global parameters and
+-- servers
+-- -----------------------------------------------------
+CREATE TABLE IF NOT EXISTS dhcp4_global_parameter_server (
+    parameter_id BIGINT(20) UNSIGNED NOT NULL,
+    server_id BIGINT(20) UNSIGNED NOT NULL,
+    modification_ts TIMESTAMP NOT NULL,
+    PRIMARY KEY (parameter_id, server_id),
+    KEY fk_dhcp4_global_parameter_server_server_id (server_id),
+    KEY key_dhcp4_global_parameter_server (modification_ts),
+    CONSTRAINT fk_dhcp4_global_parameter_server_parameter_id FOREIGN KEY (parameter_id)
+        REFERENCES dhcp4_global_parameter (id)
+        ON DELETE CASCADE ON UPDATE NO ACTION,
+    CONSTRAINT fk_dhcp4_global_parameter_server_server_id FOREIGN KEY (server_id)
+        REFERENCES dhcp4_server (id)
+        ON DELETE NO ACTION ON UPDATE NO ACTION
+) ENGINE=InnoDB;
+
+-- -----------------------------------------------------
+-- Table `dhcp4_option_def`
+-- -----------------------------------------------------
+CREATE TABLE IF NOT EXISTS dhcp4_option_def (
+    id BIGINT(20) UNSIGNED NOT NULL AUTO_INCREMENT,
+    code SMALLINT UNSIGNED NOT NULL,
+    name VARCHAR(128) NOT NULL,
+    space VARCHAR(128) NOT NULL,
+    type TINYINT UNSIGNED NOT NULL,
+    modification_ts TIMESTAMP NOT NULL,
+    is_array TINYINT(1) NOT NULL,
+    encapsulate VARCHAR(128) NOT NULL,
+    record_types VARCHAR(512) DEFAULT NULL,
+    user_context LONGTEXT,
+    PRIMARY KEY (id),
+    KEY key_dhcp4_option_def_modification_ts (modification_ts),
+    KEY key_dhcp4_option_def_code_space (code, space)
+) ENGINE=InnoDB;
+
+-- -----------------------------------------------------
+-- Table `dhcp4_option_def_server`
+-- M-to-M cross-reference between option definitions and
+-- servers
+-- -----------------------------------------------------
+CREATE TABLE IF NOT EXISTS dhcp4_option_def_server (
+    option_def_id BIGINT(20) UNSIGNED NOT NULL,
+    server_id BIGINT(20) UNSIGNED NOT NULL,
+    modification_ts TIMESTAMP NOT NULL,
+    PRIMARY KEY (option_def_id, server_id),
+    KEY fk_dhcp4_option_def_server_server_id_idx (server_id),
+    KEY key_dhcp4_option_def_server_modification_ts (modification_ts),
+    CONSTRAINT fk_dhcp4_option_def_server_option_def_id FOREIGN KEY (option_def_id)
+        REFERENCES dhcp4_option_def (id)
+        ON DELETE CASCADE ON UPDATE NO ACTION,
+    CONSTRAINT fk_dhcp4_option_def_server_server_id FOREIGN KEY (server_id)
+        REFERENCES dhcp4_server (id) ON DELETE NO ACTION ON UPDATE NO ACTION
+) ENGINE=InnoDB;
+
+-- -----------------------------------------------------
+-- Table `dhcp4_shared_network`
+-- -----------------------------------------------------
+CREATE TABLE IF NOT EXISTS dhcp4_shared_network (
+    id BIGINT(20) UNSIGNED NOT NULL AUTO_INCREMENT,
+    name VARCHAR(128) NOT NULL,
+    client_class VARCHAR(128) DEFAULT NULL,
+    interface VARCHAR(128) DEFAULT NULL,
+    match_client_id TINYINT(1) NOT NULL DEFAULT '1',
+    modification_ts TIMESTAMP NOT NULL,
+    rebind_timer INT(10) DEFAULT NULL,
+    relay LONGTEXT,
+    renew_timer INT(10) DEFAULT NULL,
+    require_client_classes LONGTEXT DEFAULT NULL,
+    reservation_mode TINYINT(3) NOT NULL DEFAULT '3',
+    user_context LONGTEXT,
+    valid_lifetime INT(10) DEFAULT NULL,
+    PRIMARY KEY (id),
+    UNIQUE KEY name_UNIQUE (name),
+    KEY key_dhcp4_shared_network_modification_ts (modification_ts)
+) ENGINE=InnoDB;
+
+-- -----------------------------------------------------
+-- Table `dhcp4_shared_network_server`
+-- M-to-M cross-reference between shared networks and
+-- servers
+-- -----------------------------------------------------
+CREATE TABLE IF NOT EXISTS dhcp4_shared_network_server (
+    shared_network_id BIGINT(20) UNSIGNED NOT NULL,
+    server_id BIGINT(20) UNSIGNED NOT NULL,
+    modification_ts TIMESTAMP NOT NULL,
+    PRIMARY KEY (shared_network_id, server_id),
+    KEY key_dhcp4_shared_network_server_modification_ts (modification_ts),
+    KEY fk_dhcp4_shared_network_server_server_id (server_id),
+    CONSTRAINT fk_dhcp4_shared_network_server_server_id FOREIGN KEY (server_id)
+        REFERENCES dhcp4_server (id)
+        ON DELETE NO ACTION ON UPDATE NO ACTION,
+    CONSTRAINT fk_dhcp4_shared_network_server_shared_network_id FOREIGN KEY (shared_network_id)
+        REFERENCES dhcp4_shared_network (id) ON DELETE CASCADE ON UPDATE NO ACTION
+) ENGINE=InnoDB;
+
+-- -----------------------------------------------------
+-- Table `dhcp4_subnet`
+-- -----------------------------------------------------
+CREATE TABLE IF NOT EXISTS dhcp4_subnet (
+    subnet_id INT(10) UNSIGNED NOT NULL,
+    subnet_prefix VARCHAR(32) NOT NULL,
+    4o6_interface VARCHAR(128) DEFAULT NULL,
+    4o6_interface_id VARCHAR(128) DEFAULT NULL,
+    4o6_subnet VARCHAR(64) DEFAULT NULL,
+    boot_file_name VARCHAR(512) DEFAULT NULL,
+    client_class VARCHAR(128) DEFAULT NULL,
+    interface VARCHAR(128) DEFAULT NULL,
+    match_client_id TINYINT(1) NOT NULL DEFAULT '1',
+    modification_ts TIMESTAMP NOT NULL,
+    next_server INT(10) UNSIGNED DEFAULT NULL,
+    rebind_timer INT(10) DEFAULT NULL,
+    relay LONGTEXT,
+    renew_timer INT(10) DEFAULT NULL,
+    require_client_classes LONGTEXT DEFAULT NULL,
+    reservation_mode TINYINT(3) NOT NULL DEFAULT '3',
+    server_hostname VARCHAR(512) DEFAULT NULL,
+    shared_network_name VARCHAR(128) DEFAULT NULL,
+    user_context LONGTEXT,
+    valid_lifetime INT(10) DEFAULT NULL,
+    PRIMARY KEY (subnet_id),
+    UNIQUE KEY subnet4_subnet_prefix (subnet_prefix),
+    KEY fk_dhcp4_subnet_shared_network (shared_network_name),
+    KEY key_dhcp4_subnet_modification_ts (modification_ts),
+    CONSTRAINT fk_dhcp4_subnet_shared_network FOREIGN KEY (shared_network_name)
+        REFERENCES dhcp4_shared_network (name)
+        ON DELETE SET NULL ON UPDATE NO ACTION
+) ENGINE=InnoDB;
+
+-- -----------------------------------------------------
+-- Table `dhcp4_pool`
+-- -----------------------------------------------------
+CREATE TABLE IF NOT EXISTS dhcp4_pool (
+    id BIGINT(20) UNSIGNED NOT NULL AUTO_INCREMENT,
+    start_address INT(10) UNSIGNED NOT NULL,
+    end_address INT(10) UNSIGNED NOT NULL,
+    subnet_id INT(10) UNSIGNED NOT NULL,
+    modification_ts TIMESTAMP NOT NULL,
+    PRIMARY KEY (id),
+    KEY key_dhcp4_pool_modification_ts (modification_ts),
+    KEY fk_dhcp4_pool_subnet_id (subnet_id),
+    CONSTRAINT fk_dhcp4_pool_subnet_id FOREIGN KEY (subnet_id)
+        REFERENCES dhcp4_subnet (subnet_id)
+        ON DELETE CASCADE ON UPDATE CASCADE
+) ENGINE=InnoDB;
+
+-- -----------------------------------------------------
+-- Table `dhcp4_subnet_server`
+-- M-to-M cross-reference between subnets and servers
+-- -----------------------------------------------------
+CREATE TABLE IF NOT EXISTS dhcp4_subnet_server (
+    subnet_id INT(10) UNSIGNED NOT NULL,
+    server_id BIGINT(20) UNSIGNED NOT NULL,
+    modification_ts TIMESTAMP NOT NULL,
+    PRIMARY KEY (subnet_id,server_id),
+    KEY fk_dhcp4_subnet_server_server_id_idx (server_id),
+    KEY key_dhcp4_subnet_server_modification_ts (modification_ts),
+    CONSTRAINT fk_dhcp4_subnet_server_server_id FOREIGN KEY (server_id)
+        REFERENCES dhcp4_server (id)
+        ON DELETE NO ACTION ON UPDATE NO ACTION,
+    CONSTRAINT fk_dhcp4_subnet_server_subnet_id FOREIGN KEY (subnet_id)
+        REFERENCES dhcp4_subnet (subnet_id)
+        ON DELETE CASCADE ON UPDATE NO ACTION
+) ENGINE=InnoDB;
+
+# Modify the primary key to BINGINT as other tables have.
+ALTER TABLE dhcp4_options MODIFY option_id BIGINT(20) UNSIGNED NOT NULL AUTO_INCREMENT;
+
+# Add configuration backend specific columns.
+ALTER TABLE dhcp4_options
+    ADD COLUMN shared_network_name VARCHAR(128) DEFAULT NULL,
+    ADD COLUMN pool_id BIGINT(20) UNSIGNED DEFAULT NULL,
+    ADD COLUMN modification_ts TIMESTAMP NOT NULL;
+
+-- -----------------------------------------------------
+-- Table `dhcp4_options_server`
+-- M-to-M cross-reference between options and servers
+-- -----------------------------------------------------
+CREATE TABLE IF NOT EXISTS dhcp4_options_server (
+    option_id BIGINT(20) UNSIGNED NOT NULL,
+    server_id BIGINT(20) UNSIGNED NOT NULL,
+    modification_ts TIMESTAMP NOT NULL,
+    PRIMARY KEY (option_id, server_id),
+    KEY fk_dhcp4_options_server_server_id (server_id),
+    KEY key_dhcp4_options_server_modification_ts (modification_ts),
+    CONSTRAINT fk_dhcp4_options_server_option_id FOREIGN KEY (option_id)
+        REFERENCES dhcp4_options (option_id)
+        ON DELETE CASCADE ON UPDATE NO ACTION,
+    CONSTRAINT fk_dhcp4_options_server_server_id FOREIGN KEY (server_id)
+        REFERENCES dhcp4_server (id)
+        ON DELETE NO ACTION ON UPDATE NO ACTION
+) ENGINE=InnoDB;
+
+# Create trigger which removes pool specific options upon removal of
+# the pool.
+DELIMITER $$
+CREATE TRIGGER dhcp4_pool_BDEL BEFORE DELETE ON dhcp4_pool FOR EACH ROW
+-- Edit trigger body code below this line. Do not edit lines above this one
+BEGIN
+DELETE FROM dhcp4_options WHERE scope_id = 5 AND pool_id = OLD.id;
+END
+$$
+DELIMITER ;
+
+-- -----------------------------------------------------
+-- Table `dhcp6_server`
+-- -----------------------------------------------------
+CREATE TABLE IF NOT EXISTS dhcp6_server (
+    id BIGINT(20) UNSIGNED NOT NULL AUTO_INCREMENT,
+    tag VARCHAR(64) NOT NULL,
+    description TEXT,
+    modification_ts TIMESTAMP NOT NULL,
+    PRIMARY KEY (id),
+    UNIQUE KEY dhcp6_server_tag_UNIQUE (tag),
+    KEY key_dhcp6_server_modification_ts (modification_ts)
+) ENGINE=InnoDB;
+
+# Special server entry meaning "all servers". This refers to
+# the configuration entries owned by all servers.
+INSERT INTO dhcp6_server(id, tag, description, modification_ts)
+    VALUES(1, "all", "special type: all servers", NOW());
+
+-- -----------------------------------------------------
+-- Table `dhcp6_audit`
+-- -----------------------------------------------------
+CREATE TABLE IF NOT EXISTS dhcp6_audit (
+    id BIGINT(20) UNSIGNED NOT NULL AUTO_INCREMENT,
+    object_type VARCHAR(256) NOT NULL,
+    object_id BIGINT(20) UNSIGNED NOT NULL,
+    modification_type TINYINT(1) NOT NULL,
+    modification_ts TIMESTAMP NOT NULL,
+    log_message TEXT,
+    PRIMARY KEY (id),
+    KEY key_dhcp6_audit_modification_ts (modification_ts),
+    KEY fk_dhcp6_audit_modification_type (modification_type),
+    CONSTRAINT fk_dhcp6_audit_modification_type FOREIGN KEY (modification_type)
+        REFERENCES modification (id)
+        ON DELETE NO ACTION ON UPDATE NO ACTION
+) ENGINE=InnoDB;
+
+-- -----------------------------------------------------
+-- Table `dhcp6_global_parameter`
+-- -----------------------------------------------------
+CREATE TABLE IF NOT EXISTS dhcp6_global_parameter (
+    id BIGINT(20) UNSIGNED NOT NULL AUTO_INCREMENT,
+    name VARCHAR(128) NOT NULL,
+    value LONGTEXT NOT NULL,
+    modification_ts timestamp NOT NULL,
+    PRIMARY KEY (id),
+    KEY key_dhcp6_global_parameter_modification_ts (modification_ts),
+    KEY key_dhcp6_global_parameter_name (name)
+) ENGINE=InnoDB;
+
+-- -----------------------------------------------------
+-- Table `dhcp6_global_parameter_server`
+-- M-to-M cross-reference between global parameters and
+-- servers
+-- -----------------------------------------------------
+CREATE TABLE IF NOT EXISTS dhcp6_global_parameter_server (
+    parameter_id BIGINT(20) UNSIGNED NOT NULL,
+    server_id BIGINT(20) UNSIGNED NOT NULL,
+    modification_ts TIMESTAMP NOT NULL,
+    PRIMARY KEY (parameter_id, server_id),
+    KEY fk_dhcp6_global_parameter_server_server_id (server_id),
+    KEY key_dhcp6_global_parameter_server (modification_ts),
+    CONSTRAINT fk_dhcp6_global_parameter_server_parameter_id FOREIGN KEY (parameter_id)
+        REFERENCES dhcp6_global_parameter (id)
+        ON DELETE CASCADE ON UPDATE NO ACTION,
+    CONSTRAINT fk_dhcp6_global_parameter_server_server_id FOREIGN KEY (server_id)
+        REFERENCES dhcp6_server (id)
+        ON DELETE NO ACTION ON UPDATE NO ACTION
+) ENGINE=InnoDB;
+
+-- -----------------------------------------------------
+-- Table `dhcp6_option_def`
+-- -----------------------------------------------------
+CREATE TABLE IF NOT EXISTS dhcp6_option_def (
+    id BIGINT(20) UNSIGNED NOT NULL AUTO_INCREMENT,
+    code SMALLINT UNSIGNED NOT NULL,
+    name VARCHAR(128) NOT NULL,
+    space VARCHAR(128) NOT NULL,
+    type TINYINT UNSIGNED NOT NULL,
+    modification_ts TIMESTAMP NOT NULL,
+    is_array TINYINT(1) NOT NULL,
+    encapsulate VARCHAR(128) NOT NULL,
+    record_types VARCHAR(512) DEFAULT NULL,
+    user_context LONGTEXT,
+    PRIMARY KEY (id),
+    KEY key_dhcp6_option_def_modification_ts (modification_ts),
+    KEY key_dhcp6_option_def_code_space (code, space)
+) ENGINE=InnoDB;
+
+-- -----------------------------------------------------
+-- Table `dhcp6_option_def_server`
+-- M-to-M cross-reference between option definitions and
+-- servers
+-- -----------------------------------------------------
+CREATE TABLE IF NOT EXISTS dhcp6_option_def_server (
+    option_def_id BIGINT(20) UNSIGNED NOT NULL,
+    server_id BIGINT(20) UNSIGNED NOT NULL,
+    modification_ts TIMESTAMP NOT NULL,
+    PRIMARY KEY (option_def_id, server_id),
+    KEY fk_dhcp6_option_def_server_server_id_idx (server_id),
+    KEY key_dhcp6_option_def_server_modification_ts (modification_ts),
+    CONSTRAINT fk_dhcp6_option_def_server_option_def_id FOREIGN KEY (option_def_id)
+        REFERENCES dhcp6_option_def (id)
+        ON DELETE CASCADE ON UPDATE NO ACTION,
+    CONSTRAINT fk_dhcp6_option_def_server_server_id FOREIGN KEY (server_id)
+        REFERENCES dhcp6_server (id) ON DELETE NO ACTION ON UPDATE NO ACTION
+) ENGINE=InnoDB;
+
+-- -----------------------------------------------------
+-- Table `dhcp6_shared_network`
+-- -----------------------------------------------------
+CREATE TABLE dhcp6_shared_network (
+    id BIGINT(20) UNSIGNED NOT NULL AUTO_INCREMENT,
+    name VARCHAR(128) NOT NULL,
+    client_class VARCHAR(128) DEFAULT NULL,
+    interface VARCHAR(128) DEFAULT NULL,
+    modification_ts TIMESTAMP NOT NULL,
+    preferred_lifetime INT(10) DEFAULT NULL,
+    rapid_commit TINYINT(1) NOT NULL DEFAULT '1',
+    rebind_timer INT(10) DEFAULT NULL,
+    relay LONGTEXT DEFAULT NULL,
+    renew_timer INT(10) DEFAULT NULL,
+    require_client_classes LONGTEXT,
+    reservation_mode TINYINT(3) NOT NULL DEFAULT '3',
+    user_context LONGTEXT,
+    valid_lifetime INT(10) DEFAULT NULL,
+    PRIMARY KEY (id),
+    UNIQUE KEY name_UNIQUE (name),
+    KEY key_dhcp6_shared_network_modification_ts (modification_ts)
+) ENGINE=InnoDB;
+
+-- -----------------------------------------------------
+-- Table `dhcp6_shared_network_server`
+-- M-to-M cross-reference between shared networks and
+-- servers
+-- -----------------------------------------------------
+CREATE TABLE IF NOT EXISTS dhcp6_shared_network_server (
+    shared_network_id BIGINT(20) UNSIGNED NOT NULL,
+    server_id BIGINT(20) UNSIGNED NOT NULL,
+    modification_ts TIMESTAMP NOT NULL,
+    KEY key_dhcp6_shared_network_server_modification_ts (modification_ts),
+    KEY fk_dhcp6_shared_network_server_server_id_idx (server_id),
+    KEY fk_dhcp6_shared_network_server_shared_network_id (shared_network_id),
+    CONSTRAINT fk_dhcp6_shared_network_server_server_id FOREIGN KEY (server_id)
+        REFERENCES dhcp6_server (id)
+        ON DELETE NO ACTION ON UPDATE NO ACTION,
+    CONSTRAINT fk_dhcp6_shared_network_server_shared_network_id FOREIGN KEY (shared_network_id)
+        REFERENCES dhcp6_shared_network (id)
+        ON DELETE CASCADE ON UPDATE NO ACTION
+) ENGINE=InnoDB;
+
+-- -----------------------------------------------------
+-- Table `dhcp6_subnet`
+-- -----------------------------------------------------
+CREATE TABLE dhcp6_subnet (
+    subnet_id INT(10) UNSIGNED NOT NULL,
+    subnet_prefix VARCHAR(64) NOT NULL,
+    client_class VARCHAR(128) DEFAULT NULL,
+    interface VARCHAR(128) DEFAULT NULL,
+    modification_ts TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
+    preferred_lifetime INT(10) DEFAULT NULL,
+    rapid_commit TINYINT(1) NOT NULL DEFAULT '1',
+    rebind_timer INT(10) DEFAULT NULL,
+    relay LONGTEXT DEFAULT NULL,
+    renew_timer INT(10) DEFAULT NULL,
+    require_client_classes LONGTEXT,
+    reservation_mode TINYINT(3) NOT NULL DEFAULT '3',
+    shared_network_name VARCHAR(128) DEFAULT NULL,
+    user_context LONGTEXT,
+    valid_lifetime INT(10) DEFAULT NULL,
+    PRIMARY KEY (subnet_id),
+    UNIQUE KEY subnet_prefix_UNIQUE (subnet_prefix),
+    KEY subnet6_subnet_prefix (subnet_prefix),
+    KEY fk_dhcp6_subnet_shared_network (shared_network_name),
+    KEY key_dhcp6_subnet_modification_ts (modification_ts),
+    CONSTRAINT fk_dhcp6_subnet_shared_network FOREIGN KEY (shared_network_name)
+        REFERENCES dhcp6_shared_network (name)
+        ON DELETE SET NULL ON UPDATE NO ACTION
+) ENGINE=InnoDB;
+
+-- -----------------------------------------------------
+-- Table `dhcp6_subnet_server`
+-- M-to-M cross-reference between subnets and servers
+-- -----------------------------------------------------
+CREATE TABLE dhcp6_subnet_server (
+    subnet_id INT(10) UNSIGNED NOT NULL,
+    server_id BIGINT(20) UNSIGNED NOT NULL,
+    modification_ts TIMESTAMP NOT NULL,
+    PRIMARY KEY (subnet_id, server_id),
+    KEY fk_dhcp6_subnet_server_server_id (server_id),
+    KEY key_dhcp6_subnet_server_modification_ts (modification_ts),
+    CONSTRAINT fk_dhcp6_subnet_server_server_id FOREIGN KEY (server_id)
+        REFERENCES dhcp6_server (id)
+        ON DELETE NO ACTION ON UPDATE NO ACTION,
+    CONSTRAINT fk_dhcp6_subnet_server_subnet_id FOREIGN KEY (subnet_id)
+        REFERENCES dhcp6_subnet (subnet_id)
+        ON DELETE CASCADE ON UPDATE NO ACTION
+) ENGINE=InnoDB;
+
+-- -----------------------------------------------------
+-- Table `dhcp6_pd_pool`
+-- -----------------------------------------------------
+CREATE TABLE IF NOT EXISTS dhcp6_pd_pool (
+    id BIGINT(20) UNSIGNED NOT NULL AUTO_INCREMENT,
+    prefix VARCHAR(45) NOT NULL,
+    prefix_length TINYINT(3) NOT NULL,
+    delegated_prefix_length TINYINT(3) NOT NULL,
+    dhcp6_subnet_id INT(10) UNSIGNED NOT NULL,
+    modification_ts TIMESTAMP NOT NULL,
+    PRIMARY KEY (id),
+    KEY fk_dhcp6_pd_pool_subnet_id (dhcp6_subnet_id),
+    KEY key_dhcp6_pd_pool_modification_ts (modification_ts),
+    CONSTRAINT fk_dhcp6_pd_pool_subnet_id FOREIGN KEY (dhcp6_subnet_id)
+        REFERENCES dhcp6_subnet (subnet_id) ON DELETE CASCADE ON UPDATE CASCADE
+) ENGINE=InnoDB;
+
+-- -----------------------------------------------------
+-- Table `dhcp6_pool`
+-- -----------------------------------------------------
+CREATE TABLE IF NOT EXISTS dhcp6_pool (
+    id BIGINT(20) UNSIGNED NOT NULL AUTO_INCREMENT,
+    start_address VARCHAR(45) NOT NULL,
+    end_address VARCHAR(45) NOT NULL,
+    dhcp6_subnet_id INT(10) UNSIGNED NOT NULL,
+    modification_ts TIMESTAMP NOT NULL,
+    PRIMARY KEY (id),
+    KEY fk_dhcp6_pool_subnet_id (dhcp6_subnet_id),
+    KEY key_dhcp6_pool_modification_ts (modification_ts),
+    CONSTRAINT fk_dhcp6_pool_subnet_id FOREIGN KEY (dhcp6_subnet_id)
+        REFERENCES dhcp6_subnet (subnet_id) ON DELETE CASCADE ON UPDATE CASCADE
+) ENGINE=InnoDB;
+
+# Modify the primary key to BINGINT as other tables have.
+ALTER TABLE dhcp6_options MODIFY option_id BIGINT(20) UNSIGNED NOT NULL AUTO_INCREMENT;
+
+# Add configuration backend specific columns.
+ALTER TABLE dhcp6_options
+    ADD COLUMN shared_network_name VARCHAR(128) DEFAULT NULL,
+    ADD COLUMN pool_id BIGINT(20) UNSIGNED DEFAULT NULL,
+    ADD COLUMN pd_pool_id BIGINT(20) UNSIGNED DEFAULT NULL,
+    ADD COLUMN modification_ts TIMESTAMP NOT NULL;
+
+-- -----------------------------------------------------
+-- Table `dhcp6_options_server`
+-- M-to-M cross-reference between options and servers
+-- -----------------------------------------------------
+CREATE TABLE IF NOT EXISTS dhcp6_options_server (
+    option_id BIGINT(20) UNSIGNED NOT NULL,
+    server_id BIGINT(20) UNSIGNED NOT NULL,
+    modification_ts TIMESTAMP NOT NULL,
+    PRIMARY KEY (option_id, server_id),
+    KEY fk_dhcp6_options_server_server_id_idx (server_id),
+    KEY key_dhcp6_options_server_modification_ts (modification_ts),
+    CONSTRAINT fk_dhcp6_options_server_option_id FOREIGN KEY (option_id)
+        REFERENCES dhcp6_options (option_id)
+        ON DELETE NO ACTION ON UPDATE NO ACTION,
+    CONSTRAINT fk_dhcp6_options_server_server_id FOREIGN KEY (server_id)
+        REFERENCES dhcp6_server (id)
+        ON DELETE CASCADE ON UPDATE NO ACTION
+) ENGINE=InnoDB;
+
+# Create trigger which removes pool specific options upon removal of
+# the pool.
+DELIMITER $$
+CREATE TRIGGER dhcp6_pool_BDEL BEFORE DELETE ON dhcp6_pool FOR EACH ROW
+-- Edit trigger body code below this line. Do not edit lines above this one
+BEGIN
+DELETE FROM dhcp6_options WHERE scope_id = 5 AND pool_id = OLD.id;
+END
+$$
+DELIMITER ;
+
+# Update the schema version number.
+UPDATE schema_version
+    SET version = '7', minor = '0';
+
+# This line concludes the schema upgrade to version 7.0.
+
+# This line starts the schema upgrade to version 8.0.
+
+ALTER TABLE dhcp4_options
+    MODIFY COLUMN modification_ts TIMESTAMP NOT NULL
+    DEFAULT CURRENT_TIMESTAMP;
+
+ALTER TABLE dhcp6_options
+    MODIFY COLUMN modification_ts TIMESTAMP NOT NULL
+    DEFAULT CURRENT_TIMESTAMP;
+
+ALTER TABLE dhcp4_subnet
+    ADD COLUMN authoritative TINYINT(1) DEFAULT NULL,
+    ADD COLUMN calculate_tee_times TINYINT(1) DEFAULT NULL,
+    ADD COLUMN t1_percent FLOAT DEFAULT NULL,
+    ADD COLUMN t2_percent FLOAT DEFAULT NULL;
+
+ALTER TABLE dhcp4_subnet
+    MODIFY COLUMN reservation_mode TINYINT(3) DEFAULT NULL;
+
+ALTER TABLE dhcp4_subnet
+    MODIFY COLUMN match_client_id TINYINT(1) DEFAULT NULL;
+
+ALTER TABLE dhcp4_shared_network
+    ADD COLUMN authoritative TINYINT(1) DEFAULT NULL,
+    ADD COLUMN calculate_tee_times TINYINT(1) DEFAULT NULL,
+    ADD COLUMN t1_percent FLOAT DEFAULT NULL,
+    ADD COLUMN t2_percent FLOAT DEFAULT NULL,
+    ADD COLUMN boot_file_name VARCHAR(512) DEFAULT NULL,
+    ADD COLUMN next_server INT(10) UNSIGNED DEFAULT NULL,
+    ADD COLUMN server_hostname VARCHAR(512) DEFAULT NULL;
+
+ALTER TABLE dhcp4_shared_network
+    MODIFY COLUMN reservation_mode TINYINT(3) DEFAULT NULL;
+
+ALTER TABLE dhcp4_shared_network
+    MODIFY COLUMN match_client_id TINYINT(1) DEFAULT NULL;
+
+ALTER TABLE dhcp6_subnet
+    ADD COLUMN calculate_tee_times TINYINT(1) DEFAULT NULL,
+    ADD COLUMN t1_percent FLOAT DEFAULT NULL,
+    ADD COLUMN t2_percent FLOAT DEFAULT NULL,
+    ADD COLUMN interface_id VARBINARY(128) DEFAULT NULL;
+
+ALTER TABLE dhcp6_subnet
+    MODIFY COLUMN reservation_mode TINYINT(3) DEFAULT NULL;
+
+ALTER TABLE dhcp6_subnet
+    MODIFY COLUMN rapid_commit TINYINT(1) DEFAULT NULL;
+
+ALTER TABLE dhcp6_shared_network
+    ADD COLUMN calculate_tee_times TINYINT(1) DEFAULT NULL,
+    ADD COLUMN t1_percent FLOAT DEFAULT NULL,
+    ADD COLUMN t2_percent FLOAT DEFAULT NULL,
+    ADD COLUMN interface_id VARBINARY(128) DEFAULT NULL;
+
+ALTER TABLE dhcp6_shared_network
+    MODIFY COLUMN reservation_mode TINYINT(3) DEFAULT NULL;
+
+ALTER TABLE dhcp6_shared_network
+    MODIFY COLUMN rapid_commit TINYINT(1) DEFAULT NULL;
+
+-- -----------------------------------------------------
+-- Make sure that constraints on the 7.0 schema tables
+-- have appropriate referential actions. All tables
+-- which join the configuration elements with the
+-- servers should perform cascade deletion.
+-- -----------------------------------------------------
+
+ALTER TABLE dhcp4_global_parameter_server
+    DROP FOREIGN KEY fk_dhcp4_global_parameter_server_server_id;
+
+ALTER TABLE dhcp4_global_parameter_server
+    ADD CONSTRAINT fk_dhcp4_global_parameter_server_server_id
+        FOREIGN KEY (server_id)
+    REFERENCES dhcp4_server (id)
+    ON DELETE CASCADE ON UPDATE NO ACTION;
+
+ALTER TABLE dhcp4_option_def_server
+    DROP FOREIGN KEY fk_dhcp4_option_def_server_server_id;
+
+ALTER TABLE dhcp4_option_def_server
+    ADD CONSTRAINT fk_dhcp4_option_def_server_server_id
+        FOREIGN KEY (server_id)
+    REFERENCES dhcp4_server (id)
+    ON DELETE CASCADE ON UPDATE NO ACTION;
+
+ALTER TABLE dhcp4_shared_network_server
+    DROP FOREIGN KEY fk_dhcp4_shared_network_server_server_id;
+
+ALTER TABLE dhcp4_shared_network_server
+    ADD CONSTRAINT fk_dhcp4_shared_network_server_server_id
+        FOREIGN KEY (server_id)
+    REFERENCES dhcp4_server (id)
+    ON DELETE CASCADE ON UPDATE NO ACTION;
+
+ALTER TABLE dhcp4_subnet_server
+    DROP FOREIGN KEY fk_dhcp4_subnet_server_server_id;
+
+ALTER TABLE dhcp4_subnet_server
+    ADD CONSTRAINT fk_dhcp4_subnet_server_server_id
+        FOREIGN KEY (server_id)
+    REFERENCES dhcp4_server (id)
+    ON DELETE CASCADE ON UPDATE NO ACTION;
+
+ALTER TABLE dhcp4_options_server
+    DROP FOREIGN KEY fk_dhcp4_options_server_server_id;
+
+ALTER TABLE dhcp4_options_server
+    ADD CONSTRAINT fk_dhcp4_options_server_server_id
+        FOREIGN KEY (server_id)
+    REFERENCES dhcp4_server (id)
+    ON DELETE CASCADE ON UPDATE NO ACTION;
+
+ALTER TABLE dhcp6_global_parameter_server
+    DROP FOREIGN KEY fk_dhcp6_global_parameter_server_server_id;
+
+ALTER TABLE dhcp6_global_parameter_server
+    ADD CONSTRAINT fk_dhcp6_global_parameter_server_server_id
+        FOREIGN KEY (server_id)
+    REFERENCES dhcp6_server (id)
+    ON DELETE CASCADE ON UPDATE NO ACTION;
+
+ALTER TABLE dhcp6_option_def_server
+    DROP FOREIGN KEY fk_dhcp6_option_def_server_server_id;
+
+ALTER TABLE dhcp6_option_def_server
+    ADD CONSTRAINT fk_dhcp6_option_def_server_server_id
+        FOREIGN KEY (server_id)
+    REFERENCES dhcp6_server (id)
+    ON DELETE CASCADE ON UPDATE NO ACTION;
+
+ALTER TABLE dhcp6_shared_network_server
+    DROP FOREIGN KEY fk_dhcp6_shared_network_server_server_id;
+
+ALTER TABLE dhcp6_shared_network_server
+    ADD CONSTRAINT fk_dhcp6_shared_network_server_server_id
+        FOREIGN KEY (server_id)
+    REFERENCES dhcp6_server (id)
+    ON DELETE CASCADE ON UPDATE NO ACTION;
+
+ALTER TABLE dhcp6_subnet_server
+    DROP FOREIGN KEY fk_dhcp6_subnet_server_server_id;
+
+ALTER TABLE dhcp6_subnet_server
+    ADD CONSTRAINT fk_dhcp6_subnet_server_server_id
+        FOREIGN KEY (server_id)
+    REFERENCES dhcp6_server (id)
+    ON DELETE CASCADE ON UPDATE NO ACTION;
+
+ALTER TABLE dhcp6_options_server
+    DROP FOREIGN KEY fk_dhcp6_options_server_option_id;
+
+ALTER TABLE dhcp6_options_server
+    ADD CONSTRAINT fk_dhcp6_options_server_option_id
+        FOREIGN KEY (option_id)
+    REFERENCES dhcp6_options (option_id)
+    ON DELETE CASCADE ON UPDATE NO ACTION;
+
+-- -----------------------------------------------------
+-- Table `dhcp4_audit_revision`
+-- -----------------------------------------------------
+CREATE TABLE IF NOT EXISTS dhcp4_audit_revision (
+    id BIGINT(20) UNSIGNED NOT NULL AUTO_INCREMENT,
+    modification_ts TIMESTAMP NOT NULL,
+    log_message TEXT,
+    server_id BIGINT(10) UNSIGNED,
+    PRIMARY KEY (id),
+    KEY key_dhcp4_audit_revision_by_modification_ts (modification_ts)
+) ENGINE=InnoDB;
+
+-- -----------------------------------------------------
+-- Drop columns from the dhcp4_audit table which now
+-- belong to the dhcp4_audit_revision.
+-- -----------------------------------------------------
+ALTER TABLE dhcp4_audit
+    DROP COLUMN modification_ts,
+    DROP COLUMN log_message;
+
+-- -----------------------------------------------------
+-- Add column revision_id and the foreign key with a
+-- reference to the dhcp4_audit_revision table.
+-- -----------------------------------------------------
+ALTER TABLE dhcp4_audit
+    ADD COLUMN revision_id BIGINT(20) UNSIGNED NOT NULL;
+
+ALTER TABLE dhcp4_audit
+    ADD CONSTRAINT fk_dhcp4_audit_revision FOREIGN KEY (revision_id)
+        REFERENCES dhcp4_audit_revision (id)
+        ON DELETE NO ACTION ON UPDATE CASCADE;
+
+-- -----------------------------------------------------
+-- Stored procedure which creates a new entry in the
+-- dhcp4_audit_revision table and sets appropriate session
+-- variables to be used while creating the audit entries
+-- by triggers. This procedure should be called at the
+-- beginning of a transaction which modifies configuration
+-- data in the database, e.g. when new subnet is added.
+--
+-- Parameters:
+-- - audit_ts timestamp to be associated with the audit
+--   revision.
+-- - server_tag is used to retrieve the server_id which
+--   associates the changes applied with the particular
+--   server or all servers.
+-- - audit_log_message is a log message associates with
+--   the audit revision.
+-- - cascade_transaction is assigned to a session
+--   variable which is used in some triggers to determine
+--   if the audit entry should be created for them or
+--   not. Specifically, this is used when DHCP options
+--   are inserted, updated or deleted. If such modification
+--   is a part of the larger change (e.g. change in the
+--   subnet the options belong to) the dedicated audit
+--   entry for options must not be created. On the other
+--   hand, if the global option is being added, the
+--   audit entry for the option must be created because
+--   it is the sole object modified in that case.
+--   Session variable disable_audit is used to disable
+--   the procedure when wiping the database during
+--   unit tests.  This avoids issues with revision_id
+--   being null.
+-- -----------------------------------------------------
+DROP PROCEDURE IF EXISTS createAuditRevisionDHCP4;
+DELIMITER $$
+CREATE PROCEDURE createAuditRevisionDHCP4(IN audit_ts TIMESTAMP,
+                                          IN server_tag VARCHAR(256),
+                                          IN audit_log_message TEXT,
+                                          IN cascade_transaction TINYINT(1))
+BEGIN
+    DECLARE srv_id BIGINT(20);
+    IF @disable_audit IS NULL OR @disable_audit = 0 THEN
+        SELECT id INTO srv_id FROM dhcp4_server WHERE tag = server_tag;
+        INSERT INTO dhcp4_audit_revision (modification_ts, server_id, log_message)
+            VALUES (audit_ts, srv_id, audit_log_message);
+        SET @audit_revision_id = LAST_INSERT_ID();
+        SET @cascade_transaction = cascade_transaction;
+    END IF;
+END $$
+DELIMITER ;
+
+-- -----------------------------------------------------
+-- Stored procedure which creates a new entry in the
+-- dhcp4_audit table. It should be called from the
+-- triggers of the tables where the config modifications
+-- are applied. The @audit_revision_id variable contains
+-- the revision id to be placed in the audit entries.
+--
+-- The following parameters are passed to this procedure:
+-- - object_type_val: name of the table to be associated
+--   with the applied changes.
+-- - object_id_val: identifier of the modified object in
+--   that table.
+-- - modification_type_val: string value indicating the
+--   type of the change, i.e. "create", "update" or
+--   "delete".
+--   Session variable disable_audit is used to disable
+--   the procedure when wiping the database during
+--   unit tests.  This avoids issues with revision_id
+--   being null.
+-- ----------------------------------------------------
+DROP PROCEDURE IF EXISTS createAuditEntryDHCP4;
+DELIMITER $$
+CREATE PROCEDURE createAuditEntryDHCP4(IN object_type_val VARCHAR(256),
+                                       IN object_id_val BIGINT(20) UNSIGNED,
+                                       IN modification_type_val VARCHAR(32))
+BEGIN
+    IF @disable_audit IS NULL OR @disable_audit = 0 THEN
+        INSERT INTO dhcp4_audit (object_type, object_id, modification_type, revision_id)
+            VALUES (object_type_val, object_id_val, \
+               (SELECT id FROM modification WHERE modification_type = modification_type_val), \
+                @audit_revision_id);
+    END IF;
+END $$
+DELIMITER ;
+
+-- -----------------------------------------------------
+-- Triggers used to create entries in the audit
+-- tables upon insertion, update or deletion of the
+-- configuration entries.
+-- -----------------------------------------------------
+
+# Create dhcp4_global_parameter insert trigger
+DELIMITER $$
+CREATE TRIGGER dhcp4_global_parameter_AINS AFTER INSERT ON dhcp4_global_parameter
+    FOR EACH ROW
+    BEGIN
+        CALL createAuditEntryDHCP4('dhcp4_global_parameter', NEW.id, "create");
+    END $$
+DELIMITER ;
+
+# Create dhcp4_global_parameter update trigger
+DELIMITER $$
+CREATE TRIGGER dhcp4_global_parameter_AUPD AFTER UPDATE ON dhcp4_global_parameter
+    FOR EACH ROW
+    BEGIN
+        CALL createAuditEntryDHCP4('dhcp4_global_parameter', NEW.id, "update");
+    END $$
+DELIMITER ;
+
+# Create dhcp4_global_parameter delete trigger
+DELIMITER $$
+CREATE TRIGGER dhcp4_global_parameter_ADEL AFTER DELETE ON dhcp4_global_parameter
+    FOR EACH ROW
+    BEGIN
+        CALL createAuditEntryDHCP4('dhcp4_global_parameter', OLD.id, "delete");
+    END $$
+DELIMITER ;
+
+# Create dhcp4_subnet insert trigger
+DELIMITER $$
+CREATE TRIGGER dhcp4_subnet_AINS AFTER INSERT ON dhcp4_subnet
+    FOR EACH ROW
+    BEGIN
+        CALL createAuditEntryDHCP4('dhcp4_subnet', NEW.subnet_id, "create");
+    END $$
+DELIMITER ;
+
+# Create dhcp4_subnet update trigger
+DELIMITER $$
+CREATE TRIGGER dhcp4_subnet_AUPD AFTER UPDATE ON dhcp4_subnet
+    FOR EACH ROW
+    BEGIN
+        CALL createAuditEntryDHCP4('dhcp4_subnet', NEW.subnet_id, "update");
+    END $$
+DELIMITER ;
+
+# Create dhcp4_subnet delete trigger
+DELIMITER $$
+CREATE TRIGGER dhcp4_subnet_ADEL AFTER DELETE ON dhcp4_subnet
+    FOR EACH ROW
+    BEGIN
+        CALL createAuditEntryDHCP4('dhcp4_subnet', OLD.subnet_id, "delete");
+    END $$
+DELIMITER ;
+
+# Create dhcp4_shared_network insert trigger
+DELIMITER $$
+CREATE TRIGGER dhcp4_shared_network_AINS AFTER INSERT ON dhcp4_shared_network
+    FOR EACH ROW
+    BEGIN
+        CALL createAuditEntryDHCP4('dhcp4_shared_network', NEW.id, "create");
+    END $$
+DELIMITER ;
+
+# Create dhcp4_shared_network update trigger
+DELIMITER $$
+CREATE TRIGGER dhcp4_shared_network_AUPD AFTER UPDATE ON dhcp4_shared_network
+    FOR EACH ROW
+    BEGIN
+        CALL createAuditEntryDHCP4('dhcp4_shared_network', NEW.id, "update");
+    END $$
+DELIMITER ;
+
+# Create dhcp4_shared_network delete trigger
+DELIMITER $$
+CREATE TRIGGER dhcp4_shared_network_ADEL AFTER DELETE ON dhcp4_shared_network
+    FOR EACH ROW
+    BEGIN
+        CALL createAuditEntryDHCP4('dhcp4_shared_network', OLD.id, "delete");
+    END $$
+DELIMITER ;
+
+# Create dhcp4_option_def insert trigger
+DELIMITER $$
+CREATE TRIGGER dhcp4_option_def_AINS AFTER INSERT ON dhcp4_option_def
+    FOR EACH ROW
+    BEGIN
+        CALL createAuditEntryDHCP4('dhcp4_option_def', NEW.id, "create");
+    END $$
+DELIMITER ;
+
+# Create dhcp4_option_def update trigger
+DELIMITER $$
+CREATE TRIGGER dhcp4_option_def_AUPD AFTER UPDATE ON dhcp4_option_def
+    FOR EACH ROW
+    BEGIN
+        CALL createAuditEntryDHCP4('dhcp4_option_def', NEW.id, "update");
+    END $$
+DELIMITER ;
+
+# Create dhcp4_option_def delete trigger
+DELIMITER $$
+CREATE TRIGGER dhcp4_option_def_ADEL AFTER DELETE ON dhcp4_option_def
+    FOR EACH ROW
+    BEGIN
+        CALL createAuditEntryDHCP4('dhcp4_option_def', OLD.id, "delete");
+    END $$
+DELIMITER ;
+
+-- -----------------------------------------------------
+-- Stored procedure which creates an audit entry for a
+-- DHCPv4 option. Depending on the scope of the option
+-- the audit entry can be created for various levels
+-- of configuration hierarchy. If this is a global
+-- option the audit entry is created for this option
+-- for CREATE, UPDATE or DELETE. If the option is being
+-- added for an owning option, e.g. for a subnet, the
+-- audit entry is created as an UPDATE to this object.
+-- From the Kea perspective such option addition will
+-- be seen as a subnet update and the server will fetch
+-- the whole subnet and merge it into its configuration.
+-- The audit entry is not created if it was already
+-- created as part of the current transaction.
+--
+-- The following parameters are passed to the procedure:
+-- - modification_type: "create", "update" or "delete"
+-- - scope_id: identifier of the option scope, e.g.
+--   global, subnet specific etc. See dhcp_option_scope
+--   for specific values.
+-- - option_id: identifier of the option.
+-- - subnet_id: identifier of the subnet if the option
+--   belongs to the subnet.
+-- - host_id: identifier of the host if the option
+-- - belongs to the host.
+-- - network_name: shared network name if the option
+--   belongs to the shared network.
+-- - pool_id: identifier of the pool if the option
+--   belongs to the pool.
+-- -----------------------------------------------------
+DROP PROCEDURE IF EXISTS createOptionAuditDHCP4;
+DELIMITER $$
+CREATE PROCEDURE createOptionAuditDHCP4(IN modification_type VARCHAR(32),
+                                        IN scope_id TINYINT(3) UNSIGNED,
+                                        IN option_id BIGINT(20) UNSIGNED,
+                                        IN subnet_id INT(10) UNSIGNED,
+                                        IN host_id INT(10) UNSIGNED,
+                                        IN network_name VARCHAR(128),
+                                        IN pool_id BIGINT(20))
+BEGIN
+    # These variables will hold shared network id and subnet id that
+    # we will select.
+    DECLARE snid VARCHAR(128);
+    DECLARE sid INT(10) UNSIGNED;
+
+    # Cascade transaction flag is set to 1 to prevent creation of
+    # the audit entries for the options when the options are
+    # created as part of the parent object creation or update.
+    # For example: when the option is added as part of the subnet
+    # addition, the cascade transaction flag is equal to 1. If
+    # the option is added into the existing subnet the cascade
+    # transaction is equal to 0. Note that depending on the option
+    # scope the audit entry will contain the object_type value
+    # of the parent object to cause the server to replace the
+    # entire subnet. The only case when the object_type will be
+    # set to 'dhcp4_options' is when a global option is added.
+    # Global options do not have the owner.
+    IF @cascade_transaction IS NULL OR @cascade_transaction = 0 THEN
+        # todo: host manager hasn't been updated to use audit
+        # mechanisms so ignore host specific options for now.
+        IF scope_id = 0 THEN
+            # If a global option is added or modified, create audit
+            # entry for the 'dhcp4_options' table.
+            CALL createAuditEntryDHCP4('dhcp4_options', option_id, modification_type);
+        ELSEIF scope_id = 1 THEN
+            # If subnet specific option is added or modified, create
+            # audit entry for the entire subnet, which indicates that
+            # it should be treated as the subnet update.
+            CALL createAuditEntryDHCP4('dhcp4_subnet', subnet_id, "update");
+        ELSEIF scope_id = 4 THEN
+            # If shared network specific option is added or modified,
+            # create audit entry for the shared network which
+            # indicates that it should be treated as the shared
+            # network update.
+           SELECT id INTO snid FROM dhcp4_shared_network WHERE name = network_name LIMIT 1;
+           CALL createAuditEntryDHCP4('dhcp4_shared_network', snid, "update");
+        ELSEIF scope_id = 5 THEN
+            # If pool specific option is added or modified, create
+            # audit entry for the subnet which this pool belongs to.
+            SELECT dhcp4_pool.subnet_id INTO sid FROM dhcp4_pool WHERE id = pool_id;
+            CALL createAuditEntryDHCP4('dhcp4_subnet', sid, "update");
+        END IF;
+    END IF;
+END $$
+DELIMITER ;
+
+# Create dhcp4_options insert trigger
+DELIMITER $$
+CREATE TRIGGER dhcp4_options_AINS AFTER INSERT ON dhcp4_options
+    FOR EACH ROW
+    BEGIN
+        CALL createOptionAuditDHCP4("create", NEW.scope_id, NEW.option_id, NEW.dhcp4_subnet_id,
+                                    NEW.host_id, NEW.shared_network_name, NEW.pool_id);
+    END $$
+DELIMITER ;
+
+# Create dhcp4_options update trigger
+DELIMITER $$
+CREATE TRIGGER dhcp4_options_AUPD AFTER UPDATE ON dhcp4_options
+    FOR EACH ROW
+    BEGIN
+        CALL createOptionAuditDHCP4("update", NEW.scope_id, NEW.option_id, NEW.dhcp4_subnet_id,
+                                    NEW.host_id, NEW.shared_network_name, NEW.pool_id);
+    END $$
+DELIMITER ;
+
+# Create dhcp4_options delete trigger
+DELIMITER $$
+CREATE TRIGGER dhcp4_options_ADEL AFTER DELETE ON dhcp4_options
+    FOR EACH ROW
+    BEGIN
+        CALL createOptionAuditDHCP4("delete", OLD.scope_id, OLD.option_id, OLD.dhcp4_subnet_id,
+                                    OLD.host_id, OLD.shared_network_name, OLD.pool_id);
+    END $$
+DELIMITER ;
+
+-- -----------------------------------------------------
+-- Table `parameter_data_type`
+-- Reflects an enum used by Kea to define supported
+-- data types for the simple configuration parameters,
+-- e.g. global parameters used by DHCP servers.
+-- -----------------------------------------------------
+CREATE TABLE IF NOT EXISTS parameter_data_type (
+    id TINYINT UNSIGNED NOT NULL PRIMARY KEY,
+    name VARCHAR(32) NOT NULL
+) ENGINE = InnoDB;
+
+START TRANSACTION;
+INSERT INTO parameter_data_type VALUES (0, 'integer');
+INSERT INTO parameter_data_type VALUES (1, 'real');
+INSERT INTO parameter_data_type VALUES (2, 'boolean');
+INSERT INTO parameter_data_type VALUES (4, 'string');
+COMMIT;
+
+ALTER TABLE dhcp4_global_parameter
+    ADD COLUMN parameter_type TINYINT UNSIGNED NOT NULL;
+
+ALTER TABLE dhcp4_global_parameter
+    ADD CONSTRAINT fk_dhcp4_global_parameter_type FOREIGN KEY (parameter_type)
+        REFERENCES parameter_data_type (id);
+
+ALTER TABLE dhcp6_global_parameter
+    ADD COLUMN parameter_type TINYINT UNSIGNED NOT NULL;
+
+ALTER TABLE dhcp6_global_parameter
+    ADD CONSTRAINT fk_dhcp6_global_parameter_type FOREIGN KEY (parameter_type)
+        REFERENCES parameter_data_type (id);
+
+-- Rename dhcp6_subnet_id column of dhcp6_pool and dhcp6_pd_pool
+
+ALTER TABLE dhcp6_pool
+    DROP FOREIGN KEY fk_dhcp6_pool_subnet_id;
+DROP INDEX fk_dhcp6_pool_subnet_id
+    ON dhcp6_pool;
+
+ALTER TABLE dhcp6_pd_pool
+    DROP FOREIGN KEY fk_dhcp6_pd_pool_subnet_id;
+DROP INDEX fk_dhcp6_pd_pool_subnet_id
+    ON dhcp6_pd_pool;
+
+ALTER TABLE dhcp6_pool
+    CHANGE dhcp6_subnet_id subnet_id INT(10) UNSIGNED NOT NULL;
+
+ALTER TABLE dhcp6_pd_pool
+    CHANGE dhcp6_subnet_id subnet_id INT(10) UNSIGNED NOT NULL;
+
+ALTER TABLE dhcp6_pool
+    ADD CONSTRAINT fk_dhcp6_pool_subnet_id
+    FOREIGN KEY (subnet_id)
+    REFERENCES dhcp6_subnet (subnet_id)
+    ON DELETE CASCADE ON UPDATE CASCADE;
+
+ALTER TABLE dhcp6_pd_pool
+    ADD CONSTRAINT fk_dhcp6_pd_pool_subnet_id
+    FOREIGN KEY (subnet_id)
+    REFERENCES dhcp6_subnet (subnet_id)
+    ON DELETE CASCADE ON UPDATE CASCADE;
+
+-- align dhcp6_shared_network_server indexes on dhcp4_shared_network_server
+
+ALTER TABLE dhcp6_shared_network_server
+    ADD PRIMARY KEY (shared_network_id, server_id);
+
+ALTER TABLE dhcp6_shared_network_server
+    DROP FOREIGN KEY fk_dhcp6_shared_network_server_shared_network_id;
+DROP INDEX fk_dhcp6_shared_network_server_shared_network_id
+    ON dhcp6_shared_network_server;
+ALTER TABLE dhcp6_shared_network_server
+    ADD CONSTRAINT fk_dhcp6_shared_network_server_shared_network_id
+    FOREIGN KEY (shared_network_id)
+    REFERENCES dhcp6_shared_network (id)
+    ON DELETE CASCADE ON UPDATE NO ACTION;
+
+-- Update dhcp4_subnet_server and dhcp6_subnet_server to allow update
+-- on the prefix too by setting the CASCADE action.
+
+ALTER TABLE dhcp4_subnet_server
+    DROP FOREIGN KEY fk_dhcp4_subnet_server_subnet_id;
+ALTER TABLE dhcp4_subnet_server
+    ADD CONSTRAINT fk_dhcp4_subnet_server_subnet_id FOREIGN KEY (subnet_id)
+    REFERENCES dhcp4_subnet (subnet_id)
+    ON DELETE CASCADE ON UPDATE CASCADE;
+
+ALTER TABLE dhcp6_subnet_server
+    DROP FOREIGN KEY fk_dhcp6_subnet_server_subnet_id;
+ALTER TABLE dhcp6_subnet_server
+    ADD CONSTRAINT fk_dhcp6_subnet_server_subnet_id FOREIGN KEY (subnet_id)
+    REFERENCES dhcp6_subnet (subnet_id)
+    ON DELETE CASCADE ON UPDATE CASCADE;
+
+-- -----------------------------------------------------
+-- Table `dhcp6_audit_revision`
+-- -----------------------------------------------------
+CREATE TABLE IF NOT EXISTS dhcp6_audit_revision (
+    id BIGINT(20) UNSIGNED NOT NULL AUTO_INCREMENT,
+    modification_ts TIMESTAMP NOT NULL,
+    log_message TEXT,
+    server_id BIGINT(10) UNSIGNED,
+    PRIMARY KEY (id),
+    KEY key_dhcp6_audit_revision_by_modification_ts (modification_ts)
+) ENGINE=InnoDB;
+
+-- -----------------------------------------------------
+-- Drop columns from the dhcp6_audit table which now
+-- belong to the dhcp6_audit_revision.
+-- -----------------------------------------------------
+ALTER TABLE dhcp6_audit
+    DROP COLUMN modification_ts,
+    DROP COLUMN log_message;
+
+-- -----------------------------------------------------
+-- Add column revision_id and the foreign key with a
+-- reference to the dhcp6_audit_revision table.
+-- -----------------------------------------------------
+ALTER TABLE dhcp6_audit
+    ADD COLUMN revision_id BIGINT(20) UNSIGNED NOT NULL;
+
+ALTER TABLE dhcp6_audit
+    ADD CONSTRAINT fk_dhcp6_audit_revision FOREIGN KEY (revision_id)
+        REFERENCES dhcp6_audit_revision (id)
+        ON DELETE NO ACTION ON UPDATE CASCADE;
+
+-- -----------------------------------------------------
+-- Stored procedure which creates a new entry in the
+-- dhcp6_audit_revision table and sets appropriate session
+-- variables to be used while creating the audit entries
+-- by triggers. This procedure should be called at the
+-- beginning of a transaction which modifies configuration
+-- data in the database, e.g. when new subnet is added.
+--
+-- Parameters:
+-- - audit_ts timestamp to be associated with the audit
+--   revision.
+-- - server_tag is used to retrieve the server_id which
+--   associates the changes applied with the particular
+--   server or all servers.
+-- - audit_log_message is a log message associates with
+--   the audit revision.
+-- - cascade_transaction is assigned to a session
+--   variable which is used in some triggers to determine
+--   if the audit entry should be created for them or
+--   not. Specifically, this is used when DHCP options
+--   are inserted, updated or deleted. If such modification
+--   is a part of the larger change (e.g. change in the
+--   subnet the options belong to) the dedicated audit
+--   entry for options must not be created. On the other
+--   hand, if the global option is being added, the
+--   audit entry for the option must be created because
+--   it is the sole object modified in that case.
+--   Session variable disable_audit is used to disable
+--   the procedure when wiping the database during
+--   unit tests.  This avoids issues with revision_id
+--   being null.
+-- -----------------------------------------------------
+DROP PROCEDURE IF EXISTS createAuditRevisionDHCP6;
+DELIMITER $$
+CREATE PROCEDURE createAuditRevisionDHCP6(IN audit_ts TIMESTAMP,
+                                          IN server_tag VARCHAR(256),
+                                          IN audit_log_message TEXT,
+                                          IN cascade_transaction TINYINT(1))
+BEGIN
+    DECLARE srv_id BIGINT(20);
+    IF @disable_audit IS NULL OR @disable_audit = 0 THEN
+        SELECT id INTO srv_id FROM dhcp6_server WHERE tag = server_tag;
+        INSERT INTO dhcp6_audit_revision (modification_ts, server_id, log_message)
+            VALUES (audit_ts, srv_id, audit_log_message);
+        SET @audit_revision_id = LAST_INSERT_ID();
+        SET @cascade_transaction = cascade_transaction;
+    END IF;
+END $$
+DELIMITER ;
+
+-- -----------------------------------------------------
+-- Stored procedure which creates a new entry in the
+-- dhcp6_audit table. It should be called from the
+-- triggers of the tables where the config modifications
+-- are applied. The @audit_revision_id variable contains
+-- the revision id to be placed in the audit entries.
+--
+-- The following parameters are passed to this procedure:
+-- - object_type_val: name of the table to be associated
+--   with the applied changes.
+-- - object_id_val: identifier of the modified object in
+--   that table.
+-- - modification_type_val: string value indicating the
+--   type of the change, i.e. "create", "update" or
+--   "delete".
+--   Session variable disable_audit is used to disable
+--   the procedure when wiping the database during
+--   unit tests.  This avoids issues with revision_id
+--   being null.
+-- ----------------------------------------------------
+DROP PROCEDURE IF EXISTS createAuditEntryDHCP6;
+DELIMITER $$
+CREATE PROCEDURE createAuditEntryDHCP6(IN object_type_val VARCHAR(256),
+                                       IN object_id_val BIGINT(20) UNSIGNED,
+                                       IN modification_type_val VARCHAR(32))
+BEGIN
+    IF @disable_audit IS NULL OR @disable_audit = 0 THEN
+        INSERT INTO dhcp6_audit (object_type, object_id, modification_type, revision_id)
+            VALUES (object_type_val, object_id_val, \
+               (SELECT id FROM modification WHERE modification_type = modification_type_val), \
+                @audit_revision_id);
+    END IF;
+END $$
+DELIMITER ;
+
+-- -----------------------------------------------------
+-- Triggers used to create entries in the audit
+-- tables upon insertion, update or deletion of the
+-- configuration entries.
+-- -----------------------------------------------------
+
+# Create dhcp6_global_parameter insert trigger
+DELIMITER $$
+CREATE TRIGGER dhcp6_global_parameter_AINS AFTER INSERT ON dhcp6_global_parameter
+    FOR EACH ROW
+    BEGIN
+        CALL createAuditEntryDHCP6('dhcp6_global_parameter', NEW.id, "create");
+    END $$
+DELIMITER ;
+
+# Create dhcp6_global_parameter update trigger
+DELIMITER $$
+CREATE TRIGGER dhcp6_global_parameter_AUPD AFTER UPDATE ON dhcp6_global_parameter
+    FOR EACH ROW
+    BEGIN
+        CALL createAuditEntryDHCP6('dhcp6_global_parameter', NEW.id, "update");
+    END $$
+DELIMITER ;
+
+# Create dhcp6_global_parameter delete trigger
+DELIMITER $$
+CREATE TRIGGER dhcp6_global_parameter_ADEL AFTER DELETE ON dhcp6_global_parameter
+    FOR EACH ROW
+    BEGIN
+        CALL createAuditEntryDHCP6('dhcp6_global_parameter', OLD.id, "delete");
+    END $$
+DELIMITER ;
+
+# Create dhcp6_subnet insert trigger
+DELIMITER $$
+CREATE TRIGGER dhcp6_subnet_AINS AFTER INSERT ON dhcp6_subnet
+    FOR EACH ROW
+    BEGIN
+        CALL createAuditEntryDHCP6('dhcp6_subnet', NEW.subnet_id, "create");
+    END $$
+DELIMITER ;
+
+# Create dhcp6_subnet update trigger
+DELIMITER $$
+CREATE TRIGGER dhcp6_subnet_AUPD AFTER UPDATE ON dhcp6_subnet
+    FOR EACH ROW
+    BEGIN
+        CALL createAuditEntryDHCP6('dhcp6_subnet', NEW.subnet_id, "update");
+    END $$
+DELIMITER ;
+
+# Create dhcp6_subnet delete trigger
+DELIMITER $$
+CREATE TRIGGER dhcp6_subnet_ADEL AFTER DELETE ON dhcp6_subnet
+    FOR EACH ROW
+    BEGIN
+        CALL createAuditEntryDHCP6('dhcp6_subnet', OLD.subnet_id, "delete");
+    END $$
+DELIMITER ;
+
+# Create dhcp6_shared_network insert trigger
+DELIMITER $$
+CREATE TRIGGER dhcp6_shared_network_AINS AFTER INSERT ON dhcp6_shared_network
+    FOR EACH ROW
+    BEGIN
+        CALL createAuditEntryDHCP6('dhcp6_shared_network', NEW.id, "create");
+    END $$
+DELIMITER ;
+
+# Create dhcp6_shared_network update trigger
+DELIMITER $$
+CREATE TRIGGER dhcp6_shared_network_AUPD AFTER UPDATE ON dhcp6_shared_network
+    FOR EACH ROW
+    BEGIN
+        CALL createAuditEntryDHCP6('dhcp6_shared_network', NEW.id, "update");
+    END $$
+DELIMITER ;
+
+# Create dhcp6_shared_network delete trigger
+DELIMITER $$
+CREATE TRIGGER dhcp6_shared_network_ADEL AFTER DELETE ON dhcp6_shared_network
+    FOR EACH ROW
+    BEGIN
+        CALL createAuditEntryDHCP6('dhcp6_shared_network', OLD.id, "delete");
+    END $$
+DELIMITER ;
+
+# Create dhcp6_option_def insert trigger
+DELIMITER $$
+CREATE TRIGGER dhcp6_option_def_AINS AFTER INSERT ON dhcp6_option_def
+    FOR EACH ROW
+    BEGIN
+        CALL createAuditEntryDHCP6('dhcp6_option_def', NEW.id, "create");
+    END $$
+DELIMITER ;
+
+# Create dhcp6_option_def update trigger
+DELIMITER $$
+CREATE TRIGGER dhcp6_option_def_AUPD AFTER UPDATE ON dhcp6_option_def
+    FOR EACH ROW
+    BEGIN
+        CALL createAuditEntryDHCP6('dhcp6_option_def', NEW.id, "update");
+    END $$
+DELIMITER ;
+
+# Create dhcp6_option_def delete trigger
+DELIMITER $$
+CREATE TRIGGER dhcp6_option_def_ADEL AFTER DELETE ON dhcp6_option_def
+    FOR EACH ROW
+    BEGIN
+        CALL createAuditEntryDHCP6('dhcp6_option_def', OLD.id, "delete");
+    END $$
+DELIMITER ;
+
+-- -----------------------------------------------------
+-- Stored procedure which creates an audit entry for a
+-- DHCPv6 option. Depending on the scope of the option
+-- the audit entry can be created for various levels
+-- of configuration hierarchy. If this is a global
+-- option the audit entry is created for this option
+-- for CREATE, UPDATE or DELETE. If the option is being
+-- added for an owning option, e.g. for a subnet, the
+-- audit entry is created as an UPDATE to this object.
+-- From the Kea perspective such option addition will
+-- be seen as a subnet update and the server will fetch
+-- the whole subnet and merge it into its configuration.
+-- The audit entry is not created if it was already
+-- created as part of the current transaction.
+--
+-- The following parameters are passed to the procedure:
+-- - modification_type: "create", "update" or "delete"
+-- - scope_id: identifier of the option scope, e.g.
+--   global, subnet specific etc.
+-- - option_id: identifier of the option.
+-- - subnet_id: identifier of the subnet if the option
+--   belongs to the subnet.
+-- - host_id: identifier of the host if the option
+-- - belongs to the host.
+-- - network_name: shared network name if the option
+--   belongs to the shared network.
+-- - pool_id: identifier of the pool if the option
+--   belongs to the pool.
+-- - pd_pool_id: identifier of the pool if the option
+--   belongs to the pd pool.
+-- -----------------------------------------------------
+DROP PROCEDURE IF EXISTS createOptionAuditDHCP6;
+DELIMITER $$
+CREATE PROCEDURE createOptionAuditDHCP6(IN modification_type VARCHAR(32),
+                                        IN scope_id TINYINT(3) UNSIGNED,
+                                        IN option_id BIGINT(20) UNSIGNED,
+                                        IN subnet_id INT(10) UNSIGNED,
+                                        IN host_id INT(10) UNSIGNED,
+                                        IN network_name VARCHAR(128),
+                                        IN pool_id BIGINT(20),
+                                        IN pd_pool_id BIGINT(20))
+BEGIN
+    # These variables will hold shared network id and subnet id that
+    # we will select.
+    DECLARE snid VARCHAR(128);
+    DECLARE sid INT(10) UNSIGNED;
+
+    # Cascade transaction flag is set to 1 to prevent creation of
+    # the audit entries for the options when the options are
+    # created as part of the parent object creation or update.
+    # For example: when the option is added as part of the subnet
+    # addition, the cascade transaction flag is equal to 1. If
+    # the option is added into the existing subnet the cascade
+    # transaction is equal to 0. Note that depending on the option
+    # scope the audit entry will contain the object_type value
+    # of the parent object to cause the server to replace the
+    # entire subnet. The only case when the object_type will be
+    # set to 'dhcp6_options' is when a global option is added.
+    # Global options do not have the owner.
+    IF @cascade_transaction IS NULL OR @cascade_transaction = 0 THEN
+        # todo: host manager hasn't been updated to use audit
+        # mechanisms so ignore host specific options for now.
+        IF scope_id = 0 THEN
+            # If a global option is added or modified, create audit
+            # entry for the 'dhcp6_options' table.
+            CALL createAuditEntryDHCP6('dhcp6_options', option_id, modification_type);
+        ELSEIF scope_id = 1 THEN
+            # If subnet specific option is added or modified, create
+            # audit entry for the entire subnet, which indicates that
+            # it should be treated as the subnet update.
+            CALL createAuditEntryDHCP6('dhcp6_subnet', subnet_id, "update");
+        ELSEIF scope_id = 4 THEN
+            # If shared network specific option is added or modified,
+            # create audit entry for the shared network which
+            # indicates that it should be treated as the shared
+            # network update.
+           SELECT id INTO snid FROM dhcp6_shared_network WHERE name = network_name LIMIT 1;
+           CALL createAuditEntryDHCP6('dhcp6_shared_network', snid, "update");
+        ELSEIF scope_id = 5 THEN
+            # If pool specific option is added or modified, create
+            # audit entry for the subnet which this pool belongs to.
+            SELECT dhcp6_pool.subnet_id INTO sid FROM dhcp6_pool WHERE id = pool_id;
+            CALL createAuditEntryDHCP6('dhcp6_subnet', sid, "update");
+        ELSEIF scope_id = 6 THEN
+            # If pd pool specific option is added or modified, create
+            # audit entry for the subnet which this pd pool belongs to.
+            SELECT dhcp6_pd_pool.subnet_id INTO sid FROM dhcp6_pd_pool WHERE id = pd_pool_id;
+            CALL createAuditEntryDHCP6('dhcp6_subnet', sid, "update");
+        END IF;
+    END IF;
+END $$
+DELIMITER ;
+
+# Create dhcp6_options insert trigger
+DELIMITER $$
+CREATE TRIGGER dhcp6_options_AINS AFTER INSERT ON dhcp6_options
+    FOR EACH ROW
+    BEGIN
+        CALL createOptionAuditDHCP6("create", NEW.scope_id, NEW.option_id, NEW.dhcp6_subnet_id,
+                                    NEW.host_id, NEW.shared_network_name, NEW.pool_id, NEW.pd_pool_id);
+    END $$
+DELIMITER ;
+
+# Create dhcp6_options update trigger
+DELIMITER $$
+CREATE TRIGGER dhcp6_options_AUPD AFTER UPDATE ON dhcp6_options
+    FOR EACH ROW
+    BEGIN
+        CALL createOptionAuditDHCP6("update", NEW.scope_id, NEW.option_id, NEW.dhcp6_subnet_id,
+                                    NEW.host_id, NEW.shared_network_name, NEW.pool_id, NEW.pd_pool_id);
+    END $$
+DELIMITER ;
+
+# Create dhcp6_options delete trigger
+DELIMITER $$
+CREATE TRIGGER dhcp6_options_ADEL AFTER DELETE ON dhcp6_options
+    FOR EACH ROW
+    BEGIN
+        CALL createOptionAuditDHCP6("delete", OLD.scope_id, OLD.option_id, OLD.dhcp6_subnet_id,
+                                    OLD.host_id, OLD.shared_network_name, OLD.pool_id, OLD.pd_pool_id);
+    END $$
+DELIMITER ;
+
+# Update the schema version number.
+UPDATE schema_version
+    SET version = '8', minor = '0';
+
+# This line concludes the schema upgrade to version 8.0.
+
+# This line starts the schema upgrade to version 8.1.
+
+# Add lifetime bounds
+ALTER TABLE dhcp4_shared_network
+    ADD COLUMN min_valid_lifetime INT(10) DEFAULT NULL,
+    ADD COLUMN max_valid_lifetime INT(10) DEFAULT NULL;
+
+ALTER TABLE dhcp4_subnet
+    ADD COLUMN min_valid_lifetime INT(10) DEFAULT NULL,
+    ADD COLUMN max_valid_lifetime INT(10) DEFAULT NULL;
+
+ALTER TABLE dhcp6_shared_network
+    ADD COLUMN min_preferred_lifetime INT(10) DEFAULT NULL,
+    ADD COLUMN max_preferred_lifetime INT(10) DEFAULT NULL,
+    ADD COLUMN min_valid_lifetime INT(10) DEFAULT NULL,
+    ADD COLUMN max_valid_lifetime INT(10) DEFAULT NULL;
+
+ALTER TABLE dhcp6_subnet
+    ADD COLUMN min_preferred_lifetime INT(10) DEFAULT NULL,
+    ADD COLUMN max_preferred_lifetime INT(10) DEFAULT NULL,
+    ADD COLUMN min_valid_lifetime INT(10) DEFAULT NULL,
+    ADD COLUMN max_valid_lifetime INT(10) DEFAULT NULL;
+
+# Create dhcp4_server insert trigger
+DELIMITER $$
+CREATE TRIGGER dhcp4_server_AINS AFTER INSERT ON dhcp4_server
+    FOR EACH ROW
+    BEGIN
+        CALL createAuditEntryDHCP4('dhcp4_server', NEW.id, "create");
+    END $$
+DELIMITER ;
+
+# Create dhcp4_server update trigger
+DELIMITER $$
+CREATE TRIGGER dhcp4_server_AUPD AFTER UPDATE ON dhcp4_server
+    FOR EACH ROW
+    BEGIN
+        CALL createAuditEntryDHCP4('dhcp4_server', NEW.id, "update");
+    END $$
+DELIMITER ;
+
+# Create dhcp4_server delete trigger
+DELIMITER $$
+CREATE TRIGGER dhcp4_server_ADEL AFTER DELETE ON dhcp4_server
+    FOR EACH ROW
+    BEGIN
+        CALL createAuditEntryDHCP4('dhcp4_server', OLD.id, "delete");
+    END $$
+DELIMITER ;
+
+# Create dhcp6_server insert trigger
+DELIMITER $$
+CREATE TRIGGER dhcp6_server_AINS AFTER INSERT ON dhcp6_server
+    FOR EACH ROW
+    BEGIN
+        CALL createAuditEntryDHCP6('dhcp6_server', NEW.id, "create");
+    END $$
+DELIMITER ;
+
+# Create dhcp6_server update trigger
+DELIMITER $$
+CREATE TRIGGER dhcp6_server_AUPD AFTER UPDATE ON dhcp6_server
+    FOR EACH ROW
+    BEGIN
+        CALL createAuditEntryDHCP6('dhcp6_server', NEW.id, "update");
+    END $$
+DELIMITER ;
+
+# Create dhcp6_server delete trigger
+DELIMITER $$
+CREATE TRIGGER dhcp6_server_ADEL AFTER DELETE ON dhcp6_server
+    FOR EACH ROW
+    BEGIN
+        CALL createAuditEntryDHCP6('dhcp6_server', OLD.id, "delete");
+    END $$
+DELIMITER ;
+
+# Put the auth key in hexadecimal (double size but far more user friendly).
+ALTER TABLE hosts
+    MODIFY COLUMN auth_key VARCHAR(32) NULL;
+
+# Update the schema version number.
+UPDATE schema_version
+    SET version = '8', minor = '1';
+
+# This line concludes the schema upgrade to version 8.1.
+
+# This line starts the schema upgrade to version 8.2.
+
+# Drop existing trigger on the dhcp4_shared_network table.
+DROP TRIGGER dhcp4_shared_network_ADEL;
+
+# Create new trigger which will delete options associated with the shared
+# network.
+DELIMITER $$
+CREATE TRIGGER dhcp4_shared_network_BDEL BEFORE DELETE ON dhcp4_shared_network
+    FOR EACH ROW
+    BEGIN
+        CALL createAuditEntryDHCP4('dhcp4_shared_network', OLD.id, "delete");
+        DELETE FROM dhcp4_options WHERE shared_network_name = OLD.name;
+    END $$
+DELIMITER ;
+
+# Drop existing trigger on the dhcp4_subnet table.
+DROP TRIGGER dhcp4_subnet_ADEL;
+
+# Create new trigger which will delete pools associated with the subnet and
+# the options associated with the subnet.
+DELIMITER $$
+CREATE TRIGGER dhcp4_subnet_BDEL BEFORE DELETE ON dhcp4_subnet
+    FOR EACH ROW
+    BEGIN
+        CALL createAuditEntryDHCP4('dhcp4_subnet', OLD.subnet_id, "delete");
+        DELETE FROM dhcp4_pool WHERE subnet_id = OLD.subnet_id;
+        DELETE FROM dhcp4_options WHERE dhcp4_subnet_id = OLD.subnet_id;
+    END $$
+DELIMITER ;
+
+# Do not perform cascade deletion of the data in the dhcp4_pool because
+# the cascade deletion does not execute triggers associated with the table.
+# Instead we are going to use triggers on the dhcp4_subnet table.
+ALTER TABLE dhcp4_pool
+    DROP FOREIGN KEY fk_dhcp4_pool_subnet_id;
+
+ALTER TABLE dhcp4_pool
+    ADD CONSTRAINT fk_dhcp4_pool_subnet_id FOREIGN KEY (subnet_id)
+    REFERENCES dhcp4_subnet (subnet_id)
+    ON DELETE NO ACTION ON UPDATE CASCADE;
+
+# Drop existing trigger on the dhcp6_shared_network table.
+DROP TRIGGER dhcp6_shared_network_ADEL;
+
+# Create new trigger which will delete options associated with the shared
+# network.
+DELIMITER $$
+CREATE TRIGGER dhcp6_shared_network_BDEL BEFORE DELETE ON dhcp6_shared_network
+    FOR EACH ROW
+    BEGIN
+        CALL createAuditEntryDHCP6('dhcp6_shared_network', OLD.id, "delete");
+        DELETE FROM dhcp6_options WHERE shared_network_name = OLD.name;
+    END $$
+DELIMITER ;
+
+# Drop existing trigger on the dhcp6_subnet table.
+DROP TRIGGER dhcp6_subnet_ADEL;
+
+# Create new trigger which will delete pools associated with the subnet and
+# the options associated with the subnet.
+DELIMITER $$
+CREATE TRIGGER dhcp6_subnet_BDEL BEFORE DELETE ON dhcp6_subnet
+    FOR EACH ROW
+    BEGIN
+        CALL createAuditEntryDHCP6('dhcp6_subnet', OLD.subnet_id, "delete");
+        DELETE FROM dhcp6_pool WHERE subnet_id = OLD.subnet_id;
+        DELETE FROM dhcp6_pd_pool WHERE subnet_id = OLD.subnet_id;
+        DELETE FROM dhcp6_options WHERE dhcp6_subnet_id = OLD.subnet_id;
+    END $$
+DELIMITER ;
+
+# Do not perform cascade deletion of the data in the dhcp6_pool and dhcp6_pd_pool
+# because the cascaded deletion does not execute triggers associated with the table.
+# Instead we are going to use triggers on the dhcp6_subnet table.
+ALTER TABLE dhcp6_pool
+    DROP FOREIGN KEY fk_dhcp6_pool_subnet_id;
+
+ALTER TABLE dhcp6_pd_pool
+    DROP FOREIGN KEY fk_dhcp6_pd_pool_subnet_id;
+
+ALTER TABLE dhcp6_pool
+    ADD CONSTRAINT fk_dhcp6_pool_subnet_id FOREIGN KEY (subnet_id)
+    REFERENCES dhcp6_subnet (subnet_id)
+    ON DELETE NO ACTION ON UPDATE CASCADE;
+
+ALTER TABLE dhcp6_pd_pool
+    ADD CONSTRAINT fk_dhcp6_pd_pool_subnet_id FOREIGN KEY (subnet_id)
+    REFERENCES dhcp6_subnet (subnet_id)
+    ON DELETE NO ACTION ON UPDATE CASCADE;
+
+# Create trigger which removes pool specific options upon removal of
+# the pool.
+DELIMITER $$
+CREATE TRIGGER dhcp6_pd_pool_BDEL BEFORE DELETE ON dhcp6_pd_pool FOR EACH ROW
+BEGIN
+DELETE FROM dhcp6_options WHERE scope_id = 6 AND pd_pool_id = OLD.id;
+END
+$$
+DELIMITER ;
+
+# Add missing columns in pools.
+ALTER TABLE dhcp4_pool
+    ADD COLUMN client_class VARCHAR(128) DEFAULT NULL,
+    ADD COLUMN require_client_classes LONGTEXT,
+    ADD COLUMN user_context LONGTEXT;
+
+ALTER TABLE dhcp6_pd_pool
+    ADD COLUMN excluded_prefix VARCHAR(45) DEFAULT NULL,
+    ADD COLUMN excluded_prefix_length TINYINT(3) NOT NULL,
+    ADD COLUMN client_class VARCHAR(128) DEFAULT NULL,
+    ADD COLUMN require_client_classes LONGTEXT,
+    ADD COLUMN user_context LONGTEXT;
+
+ALTER TABLE dhcp6_pool
+    ADD COLUMN client_class VARCHAR(128) DEFAULT NULL,
+    ADD COLUMN require_client_classes LONGTEXT,
+    ADD COLUMN user_context LONGTEXT;
+
+-- -----------------------------------------------------
+--
+-- New version of the createOptionAuditDHCP4 stored
+-- procedure which updates modification timestamp of
+-- a parent object when an option is modified.
+--
+-- The following parameters are passed to the procedure:
+-- - modification_type: "create", "update" or "delete"
+-- - scope_id: identifier of the option scope, e.g.
+--   global, subnet specific etc.
+-- - option_id: identifier of the option.
+-- - subnet_id: identifier of the subnet if the option
+--   belongs to the subnet.
+-- - host_id: identifier of the host if the option
+-- - belongs to the host.
+-- - network_name: shared network name if the option
+--   belongs to the shared network.
+-- - pool_id: identifier of the pool if the option
+--   belongs to the pool.
+-- - modification_ts: modification timestamp of the
+--   option.
+-- -----------------------------------------------------
+DROP PROCEDURE IF EXISTS createOptionAuditDHCP4;
+DELIMITER $$
+CREATE PROCEDURE createOptionAuditDHCP4(IN modification_type VARCHAR(32),
+                                        IN scope_id TINYINT(3) UNSIGNED,
+                                        IN option_id BIGINT(20) UNSIGNED,
+                                        IN subnet_id INT(10) UNSIGNED,
+                                        IN host_id INT(10) UNSIGNED,
+                                        IN network_name VARCHAR(128),
+                                        IN pool_id BIGINT(20),
+                                        IN modification_ts TIMESTAMP)
+BEGIN
+    # These variables will hold shared network id and subnet id that
+    # we will select.
+    DECLARE snid VARCHAR(128);
+    DECLARE sid INT(10) UNSIGNED;
+
+    # Cascade transaction flag is set to 1 to prevent creation of
+    # the audit entries for the options when the options are
+    # created as part of the parent object creation or update.
+    # For example: when the option is added as part of the subnet
+    # addition, the cascade transaction flag is equal to 1. If
+    # the option is added into the existing subnet the cascade
+    # transaction is equal to 0. Note that depending on the option
+    # scope the audit entry will contain the object_type value
+    # of the parent object to cause the server to replace the
+    # entire subnet. The only case when the object_type will be
+    # set to 'dhcp4_options' is when a global option is added.
+    # Global options do not have the owner.
+    IF @cascade_transaction IS NULL OR @cascade_transaction = 0 THEN
+        # todo: host manager hasn't been updated to use audit
+        # mechanisms so ignore host specific options for now.
+        IF scope_id = 0 THEN
+            # If a global option is added or modified, create audit
+            # entry for the 'dhcp4_options' table.
+            CALL createAuditEntryDHCP4('dhcp4_options', option_id, modification_type);
+        ELSEIF scope_id = 1 THEN
+            # If subnet specific option is added or modified, update
+            # the modification timestamp of this subnet to allow the
+            # servers to refresh the subnet information. This will
+            # also result in creating an audit entry for this subnet.
+            UPDATE dhcp4_subnet AS s SET s.modification_ts = modification_ts
+                WHERE s.subnet_id = subnet_id;
+        ELSEIF scope_id = 4 THEN
+            # If shared network specific option is added or modified,
+            # update the modification timestamp of this shared network
+            # to allow the servers to refresh the shared network
+            # information. This will also result in creating an
+            # audit entry for this shared network.
+           SELECT id INTO snid FROM dhcp4_shared_network WHERE name = network_name LIMIT 1;
+           UPDATE dhcp4_shared_network AS n SET n.modification_ts = modification_ts
+                WHERE n.id = snid;
+        ELSEIF scope_id = 5 THEN
+            # If pool specific option is added or modified, update
+            # the modification timestamp of the owning subnet.
+            SELECT dhcp4_pool.subnet_id INTO sid FROM dhcp4_pool WHERE id = pool_id;
+            UPDATE dhcp4_subnet AS s SET s.modification_ts = modification_ts
+                WHERE s.subnet_id = sid;
+        END IF;
+    END IF;
+END $$
+DELIMITER ;
+
+# Recreate dhcp4_options_AINS trigger to pass timestamp to the updated
+# version of the createOptionAuditDHCP4.
+DROP TRIGGER IF EXISTS dhcp4_options_AINS;
+
+# This trigger is executed after inserting a DHCPv4 option into the
+# database. It creates appropriate audit entry for this option or
+# a parent object owning this option.
+DELIMITER $$
+CREATE TRIGGER dhcp4_options_AINS AFTER INSERT ON dhcp4_options
+    FOR EACH ROW
+    BEGIN
+        CALL createOptionAuditDHCP4("create", NEW.scope_id, NEW.option_id, NEW.dhcp4_subnet_id,
+                                    NEW.host_id, NEW.shared_network_name, NEW.pool_id,
+                                    NEW.modification_ts);
+    END $$
+DELIMITER ;
+
+# Recreate dhcp4_options_AUPD trigger to pass timestamp to the updated
+# version of the createOptionAuditDHCP4.
+DROP TRIGGER IF EXISTS dhcp4_options_AUPD;
+
+# This trigger is executed after updating a DHCPv4 option in the
+# database. It creates appropriate audit entry for this option or
+# a parent object owning this option.
+DELIMITER $$
+CREATE TRIGGER dhcp4_options_AUPD AFTER UPDATE ON dhcp4_options
+    FOR EACH ROW
+    BEGIN
+        CALL createOptionAuditDHCP4("update", NEW.scope_id, NEW.option_id, NEW.dhcp4_subnet_id,
+                                    NEW.host_id, NEW.shared_network_name, NEW.pool_id,
+                                    NEW.modification_ts);
+    END $$
+DELIMITER ;
+
+# Recreate dhcp4_options_ADEL trigger to pass timestamp to the updated
+# version of the createOptionAuditDHCP4.
+DROP TRIGGER IF EXISTS dhcp4_options_ADEL;
+
+# This trigger is executed after deleting a DHCPv4 option in the
+# database. It creates appropriate audit entry for this option or
+# a parent object owning this option.
+DELIMITER $$
+CREATE TRIGGER dhcp4_options_ADEL AFTER DELETE ON dhcp4_options
+    FOR EACH ROW
+    BEGIN
+        CALL createOptionAuditDHCP4("delete", OLD.scope_id, OLD.option_id, OLD.dhcp4_subnet_id,
+                                    OLD.host_id, OLD.shared_network_name, OLD.pool_id,
+                                    NOW());
+    END $$
+DELIMITER ;
+
+-- -----------------------------------------------------
+--
+-- New version of the createOptionAuditDHCP4 stored
+-- procedure which updates modification timestamp of
+-- a parent object when an option is modified.
+--
+-- The following parameters are passed to the procedure:
+-- - modification_type: "create", "update" or "delete"
+-- - scope_id: identifier of the option scope, e.g.
+--   global, subnet specific etc. See dhcp_option_scope
+--   for specific values.
+-- - option_id: identifier of the option.
+-- - subnet_id: identifier of the subnet if the option
+--   belongs to the subnet.
+-- - host_id: identifier of the host if the option
+-- - belongs to the host.
+-- - network_name: shared network name if the option
+--   belongs to the shared network.
+-- - pool_id: identifier of the pool if the option
+--   belongs to the pool.
+-- - pd_pool_id: identifier of the pool if the option
+--   belongs to the pd pool.
+-- - modification_ts: modification timestamp of the
+--   option.
+-- -----------------------------------------------------
+DROP PROCEDURE IF EXISTS createOptionAuditDHCP6;
+DELIMITER $$
+CREATE PROCEDURE createOptionAuditDHCP6(IN modification_type VARCHAR(32),
+                                        IN scope_id TINYINT(3) UNSIGNED,
+                                        IN option_id BIGINT(20) UNSIGNED,
+                                        IN subnet_id INT(10) UNSIGNED,
+                                        IN host_id INT(10) UNSIGNED,
+                                        IN network_name VARCHAR(128),
+                                        IN pool_id BIGINT(20),
+                                        IN pd_pool_id BIGINT(20),
+                                        IN modification_ts TIMESTAMP)
+BEGIN
+    # These variables will hold shared network id and subnet id that
+    # we will select.
+    DECLARE snid VARCHAR(128);
+    DECLARE sid INT(10) UNSIGNED;
+
+    # Cascade transaction flag is set to 1 to prevent creation of
+    # the audit entries for the options when the options are
+    # created as part of the parent object creation or update.
+    # For example: when the option is added as part of the subnet
+    # addition, the cascade transaction flag is equal to 1. If
+    # the option is added into the existing subnet the cascade
+    # transaction is equal to 0. Note that depending on the option
+    # scope the audit entry will contain the object_type value
+    # of the parent object to cause the server to replace the
+    # entire subnet. The only case when the object_type will be
+    # set to 'dhcp6_options' is when a global option is added.
+    # Global options do not have the owner.
+    IF @cascade_transaction IS NULL OR @cascade_transaction = 0 THEN
+        # todo: host manager hasn't been updated to use audit
+        # mechanisms so ignore host specific options for now.
+        IF scope_id = 0 THEN
+            # If a global option is added or modified, create audit
+            # entry for the 'dhcp6_options' table.
+            CALL createAuditEntryDHCP6('dhcp6_options', option_id, modification_type);
+        ELSEIF scope_id = 1 THEN
+            # If subnet specific option is added or modified, update
+            # the modification timestamp of this subnet to allow the
+            # servers to refresh the subnet information. This will
+            # also result in creating an audit entry for this subnet.
+            UPDATE dhcp6_subnet AS s SET s.modification_ts = modification_ts
+                WHERE s.subnet_id = subnet_id;
+        ELSEIF scope_id = 4 THEN
+            # If shared network specific option is added or modified,
+            # update the modification timestamp of this shared network
+            # to allow the servers to refresh the shared network
+            # information. This will also result in creating an
+            # audit entry for this shared network.
+           SELECT id INTO snid FROM dhcp6_shared_network WHERE name = network_name LIMIT 1;
+           UPDATE dhcp6_shared_network AS n SET n.modification_ts = modification_ts
+               WHERE n.id = snid;
+        ELSEIF scope_id = 5 THEN
+            # If pool specific option is added or modified, update
+            # the modification timestamp of the owning subnet.
+            SELECT dhcp6_pool.subnet_id INTO sid FROM dhcp6_pool WHERE id = pool_id;
+            UPDATE dhcp6_subnet AS s SET s.modification_ts = modification_ts
+                WHERE s.subnet_id = sid;
+        ELSEIF scope_id = 6 THEN
+            # If pd pool specific option is added or modified, create
+            # audit entry for the subnet which this pool belongs to.
+            SELECT dhcp6_pd_pool.subnet_id INTO sid FROM dhcp6_pd_pool WHERE id = pd_pool_id;
+            UPDATE dhcp6_subnet AS s SET s.modification_ts = modification_ts
+                WHERE s.subnet_id = sid;
+        END IF;
+    END IF;
+END $$
+DELIMITER ;
+
+# Recreate dhcp6_options_AINS trigger to pass timestamp to the updated
+# version of the createOptionAuditDHCP6.
+DROP TRIGGER IF EXISTS dhcp6_options_AINS;
+
+# This trigger is executed after inserting a DHCPv6 option into the
+# database. It creates appropriate audit entry for this option or
+# a parent object owning this option.
+DELIMITER $$
+CREATE TRIGGER dhcp6_options_AINS AFTER INSERT ON dhcp6_options
+    FOR EACH ROW
+    BEGIN
+        CALL createOptionAuditDHCP6("create", NEW.scope_id, NEW.option_id, NEW.dhcp6_subnet_id,
+                                    NEW.host_id, NEW.shared_network_name, NEW.pool_id,
+                                    NEW.pd_pool_id, NEW.modification_ts);
+    END $$
+DELIMITER ;
+
+# Recreate dhcp6_options_AUPD trigger to pass timestamp to the updated
+# version of the createOptionAuditDHCP6.
+DROP TRIGGER IF EXISTS dhcp6_options_AUPD;
+
+# This trigger is executed after updating a DHCPv6 option in the
+# database. It creates appropriate audit entry for this option or
+# a parent object owning this option.
+DELIMITER $$
+CREATE TRIGGER dhcp6_options_AUPD AFTER UPDATE ON dhcp6_options
+    FOR EACH ROW
+    BEGIN
+        CALL createOptionAuditDHCP6("update", NEW.scope_id, NEW.option_id, NEW.dhcp6_subnet_id,
+                                    NEW.host_id, NEW.shared_network_name, NEW.pool_id,
+                                    NEW.pd_pool_id, NEW.modification_ts);
+    END $$
+DELIMITER ;
+
+# Recreate dhcp6_options_ADEL trigger to pass timestamp to the updated
+# version of the createOptionAuditDHCP6.
+DROP TRIGGER IF EXISTS dhcp6_options_ADEL;
+
+# This trigger is executed after deleting a DHCPv6 option in the
+# database. It creates appropriate audit entry for this option or
+# a parent object owning this option.
+DELIMITER $$
+CREATE TRIGGER dhcp6_options_ADEL AFTER DELETE ON dhcp6_options
+    FOR EACH ROW
+    BEGIN
+        CALL createOptionAuditDHCP6("delete", OLD.scope_id, OLD.option_id, OLD.dhcp6_subnet_id,
+                                    OLD.host_id, OLD.shared_network_name, OLD.pool_id,
+                                    OLD.pd_pool_id, NOW());
+    END $$
+DELIMITER ;
+
+# Update the schema version number.
+UPDATE schema_version
+    SET version = '8', minor = '2';
+
+# This line concludes the schema upgrade to version 8.2.
+
+# This line starts the schema upgrade to version 9.0.
+
+# Create hostname index for host reservations
+CREATE INDEX hosts_by_hostname ON hosts (hostname);
+
+# Create hostname index for lease4
+CREATE INDEX lease4_by_hostname ON lease4 (hostname);
+
+# Create hostname index for lease6
+CREATE INDEX lease6_by_hostname ON lease6 (hostname);
+
+# Update the schema version number.
+UPDATE schema_version
+    SET version = '9', minor = '0';
+
+# This line concludes the schema upgrade to version 9.0.
+
+# This line starts the schema upgrade to version 9.1.
+
+# Add new DDNS related columns to shared networks and subnets
+ALTER TABLE dhcp4_shared_network
+    ADD COLUMN ddns_send_updates TINYINT(1) DEFAULT NULL,
+    ADD COLUMN ddns_override_no_update TINYINT(1) DEFAULT NULL,
+    ADD COLUMN ddns_override_client_update TINYINT(1) DEFAULT NULL,
+    ADD COLUMN ddns_replace_client_name TINYINT(3) DEFAULT NULL,
+    ADD COLUMN ddns_generated_prefix VARCHAR(255) DEFAULT NULL,
+    ADD COLUMN ddns_qualifying_suffix VARCHAR(255) DEFAULT NULL;
+
+ALTER TABLE dhcp6_shared_network
+    ADD COLUMN ddns_send_updates TINYINT(1) DEFAULT NULL,
+    ADD COLUMN ddns_override_no_update TINYINT(1) DEFAULT NULL,
+    ADD COLUMN ddns_override_client_update TINYINT(1) DEFAULT NULL,
+    ADD COLUMN ddns_replace_client_name TINYINT(3) DEFAULT NULL,
+    ADD COLUMN ddns_generated_prefix VARCHAR(255) DEFAULT NULL,
+    ADD COLUMN ddns_qualifying_suffix VARCHAR(255) DEFAULT NULL;
+
+ALTER TABLE dhcp4_subnet
+    ADD COLUMN ddns_send_updates TINYINT(1) DEFAULT NULL,
+    ADD COLUMN ddns_override_no_update TINYINT(1) DEFAULT NULL,
+    ADD COLUMN ddns_override_client_update TINYINT(1) DEFAULT NULL,
+    ADD COLUMN ddns_replace_client_name TINYINT(3) DEFAULT NULL,
+    ADD COLUMN ddns_generated_prefix VARCHAR(255) DEFAULT NULL,
+    ADD COLUMN ddns_qualifying_suffix VARCHAR(255) DEFAULT NULL;
+
+ALTER TABLE dhcp6_subnet
+    ADD COLUMN ddns_send_updates TINYINT(1) DEFAULT NULL,
+    ADD COLUMN ddns_override_no_update TINYINT(1) DEFAULT NULL,
+    ADD COLUMN ddns_override_client_update TINYINT(1) DEFAULT NULL,
+    ADD COLUMN ddns_replace_client_name TINYINT(3) DEFAULT NULL,
+    ADD COLUMN ddns_generated_prefix VARCHAR(255) DEFAULT NULL,
+    ADD COLUMN ddns_qualifying_suffix VARCHAR(255) DEFAULT NULL;
+
+# Update the schema version number.
+UPDATE schema_version
+    SET version = '9', minor = '1';
+
+# This line concludes the schema upgrade to version 9.1.
+
+# This line starts the schema upgrade to version 9.2.
+
+# Add missing indexes (foreign keys) to the dhcp4_options table.
+ALTER TABLE dhcp4_options ADD CONSTRAINT fk_dhcp4_options_shared_network
+    FOREIGN KEY (shared_network_name)
+        REFERENCES dhcp4_shared_network(name)
+        ON DELETE CASCADE ON UPDATE CASCADE;
+
+ALTER TABLE dhcp4_options ADD CONSTRAINT fk_dhcp4_options_subnet
+    FOREIGN KEY (dhcp4_subnet_id)
+        REFERENCES dhcp4_subnet(subnet_id)
+        ON DELETE CASCADE ON UPDATE CASCADE;
+
+ALTER TABLE dhcp4_options ADD CONSTRAINT fk_dhcp4_options_pool
+    FOREIGN KEY (pool_id)
+        REFERENCES dhcp4_pool(id)
+        ON DELETE CASCADE ON UPDATE CASCADE;
+
+# Add missing indexes (foreign keys) to the dhcp6_options table.
+ALTER TABLE dhcp6_options ADD CONSTRAINT fk_dhcp6_options_shared_network
+    FOREIGN KEY (shared_network_name)
+        REFERENCES dhcp6_shared_network(name)
+        ON DELETE CASCADE ON UPDATE CASCADE;
+
+ALTER TABLE dhcp6_options ADD CONSTRAINT fk_dhcp6_options_subnet
+    FOREIGN KEY (dhcp6_subnet_id)
+        REFERENCES dhcp6_subnet(subnet_id)
+        ON DELETE CASCADE ON UPDATE CASCADE;
+
+ALTER TABLE dhcp6_options ADD CONSTRAINT fk_dhcp6_options_pool
+    FOREIGN KEY (pool_id)
+        REFERENCES dhcp6_pool(id)
+        ON DELETE CASCADE ON UPDATE CASCADE;
+
+ALTER TABLE dhcp6_options ADD CONSTRAINT fk_dhcp6_options_pd_pool
+    FOREIGN KEY (pd_pool_id)
+        REFERENCES dhcp6_pd_pool(id)
+        ON DELETE CASCADE ON UPDATE CASCADE;
+
+# Update the schema version number.
+UPDATE schema_version
+    SET version = '9', minor = '2';
+
+# This line concludes the schema upgrade to version 9.2.
+
+# This line starts the schema upgrade to version 9.3.
+
+# Fix stat_lease4_update trigger
+DROP TRIGGER stat_lease4_update;
+
+DELIMITER $$
+CREATE TRIGGER stat_lease4_update AFTER UPDATE ON lease4
+    FOR EACH ROW
+    BEGIN
+        IF OLD.subnet_id != NEW.subnet_id OR OLD.state != NEW.state THEN
+            IF OLD.state = 0 OR OLD.state = 1 THEN
+                # Decrement the old state count if record exists
+                UPDATE lease4_stat
+                SET leases = IF(leases > 0, leases - 1, 0)
+                WHERE subnet_id = OLD.subnet_id AND state = OLD.state;
+            END IF;
+
+            IF NEW.state = 0 OR NEW.state = 1 THEN
+                # Increment the new state count if record exists
+                UPDATE lease4_stat SET leases = leases + 1
+                WHERE subnet_id = NEW.subnet_id AND state = NEW.state;
+
+                # Insert new state record if it does not exist
+                IF ROW_COUNT() <= 0 THEN
+                    INSERT INTO lease4_stat VALUES (NEW.subnet_id, NEW.state, 1);
+                END IF;
+            END IF;
+        END IF;
+    END $$
+DELIMITER ;
+
+# Fix stat_lease4_delete trigger
+DROP TRIGGER stat_lease4_delete;
+
+DELIMITER $$
+CREATE TRIGGER stat_lease4_delete AFTER DELETE ON lease4
+    FOR EACH ROW
+    BEGIN
+        IF OLD.state = 0 OR OLD.state = 1 THEN
+            # Decrement the state count if record exists
+            UPDATE lease4_stat
+            SET leases = IF(leases > 0, leases - 1, 0)
+            WHERE subnet_id = OLD.subnet_id AND OLD.state = state;
+        END IF;
+    END $$
+DELIMITER ;
+
+# Fix stat_lease6_update trigger
+DROP TRIGGER stat_lease6_update;
+
+DELIMITER $$
+CREATE TRIGGER stat_lease6_update AFTER UPDATE ON lease6
+    FOR EACH ROW
+    BEGIN
+        IF OLD.subnet_id != NEW.subnet_id OR
+           OLD.lease_type != NEW.lease_type OR
+           OLD.state != NEW.state THEN
+            IF OLD.state = 0 OR OLD.state = 1 THEN
+                # Decrement the old state count if record exists
+                UPDATE lease6_stat
+                SET leases = IF(leases > 0, leases - 1, 0)
+                WHERE subnet_id = OLD.subnet_id AND lease_type = OLD.lease_type
+                AND state = OLD.state;
+            END IF;
+
+            IF NEW.state = 0 OR NEW.state = 1 THEN
+                # Increment the new state count if record exists
+                UPDATE lease6_stat SET leases = leases + 1
+                WHERE subnet_id = NEW.subnet_id AND lease_type = NEW.lease_type
+                AND state = NEW.state;
+
+                # Insert new state record if it does not exist
+                IF ROW_COUNT() <= 0 THEN
+                    INSERT INTO lease6_stat
+                    VALUES (NEW.subnet_id, NEW.lease_type, NEW.state, 1);
+                END IF;
+            END IF;
+        END IF;
+    END $$
+DELIMITER ;
+
+# Fix stat_lease6_delete trigger
+DROP TRIGGER stat_lease6_delete;
+
+DELIMITER $$
+CREATE TRIGGER stat_lease6_delete AFTER DELETE ON lease6
+    FOR EACH ROW
+    BEGIN
+        IF OLD.state = 0 OR OLD.state = 1 THEN
+            # Decrement the state count if record exists
+            UPDATE lease6_stat
+            SET leases = IF(leases > 0, leases - 1, 0)
+            WHERE subnet_id = OLD.subnet_id AND lease_type = OLD.lease_type
+            AND state = OLD.state;
+        END IF;
+    END $$
+DELIMITER ;
+
+# Update the schema version number.
+UPDATE schema_version
+    SET version = '9', minor = '3';
+
+# This line concludes the schema upgrade to version 9.3.
+
+# This line starts the schema upgrade to version 9.4.
+
+# Starting from this version we allow specifying multiple IP reservations
+# for the same address in certain DHCP configurations. The server may check
+# uniqueness of the IP addresses on its own. This is no longer checked at
+# the database level to facilitate the use cases when a single host may
+# get the same reserved IP address via different interfaces.
+
+# Replace the unique index with non-unique index so the queries for
+# hosts by IPv4 address are still efficient.
+DROP INDEX key_dhcp4_ipv4_address_subnet_id ON hosts;
+CREATE INDEX key_dhcp4_ipv4_address_subnet_id_identifier
+    ON hosts (ipv4_address ASC, dhcp4_subnet_id ASC);
+
+# Replace the unique index with non-unique index so the queries for
+# hosts by IPv6 address are still efficient.
+DROP INDEX key_dhcp6_address_prefix_len ON ipv6_reservations;
+CREATE INDEX key_dhcp6_address_prefix_len
+    ON ipv6_reservations (address ASC, prefix_len ASC);
+
+# Stop using a trigger to delete entries dependent on hosts table.
+# Use cascade action instead. This works better with complex delete
+# statements.
+DROP TRIGGER IF EXISTS host_BDEL;
+
+# Replace existing constraint to set cascade actions.
+ALTER TABLE ipv6_reservations DROP FOREIGN KEY fk_ipv6_reservations_Host;
+ALTER TABLE ipv6_reservations ADD CONSTRAINT fk_ipv6_reservations_Host
+    FOREIGN KEY (host_id)
+        REFERENCES hosts(host_id)
+        ON DELETE CASCADE ON UPDATE CASCADE;
+
+ALTER TABLE dhcp4_options ADD CONSTRAINT fk_dhcp4_options_Host
+    FOREIGN KEY (host_id)
+        REFERENCES hosts(host_id)
+        ON DELETE CASCADE ON UPDATE CASCADE;
+
+ALTER TABLE dhcp6_options ADD CONSTRAINT fk_dhcp6_options_Host
+    FOREIGN KEY (host_id)
+        REFERENCES hosts(host_id)
+        ON DELETE CASCADE ON UPDATE CASCADE;
+
+# Update the schema version number.
+UPDATE schema_version
+    SET version = '9', minor = '4';
+
+# This line concludes the schema upgrade to version 9.4.
+
+# This line starts the schema upgrade to version 9.5.
+
+# Add new reservations flags.
+ALTER TABLE dhcp4_subnet
+    ADD COLUMN reservations_global BOOL DEFAULT NULL,
+    ADD COLUMN reservations_in_subnet BOOL DEFAULT NULL,
+    ADD COLUMN reservations_out_of_pool BOOL DEFAULT NULL;
+
+ALTER TABLE dhcp4_shared_network
+    ADD COLUMN reservations_global BOOL DEFAULT NULL,
+    ADD COLUMN reservations_in_subnet BOOL DEFAULT NULL,
+    ADD COLUMN reservations_out_of_pool BOOL DEFAULT NULL;
+
+ALTER TABLE dhcp6_subnet
+    ADD COLUMN reservations_global BOOL DEFAULT NULL,
+    ADD COLUMN reservations_in_subnet BOOL DEFAULT NULL,
+    ADD COLUMN reservations_out_of_pool BOOL DEFAULT NULL;
+
+ALTER TABLE dhcp6_shared_network
+    ADD COLUMN reservations_global BOOL DEFAULT NULL,
+    ADD COLUMN reservations_in_subnet BOOL DEFAULT NULL,
+    ADD COLUMN reservations_out_of_pool BOOL DEFAULT NULL;
+
+# DROP reservation_mode
+ALTER TABLE dhcp4_subnet DROP COLUMN reservation_mode;
+ALTER TABLE dhcp4_shared_network DROP COLUMN reservation_mode;
+ALTER TABLE dhcp6_subnet DROP COLUMN reservation_mode;
+ALTER TABLE dhcp6_shared_network DROP COLUMN reservation_mode;
+
+# Update the schema version number.
+UPDATE schema_version
+    SET version = '9', minor = '5';
+
+# This line concludes the schema upgrade to version 9.5.
+
+# This line starts the schema upgrade to version 9.6.
+
+# Add new lease cache parameters.
+ALTER TABLE dhcp4_subnet
+    ADD COLUMN cache_threshold FLOAT DEFAULT NULL,
+    ADD COLUMN cache_max_age INT(10) DEFAULT NULL;
+
+ALTER TABLE dhcp4_shared_network
+    ADD COLUMN cache_threshold FLOAT DEFAULT NULL,
+    ADD COLUMN cache_max_age INT(10) DEFAULT NULL;
+
+ALTER TABLE dhcp6_subnet
+    ADD COLUMN cache_threshold FLOAT DEFAULT NULL,
+    ADD COLUMN cache_max_age INT(10) DEFAULT NULL;
+
+ALTER TABLE dhcp6_shared_network
+    ADD COLUMN cache_threshold FLOAT DEFAULT NULL,
+    ADD COLUMN cache_max_age INT(10) DEFAULT NULL;
+
+# Add an auto-increment ID as primary key to support Percona.
+ALTER TABLE logs
+    ADD id INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY;
+
+# Update the schema version number.
+UPDATE schema_version
+    SET version = '9', minor = '6';
+
+# This line concludes the schema upgrade to version 9.6.
+
+# This line starts the schema upgrade to version 10.0.
+
+-- -----------------------------------------------------------------------
+-- Create a table holding the DHCPv4 client classes. Most table
+-- columns map directly to respective client class properties in
+-- Kea configuration. The depend_on_known_directly column is
+-- explicitly set in an insert or update statement to indicate
+-- if the client class directly depends on KNOWN or UNKNOWN
+-- built-in classes. A caller should determine it by evaluating
+-- a test expression before inserting or updating the client
+-- class in the database. The nullable follow_class_name column
+-- can be used for positioning the inserted or updated client
+-- class within the class hierarchy. Set this column value to
+-- an existing class name, after which this class should be
+-- placed in the class hierarchy. See dhcp4_client_class_order
+-- description for the details of how classes are ordered.
+-- -----------------------------------------------------------------------
+CREATE TABLE IF NOT EXISTS dhcp4_client_class (
+    id BIGINT UNSIGNED NOT NULL AUTO_INCREMENT,
+    name VARCHAR(128) NOT NULL,
+    test TEXT,
+    next_server INT UNSIGNED DEFAULT NULL,
+    server_hostname VARCHAR(128) DEFAULT NULL,
+    boot_file_name VARCHAR(512) DEFAULT NULL,
+    only_if_required TINYINT NOT NULL DEFAULT '0',
+    valid_lifetime INT DEFAULT NULL,
+    min_valid_lifetime INT DEFAULT NULL,
+    max_valid_lifetime INT DEFAULT NULL,
+    depend_on_known_directly TINYINT NOT NULL DEFAULT '0',
+    follow_class_name VARCHAR(128) DEFAULT NULL,
+    modification_ts TIMESTAMP NOT NULL,
+    PRIMARY KEY (id),
+    UNIQUE KEY id_UNIQUE (id),
+    UNIQUE KEY name_UNIQUE (name),
+    KEY key_dhcp4_client_class_modification_ts (modification_ts)
+) ENGINE=InnoDB;
+
+-- -----------------------------------------------------------------------
+-- Create a table for ordering client classes and holding information
+-- about indirect dependencies on KNOWN/UKNOWN built-in client classes.
+-- Each class in the dhcp4_client_class table has a corresponding row
+-- in the dhcp4_client_class_order table. A caller should not modify
+-- the contents of this table. Its entries are automatically created
+-- upon inserting or updating client classes in the dhcp4_client_classes
+-- using triggers. The order_index designates the position of the client
+-- class within the class hierarchy. If the follow_class_name value of
+-- the dhcp4_client_class table is set to NULL, the client class is
+-- appended at the end of the hierarchy. The assigned order_index
+-- value for that class is set to a maximum current value + 1.
+-- If the follow_client_class specifies a name of an existing class,
+-- the generated order_index is set to an id of that class + 1, and
+-- the order_index values of the later classes are incremented by 1.
+-- The depend_on_known_indirectly column holds a boolean value indicating
+-- whether the given class depends on KNOWN/UKNOWN built-in classes
+-- via other classes, i.e. it depends on classes that directly or
+-- indirectly depend on these built-ins. This value is auto-generated
+-- by a trigger on the dhcp4_client_class_dependency table.
+-- -----------------------------------------------------------------------
+CREATE TABLE IF NOT EXISTS dhcp4_client_class_order (
+    class_id BIGINT UNSIGNED NOT NULL,
+    order_index BIGINT UNSIGNED NOT NULL,
+    depend_on_known_indirectly TINYINT NOT NULL DEFAULT '0',
+    PRIMARY KEY (class_id),
+    KEY key_dhcp4_client_class_order_index (order_index),
+    CONSTRAINT fk_dhcp4_client_class_order_class_id FOREIGN KEY (class_id)
+        REFERENCES dhcp4_client_class (id) ON DELETE CASCADE
+) ENGINE=InnoDB;
+
+DROP TRIGGER IF EXISTS dhcp4_client_class_AINS;
+DROP TRIGGER IF EXISTS dhcp4_client_class_AUPD;
+DROP TRIGGER IF EXISTS dhcp4_client_class_ADEL;
+DROP PROCEDURE IF EXISTS setClientClass4Order;
+
+-- -----------------------------------------------------------------------
+-- Stored procedure positioning an inserted or updated client class
+-- within the class hierarchy, depending on the value of the
+-- follow_class_name parameter.
+--
+-- Parameters:
+-- - id id of the positioned class,
+-- - follow_class_name name of the class after which this class should be
+--   positioned within the class hierarchy.
+-- - old_follow_class_name previous name of the class after which this
+--   class was positioned within the class hierarchy.
+-- -----------------------------------------------------------------------
+DELIMITER $$
+CREATE PROCEDURE setClientClass4Order(IN id BIGINT UNSIGNED,
+                                      IN follow_class_name VARCHAR(128),
+                                      IN old_follow_class_name VARCHAR(128))
+proc_label:BEGIN
+    -- This variable will be optionally set if the follow_class_name
+    -- column value is specified.
+    DECLARE follow_class_index BIGINT UNSIGNED;
+    DECLARE msg TEXT;
+
+    -- Remember currently used value of depend_on_known_indirectly.
+    SET @depend_on_known_indirectly = (
+        SELECT depend_on_known_indirectly FROM dhcp4_client_class_order WHERE id = class_id
+    );
+
+    -- Bail if the class is updated without re-positioning.
+    IF(
+        @depend_on_known_indirectly IS NOT NULL AND
+        ((follow_class_name IS NULL AND old_follow_class_name IS NULL) OR
+         (follow_class_name = old_follow_class_name))
+    ) THEN
+        -- The depend_on_known_indirectly is set to 0 because this procedure is invoked
+        -- whenever the dhcp4_client_class record is updated. Such update may include
+        -- test expression changes impacting the dependency on KNOWN/UNKNOWN classes.
+        -- This value will be later adjusted when dependencies are inserted.
+        UPDATE dhcp4_client_class_order SET depend_on_known_indirectly = 0
+            WHERE class_id = id;
+        LEAVE proc_label;
+    END IF;
+
+    IF follow_class_name IS NOT NULL THEN
+        -- Get the position of the class after which the new class should be added.
+        SET follow_class_index = (
+            SELECT o.order_index FROM dhcp4_client_class AS c
+                INNER JOIN dhcp4_client_class_order AS o
+                    ON c.id = o.class_id
+            WHERE c.name = follow_class_name
+        );
+        IF follow_class_index IS NULL THEN
+            -- The class with a name specified with follow_class_name does
+            -- not exist.
+            SET msg = CONCAT('Class ', follow_class_name, ' does not exist.');
+            SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = msg;
+        END IF;
+        -- We need to place the new class at the position of follow_class_index + 1.
+        -- There may be a class at this position already.
+        IF EXISTS(SELECT * FROM dhcp4_client_class_order WHERE order_index = follow_class_index + 1) THEN
+            -- There is a class at this position already. Let's move all classes
+            -- starting from this position by one to create a spot for the new
+            -- class.
+            UPDATE dhcp4_client_class_order
+                SET order_index = order_index + 1
+            WHERE order_index >= follow_class_index + 1
+            ORDER BY order_index DESC;
+        END IF;
+    ELSE
+        -- A caller did not specify the follow_class_name value. Let's append the
+        -- new class at the end of the hierarchy.
+        SET follow_class_index = (SELECT MAX(order_index) FROM dhcp4_client_class_order);
+        IF follow_class_index IS NULL THEN
+            -- Apparently, there are no classes. Let's start from 0.
+            SET follow_class_index = 0;
+        END IF;
+    END IF;
+
+    -- Check if moving the class doesn't break dependent classes.
+    IF EXISTS(
+        SELECT 1 FROM dhcp4_client_class_dependency AS d
+            INNER JOIN dhcp4_client_class_order AS o
+                ON d.class_id = o.class_id
+            WHERE d.dependency_id = id AND o.order_index < follow_class_index + 1
+        LIMIT 1
+    ) THEN
+        SET msg = CONCAT('Unable to move class with id ', id, ' because it would break its dependencies');
+        SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = msg;
+    END IF;
+
+    -- The depend_on_known_indirectly is set to 0 because this procedure is invoked
+    -- whenever the dhcp4_client_class record is updated. Such update may include
+    -- test expression changes impacting the dependency on KNOWN/UNKNOWN classes.
+    -- This value will be later adjusted when dependencies are inserted.
+    REPLACE INTO dhcp4_client_class_order(class_id, order_index, depend_on_known_indirectly)
+        VALUES (id, follow_class_index + 1, 0);
+END $$
+DELIMITER ;
+
+-- -----------------------------------------------------------------------
+-- Trigger to position an inserted class within the class hierarchy
+-- and create audit.
+-- -----------------------------------------------------------------------
+DELIMITER $$
+CREATE TRIGGER dhcp4_client_class_AINS AFTER INSERT ON dhcp4_client_class FOR EACH ROW BEGIN
+    CALL setClientClass4Order(NEW.id, NEW.follow_class_name, NULL);
+    CALL createAuditEntryDHCP4('dhcp4_client_class', NEW.id, "create");
+END $$
+DELIMITER ;
+
+-- -----------------------------------------------------------------------
+-- Trigger to position an updated class within the class hierarchy,
+-- create audit and remember the direct dependency on the
+-- KNOWN/UNKNOWN built-in classes before the class update.
+-- When updating a client class, it is very important to ensure that
+-- its dependency on KNOWN or UNKNOWN built-in client classes is not
+-- changed. It is because there may be other classes that depend on
+-- these built-ins via this class. Changing the dependency would break
+-- the chain of dependencies for other classes. Here, we store the
+-- information about the dependency in the session variables. Their
+-- values will be compared with the new dependencies after an update.
+-- If they change, an error will be signaled.
+-- -----------------------------------------------------------------------
+DELIMITER $$
+CREATE TRIGGER dhcp4_client_class_AUPD AFTER UPDATE ON dhcp4_client_class FOR EACH ROW BEGIN
+    SET @depend_on_known_directly = OLD.depend_on_known_directly;
+    SET @client_class_id = NEW.id;
+    CALL setClientClass4Order(NEW.id, NEW.follow_class_name, OLD.follow_class_name);
+    CALL createAuditEntryDHCP4('dhcp4_client_class', NEW.id, "update");
+END $$
+DELIMITER ;
+
+-- -----------------------------------------------------------------------
+-- Trigger to create dhcp4_client_class audit.
+-- -----------------------------------------------------------------------
+DELIMITER $$
+CREATE TRIGGER dhcp4_client_class_ADEL AFTER DELETE ON dhcp4_client_class FOR EACH ROW BEGIN
+    CALL createAuditEntryDHCP4('dhcp4_client_class', OLD.id, "delete");
+END $$
+DELIMITER ;
+
+-- -----------------------------------------------------------------------
+-- Create a table associating client classes stored in the
+-- dhcp4_client_class table with their dependencies. There is
+-- an M:N relationship between these tables. Each class may have
+-- many dependencies (created using member operator in test expression),
+-- and each class may be a dependency for many other classes. A caller
+-- is responsible for inserting dependencies for a class after inserting
+-- or updating it in the dhcp4_client_class table. A caller should
+-- delete all existing dependencies for an updated client class, evaluate
+-- test expression to discover new dependencies (in case test expression
+-- has changed), and insert new dependencies to this table.
+-- -----------------------------------------------------------------------
+CREATE TABLE IF NOT EXISTS dhcp4_client_class_dependency (
+    class_id BIGINT UNSIGNED NOT NULL,
+    dependency_id BIGINT UNSIGNED NOT NULL,
+    PRIMARY KEY (class_id,dependency_id),
+    KEY dhcp4_client_class_dependency_id_idx (dependency_id),
+    CONSTRAINT dhcp4_client_class_class_id FOREIGN KEY (class_id)
+        REFERENCES dhcp4_client_class (id) ON DELETE CASCADE,
+    CONSTRAINT dhcp4_client_class_dependency_id FOREIGN KEY (dependency_id)
+        REFERENCES dhcp4_client_class (id)
+) ENGINE=InnoDB;
+
+DROP TRIGGER IF EXISTS dhcp4_client_class_dependency_BINS;
+DROP PROCEDURE IF EXISTS checkDHCPv4ClientClassDependency;
+
+-- -----------------------------------------------------------------------
+-- Stored procedure verifying if class dependency is met. It includes
+-- checking if referenced classes exist, are associated with the same
+-- server or all servers, and are defined before the class specified with
+-- class_id.
+--
+-- Parameters:
+-- - class_id id client class,
+-- - dependency_id id of the dependency.
+-- -----------------------------------------------------------------------
+DELIMITER $$
+CREATE PROCEDURE checkDHCPv4ClientClassDependency(IN class_id BIGINT UNSIGNED,
+                                                  IN dependency_id BIGINT UNSIGNED)
+BEGIN
+    DECLARE class_index BIGINT UNSIGNED;
+    DECLARE dependency_index BIGINT UNSIGNED;
+    DECLARE err_msg TEXT;
+
+    -- We could check the same with a constraint but later in this
+    -- trigger we use this value to verify if the dependencies are
+    -- met.
+    IF class_id IS NULL THEN
+        SIGNAL SQLSTATE '45000'
+            SET MESSAGE_TEXT = 'Client class id must not be NULL.';
+    END IF;
+    IF dependency_id IS NULL THEN
+        SIGNAL SQLSTATE '45000'
+            SET MESSAGE_TEXT = 'Class dependency id must not be NULL.';
+    END IF;
+    -- Dependencies on self make no sense.
+    IF class_id = dependency_id THEN
+        SIGNAL SQLSTATE '45000'
+            SET MESSAGE_TEXT = 'Client class must not have dependency on self.';
+    END IF;
+    -- Check position of our class in the hierarchy.
+    SET class_index = (
+        SELECT o.order_index FROM dhcp4_client_class AS c
+            INNER JOIN dhcp4_client_class_order AS o
+                ON c.id = o.class_id
+        WHERE c.id = class_id);
+    IF class_index IS NULL THEN
+        SET err_msg = CONCAT('Client class with id ', class_id, ' does not exist.');
+        SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = err_msg;
+    END IF;
+    -- Check position of the dependency.
+    SET dependency_index = (
+        SELECT o.order_index FROM dhcp4_client_class AS c
+            INNER JOIN dhcp4_client_class_order AS o ON c.id = o.class_id
+        WHERE c.id = dependency_id
+    );
+    IF dependency_index IS NULL THEN
+        SET err_msg = CONCAT('Client class with id ', dependency_id, ' does not exist.');
+        SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = err_msg;
+    END IF;
+    -- The dependency must not be later than our class.
+    IF dependency_index > class_index THEN
+        SET err_msg = CONCAT('Client class with id ', class_id, ' must not depend on class defined later with id ', dependency_id);
+        SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = err_msg;
+    END IF;
+
+    -- Check if all servers associated with the new class have dependent
+    -- classes configured. This catches the cases that class A belongs to
+    -- server1 and depends on class B which belongs only to server 2.
+    -- It is fine if the class B belongs to all servers in this case.
+    -- Make a SELECT on the dhcp4_client_class_server table to gather
+    -- all servers to which the class belongs. LEFT JOIN it with the
+    -- same table, selecting all records matching the dependency class
+    -- and the servers to which the new class belongs. If there are
+    -- any NULL records joined it implies that some dependencies are
+    -- not met (didn't find a dependency for at least one server).
+    IF EXISTS(
+        SELECT 1 FROM dhcp4_client_class_server AS t1
+            LEFT JOIN dhcp4_client_class_server AS t2
+                ON t2.class_id = dependency_id AND (t2.server_id = 1 OR t2.server_id = t1.server_id)
+        WHERE t1.class_id = class_id AND t2.server_id IS NULL
+        LIMIT 1
+    ) THEN
+        SET err_msg = CONCAT('Unmet dependencies for client class with id ', class_id);
+        SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = err_msg;
+    END IF;
+END $$
+DELIMITER ;
+
+-- -----------------------------------------------------------------------
+-- Trigger verifying if class dependency is met. It includes checking
+-- if referenced classes exist, are associated with the same server
+-- or all servers, and are defined before the class specified with
+-- class_id.
+-- -----------------------------------------------------------------------
+DELIMITER $$
+CREATE TRIGGER dhcp4_client_class_check_dependency_BINS BEFORE INSERT ON dhcp4_client_class_dependency FOR EACH ROW
+BEGIN
+    CALL checkDHCPv4ClientClassDependency(NEW.class_id, NEW.dependency_id);
+END $$
+DELIMITER ;
+
+DROP TRIGGER IF EXISTS dhcp4_client_class_dependency_AINS;
+DROP PROCEDURE IF EXISTS updateDHCPv4ClientClassKnownDependency;
+
+-- -----------------------------------------------------------------------
+-- Stored procedure setting client class indirect dependency on KNOWN or
+-- UNKNOWN built-in classes by checking this flag for the client classes
+-- on which it depends.
+--
+-- Parameters:
+-- - client_class_id id of the client class which dependency is set,
+-- - dependency_id id of the client class on which the given class depends.
+-- -----------------------------------------------------------------------
+DELIMITER $$
+CREATE PROCEDURE updateDHCPv4ClientClassKnownDependency(IN client_class_id BIGINT UNSIGNED,
+                                                        IN dependency_id BIGINT UNSIGNED)
+BEGIN
+    DECLARE dependency TINYINT;
+    -- Check if the dependency class references KNOWN/UNKNOWN.
+    SET dependency = (
+        SELECT depend_on_known_directly FROM dhcp4_client_class
+        WHERE id = dependency_id
+    );
+    -- If it doesn't, check if the dependency references KNOWN/UNKNOWN
+    -- indirectly (via other classes).
+    IF dependency = 0 THEN
+        SET dependency = (
+            SELECT depend_on_known_indirectly FROM dhcp4_client_class_order
+            WHERE class_id = dependency_id
+        );
+    END IF;
+    IF dependency <> 0 THEN
+        UPDATE dhcp4_client_class_order
+            SET depend_on_known_indirectly = 1
+        WHERE class_id = client_class_id;
+    END IF;
+END $$
+DELIMITER ;
+
+-- -----------------------------------------------------------------------
+-- Trigger setting client class indirect dependency on KNOWN or UNKNOWN
+-- built-in classes by checking this flag for the client classes on which
+-- it depends.
+-- -----------------------------------------------------------------------
+DELIMITER $$
+CREATE TRIGGER dhcp4_client_class_dependency_AINS AFTER INSERT ON dhcp4_client_class_dependency FOR EACH ROW
+BEGIN
+    CALL updateDHCPv4ClientClassKnownDependency(NEW.class_id, NEW.dependency_id);
+END $$
+DELIMITER ;
+
+DROP PROCEDURE IF EXISTS checkDHCPv4ClientClassKnownDependencyChange;
+
+-- -----------------------------------------------------------------------
+-- Stored procedure to be executed before committing a transaction
+-- updating a DHCPv4 client class. It verifies if the class dependency on
+-- KNOWN or UNKNOWN built-in classes has changed as a result of the
+-- update. It signals an error if it has changed and there is at least
+-- one class depending on this class.
+-- -----------------------------------------------------------------------
+DELIMITER $$
+CREATE PROCEDURE checkDHCPv4ClientClassKnownDependencyChange()
+BEGIN
+    DECLARE depended TINYINT DEFAULT 0;
+    DECLARE depends TINYINT DEFAULT 0;
+
+    -- Session variables are set upon a client class update.
+    IF @client_class_id IS NOT NULL THEN
+        -- Check if any of the classes depend on this class. If not,
+        -- it is ok to change the dependency on KNOWN/UNKNOWN.
+        IF EXISTS(
+            SELECT 1 FROM dhcp4_client_class_dependency
+            WHERE dependency_id = @client_class_id LIMIT 1
+        ) THEN
+            -- Using the session variables, determine whether the client class
+            -- depended on KNOWN/UNKNOWN before the update.
+            IF @depend_on_known_directly <> 0 OR @depend_on_known_indirectly <> 0 THEN
+                SET depended = 1;
+            END IF;
+            -- Check if the client class depends on KNOWN/UNKNOWN after the update.
+            SET depends = (
+                SELECT depend_on_known_directly FROM dhcp4_client_class
+                WHERE id = @client_class_id
+            );
+            -- If it doesn't depend directly, check indirect dependencies.
+            IF depends = 0 THEN
+                SET depends = (
+                    SELECT depend_on_known_indirectly FROM dhcp4_client_class_order
+                    WHERE class_id = @client_class_id
+                );
+            END IF;
+            -- The resulting dependency on KNOWN/UNKNOWN must not change.
+            IF depended <> depends THEN
+                SIGNAL SQLSTATE '45000'
+                    SET MESSAGE_TEXT = 'Class dependency on KNOWN/UNKNOWN built-in classes must not change.';
+            END IF;
+        END IF;
+    END IF;
+END $$
+DELIMITER ;
+
+-- -----------------------------------------------------------------------
+-- Create table matching DHCPv4 classes with the servers.
+-- -----------------------------------------------------------------------
+CREATE TABLE IF NOT EXISTS dhcp4_client_class_server (
+    class_id bigint unsigned NOT NULL,
+    server_id bigint unsigned NOT NULL,
+    modification_ts timestamp NULL DEFAULT NULL,
+    PRIMARY KEY (class_id,server_id),
+    KEY fk_dhcp4_client_class_server_id (server_id),
+    CONSTRAINT fk_dhcp4_client_class_class_id FOREIGN KEY (class_id)
+        REFERENCES dhcp4_client_class (id)
+        ON DELETE CASCADE,
+    CONSTRAINT fk_dhcp4_client_class_server_id FOREIGN KEY (server_id)
+        REFERENCES dhcp4_server (id)
+) ENGINE=InnoDB;
+
+-- -----------------------------------------------------------------------
+-- Extend the table holding DHCPv4 option definitions with a nullable
+-- column matching option defintions with client classes.
+-- -----------------------------------------------------------------------
+ALTER TABLE dhcp4_option_def
+    ADD COLUMN class_id BIGINT UNSIGNED NULL DEFAULT NULL;
+
+ALTER TABLE dhcp4_option_def
+  ADD CONSTRAINT fk_dhcp4_option_def_client_class_id
+    FOREIGN KEY (class_id)
+    REFERENCES dhcp4_client_class (id)
+    ON DELETE CASCADE
+    ON UPDATE CASCADE;
+
+-- -----------------------------------------------------------------------
+-- Create a table holding the DHCPv6 client classes. Most table
+-- columns map directly to respective client class properties in
+-- Kea configuration. The depend_on_known_directly column is
+-- explicitly set in an insert or update statement to indicate
+-- if the client class directly depends on KNOWN or UNKNOWN
+-- built-in classes. A caller should determine it by evaluating
+-- a test expression before inserting or updating the client
+-- class in the database. The nullable follow_class_name column
+-- can be used for positioning the inserted or updated client
+-- class within the class hierarchy. Set this column value to
+-- an existing class name, after which this class should be
+-- placed in the class hierarchy. See dhcp6_client_class_order
+-- description for the details of how classes are ordered.
+-- -----------------------------------------------------------------------
+CREATE TABLE IF NOT EXISTS dhcp6_client_class (
+    id BIGINT UNSIGNED NOT NULL AUTO_INCREMENT,
+    name VARCHAR(128) NOT NULL,
+    test TEXT,
+    only_if_required TINYINT NOT NULL DEFAULT '0',
+    valid_lifetime INT DEFAULT NULL,
+    min_valid_lifetime INT DEFAULT NULL,
+    max_valid_lifetime INT DEFAULT NULL,
+    depend_on_known_directly TINYINT NOT NULL DEFAULT '0',
+    follow_class_name VARCHAR(128) DEFAULT NULL,
+    modification_ts TIMESTAMP NOT NULL,
+    PRIMARY KEY (id),
+    UNIQUE KEY id_UNIQUE (id),
+    UNIQUE KEY name_UNIQUE (name),
+    KEY key_dhcp6_client_class_modification_ts (modification_ts)
+) ENGINE=InnoDB;
+
+-- -----------------------------------------------------------------------
+-- Create a table for ordering client classes and holding information
+-- about indirect dependencies on KNOWN/UKNOWN built-in client classes.
+-- Each class in the dhcp6_client_class table has a corresponding row
+-- in the dhcp6_client_class_order table. A caller should not modify
+-- the contents of this table. Its entries are automatically created
+-- upon inserting or updating client classes in the dhcp6_client_classes
+-- using triggers. The order_index designates the position of the client
+-- class within the class hierarchy. If the follow_class_name value of
+-- the dhcp6_client_class table is set to NULL, the client class is
+-- appended at the end of the hierarchy. The assigned order_index
+-- value for that class is set to a maximum current value + 1.
+-- If the follow_client_class specifies a name of an existing class,
+-- the generated order_index is set to an id of that class + 1, and
+-- the order_index values of the later classes are incremented by 1.
+-- The depend_on_known_indirectly column holds a boolean value indicating
+-- whether the given class depends on KNOWN/UKNOWN built-in classes
+-- via other classes, i.e. it depends on classes that directly or
+-- indirectly depend on these built-ins. This value is auto-generated
+-- by a trigger on the dhcp6_client_class_dependency table.
+-- -----------------------------------------------------------------------
+CREATE TABLE IF NOT EXISTS dhcp6_client_class_order (
+    class_id BIGINT UNSIGNED NOT NULL,
+    order_index BIGINT UNSIGNED NOT NULL,
+    depend_on_known_indirectly TINYINT NOT NULL DEFAULT '0',
+    PRIMARY KEY (class_id),
+    KEY key_dhcp6_client_class_order_index (order_index),
+    CONSTRAINT fk_dhcp6_client_class_order_class_id FOREIGN KEY (class_id)
+        REFERENCES dhcp6_client_class (id) ON DELETE CASCADE
+) ENGINE=InnoDB;
+
+DROP TRIGGER IF EXISTS dhcp6_client_class_AINS;
+DROP TRIGGER IF EXISTS dhcp6_client_class_AUPD;
+DROP TRIGGER IF EXISTS dhcp6_client_class_ADEL;
+DROP PROCEDURE IF EXISTS setClientClass6Order;
+
+-- -----------------------------------------------------------------------
+-- Stored procedure positioning an inserted or updated client class
+-- within the class hierarchy, depending on the value of the
+-- follow_class_name parameter.
+--
+-- Parameters:
+-- - id id of the positioned class,
+-- - follow_class_name name of the class after which this class should be
+--   positioned within the class hierarchy.
+-- - old_follow_class_name name of the previous class after which this
+--   class was positioned within the class hierarchy.
+-- -----------------------------------------------------------------------
+DELIMITER $$
+CREATE PROCEDURE setClientClass6Order(IN id BIGINT UNSIGNED,
+                                      IN follow_class_name VARCHAR(128),
+                                      IN old_follow_class_name VARCHAR(128))
+proc_label:BEGIN
+    -- This variable will be optionally set if the follow_class_name
+    -- column value is specified.
+    DECLARE follow_class_index BIGINT UNSIGNED;
+    DECLARE msg TEXT;
+
+    -- Remember currently used value of depend_on_known_indirectly.
+    SET @depend_on_known_indirectly = (
+        SELECT depend_on_known_indirectly FROM dhcp6_client_class_order WHERE id = class_id
+    );
+
+    -- Bail if the class is updated without re-positioning.
+    IF(
+        @depend_on_known_indirectly IS NOT NULL AND
+        ((follow_class_name IS NULL AND old_follow_class_name IS NULL) OR
+         (follow_class_name = old_follow_class_name))
+    ) THEN
+        -- The depend_on_known_indirectly is set to 0 because this procedure is invoked
+        -- whenever the dhcp6_client_class record is updated. Such update may include
+        -- test expression changes impacting the dependency on KNOWN/UNKNOWN classes.
+        -- This value will be later adjusted when dependencies are inserted.
+        UPDATE dhcp6_client_class_order SET depend_on_known_indirectly = 0
+            WHERE class_id = id;
+        LEAVE proc_label;
+    END IF;
+
+    IF follow_class_name IS NOT NULL THEN
+        -- Get the position of the class after which the new class should be added.
+        SET follow_class_index = (
+            SELECT o.order_index FROM dhcp6_client_class AS c
+                INNER JOIN dhcp6_client_class_order AS o
+                    ON c.id = o.class_id
+            WHERE c.name = follow_class_name
+        );
+        IF follow_class_index IS NULL THEN
+            -- The class with a name specified with follow_class_name does
+            -- not exist.
+            SET msg = CONCAT('Class ', follow_class_name, ' does not exist.');
+            SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = msg;
+        END IF;
+        -- We need to place the new class at the position of follow_class_index + 1.
+        -- There may be a class at this position already.
+        IF EXISTS(SELECT * FROM dhcp6_client_class_order WHERE order_index = follow_class_index + 1) THEN
+            -- There is a class at this position already. Let's move all classes
+            -- starting from this position by one to create a spot for the new
+            -- class.
+            UPDATE dhcp6_client_class_order
+                SET order_index = order_index + 1
+            WHERE order_index >= follow_class_index + 1
+            ORDER BY order_index DESC;
+        END IF;
+    ELSE
+        -- A caller did not specify the follow_class_name value. Let's append the
+        -- new class at the end of the hierarchy.
+        SET follow_class_index = (SELECT MAX(order_index) FROM dhcp6_client_class_order);
+        IF follow_class_index IS NULL THEN
+            -- Apparently, there are no classes. Let's start from 0.
+            SET follow_class_index = 0;
+        END IF;
+    END IF;
+
+    -- Check if moving the class doesn't break dependent classes.
+    IF EXISTS(
+        SELECT 1 FROM dhcp6_client_class_dependency AS d
+            INNER JOIN dhcp6_client_class_order AS o
+                ON d.class_id = o.class_id
+            WHERE d.dependency_id = id AND o.order_index < follow_class_index + 1
+        LIMIT 1
+    ) THEN
+        SET msg = CONCAT('Unable to move class with id ', id, ' because it would break its dependencies');
+        SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = msg;
+    END IF;
+
+    -- The depend_on_known_indirectly is set to 0 because this procedure is invoked
+    -- whenever the dhcp6_client_class record is updated. Such update may include
+    -- test expression changes impacting the dependency on KNOWN/UNKNOWN classes.
+    -- This value will be later adjusted when dependencies are inserted.
+    REPLACE INTO dhcp6_client_class_order(class_id, order_index, depend_on_known_indirectly)
+        VALUES (id, follow_class_index + 1, 0);
+END $$
+DELIMITER ;
+
+-- -----------------------------------------------------------------------
+-- Trigger to position an inserted class within the class hierarchy
+-- and create audit.
+-- -----------------------------------------------------------------------
+DELIMITER $$
+CREATE TRIGGER dhcp6_client_class_AINS AFTER INSERT ON dhcp6_client_class FOR EACH ROW BEGIN
+    CALL setClientClass6Order(NEW.id, NEW.follow_class_name, NULL);
+    CALL createAuditEntryDHCP6('dhcp6_client_class', NEW.id, "create");
+END $$
+DELIMITER ;
+
+-- -----------------------------------------------------------------------
+-- Trigger to position an updated class within the class hierarchy,
+-- create audit and remember the direct dependency on the
+-- KNOWN/UNKNOWN built-in classes before the class update.
+-- When updating a client class, it is very important to ensure that
+-- its dependency on KNOWN or UNKNOWN built-in client classes is not
+-- changed. It is because there may be other classes that depend on
+-- these built-ins via this class. Changing the dependency would break
+-- the chain of dependencies for other classes. Here, we store the
+-- information about the dependency in the session variables. Their
+-- values will be compared with the new dependencies after an update.
+-- If they change, an error will be signaled.
+-- -----------------------------------------------------------------------
+DELIMITER $$
+CREATE TRIGGER dhcp6_client_class_AUPD AFTER UPDATE ON dhcp6_client_class FOR EACH ROW BEGIN
+    SET @depend_on_known_directly = OLD.depend_on_known_directly;
+    SET @client_class_id = NEW.id;
+    CALL setClientClass6Order(NEW.id, NEW.follow_class_name, OLD.follow_class_name);
+    CALL createAuditEntryDHCP6('dhcp6_client_class', NEW.id, "update");
+END $$
+DELIMITER ;
+
+-- -----------------------------------------------------------------------
+-- Trigger to create dhcp6_client_class audit.
+-- -----------------------------------------------------------------------
+DELIMITER $$
+CREATE TRIGGER dhcp6_client_class_ADEL AFTER DELETE ON dhcp6_client_class FOR EACH ROW BEGIN
+    CALL createAuditEntryDHCP6('dhcp6_client_class', OLD.id, "delete");
+END $$
+DELIMITER ;
+
+-- -----------------------------------------------------------------------
+-- Create a table associating client classes stored in the
+-- dhcp6_client_class table with their dependencies. There is
+-- an M:N relationship between these tables. Each class may have
+-- many dependencies (created using member operator in test expression),
+-- and each class may be a dependency for many other classes. A caller
+-- is responsible for inserting dependencies for a class after inserting
+-- or updating it in the dhcp6_client_class table. A caller should
+-- delete all existing dependencies for an updated client class, evaluate
+-- test expression to discover new dependencies (in case test expression
+-- has changed), and insert new dependencies to this table.
+-- -----------------------------------------------------------------------
+CREATE TABLE IF NOT EXISTS dhcp6_client_class_dependency (
+    class_id BIGINT UNSIGNED NOT NULL,
+    dependency_id BIGINT UNSIGNED NOT NULL,
+    PRIMARY KEY (class_id,dependency_id),
+    KEY dhcp6_client_class_dependency_id_idx (dependency_id),
+    CONSTRAINT dhcp6_client_class_class_id FOREIGN KEY (class_id)
+        REFERENCES dhcp6_client_class (id) ON DELETE CASCADE,
+    CONSTRAINT dhcp6_client_class_dependency_id FOREIGN KEY (dependency_id)
+        REFERENCES dhcp6_client_class (id)
+) ENGINE=InnoDB;
+
+DROP TRIGGER IF EXISTS dhcp6_client_class_dependency_BINS;
+DROP PROCEDURE IF EXISTS checkDHCPv6ClientClassDependency;
+
+-- -----------------------------------------------------------------------
+-- Stored procedure verifying if class dependency is met. It includes
+-- checking if referenced classes exist, are associated with the same
+-- server or all servers, and are defined before the class specified with
+-- class_id.
+--
+-- Parameters:
+-- - class_id id client class,
+-- - dependency_id id of the dependency.
+-- -----------------------------------------------------------------------
+DELIMITER $$
+CREATE PROCEDURE checkDHCPv6ClientClassDependency(IN class_id BIGINT UNSIGNED,
+                                                  IN dependency_id BIGINT UNSIGNED)
+BEGIN
+    DECLARE class_index BIGINT UNSIGNED;
+    DECLARE dependency_index BIGINT UNSIGNED;
+    DECLARE err_msg TEXT;
+
+    -- We could check the same with a constraint but later in this
+    -- trigger we use this value to verify if the dependencies are
+    -- met.
+    IF class_id IS NULL THEN
+        SIGNAL SQLSTATE '45000'
+            SET MESSAGE_TEXT = 'Client class id must not be NULL.';
+    END IF;
+    IF dependency_id IS NULL THEN
+        SIGNAL SQLSTATE '45000'
+            SET MESSAGE_TEXT = 'Class dependency id must not be NULL.';
+    END IF;
+    -- Dependencies on self make no sense.
+    IF class_id = dependency_id THEN
+        SIGNAL SQLSTATE '45000'
+            SET MESSAGE_TEXT = 'Client class must not have dependency on self.';
+    END IF;
+    -- Check position of our class in the hierarchy.
+    SET class_index = (
+        SELECT o.order_index FROM dhcp6_client_class AS c
+            INNER JOIN dhcp6_client_class_order AS o
+                ON c.id = o.class_id
+        WHERE c.id = class_id);
+    IF class_index IS NULL THEN
+        SET err_msg = CONCAT('Client class with id ', class_id, ' does not exist.');
+        SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = err_msg;
+    END IF;
+    -- Check position of the dependency.
+    SET dependency_index = (
+        SELECT o.order_index FROM dhcp6_client_class AS c
+            INNER JOIN dhcp6_client_class_order AS o ON c.id = o.class_id
+        WHERE c.id = dependency_id
+    );
+    IF dependency_index IS NULL THEN
+        SET err_msg = CONCAT('Client class with id ', dependency_id, ' does not exist.');
+        SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = err_msg;
+    END IF;
+    -- The dependency must not be later than our class.
+    IF dependency_index > class_index THEN
+        SET err_msg = CONCAT('Client class with id ', class_id, ' must not depend on class defined later with id ', dependency_id);
+        SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = err_msg;
+    END IF;
+
+    -- Check if all servers associated with the new class have dependent
+    -- classes configured. This catches the cases that class A belongs to
+    -- server1 and depends on class B which belongs only to server 2.
+    -- It is fine if the class B belongs to all servers in this case.
+    -- Make a SELECT on the dhcp6_client_class_server table to gather
+    -- all servers to which the class belongs. LEFT JOIN it with the
+    -- same table, selecting all records matching the dependency class
+    -- and the servers to which the new class belongs. If there are
+    -- any NULL records joined it implies that some dependencies are
+    -- not met (didn't find a dependency for at least one server).
+    IF EXISTS(
+        SELECT 1 FROM dhcp6_client_class_server AS t1
+            LEFT JOIN dhcp6_client_class_server AS t2
+                ON t2.class_id = dependency_id AND (t2.server_id = 1 OR t2.server_id = t1.server_id)
+        WHERE t1.class_id = class_id AND t2.server_id IS NULL
+        LIMIT 1
+    ) THEN
+        SET err_msg = CONCAT('Unmet dependencies for client class with id ', class_id);
+        SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = err_msg;
+    END IF;
+END $$
+DELIMITER ;
+
+-- -----------------------------------------------------------------------
+-- Trigger verifying if class dependency is met. It includes checking
+-- if referenced classes exist, are associated with the same server
+-- or all servers, and are defined before the class specified with
+-- class_id.
+-- -----------------------------------------------------------------------
+DELIMITER $$
+CREATE TRIGGER dhcp6_client_class_check_dependency_BINS BEFORE INSERT ON dhcp6_client_class_dependency FOR EACH ROW
+BEGIN
+    CALL checkDHCPv6ClientClassDependency(NEW.class_id, NEW.dependency_id);
+END $$
+DELIMITER ;
+
+DROP TRIGGER IF EXISTS dhcp6_client_class_dependency_AINS;
+DROP PROCEDURE IF EXISTS updateDHCPv6ClientClassKnownDependency;
+
+-- -----------------------------------------------------------------------
+-- Stored procedure setting client class indirect dependency on KNOWN or
+-- UNKNOWN built-in classes by checking this flag for the client classes
+-- on which it depends.
+--
+-- Parameters:
+-- - client_class_id id of the client class which dependency is set,
+-- - dependency_id id of the client class on which the given class depends.
+-- -----------------------------------------------------------------------
+DELIMITER $$
+CREATE PROCEDURE updateDHCPv6ClientClassKnownDependency(IN client_class_id BIGINT UNSIGNED,
+                                                        IN dependency_id BIGINT UNSIGNED)
+BEGIN
+    DECLARE dependency TINYINT;
+    -- Check if the dependency class references KNOWN/UNKNOWN.
+    SET dependency = (
+        SELECT depend_on_known_directly FROM dhcp6_client_class
+        WHERE id = dependency_id
+    );
+    -- If it doesn't, check if the dependency references KNOWN/UNKNOWN
+    -- indirectly (via other classes).
+    IF dependency = 0 THEN
+        SET dependency = (
+            SELECT depend_on_known_indirectly FROM dhcp6_client_class_order
+            WHERE class_id = dependency_id
+        );
+    END IF;
+    IF dependency <> 0 THEN
+        UPDATE dhcp6_client_class_order
+            SET depend_on_known_indirectly = 1
+        WHERE class_id = client_class_id;
+    END IF;
+END $$
+DELIMITER ;
+
+-- -----------------------------------------------------------------------
+-- Trigger setting client class indirect dependency on KNOWN or UNKNOWN
+-- built-in classes by checking this flag for the client classes on which
+-- it depends.
+-- -----------------------------------------------------------------------
+DELIMITER $$
+CREATE TRIGGER dhcp6_client_class_dependency_AINS AFTER INSERT ON dhcp6_client_class_dependency FOR EACH ROW
+BEGIN
+    CALL updateDHCPv6ClientClassKnownDependency(NEW.class_id, NEW.dependency_id);
+END $$
+DELIMITER ;
+
+DROP PROCEDURE IF EXISTS checkDHCPv6ClientClassKnownDependencyChange;
+
+-- -----------------------------------------------------------------------
+-- Stored procedure to be executed before committing a transaction
+-- updating a DHCPv6 client class. It verifies if the class dependency on
+-- KNOWN or UNKNOWN built-in classes has changed as a result of the
+-- update. It signals an error if it has changed and there is at least
+-- one class depending on this class.
+-- -----------------------------------------------------------------------
+DELIMITER $$
+CREATE PROCEDURE checkDHCPv6ClientClassKnownDependencyChange()
+BEGIN
+    DECLARE depended TINYINT DEFAULT 0;
+    DECLARE depends TINYINT DEFAULT 0;
+
+    -- Session variables are set upon a client class update.
+    IF @client_class_id IS NOT NULL THEN
+        -- Check if any of the classes depend on this class. If not,
+        -- it is ok to change the dependency on KNOWN/UNKNOWN.
+        IF EXISTS(
+            SELECT 1 FROM dhcp6_client_class_dependency
+            WHERE dependency_id = @client_class_id LIMIT 1
+        ) THEN
+            -- Using the session variables, determine whether the client class
+            -- depended on KNOWN/UNKNOWN before the update.
+            IF @depend_on_known_directly <> 0 OR @depend_on_known_indirectly <> 0 THEN
+                SET depended = 1;
+            END IF;
+            -- Check if the client class depends on KNOWN/UNKNOWN after the update.
+            SET depends = (
+                SELECT depend_on_known_directly FROM dhcp6_client_class
+                WHERE id = @client_class_id
+            );
+            -- If it doesn't depend directly, check indirect dependencies.
+            IF depends = 0 THEN
+                SET depends = (
+                    SELECT depend_on_known_indirectly FROM dhcp6_client_class_order
+                    WHERE class_id = @client_class_id
+                );
+            END IF;
+            -- The resulting dependency on KNOWN/UNKNOWN must not change.
+            IF depended <> depends THEN
+                SIGNAL SQLSTATE '45000'
+                    SET MESSAGE_TEXT = 'Class dependency on KNOWN/UNKNOWN built-in classes must not change.';
+            END IF;
+        END IF;
+    END IF;
+END $$
+DELIMITER ;
+
+-- -----------------------------------------------------------------------
+-- Create table matching DHCPv6 classes with the servers.
+-- -----------------------------------------------------------------------
+CREATE TABLE IF NOT EXISTS dhcp6_client_class_server (
+    class_id bigint unsigned NOT NULL,
+    server_id bigint unsigned NOT NULL,
+    modification_ts timestamp NULL DEFAULT NULL,
+    PRIMARY KEY (class_id,server_id),
+    KEY fk_dhcp6_client_class_server_id (server_id),
+    CONSTRAINT fk_dhcp6_client_class_class_id FOREIGN KEY (class_id)
+        REFERENCES dhcp6_client_class (id)
+        ON DELETE CASCADE,
+    CONSTRAINT fk_dhcp6_client_class_server_id FOREIGN KEY (server_id)
+        REFERENCES dhcp6_server (id)
+) ENGINE=InnoDB;
+
+-- -----------------------------------------------------------------------
+-- Extend the table holding DHCPv6 option definitions with a nullable
+-- column matching option defintions with client classes.
+-- -----------------------------------------------------------------------
+ALTER TABLE dhcp6_option_def
+    ADD COLUMN class_id BIGINT UNSIGNED NULL DEFAULT NULL;
+
+ALTER TABLE dhcp6_option_def
+  ADD CONSTRAINT fk_dhcp6_option_def_client_class_id
+    FOREIGN KEY (class_id)
+    REFERENCES dhcp6_client_class (id)
+    ON DELETE CASCADE
+    ON UPDATE CASCADE;
+
+# Update the schema version number.
+UPDATE schema_version
+    SET version = '10', minor = '0';
+
+# This line concludes the schema upgrade to version 10.0.
+
+# This line starts the schema upgrade to version 11.0.
+
+# Reverse index order to improve reclamation query performance
+# Add a constraint that any state value added to the lease4 must
+# map to a value in the lease_state table.  Note we have to drop
+# the foreign keys first, then add them back.
+ALTER TABLE lease4 DROP FOREIGN KEY fk_lease4_state;
+DROP INDEX lease4_by_state_expire ON lease4;
+CREATE INDEX lease4_by_expire_state ON lease4 (expire ASC, state ASC);
+ALTER TABLE lease4
+    ADD CONSTRAINT fk_lease4_state FOREIGN KEY (state)
+    REFERENCES lease_state (state);
+
+ALTER TABLE lease6 DROP FOREIGN KEY fk_lease6_state;
+CREATE INDEX lease6_by_expire_state ON lease6 (expire ASC, state ASC);
+DROP INDEX lease6_by_state_expire ON lease6;
+ALTER TABLE lease6
+    ADD CONSTRAINT fk_lease6_state FOREIGN KEY (state)
+    REFERENCES lease_state (state);
+
+# Added preferred lifetime columns v6 client classes.
+ALTER TABLE dhcp6_client_class
+    ADD COLUMN preferred_lifetime INT(10) DEFAULT NULL,
+    ADD COLUMN min_preferred_lifetime INT(10) DEFAULT NULL,
+    ADD COLUMN max_preferred_lifetime INT(10) DEFAULT NULL;
+
+# Update the schema version number.
+UPDATE schema_version
+    SET version = '11', minor = '0';
+
+# This line concludes the schema upgrade to version 11.0.
+
+# This line starts the schema upgrade to version 12.0.
+
+# Ensure that dhcp_client_class is NULL when an option does not
+# belong to any client class. Later, we will add foreign keys for
+# the dhcp_client_class columns, and it requires that the columns
+# are NULL when there are no corresponding client classes.
+SET @disable_audit = 1;
+UPDATE dhcp4_options SET dhcp_client_class = NULL
+    WHERE scope_id <> 2;
+UPDATE dhcp6_options SET dhcp_client_class = NULL
+    WHERE scope_id <> 2;
+SET @disable_audit = 0;
+
+# Add a foreign keys referencing a client classes. If an option is
+# associated with a client class, the option will be deleted
+# along with the deleted client class.
+ALTER TABLE dhcp4_options
+    ADD CONSTRAINT fk_dhcp4_options_client_class
+        FOREIGN KEY (dhcp_client_class)
+    REFERENCES dhcp4_client_class (name)
+    ON DELETE CASCADE ON UPDATE CASCADE;
+
+ALTER TABLE dhcp6_options
+    ADD CONSTRAINT fk_dhcp6_options_client_class
+        FOREIGN KEY (dhcp_client_class)
+    REFERENCES dhcp6_client_class (name)
+    ON DELETE CASCADE ON UPDATE CASCADE;
+
+# Update the schema version number.
+UPDATE schema_version
+    SET version = '12', minor = '0';
+
+-- This line concludes the schema upgrade to version 12.0.
+
+-- This line starts the schema upgrade to version 13.0.
+
+-- Create a function that separates a contiguous hexadecimal string
+-- into groups of two hexadecimals separated by colons.
+DROP FUNCTION IF EXISTS colonSeparatedHex;
+DELIMITER $$
+CREATE FUNCTION colonSeparatedHex(hex VARCHAR(64))
+RETURNS VARCHAR(64)
+DETERMINISTIC
+BEGIN
+    -- Declarations
+    DECLARE i INT;
+    DECLARE length INT;
+    DECLARE output VARCHAR(64);
+
+    -- Initializations
+    SET i = 3;
+    SET length = LENGTH(hex);
+
+    -- Add a leading zero if the first octet has a single hexadecimal character.
+    IF MOD(length, 2) = 1 THEN
+        SET hex = CONCAT('0', hex);
+        SET length = length + 1;
+    END IF;
+
+    -- Start with the first octet.
+    SET output = SUBSTR(hex, 1, 2);
+
+    -- Add one octet at a time and a leading colon with each.
+    label: WHILE i < length DO
+        SET output = CONCAT(output, ':', SUBSTR(hex, i, 2));
+        SET i = i + 2;
+    END WHILE label;
+
+    -- Memfile uses lowercase hexadecimals.
+    SET output = LOWER(output);
+
+    RETURN output;
+END $$
+DELIMITER ;
+
+-- Modify the procedure to output a memfile-ready CSV file.
+DROP PROCEDURE IF EXISTS lease4DumpData;
+DELIMITER $$
+CREATE PROCEDURE lease4DumpData()
+BEGIN
+    SELECT
+        INET_NTOA(address),
+        IFNULL(colonSeparatedHex(HEX(hwaddr)), ''),
+        IFNULL(colonSeparatedHex(HEX(client_id)), ''),
+        valid_lifetime,
+        UNIX_TIMESTAMP(expire),
+        subnet_id,
+        fqdn_fwd,
+        fqdn_rev,
+        REPLACE(hostname, ',', '&#x2c'),
+        state,
+        REPLACE(IFNULL(user_context, ''), ',', '&#x2c')
+    FROM lease4
+    ORDER BY address;
+END $$
+DELIMITER ;
+
+-- hwtype and hwaddr_source need to be last to match memfile format.
+DROP PROCEDURE IF EXISTS lease6DumpHeader;
+DELIMITER $$
+CREATE PROCEDURE lease6DumpHeader()
+BEGIN
+    SELECT 'address,duid,valid_lifetime,expire,subnet_id,pref_lifetime,lease_type,iaid,prefix_len,fqdn_fwd,fqdn_rev,hostname,hwaddr,state,user_context,hwtype,hwaddr_source';
+END $$
+DELIMITER ;
+
+-- Modify the procedure to output a memfile-ready CSV file.
+DROP PROCEDURE IF EXISTS lease6DumpData;
+DELIMITER $$
+CREATE PROCEDURE lease6DumpData()
+BEGIN
+    SELECT
+        address,
+        IFNULL(colonSeparatedHex(HEX(duid)), ''),
+        valid_lifetime,
+        UNIX_TIMESTAMP(expire),
+        subnet_id,
+        pref_lifetime,
+        lease_type,
+        iaid,
+        prefix_len,
+        fqdn_fwd,
+        fqdn_rev,
+        REPLACE(hostname, ',', '&#x2c'),
+        IFNULL(colonSeparatedHex(HEX(hwaddr)), ''),
+        state,
+        REPLACE(IFNULL(user_context, ''), ',', '&#x2c'),
+        hwtype,
+        hwaddr_source
+    FROM lease6
+    ORDER BY address;
+END $$
+DELIMITER ;
+
+-- Create a procedure that inserts a v4 lease from memfile data.
+DELIMITER $$
+CREATE PROCEDURE lease4Upload(
+    IN address VARCHAR(15),
+    IN hwaddr VARCHAR(20),
+    IN client_id VARCHAR(128),
+    IN valid_lifetime INT UNSIGNED,
+    IN expire BIGINT UNSIGNED,
+    IN subnet_id INT UNSIGNED,
+    IN fqdn_fwd TINYINT,
+    IN fqdn_rev TINYINT,
+    IN hostname VARCHAR(255),
+    IN state INT UNSIGNED,
+    IN user_context TEXT
+)
+BEGIN
+    INSERT INTO lease4 (
+        address,
+        hwaddr,
+        client_id,
+        valid_lifetime,
+        expire,
+        subnet_id,
+        fqdn_fwd,
+        fqdn_rev,
+        hostname,
+        state,
+        user_context
+    ) VALUES (
+        INET_ATON(address),
+        UNHEX(REPLACE(hwaddr, ':', '')),
+        UNHEX(REPLACE(client_id, ':', '')),
+        valid_lifetime,
+        FROM_UNIXTIME(expire),
+        subnet_id,
+        fqdn_fwd,
+        fqdn_rev,
+        REPLACE(hostname, '&#x2c', ','),
+        state,
+        REPLACE(user_context, '&#x2c', ',')
+    );
+END $$
+DELIMITER ;
+
+-- Create a procedure that inserts a v6 lease from memfile data.
+DELIMITER $$
+CREATE PROCEDURE lease6Upload(
+    IN address VARCHAR(39),
+    IN duid VARCHAR(128),
+    IN valid_lifetime INT UNSIGNED,
+    IN expire BIGINT UNSIGNED,
+    IN subnet_id INT UNSIGNED,
+    IN pref_lifetime INT UNSIGNED,
+    IN lease_type TINYINT,
+    IN iaid INT UNSIGNED,
+    IN prefix_len TINYINT UNSIGNED,
+    IN fqdn_fwd TINYINT,
+    IN fqdn_rev TINYINT,
+    IN hostname VARCHAR(255),
+    IN hwaddr VARCHAR(64),
+    IN state INT UNSIGNED,
+    IN user_context TEXT,
+    IN hwtype SMALLINT,
+    IN hwaddr_source INT UNSIGNED
+)
+BEGIN
+    INSERT INTO lease6 (
+        address,
+        duid,
+        valid_lifetime,
+        expire,
+        subnet_id,
+        pref_lifetime,
+        lease_type,
+        iaid,
+        prefix_len,
+        fqdn_fwd,
+        fqdn_rev,
+        hostname,
+        hwaddr,
+        state,
+        user_context,
+        hwtype,
+        hwaddr_source
+    ) VALUES (
+        address,
+        UNHEX(REPLACE(duid, ':', '')),
+        valid_lifetime,
+        FROM_UNIXTIME(expire),
+        subnet_id,
+        pref_lifetime,
+        lease_type,
+        iaid,
+        prefix_len,
+        fqdn_fwd,
+        fqdn_rev,
+        REPLACE(hostname, '&#x2c', ','),
+        UNHEX(REPLACE(hwaddr, ':', '')),
+        state,
+        REPLACE(user_context, '&#x2c', ','),
+        hwtype,
+        hwaddr_source
+    );
+END $$
+DELIMITER ;
+
+-- Update the schema version number.
+UPDATE schema_version
+    SET version = '13', minor = '0';
+
+-- This line concludes the schema upgrade to version 13.0.
+
+-- This line starts the schema upgrade to version 14.0.
+
+-- Modify shared-network-name foreign key constraint on dhcp4_subnet to not perform
+-- the update when the network is deleted the cascaded update will not execute
+-- dhcp4_subnet update trigger leaving the updated subnets without audit_entries.
+ALTER TABLE dhcp4_subnet
+    DROP FOREIGN KEY fk_dhcp4_subnet_shared_network;
+
+ALTER TABLE dhcp4_subnet
+    ADD CONSTRAINT fk_dhcp4_subnet_shared_network FOREIGN KEY (shared_network_name)
+        REFERENCES dhcp4_shared_network (name)
+        ON DELETE NO ACTION ON UPDATE NO ACTION;
+
+-- Modify BEFORE delete trigger on dhcp4_shared_network to explicitly
+-- update dhcp4_subnets. This ensures there are audit entries for updated
+-- subnets.
+DROP TRIGGER dhcp4_shared_network_BDEL;
+
+DELIMITER $$
+CREATE TRIGGER dhcp4_shared_network_BDEL BEFORE DELETE ON dhcp4_shared_network
+    FOR EACH ROW
+    BEGIN
+        CALL createAuditEntryDHCP4('dhcp4_shared_network', OLD.id, "delete");
+        -- In MySQL Foreign key constraint triggered updates will not cascade, so we explicitly
+        -- update subnets first which should ensure they get audit entries.
+        UPDATE dhcp4_subnet SET shared_network_name = NULL WHERE shared_network_name = OLD.name;
+        DELETE FROM dhcp4_options WHERE shared_network_name = OLD.name;
+    END $$
+DELIMITER ;
+
+-- Modify shared-network-name foreign key constraint on dhcp6_subnet to not perform
+-- the update when the network is deleted the cascaded update will not execute
+-- dhcp6_subnet update trigger leaving the updated subnets without audit_entries.
+ALTER TABLE dhcp6_subnet
+    DROP FOREIGN KEY fk_dhcp6_subnet_shared_network;
+
+ALTER TABLE dhcp6_subnet
+    ADD CONSTRAINT fk_dhcp6_subnet_shared_network FOREIGN KEY (shared_network_name)
+        REFERENCES dhcp6_shared_network (name)
+        ON DELETE NO ACTION ON UPDATE NO ACTION;
+
+-- Modify BEFORE delete trigger on dhcp6_shared_network to explicitly
+-- update dhcp6_subnets. This ensures there are audit entries for updated
+-- subnets.
+DROP TRIGGER dhcp6_shared_network_BDEL;
+
+DELIMITER $$
+CREATE TRIGGER dhcp6_shared_network_BDEL BEFORE DELETE ON dhcp6_shared_network
+    FOR EACH ROW
+    BEGIN
+        CALL createAuditEntryDHCP6('dhcp6_shared_network', OLD.id, "delete");
+        -- In MySQL Foreign key constraint triggered updates will not cascade, so we explicitly
+        -- update subnets first which should ensure they get audit entries.
+        UPDATE dhcp6_subnet SET shared_network_name = NULL WHERE shared_network_name = OLD.name;
+        DELETE FROM dhcp6_options WHERE shared_network_name = OLD.name;
+    END $$
+DELIMITER ;
+
+-- Add user_context column to client class tables.
+ALTER TABLE dhcp4_client_class ADD COLUMN user_context LONGTEXT NULL;
+ALTER TABLE dhcp6_client_class ADD COLUMN user_context LONGTEXT NULL;
+
+-- Schema changes related to lease limiting start here. --
+
+-- Recreate the triggers that update the leaseX_stat tables as stored procedures. --
+
+DROP PROCEDURE IF EXISTS lease4_AINS_lease4_stat;
+DELIMITER $$
+CREATE PROCEDURE lease4_AINS_lease4_stat(IN new_state TINYINT,
+                                         IN new_subnet_id INT UNSIGNED)
+BEGIN
+    IF new_state = 0 OR new_state = 1 THEN
+        -- Update the state count if it exists.
+        UPDATE lease4_stat SET leases = leases + 1
+            WHERE subnet_id = new_subnet_id AND state = new_state;
+
+        -- Insert the state count record if it does not exist.
+        IF ROW_COUNT() <= 0 THEN
+            INSERT INTO lease4_stat VALUES (new_subnet_id, new_state, 1);
+        END IF;
+    END IF;
+END $$
+DELIMITER ;
+
+DROP PROCEDURE IF EXISTS lease4_AUPD_lease4_stat;
+DELIMITER $$
+CREATE PROCEDURE lease4_AUPD_lease4_stat(IN old_state TINYINT,
+                                         IN old_subnet_id INT UNSIGNED,
+                                         IN new_state TINYINT,
+                                         IN new_subnet_id INT UNSIGNED)
+BEGIN
+    IF old_subnet_id != new_subnet_id OR old_state != new_state THEN
+        IF old_state = 0 OR old_state = 1 THEN
+            -- Decrement the old state count if record exists.
+            UPDATE lease4_stat
+                SET leases = IF(leases > 0, leases - 1, 0)
+                WHERE subnet_id = old_subnet_id AND state = old_state;
+        END IF;
+
+        IF new_state = 0 OR new_state = 1 THEN
+            -- Increment the new state count if record exists.
+            UPDATE lease4_stat SET leases = leases + 1
+                WHERE subnet_id = new_subnet_id AND state = new_state;
+
+            -- Insert new state record if it does not exist.
+            IF ROW_COUNT() <= 0 THEN
+                INSERT INTO lease4_stat VALUES (new_subnet_id, new_state, 1);
+            END IF;
+        END IF;
+    END IF;
+END $$
+DELIMITER ;
+
+DROP PROCEDURE IF EXISTS lease4_ADEL_lease4_stat;
+DELIMITER $$
+CREATE PROCEDURE lease4_ADEL_lease4_stat(IN old_state TINYINT,
+                                         IN old_subnet_id INT UNSIGNED)
+BEGIN
+    IF old_state = 0 OR old_state = 1 THEN
+        -- Decrement the state count if record exists.
+        UPDATE lease4_stat
+            SET leases = IF(leases > 0, leases - 1, 0)
+            WHERE subnet_id = old_subnet_id AND old_state = state;
+    END IF;
+END $$
+DELIMITER ;
+
+DROP PROCEDURE IF EXISTS lease6_AINS_lease6_stat;
+DELIMITER $$
+CREATE PROCEDURE lease6_AINS_lease6_stat(IN new_state TINYINT,
+                                         IN new_subnet_id INT UNSIGNED,
+                                         IN new_lease_type TINYINT)
+BEGIN
+    IF new_state = 0 OR new_state = 1 THEN
+        -- Update the state count if it exists.
+        UPDATE lease6_stat SET leases = leases + 1
+            WHERE subnet_id = new_subnet_id AND lease_type = new_lease_type
+            AND state = new_state;
+
+        -- Insert the state count record if it does not exist.
+        IF ROW_COUNT() <= 0 THEN
+            INSERT INTO lease6_stat VALUES (new_subnet_id, new_lease_type, new_state, 1);
+        END IF;
+    END IF;
+END $$
+DELIMITER ;
+
+DROP PROCEDURE IF EXISTS lease6_AUPD_lease6_stat;
+DELIMITER $$
+CREATE PROCEDURE lease6_AUPD_lease6_stat(IN old_state TINYINT,
+                                         IN old_subnet_id INT UNSIGNED,
+                                         IN old_lease_type TINYINT,
+                                         IN new_state TINYINT,
+                                         IN new_subnet_id INT UNSIGNED,
+                                         IN new_lease_type TINYINT)
+BEGIN
+    IF old_subnet_id != new_subnet_id OR
+       old_lease_type != new_lease_type OR
+       old_state != new_state THEN
+        IF old_state = 0 OR old_state = 1 THEN
+            -- Decrement the old state count if record exists.
+            UPDATE lease6_stat
+                SET leases = IF(leases > 0, leases - 1, 0)
+                WHERE subnet_id = old_subnet_id AND lease_type = old_lease_type
+                AND state = old_state;
+        END IF;
+
+        IF new_state = 0 OR new_state = 1 THEN
+            -- Increment the new state count if record exists
+            UPDATE lease6_stat SET leases = leases + 1
+                WHERE subnet_id = new_subnet_id AND lease_type = new_lease_type
+                AND state = new_state;
+
+            -- Insert new state record if it does not exist
+            IF ROW_COUNT() <= 0 THEN
+                INSERT INTO lease6_stat
+                VALUES (new_subnet_id, new_lease_type, new_state, 1);
+            END IF;
+        END IF;
+    END IF;
+END $$
+DELIMITER ;
+
+DROP PROCEDURE IF EXISTS lease6_ADEL_lease6_stat;
+DELIMITER $$
+CREATE PROCEDURE lease6_ADEL_lease6_stat(IN old_state TINYINT,
+                                         IN old_subnet_id INT UNSIGNED,
+                                         IN old_lease_type TINYINT)
+BEGIN
+    IF old_state = 0 OR old_state = 1 THEN
+        -- Decrement the state count if record exists
+        UPDATE lease6_stat
+            SET leases = IF(leases > 0, leases - 1, 0)
+            WHERE subnet_id = old_subnet_id AND lease_type = old_lease_type
+            AND state = old_state;
+    END IF;
+END $$
+DELIMITER ;
+
+-- Create tables that contain the number of active leases. --
+
+DROP TABLE IF EXISTS lease4_stat_by_client_class;
+CREATE TABLE lease4_stat_by_client_class (
+    client_class VARCHAR(128) NOT NULL PRIMARY KEY,
+    leases BIGINT UNSIGNED NOT NULL
+) ENGINE = InnoDB;
+
+DROP TABLE IF EXISTS lease6_stat_by_client_class;
+CREATE TABLE lease6_stat_by_client_class (
+    client_class VARCHAR(128) NOT NULL,
+    lease_type TINYINT NOT NULL,
+    leases BIGINT UNSIGNED NOT NULL,
+    PRIMARY KEY (client_class, lease_type),
+    CONSTRAINT fk_lease6_stat_by_client_class_lease_type FOREIGN KEY (lease_type)
+        REFERENCES lease6_types (lease_type)
+) ENGINE = InnoDB;
+
+-- Create procedures to be called for each row in after-event triggers for
+-- INSERT, UPDATE and DELETE on lease tables.
+
+DROP PROCEDURE IF EXISTS lease4_AINS_lease4_stat_by_client_class;
+DELIMITER $$
+CREATE PROCEDURE lease4_AINS_lease4_stat_by_client_class(IN new_state TINYINT,
+                                                         IN new_user_context TEXT)
+BEGIN
+    -- Declarations
+    DECLARE client_classes TEXT;
+    DECLARE class VARCHAR(255);
+    DECLARE length INT;
+    DECLARE i INT;
+
+    -- Ignore ERROR 3141 (22032) at line 1: Invalid JSON text in argument 1 to
+    --      function json_extract: "The document is empty." at position 0.
+    -- Ignore ERROR 4037 (HY000): Unexpected end of JSON text in argument 1 to function 'json_extract'
+    -- These situations are handled with a propagating NULL result from JSON_EXTRACT.
+    DECLARE CONTINUE HANDLER FOR 3141 BEGIN END;
+    DECLARE CONTINUE HANDLER FOR 4037 BEGIN END;
+
+    -- Only state 0 is needed for lease limiting.
+    IF new_state = 0 THEN
+        -- Dive into client classes.
+        SET client_classes = JSON_EXTRACT(new_user_context, '$."ISC"."client-classes"');
+        SET length = JSON_LENGTH(client_classes);
+
+        -- Iterate through all the client classes and increment the lease count for each.
+        SET i = 0;
+        label: WHILE i < length DO
+            SET class = JSON_UNQUOTE(JSON_EXTRACT(client_classes, CONCAT('\$[', i, ']')));
+
+            -- Upsert to increment the lease count.
+            UPDATE lease4_stat_by_client_class SET leases = leases + 1
+                WHERE client_class = class;
+            IF ROW_COUNT() = 0 THEN
+                INSERT INTO lease4_stat_by_client_class VALUES (class, 1);
+            END IF;
+
+            SET i = i + 1;
+        END WHILE label;
+    END IF;
+END $$
+DELIMITER ;
+
+DROP PROCEDURE IF EXISTS lease4_AUPD_lease4_stat_by_client_class;
+DELIMITER $$
+CREATE PROCEDURE lease4_AUPD_lease4_stat_by_client_class(IN old_state TINYINT,
+                                                         IN old_user_context TEXT,
+                                                         IN new_state TINYINT,
+                                                         IN new_user_context TEXT)
+BEGIN
+    -- Declarations
+    DECLARE old_client_classes TEXT;
+    DECLARE new_client_classes TEXT;
+    DECLARE class VARCHAR(255);
+    DECLARE length INT;
+    DECLARE i INT;
+
+    SET old_client_classes = JSON_EXTRACT(old_user_context, '$."ISC"."client-classes"');
+    SET new_client_classes = JSON_EXTRACT(new_user_context, '$."ISC"."client-classes"');
+
+    IF old_state != new_state OR old_client_classes != new_client_classes THEN
+        -- Check if it's moving away from a counted state.
+        IF old_state = 0 THEN
+            -- Dive into client classes.
+            SET length = JSON_LENGTH(old_client_classes);
+            SET i = 0;
+            label: WHILE i < length DO
+                SET class = JSON_UNQUOTE(JSON_EXTRACT(old_client_classes, CONCAT('\$[', i, ']')));
+
+                -- Decrement the lease count if the record exists.
+                UPDATE lease4_stat_by_client_class SET leases = IF(leases > 0, leases - 1, 0)
+                    WHERE client_class = class;
+
+                SET i = i + 1;
+            END WHILE label;
+        END IF;
+
+        -- Check if it's moving into a counted state.
+        IF new_state = 0 THEN
+            -- Dive into client classes.
+            SET length = JSON_LENGTH(new_client_classes);
+            SET i = 0;
+            label: WHILE i < length DO
+                SET class = JSON_UNQUOTE(JSON_EXTRACT(new_client_classes, CONCAT('\$[', i, ']')));
+
+                -- Upsert to increment the lease count.
+                UPDATE lease4_stat_by_client_class SET leases = leases + 1
+                    WHERE client_class = class;
+                IF ROW_COUNT() <= 0 THEN
+                    INSERT INTO lease4_stat_by_client_class VALUES (class, 1);
+                END IF;
+
+                SET i = i + 1;
+            END WHILE label;
+        END IF;
+    END IF;
+END $$
+DELIMITER ;
+
+DROP PROCEDURE IF EXISTS lease4_ADEL_lease4_stat_by_client_class;
+DELIMITER $$
+CREATE PROCEDURE lease4_ADEL_lease4_stat_by_client_class(IN old_state TINYINT,
+                                                         IN old_user_context TEXT)
+BEGIN
+    -- Declarations
+    DECLARE client_classes TEXT;
+    DECLARE class VARCHAR(255);
+    DECLARE length INT;
+    DECLARE i INT;
+
+    -- Ignore ERROR 3141 (22032) at line 1: Invalid JSON text in argument 1 to
+    --      function json_extract: "The document is empty." at position 0.
+    -- Ignore ERROR 4037 (HY000): Unexpected end of JSON text in argument 1 to function 'json_extract'
+    -- These situations are handled with a propagating NULL result from JSON_EXTRACT.
+    DECLARE CONTINUE HANDLER FOR 3141 BEGIN END;
+    DECLARE CONTINUE HANDLER FOR 4037 BEGIN END;
+
+    -- Only state 0 is accounted for in lease limiting.
+    IF old_state = 0 THEN
+        -- Dive into client classes.
+        SET client_classes = JSON_EXTRACT(old_user_context, '$."ISC"."client-classes"');
+        SET length = JSON_LENGTH(client_classes);
+
+        SET i = 0;
+        label: WHILE i < length DO
+            SET class = JSON_UNQUOTE(JSON_EXTRACT(client_classes, CONCAT('\$[', i, ']')));
+
+            -- Decrement the lease count if the record exists.
+            UPDATE lease4_stat_by_client_class SET leases = IF(leases > 0, leases - 1, 0)
+                WHERE client_class = class;
+
+            SET i = i + 1;
+        END WHILE label;
+    END IF;
+END $$
+DELIMITER ;
+
+DROP PROCEDURE IF EXISTS lease6_AINS_lease6_stat_by_client_class;
+DELIMITER $$
+CREATE PROCEDURE lease6_AINS_lease6_stat_by_client_class(IN new_state TINYINT,
+                                                         IN new_user_context TEXT,
+                                                         IN new_lease_type TINYINT)
+BEGIN
+    -- Declarations
+    DECLARE client_classes TEXT;
+    DECLARE class VARCHAR(255);
+    DECLARE length INT;
+    DECLARE i INT;
+
+    -- Ignore ERROR 3141 (22032) at line 1: Invalid JSON text in argument 1 to
+    --      function json_extract: "The document is empty." at position 0.
+    -- Ignore ERROR 4037 (HY000): Unexpected end of JSON text in argument 1 to function 'json_extract'
+    -- These situations are handled with a propagating NULL result from JSON_EXTRACT.
+    DECLARE CONTINUE HANDLER FOR 3141 BEGIN END;
+    DECLARE CONTINUE HANDLER FOR 4037 BEGIN END;
+
+    -- Only state 0 is needed for lease limiting.
+    IF new_state = 0 THEN
+        -- Dive into client classes.
+        SET client_classes = JSON_EXTRACT(new_user_context, '$."ISC"."client-classes"');
+        SET length = JSON_LENGTH(client_classes);
+
+        SET i = 0;
+        label: WHILE i < length DO
+            SET class = JSON_UNQUOTE(JSON_EXTRACT(client_classes, CONCAT('\$[', i, ']')));
+
+            -- Upsert to increment the lease count.
+            UPDATE lease6_stat_by_client_class SET leases = leases + 1
+                WHERE client_class = class AND lease_type = new_lease_type;
+            IF ROW_COUNT() <= 0 THEN
+                INSERT INTO lease6_stat_by_client_class VALUES (class, new_lease_type, 1);
+            END IF;
+
+            SET i = i + 1;
+        END WHILE label;
+    END IF;
+END $$
+DELIMITER ;
+
+DROP PROCEDURE IF EXISTS lease6_AUPD_lease6_stat_by_client_class;
+DELIMITER $$
+CREATE PROCEDURE lease6_AUPD_lease6_stat_by_client_class(IN old_state TINYINT,
+                                                         IN old_user_context TEXT,
+                                                         IN old_lease_type TINYINT,
+                                                         IN new_state TINYINT,
+                                                         IN new_user_context TEXT,
+                                                         IN new_lease_type TINYINT)
+BEGIN
+    -- Declarations
+    DECLARE old_client_classes TEXT;
+    DECLARE new_client_classes TEXT;
+    DECLARE class VARCHAR(255);
+    DECLARE length INT;
+    DECLARE i INT;
+
+    SET old_client_classes = JSON_EXTRACT(old_user_context, '$."ISC"."client-classes"');
+    SET new_client_classes = JSON_EXTRACT(new_user_context, '$."ISC"."client-classes"');
+
+    IF old_state != new_state OR old_client_classes != new_client_classes OR old_lease_type != new_lease_type THEN
+        -- Check if it's moving away from a counted state.
+        IF old_state = 0 THEN
+            -- Dive into client classes.
+            SET length = JSON_LENGTH(old_client_classes);
+            SET i = 0;
+            label: WHILE i < length DO
+                SET class = JSON_UNQUOTE(JSON_EXTRACT(old_client_classes, CONCAT('\$[', i, ']')));
+
+                -- Decrement the lease count if the record exists.
+                UPDATE lease6_stat_by_client_class SET leases = IF(leases > 0, leases - 1, 0)
+                    WHERE client_class = class AND lease_type = old_lease_type;
+
+                SET i = i + 1;
+            END WHILE label;
+        END IF;
+
+        -- Check if it's moving into a counted state.
+        IF new_state = 0 THEN
+            -- Dive into client classes.
+            SET length = JSON_LENGTH(new_client_classes);
+            SET i = 0;
+            label: WHILE i < length DO
+                SET class = JSON_UNQUOTE(JSON_EXTRACT(new_client_classes, CONCAT('\$[', i, ']')));
+
+                -- Upsert to increment the lease count.
+                UPDATE lease6_stat_by_client_class SET leases = leases + 1
+                    WHERE client_class = class AND lease_type = new_lease_type;
+                IF ROW_COUNT() <= 0 THEN
+                    INSERT INTO lease6_stat_by_client_class VALUES (class, new_lease_type, 1);
+                END IF;
+
+                SET i = i + 1;
+            END WHILE label;
+        END IF;
+    END IF;
+END $$
+DELIMITER ;
+
+DROP PROCEDURE IF EXISTS lease6_ADEL_lease6_stat_by_client_class;
+DELIMITER $$
+CREATE PROCEDURE lease6_ADEL_lease6_stat_by_client_class(IN old_state TINYINT,
+                                                         IN old_user_context TEXT,
+                                                         IN old_lease_type TINYINT)
+BEGIN
+    -- Declarations
+    DECLARE client_classes TEXT;
+    DECLARE class VARCHAR(255);
+    DECLARE length INT;
+    DECLARE i INT;
+
+    -- Ignore ERROR 3141 (22032) at line 1: Invalid JSON text in argument 1 to
+    --      function json_extract: "The document is empty." at position 0.
+    -- Ignore ERROR 4037 (HY000): Unexpected end of JSON text in argument 1 to function 'json_extract'
+    -- These situations are handled with a propagating NULL result from JSON_EXTRACT.
+    DECLARE CONTINUE HANDLER FOR 3141 BEGIN END;
+    DECLARE CONTINUE HANDLER FOR 4037 BEGIN END;
+
+    -- Only state 0 is accounted for in lease limiting. But check both states to be consistent with lease6_stat.
+    IF old_state = 0 THEN
+        -- Dive into client classes.
+        SET client_classes = JSON_EXTRACT(old_user_context, '$."ISC"."client-classes"');
+        SET length = JSON_LENGTH(client_classes);
+
+        SET i = 0;
+        label: WHILE i < length DO
+            SET class = JSON_UNQUOTE(JSON_EXTRACT(client_classes, CONCAT('\$[', i, ']')));
+
+            -- Decrement the lease count if the record exists.
+            UPDATE lease6_stat_by_client_class SET leases = IF(leases > 0, leases - 1, 0)
+                WHERE client_class = class AND lease_type = old_lease_type;
+
+            SET i = i + 1;
+        END WHILE label;
+    END IF;
+END $$
+DELIMITER ;
+
+-- Recreate the after-event triggers for INSERT, UPDATE and DELETE on lease tables to call the --
+-- stored procedures above in pairs of two: for client classes and for subnets. --
+
+-- Function that establishes whether JSON functions are supported.
+-- They should be provided with MySQL>= 5.7, MariaDB >= 10.2.3.
+DROP FUNCTION IF EXISTS isJsonSupported;
+DELIMITER $$
+CREATE FUNCTION isJsonSupported()
+RETURNS BOOL
+DETERMINISTIC
+BEGIN
+    DECLARE dummy BOOL;
+    DECLARE CONTINUE HANDLER FOR SQLEXCEPTION
+        RETURN false;
+
+    SELECT JSON_EXTRACT('{ "foo-bar": 1 }', '$."foo-bar"') INTO dummy;
+    RETURN true;
+END $$
+DELIMITER ;
+
+DROP TRIGGER IF EXISTS stat_lease4_insert;
+DROP TRIGGER IF EXISTS lease4_AINS;
+DELIMITER $$
+CREATE TRIGGER lease4_AINS AFTER INSERT ON lease4 FOR EACH ROW
+BEGIN
+    CALL lease4_AINS_lease4_stat(NEW.state, NEW.subnet_id);
+    IF @json_supported IS NULL THEN
+        SELECT isJsonSupported() INTO @json_supported;
+    END IF;
+    IF @json_supported = 1 THEN
+        CALL lease4_AINS_lease4_stat_by_client_class(NEW.state, NEW.user_context);
+    END IF;
+END $$
+DELIMITER ;
+
+DROP TRIGGER IF EXISTS stat_lease4_update;
+DROP TRIGGER IF EXISTS lease4_AUPD;
+DELIMITER $$
+CREATE TRIGGER lease4_AUPD AFTER UPDATE ON lease4 FOR EACH ROW
+BEGIN
+    CALL lease4_AUPD_lease4_stat(OLD.state, OLD.subnet_id, NEW.state, NEW.subnet_id);
+    IF @json_supported IS NULL THEN
+        SELECT isJsonSupported() INTO @json_supported;
+    END IF;
+    IF @json_supported = 1 THEN
+        CALL lease4_AUPD_lease4_stat_by_client_class(OLD.state, OLD.user_context, NEW.state, NEW.user_context);
+    END IF;
+END $$
+DELIMITER ;
+
+DROP TRIGGER IF EXISTS stat_lease4_delete;
+DROP TRIGGER IF EXISTS lease4_ADEL;
+DELIMITER $$
+CREATE TRIGGER lease4_ADEL AFTER DELETE ON lease4 FOR EACH ROW
+BEGIN
+    CALL lease4_ADEL_lease4_stat(OLD.state, OLD.subnet_id);
+    IF @json_supported IS NULL THEN
+        SELECT isJsonSupported() INTO @json_supported;
+    END IF;
+    IF @json_supported = 1 THEN
+        CALL lease4_ADEL_lease4_stat_by_client_class(OLD.state, OLD.user_context);
+    END IF;
+END $$
+DELIMITER ;
+
+DROP TRIGGER IF EXISTS stat_lease6_insert;
+DROP TRIGGER IF EXISTS lease6_AINS;
+DELIMITER $$
+CREATE TRIGGER lease6_AINS AFTER INSERT ON lease6 FOR EACH ROW
+BEGIN
+    CALL lease6_AINS_lease6_stat(NEW.state, NEW.subnet_id, NEW.lease_type);
+    IF @json_supported IS NULL THEN
+        SELECT isJsonSupported() INTO @json_supported;
+    END IF;
+    IF @json_supported = 1 THEN
+        CALL lease6_AINS_lease6_stat_by_client_class(NEW.state, NEW.user_context, NEW.lease_type);
+    END IF;
+END $$
+DELIMITER ;
+
+DROP TRIGGER IF EXISTS stat_lease6_update;
+DROP TRIGGER IF EXISTS lease6_AUPD;
+DELIMITER $$
+CREATE TRIGGER lease6_AUPD AFTER UPDATE ON lease6 FOR EACH ROW
+BEGIN
+    CALL lease6_AUPD_lease6_stat(OLD.state, OLD.subnet_id, OLD.lease_type, NEW.state, NEW.subnet_id, NEW.lease_type);
+    IF @json_supported IS NULL THEN
+        SELECT isJsonSupported() INTO @json_supported;
+    END IF;
+    IF @json_supported = 1 THEN
+        CALL lease6_AUPD_lease6_stat_by_client_class(OLD.state, OLD.user_context, OLD.lease_type, NEW.state, NEW.user_context, NEW.lease_type);
+    END IF;
+END $$
+DELIMITER ;
+
+DROP TRIGGER IF EXISTS stat_lease6_delete;
+DROP TRIGGER IF EXISTS lease6_ADEL;
+DELIMITER $$
+CREATE TRIGGER lease6_ADEL AFTER DELETE ON lease6 FOR EACH ROW
+BEGIN
+    CALL lease6_ADEL_lease6_stat(OLD.state, OLD.subnet_id, OLD.lease_type);
+    IF @json_supported IS NULL THEN
+        SELECT isJsonSupported() INTO @json_supported;
+    END IF;
+    IF @json_supported = 1 THEN
+        CALL lease6_ADEL_lease6_stat_by_client_class(OLD.state, OLD.user_context, OLD.lease_type);
+    END IF;
+END $$
+DELIMITER ;
+
+-- Create functions that check if the lease limits set in the given user context are exceeded.
+-- They return a string describing a limit that is being exceeded, or an empty
+-- string if no limits are exceeded. The following format for is assumed for user_context
+-- (not all nodes are mandatory and values are given only as examples):
+-- { "ISC": { "limits": { "client-classes": [ { "name": "foo", "address-limit": 2, "prefix-limit": 1 } ],
+--                        "subnet": { "id": 1, "address-limit": 2, "prefix-limit": 1 } } } }
+
+DROP FUNCTION IF EXISTS checkLease4Limits;
+DELIMITER $$
+CREATE FUNCTION checkLease4Limits(user_context TEXT)
+RETURNS TEXT
+READS SQL DATA
+BEGIN
+    -- Declarations
+    DECLARE json_element TEXT;
+    DECLARE length INT;
+    DECLARE class TEXT;
+    DECLARE name VARCHAR(255);
+    DECLARE i INT;
+    DECLARE lease_limit INT;
+    DECLARE lease_count INT;
+
+    -- Dive into client class limits.
+    SET json_element = JSON_EXTRACT(user_context, '$."ISC"."limits"."client-classes"');
+    SET length = JSON_LENGTH(json_element);
+
+    SET i = 0;
+    label: WHILE i < length DO
+        -- Get the lease limit for this client class.
+        SET class = JSON_EXTRACT(json_element, CONCAT('\$[', i, ']'));
+        SET name = JSON_UNQUOTE(JSON_EXTRACT(class, '$.name'));
+        SET lease_limit = JSON_EXTRACT(class, '$."address-limit"');
+
+        IF lease_limit IS NOT NULL THEN
+            -- Get the lease count for this client class.
+            SET lease_count = (SELECT leases FROM lease4_stat_by_client_class WHERE client_class = name);
+            IF lease_count IS NULL THEN
+                SET lease_count = 0;
+            END IF;
+
+            -- Compare. Return immediately if the limit is exceeded.
+            IF lease_limit <= lease_count THEN
+                RETURN CONCAT('address limit ', lease_limit, ' for client class "', name, '", current lease count ', lease_count);
+            END IF;
+        END IF;
+
+        SET i = i + 1;
+    END WHILE label;
+
+    -- Dive into subnet limits. Reuse i as subnet ID.
+    SET json_element = JSON_EXTRACT(user_context, '$.ISC.limits.subnet');
+    SET i = JSON_EXTRACT(json_element, '$.id');
+    SET lease_limit = JSON_EXTRACT(json_element, '$."address-limit"');
+
+    IF lease_limit IS NOT NULL THEN
+        -- Get the lease count for this client class.
+        SET lease_count = (SELECT leases FROM lease4_stat WHERE subnet_id = i AND state = 0);
+        IF lease_count IS NULL THEN
+            SET lease_count = 0;
+        END IF;
+
+        -- Compare. Return immediately if the limit is exceeded.
+        IF lease_limit <= lease_count THEN
+                RETURN CONCAT('address limit ', lease_limit, ' for subnet ID ', i, ', current lease count ', lease_count);
+        END IF;
+    END IF;
+
+    RETURN '';
+END $$
+DELIMITER ;
+
+DROP FUNCTION IF EXISTS checkLease6Limits;
+DELIMITER $$
+CREATE FUNCTION checkLease6Limits(user_context TEXT)
+RETURNS TEXT
+READS SQL DATA
+BEGIN
+    -- Declarations
+    DECLARE json_element TEXT;
+    DECLARE length INT;
+    DECLARE class TEXT;
+    DECLARE name VARCHAR(255);
+    DECLARE i INT;
+    DECLARE lease_limit INT;
+    DECLARE lease_count INT;
+
+    -- Dive into client class limits.
+    SET json_element = JSON_EXTRACT(user_context, '$."ISC"."limits"."client-classes"');
+    SET length = JSON_LENGTH(json_element);
+
+    SET i = 0;
+    label: WHILE i < length DO
+        -- Get the lease limit for this client class.
+        SET class = JSON_EXTRACT(json_element, CONCAT('\$[', i, ']'));
+        SET name = JSON_UNQUOTE(JSON_EXTRACT(class, '$.name'));
+
+        SET lease_limit = JSON_EXTRACT(class, '$."address-limit"');
+        IF lease_limit IS NOT NULL THEN
+            -- Get the address count for this client class.
+            SET lease_count = (SELECT leases FROM lease6_stat_by_client_class WHERE client_class = name AND lease_type = 0);
+            IF lease_count IS NULL THEN
+                SET lease_count = 0;
+            END IF;
+
+            -- Compare. Return immediately if the limit is exceeded.
+            IF lease_limit <= lease_count THEN
+                RETURN CONCAT('address limit ', lease_limit, ' for client class "', name, '", current lease count ', lease_count);
+            END IF;
+        END IF;
+
+        SET lease_limit = JSON_EXTRACT(class, '$."prefix-limit"');
+        IF lease_limit IS NOT NULL THEN
+            -- Get the prefix count for this client class.
+            SET lease_count = (SELECT leases FROM lease6_stat_by_client_class WHERE client_class = name AND lease_type = 2);
+            IF lease_count IS NULL THEN
+                SET lease_count = 0;
+            END IF;
+
+            -- Compare. Return immediately if the limit is exceeded.
+            IF lease_limit <= lease_count THEN
+                RETURN CONCAT('prefix limit ', lease_limit, ' for client class "', name, '", current lease count ', lease_count);
+            END IF;
+        END IF;
+
+        SET i = i + 1;
+    END WHILE label;
+
+    -- Dive into subnet limits. Reuse i as subnet ID.
+    SET json_element = JSON_EXTRACT(user_context, '$.ISC.limits.subnet');
+    SET i = JSON_EXTRACT(json_element, '$.id');
+    SET lease_limit = JSON_EXTRACT(json_element, '$."address-limit"');
+    IF lease_limit IS NOT NULL THEN
+        -- Get the lease count for this client class.
+        SET lease_count = (SELECT leases FROM lease6_stat WHERE subnet_id = i AND lease_type = 0 AND state = 0);
+        IF lease_count IS NULL THEN
+            SET lease_count = 0;
+        END IF;
+
+        -- Compare. Return immediately if the limit is exceeded.
+        IF lease_limit <= lease_count THEN
+                RETURN CONCAT('address limit ', lease_limit, ' for subnet ID ', i, ', current lease count ', lease_count);
+        END IF;
+    END IF;
+    SET lease_limit = JSON_EXTRACT(json_element, '$."prefix-limit"');
+    IF lease_limit IS NOT NULL THEN
+        -- Get the lease count for this client class.
+        SET lease_count = (SELECT leases FROM lease6_stat WHERE subnet_id = i AND lease_type = 2 AND state = 0);
+        IF lease_count IS NULL THEN
+            SET lease_count = 0;
+        END IF;
+
+        -- Compare. Return immediately if the limit is exceeded.
+        IF lease_limit <= lease_count THEN
+            RETURN CONCAT('prefix limit ', lease_limit, ' for subnet ID ', i, ', current lease count ', lease_count);
+        END IF;
+    END IF;
+
+    RETURN '';
+END $$
+DELIMITER ;
+
+-- Update the schema version number.
+UPDATE schema_version
+    SET version = '14', minor = '0';
+
+-- This line concludes the schema upgrade to version 14.0.
+
+-- This line starts the schema upgrade to version 15.0.
+
+-- Add cancelled (aka never-send) column to option tables.
+ALTER TABLE dhcp4_options
+    ADD COLUMN cancelled TINYINT(1) NOT NULL DEFAULT 0;
+
+ALTER TABLE dhcp6_options
+    ADD COLUMN cancelled TINYINT(1) NOT NULL DEFAULT 0;
+
+-- Add offer_lifetime column to v4 tables.
+ALTER TABLE dhcp4_shared_network
+    ADD COLUMN offer_lifetime INT(10) DEFAULT NULL;
+
+ALTER TABLE dhcp4_subnet
+    ADD COLUMN offer_lifetime INT(10) DEFAULT NULL;
+
+ALTER TABLE dhcp4_client_class
+    ADD COLUMN offer_lifetime INT(10) DEFAULT NULL;
+
+-- Update the schema version number.
+UPDATE schema_version
+    SET version = '15', minor = '0';
+
+-- This line concludes the schema upgrade to version 15.0.
+
+-- This line starts the schema upgrade to version 16.0.
+
+-- Add relay and remote id columns to DHCPv4 leases.
+--
+-- Note: these columns are only used for indexes, in particular they are
+-- not exported by lease4 dump as values are also in the user context
+ALTER TABLE lease4
+    ADD COLUMN relay_id VARBINARY(128) DEFAULT NULL,
+    ADD COLUMN remote_id VARBINARY(128) DEFAULT NULL;
+
+-- Create relay and remote id indexes.
+CREATE INDEX lease4_by_relay_id ON lease4 (relay_id);
+CREATE INDEX lease4_by_remote_id ON lease4 (remote_id);
+
+-- Update the schema version number.
+UPDATE schema_version
+    SET version = '16', minor = '0';
+
+-- This line concludes the schema upgrade to version 16.0.
+
+-- This line starts the schema upgrade to version 17.0.
+
+-- Add the allocator column to the DHCPv4 tables.
+ALTER TABLE dhcp4_subnet ADD COLUMN allocator TEXT NULL;
+ALTER TABLE dhcp4_shared_network ADD COLUMN allocator TEXT NULL;
+
+-- Add allocator and pd_allocator to the DHCPv6 subnet tables.
+ALTER TABLE dhcp6_subnet ADD COLUMN allocator TEXT NULL;
+ALTER TABLE dhcp6_subnet ADD COLUMN pd_allocator TEXT NULL;
+
+-- Add allocator and pd_allocator to the DHCPv6 shared network tables.
+ALTER TABLE dhcp6_shared_network ADD COLUMN allocator TEXT NULL;
+ALTER TABLE dhcp6_shared_network ADD COLUMN pd_allocator TEXT NULL;
+
+-- Update the schema version number.
+UPDATE schema_version
+    SET version = '17', minor = '0';
+
+-- This line concludes the schema upgrade to version 17.0.
+
+-- This line starts the schema upgrade to version 18.0.
+
+-- Extend lease4 client_id to 255 bytes.
+ALTER TABLE lease4
+    MODIFY COLUMN client_id VARBINARY(255);
+
+-- Extend hosts dhcp_identifier to 255 bytes.
+ALTER TABLE hosts
+    MODIFY COLUMN dhcp_identifier VARBINARY(255) NOT NULL;
+
+-- Extend hosts relay_id to 255 bytes.
+ALTER TABLE lease4
+    MODIFY COLUMN relay_id VARBINARY(255) DEFAULT NULL;
+
+-- Extend hosts remote_id to 255 bytes.
+ALTER TABLE lease4
+    MODIFY COLUMN remote_id VARBINARY(255) DEFAULT NULL;
+
+-- Extend lease6 duid to 130 bytes.
+ALTER TABLE lease6
+    MODIFY COLUMN duid VARBINARY(130);
+
+UPDATE lease6 SET duid = UNHEX('000000') WHERE duid = UNHEX('00');
+
+# Add pool_id column to the lease4 table.
+ALTER TABLE lease4
+    ADD COLUMN pool_id INT UNSIGNED NOT NULL DEFAULT 0;
+
+# Add pool_id column to the lease6 table.
+ALTER TABLE lease6
+    ADD COLUMN pool_id INT UNSIGNED NOT NULL DEFAULT 0;
+
+# Create lease4_pool_stat table
+CREATE TABLE lease4_pool_stat (
+    subnet_id INT UNSIGNED NOT NULL,
+    pool_id INT UNSIGNED NOT NULL,
+    state INT UNSIGNED NOT NULL,
+    leases BIGINT,
+    PRIMARY KEY (subnet_id, pool_id, state)
+) ENGINE = INNODB;
+
+# Create lease6_pool_stat table
+CREATE TABLE lease6_pool_stat (
+    subnet_id INT UNSIGNED NOT NULL,
+    pool_id INT UNSIGNED NOT NULL,
+    lease_type INT UNSIGNED NOT NULL,
+    state INT UNSIGNED NOT NULL,
+    leases BIGINT,
+    PRIMARY KEY (subnet_id, pool_id, lease_type, state)
+) ENGINE = INNODB;
+
+DROP PROCEDURE IF EXISTS lease4_AINS_lease4_pool_stat;
+DELIMITER $$
+CREATE PROCEDURE lease4_AINS_lease4_pool_stat(IN new_state TINYINT,
+                                              IN new_subnet_id INT UNSIGNED,
+                                              IN new_pool_id INT UNSIGNED)
+BEGIN
+    IF new_state = 0 OR new_state = 1 THEN
+        -- Update the state count if it exists.
+        UPDATE lease4_pool_stat SET leases = leases + 1
+            WHERE subnet_id = new_subnet_id AND pool_id = new_pool_id
+            AND state = new_state;
+
+        -- Insert the state count record if it does not exist.
+        IF ROW_COUNT() <= 0 THEN
+            INSERT INTO lease4_pool_stat
+            VALUES (new_subnet_id, new_pool_id, new_state, 1);
+        END IF;
+    END IF;
+END $$
+DELIMITER ;
+
+DROP PROCEDURE IF EXISTS lease4_AUPD_lease4_pool_stat;
+DELIMITER $$
+CREATE PROCEDURE lease4_AUPD_lease4_pool_stat(IN old_state TINYINT,
+                                              IN old_subnet_id INT UNSIGNED,
+                                              IN old_pool_id INT UNSIGNED,
+                                              IN new_state TINYINT,
+                                              IN new_subnet_id INT UNSIGNED,
+                                              IN new_pool_id INT UNSIGNED)
+BEGIN
+    IF old_subnet_id != new_subnet_id OR
+       old_pool_id != new_pool_id OR
+       old_state != new_state THEN
+        IF old_state = 0 OR old_state = 1 THEN
+            -- Decrement the old state count if record exists.
+            UPDATE lease4_pool_stat
+                SET leases = IF(leases > 0, leases - 1, 0)
+                WHERE subnet_id = old_subnet_id AND pool_id = old_pool_id
+                AND state = old_state;
+        END IF;
+
+        IF new_state = 0 OR new_state = 1 THEN
+            -- Increment the new state count if record exists.
+            UPDATE lease4_pool_stat SET leases = leases + 1
+                WHERE subnet_id = new_subnet_id AND pool_id = new_pool_id
+                AND state = new_state;
+
+            -- Insert new state record if it does not exist.
+            IF ROW_COUNT() <= 0 THEN
+                INSERT INTO lease4_pool_stat
+                VALUES (new_subnet_id, new_pool_id, new_state, 1);
+            END IF;
+        END IF;
+    END IF;
+END $$
+DELIMITER ;
+
+DROP PROCEDURE IF EXISTS lease4_ADEL_lease4_pool_stat;
+DELIMITER $$
+CREATE PROCEDURE lease4_ADEL_lease4_pool_stat(IN old_state TINYINT,
+                                              IN old_subnet_id INT UNSIGNED,
+                                              IN old_pool_id INT UNSIGNED)
+BEGIN
+    IF old_state = 0 OR old_state = 1 THEN
+        -- Decrement the state count if record exists.
+        UPDATE lease4_pool_stat
+            SET leases = IF(leases > 0, leases - 1, 0)
+            WHERE subnet_id = old_subnet_id AND pool_id = old_pool_id
+            AND state = old_state;
+    END IF;
+END $$
+DELIMITER ;
+
+DROP PROCEDURE IF EXISTS lease6_AINS_lease6_pool_stat;
+DELIMITER $$
+CREATE PROCEDURE lease6_AINS_lease6_pool_stat(IN new_state TINYINT,
+                                              IN new_subnet_id INT UNSIGNED,
+                                              IN new_pool_id INT UNSIGNED,
+                                              IN new_lease_type TINYINT)
+BEGIN
+    IF new_state = 0 OR new_state = 1 THEN
+        -- Update the state count if it exists.
+        UPDATE lease6_pool_stat SET leases = leases + 1
+            WHERE subnet_id = new_subnet_id AND pool_id = new_pool_id
+            AND lease_type = new_lease_type AND state = new_state;
+
+        -- Insert the state count record if it does not exist.
+        IF ROW_COUNT() <= 0 THEN
+            INSERT INTO lease6_pool_stat
+            VALUES (new_subnet_id, new_pool_id, new_lease_type, new_state, 1);
+        END IF;
+    END IF;
+END $$
+DELIMITER ;
+
+DROP PROCEDURE IF EXISTS lease6_AUPD_lease6_pool_stat;
+DELIMITER $$
+CREATE PROCEDURE lease6_AUPD_lease6_pool_stat(IN old_state TINYINT,
+                                              IN old_subnet_id INT UNSIGNED,
+                                              IN old_pool_id INT UNSIGNED,
+                                              IN old_lease_type TINYINT,
+                                              IN new_state TINYINT,
+                                              IN new_subnet_id INT UNSIGNED,
+                                              IN new_pool_id INT UNSIGNED,
+                                              IN new_lease_type TINYINT)
+BEGIN
+    IF old_subnet_id != new_subnet_id OR
+       old_pool_id != new_pool_id OR
+       old_lease_type != new_lease_type OR
+       old_state != new_state THEN
+        IF old_state = 0 OR old_state = 1 THEN
+            -- Decrement the old state count if record exists.
+            UPDATE lease6_pool_stat
+                SET leases = IF(leases > 0, leases - 1, 0)
+                WHERE subnet_id = old_subnet_id AND pool_id = old_pool_id
+                AND lease_type = old_lease_type AND state = old_state;
+        END IF;
+
+        IF new_state = 0 OR new_state = 1 THEN
+            -- Increment the new state count if record exists
+            UPDATE lease6_pool_stat SET leases = leases + 1
+                WHERE subnet_id = new_subnet_id AND pool_id = new_pool_id
+                AND lease_type = new_lease_type AND state = new_state;
+
+            -- Insert new state record if it does not exist
+            IF ROW_COUNT() <= 0 THEN
+                INSERT INTO lease6_pool_stat
+                VALUES (new_subnet_id, new_pool_id, new_lease_type, new_state, 1);
+            END IF;
+        END IF;
+    END IF;
+END $$
+DELIMITER ;
+
+DROP PROCEDURE IF EXISTS lease6_ADEL_lease6_pool_stat;
+DELIMITER $$
+CREATE PROCEDURE lease6_ADEL_lease6_pool_stat(IN old_state TINYINT,
+                                              IN old_subnet_id INT UNSIGNED,
+                                              IN old_pool_id INT UNSIGNED,
+                                              IN old_lease_type TINYINT)
+BEGIN
+    IF old_state = 0 OR old_state = 1 THEN
+        -- Decrement the state count if record exists
+        UPDATE lease6_pool_stat
+            SET leases = IF(leases > 0, leases - 1, 0)
+            WHERE subnet_id = old_subnet_id AND pool_id = old_pool_id
+            AND lease_type = old_lease_type AND state = old_state;
+    END IF;
+END $$
+DELIMITER ;
+
+DROP TRIGGER IF EXISTS lease4_AINS;
+DELIMITER $$
+CREATE TRIGGER lease4_AINS AFTER INSERT ON lease4 FOR EACH ROW
+BEGIN
+    CALL lease4_AINS_lease4_stat(NEW.state, NEW.subnet_id);
+    CALL lease4_AINS_lease4_pool_stat(NEW.state, NEW.subnet_id, NEW.pool_id);
+    IF @json_supported IS NULL THEN
+        SELECT isJsonSupported() INTO @json_supported;
+    END IF;
+    IF @json_supported = 1 THEN
+        CALL lease4_AINS_lease4_stat_by_client_class(NEW.state, NEW.user_context);
+    END IF;
+END $$
+DELIMITER ;
+
+DROP TRIGGER IF EXISTS lease4_AUPD;
+DELIMITER $$
+CREATE TRIGGER lease4_AUPD AFTER UPDATE ON lease4 FOR EACH ROW
+BEGIN
+    CALL lease4_AUPD_lease4_stat(OLD.state, OLD.subnet_id, NEW.state, NEW.subnet_id);
+    CALL lease4_AUPD_lease4_pool_stat(OLD.state, OLD.subnet_id, OLD.pool_id, NEW.state, NEW.subnet_id, NEW.pool_id);
+    IF @json_supported IS NULL THEN
+        SELECT isJsonSupported() INTO @json_supported;
+    END IF;
+    IF @json_supported = 1 THEN
+        CALL lease4_AUPD_lease4_stat_by_client_class(OLD.state, OLD.user_context, NEW.state, NEW.user_context);
+    END IF;
+END $$
+DELIMITER ;
+
+DROP TRIGGER IF EXISTS lease4_ADEL;
+DELIMITER $$
+CREATE TRIGGER lease4_ADEL AFTER DELETE ON lease4 FOR EACH ROW
+BEGIN
+    CALL lease4_ADEL_lease4_stat(OLD.state, OLD.subnet_id);
+    CALL lease4_ADEL_lease4_pool_stat(OLD.state, OLD.subnet_id, OLD.pool_id);
+    IF @json_supported IS NULL THEN
+        SELECT isJsonSupported() INTO @json_supported;
+    END IF;
+    IF @json_supported = 1 THEN
+        CALL lease4_ADEL_lease4_stat_by_client_class(OLD.state, OLD.user_context);
+    END IF;
+END $$
+DELIMITER ;
+
+DROP TRIGGER IF EXISTS lease6_AINS;
+DELIMITER $$
+CREATE TRIGGER lease6_AINS AFTER INSERT ON lease6 FOR EACH ROW
+BEGIN
+    CALL lease6_AINS_lease6_stat(NEW.state, NEW.subnet_id, NEW.lease_type);
+    CALL lease6_AINS_lease6_pool_stat(NEW.state, NEW.subnet_id, NEW.pool_id, NEW.lease_type);
+    IF @json_supported IS NULL THEN
+        SELECT isJsonSupported() INTO @json_supported;
+    END IF;
+    IF @json_supported = 1 THEN
+        CALL lease6_AINS_lease6_stat_by_client_class(NEW.state, NEW.user_context, NEW.lease_type);
+    END IF;
+END $$
+DELIMITER ;
+
+DROP TRIGGER IF EXISTS lease6_AUPD;
+DELIMITER $$
+CREATE TRIGGER lease6_AUPD AFTER UPDATE ON lease6 FOR EACH ROW
+BEGIN
+    CALL lease6_AUPD_lease6_stat(OLD.state, OLD.subnet_id, OLD.lease_type, NEW.state, NEW.subnet_id, NEW.lease_type);
+    CALL lease6_AUPD_lease6_pool_stat(OLD.state, OLD.subnet_id, OLD.pool_id, OLD.lease_type, NEW.state, NEW.subnet_id, NEW.pool_id, NEW.lease_type);
+    IF @json_supported IS NULL THEN
+        SELECT isJsonSupported() INTO @json_supported;
+    END IF;
+    IF @json_supported = 1 THEN
+        CALL lease6_AUPD_lease6_stat_by_client_class(OLD.state, OLD.user_context, OLD.lease_type, NEW.state, NEW.user_context, NEW.lease_type);
+    END IF;
+END $$
+DELIMITER ;
+
+DROP TRIGGER IF EXISTS lease6_ADEL;
+DELIMITER $$
+CREATE TRIGGER lease6_ADEL AFTER DELETE ON lease6 FOR EACH ROW
+BEGIN
+    CALL lease6_ADEL_lease6_stat(OLD.state, OLD.subnet_id, OLD.lease_type);
+    CALL lease6_ADEL_lease6_pool_stat(OLD.state, OLD.subnet_id, OLD.pool_id, OLD.lease_type);
+    IF @json_supported IS NULL THEN
+        SELECT isJsonSupported() INTO @json_supported;
+    END IF;
+    IF @json_supported = 1 THEN
+        CALL lease6_ADEL_lease6_stat_by_client_class(OLD.state, OLD.user_context, OLD.lease_type);
+    END IF;
+END $$
+DELIMITER ;
+
+DROP PROCEDURE IF EXISTS lease4DumpHeader;
+DELIMITER $$
+CREATE PROCEDURE lease4DumpHeader()
+BEGIN
+SELECT 'address,hwaddr,client_id,valid_lifetime,expire,subnet_id,fqdn_fwd,fqdn_rev,hostname,state,user_context,pool_id';
+END $$
+DELIMITER ;
+
+-- Adding support for pool ID in procedure to output a memfile-ready CSV file.
+DROP PROCEDURE IF EXISTS lease4DumpData;
+DELIMITER $$
+CREATE PROCEDURE lease4DumpData()
+BEGIN
+    SELECT
+        INET_NTOA(address),
+        IFNULL(colonSeparatedHex(HEX(hwaddr)), ''),
+        IFNULL(colonSeparatedHex(HEX(client_id)), ''),
+        valid_lifetime,
+        UNIX_TIMESTAMP(expire),
+        subnet_id,
+        fqdn_fwd,
+        fqdn_rev,
+        REPLACE(hostname, ',', '&#x2c'),
+        state,
+        REPLACE(IFNULL(user_context, ''), ',', '&#x2c'),
+        pool_id
+    FROM lease4
+    ORDER BY address;
+END $$
+DELIMITER ;
+
+DROP PROCEDURE IF EXISTS lease6DumpHeader;
+DELIMITER $$
+CREATE PROCEDURE lease6DumpHeader()
+BEGIN
+    SELECT 'address,duid,valid_lifetime,expire,subnet_id,pref_lifetime,lease_type,iaid,prefix_len,fqdn_fwd,fqdn_rev,hostname,hwaddr,state,user_context,hwtype,hwaddr_source,pool_id';
+END $$
+DELIMITER ;
+
+-- Adding support for pool ID in procedure to output a memfile-ready CSV file.
+DROP PROCEDURE IF EXISTS lease6DumpData;
+DELIMITER $$
+CREATE PROCEDURE lease6DumpData()
+BEGIN
+    SELECT
+        address,
+        IFNULL(colonSeparatedHex(HEX(duid)), ''),
+        valid_lifetime,
+        UNIX_TIMESTAMP(expire),
+        subnet_id,
+        pref_lifetime,
+        lease_type,
+        iaid,
+        prefix_len,
+        fqdn_fwd,
+        fqdn_rev,
+        REPLACE(hostname, ',', '&#x2c'),
+        IFNULL(colonSeparatedHex(HEX(hwaddr)), ''),
+        state,
+        REPLACE(IFNULL(user_context, ''), ',', '&#x2c'),
+        hwtype,
+        hwaddr_source,
+        pool_id
+    FROM lease6
+    ORDER BY address;
+END $$
+DELIMITER ;
+
+-- Drop and create lease4Upload stored procedure with 255 bytes long client_id and support for pool_id.
+DROP PROCEDURE IF EXISTS lease4Upload;
+DELIMITER $$
+CREATE PROCEDURE lease4Upload(
+    IN address VARCHAR(15),
+    IN hwaddr VARCHAR(20),
+    IN client_id VARCHAR(255),
+    IN valid_lifetime INT UNSIGNED,
+    IN expire BIGINT UNSIGNED,
+    IN subnet_id INT UNSIGNED,
+    IN fqdn_fwd TINYINT,
+    IN fqdn_rev TINYINT,
+    IN hostname VARCHAR(255),
+    IN state INT UNSIGNED,
+    IN user_context TEXT,
+    IN pool_id INT UNSIGNED
+)
+BEGIN
+    INSERT INTO lease4 (
+        address,
+        hwaddr,
+        client_id,
+        valid_lifetime,
+        expire,
+        subnet_id,
+        fqdn_fwd,
+        fqdn_rev,
+        hostname,
+        state,
+        user_context,
+        pool_id
+    ) VALUES (
+        INET_ATON(address),
+        UNHEX(REPLACE(hwaddr, ':', '')),
+        UNHEX(REPLACE(client_id, ':', '')),
+        valid_lifetime,
+        FROM_UNIXTIME(expire),
+        subnet_id,
+        fqdn_fwd,
+        fqdn_rev,
+        REPLACE(hostname, '&#x2c', ','),
+        state,
+        REPLACE(user_context, '&#x2c', ','),
+        pool_id
+    );
+END $$
+DELIMITER ;
+
+-- Drop and create lease6Upload stored procedure with 130 bytes long duid and support for pool_id.
+DROP PROCEDURE IF EXISTS lease6Upload;
+DELIMITER $$
+CREATE PROCEDURE lease6Upload(
+    IN address VARCHAR(39),
+    IN duid VARCHAR(130),
+    IN valid_lifetime INT UNSIGNED,
+    IN expire BIGINT UNSIGNED,
+    IN subnet_id INT UNSIGNED,
+    IN pref_lifetime INT UNSIGNED,
+    IN lease_type TINYINT,
+    IN iaid INT UNSIGNED,
+    IN prefix_len TINYINT UNSIGNED,
+    IN fqdn_fwd TINYINT,
+    IN fqdn_rev TINYINT,
+    IN hostname VARCHAR(255),
+    IN hwaddr VARCHAR(64),
+    IN state INT UNSIGNED,
+    IN user_context TEXT,
+    IN hwtype SMALLINT,
+    IN hwaddr_source INT UNSIGNED,
+    IN pool_id INT UNSIGNED
+)
+BEGIN
+    INSERT INTO lease6 (
+        address,
+        duid,
+        valid_lifetime,
+        expire,
+        subnet_id,
+        pref_lifetime,
+        lease_type,
+        iaid,
+        prefix_len,
+        fqdn_fwd,
+        fqdn_rev,
+        hostname,
+        hwaddr,
+        state,
+        user_context,
+        hwtype,
+        hwaddr_source,
+        pool_id
+    ) VALUES (
+        address,
+        UNHEX(REPLACE(duid, ':', '')),
+        valid_lifetime,
+        FROM_UNIXTIME(expire),
+        subnet_id,
+        pref_lifetime,
+        lease_type,
+        iaid,
+        prefix_len,
+        fqdn_fwd,
+        fqdn_rev,
+        REPLACE(hostname, '&#x2c', ','),
+        UNHEX(REPLACE(hwaddr, ':', '')),
+        state,
+        REPLACE(user_context, '&#x2c', ','),
+        hwtype,
+        hwaddr_source,
+        pool_id
+    );
+END $$
+DELIMITER ;
+
+INSERT INTO lease4_pool_stat (subnet_id, pool_id, state, leases)
+    SELECT subnet_id, pool_id, state, count(*) FROM lease4
+    WHERE state = 0 OR state = 1 GROUP BY subnet_id, pool_id, state;
+
+INSERT INTO lease6_pool_stat (subnet_id, pool_id, lease_type, state, leases)
+    SELECT subnet_id, pool_id, lease_type, state, count(*) FROM lease6
+    WHERE state = 0 OR state = 1 GROUP BY subnet_id, pool_id, lease_type, state;
+
+-- Add the binary version of the IPv6 address for v6 BLQ prefix filter.
+ALTER TABLE lease6
+    ADD COLUMN binaddr BINARY(16) DEFAULT NULL;
+CREATE INDEX lease6_by_binaddr ON lease6 (binaddr ASC);
+
+-- Create table for v6 BLQ by-relay-id.
+CREATE TABLE lease6_relay_id (
+    extended_info_id INT UNSIGNED NOT NULL AUTO_INCREMENT,
+    relay_id VARBINARY(130) NOT NULL,
+    lease_addr BINARY(16) NOT NULL,
+    PRIMARY KEY (extended_info_id),
+    INDEX key_lease6_relay_id_by_id (relay_id, lease_addr ASC),
+    INDEX key_lease6_relay_id_by_address (lease_addr)
+)  ENGINE = INNODB;
+
+-- Create table for v6 BLQ by-remote-id.
+CREATE TABLE lease6_remote_id (
+    extended_info_id INT UNSIGNED NOT NULL AUTO_INCREMENT,
+    remote_id VARBINARY(255) NOT NULL,
+    lease_addr BINARY(16) NOT NULL,
+    PRIMARY KEY (extended_info_id),
+    INDEX key_lease6_remote_id_by_id (remote_id, lease_addr ASC),
+    INDEX key_lease6_remote_id_by_address (lease_addr)
+)  ENGINE = INNODB;
+
+-- Update the schema version number.
+UPDATE schema_version
+    SET version = '18', minor = '0';
+
+-- This line concludes the schema upgrade to version 18.0.
+
+-- This line starts the schema upgrade to version 19.0.
+-- We have to play some games to make lease address
+-- binary, primary key and retain its place as first
+-- column.
+-- Store binary values for address in binaddr column
+DROP INDEX lease6_by_binaddr ON lease6;
+UPDATE lease6 set binaddr = inet6_aton(address);
+ALTER TABLE lease6 DROP PRIMARY KEY, ADD PRIMARY KEY (binaddr);
+-- Wipe existing address column contents so we can change data type
+-- First remove the NULL constraint then set contents NULL
+ALTER TABLE lease6 MODIFY COLUMN address VARCHAR(39) DEFAULT NULL;
+UPDATE lease6 set address = NULL;
+-- Change address data type
+ALTER TABLE lease6 MODIFY COLUMN address BINARY(16);
+-- Copy the binary values back to address
+UPDATE lease6 set address = binaddr;
+-- Restore address as primary key
+ALTER TABLE lease6 DROP PRIMARY KEY, ADD PRIMARY KEY (address);
+-- Drop binaddr column
+ALTER TABLE lease6 DROP COLUMN binaddr;
+
+-- Change data type of ipv6_reservations.address column.
+-- Convert existing data via a temporary binary address column.
+ALTER TABLE ipv6_reservations ADD COLUMN binaddr  BINARY(16);
+UPDATE ipv6_reservations set binaddr = inet6_aton(address);
+-- Wipe existing address column contents so we can change data type
+-- First remove the NULL constraint then set contents NULL
+ALTER TABLE ipv6_reservations MODIFY COLUMN address VARCHAR(39) DEFAULT NULL;
+UPDATE ipv6_reservations set address = NULL;
+ALTER TABLE ipv6_reservations MODIFY COLUMN address BINARY(16);
+UPDATE ipv6_reservations set address = binaddr;
+ALTER TABLE ipv6_reservations MODIFY COLUMN address BINARY(16) NOT NULL;
+ALTER TABLE ipv6_reservations DROP COLUMN binaddr;
+
+-- Convert binary lease6 address to text
+DROP PROCEDURE IF EXISTS lease6DumpData;
+DELIMITER $$
+CREATE PROCEDURE lease6DumpData()
+BEGIN
+    SELECT
+        INET6_NTOA(address),
+        IFNULL(colonSeparatedHex(HEX(duid)), ''),
+        valid_lifetime,
+        UNIX_TIMESTAMP(expire),
+        subnet_id,
+        pref_lifetime,
+        lease_type,
+        iaid,
+        prefix_len,
+        fqdn_fwd,
+        fqdn_rev,
+        REPLACE(hostname, ',', '&#x2c'),
+        IFNULL(colonSeparatedHex(HEX(hwaddr)), ''),
+        state,
+        REPLACE(IFNULL(user_context, ''), ',', '&#x2c'),
+        hwtype,
+        hwaddr_source,
+        pool_id
+    FROM lease6
+    ORDER BY address;
+END $$
+DELIMITER ;
+
+-- Drop and create lease6Upload stored procedure with conversion to
+-- address to binary
+DROP PROCEDURE IF EXISTS lease6Upload;
+DELIMITER $$
+CREATE PROCEDURE lease6Upload(
+    IN address VARCHAR(39),
+    IN duid VARCHAR(130),
+    IN valid_lifetime INT UNSIGNED,
+    IN expire BIGINT UNSIGNED,
+    IN subnet_id INT UNSIGNED,
+    IN pref_lifetime INT UNSIGNED,
+    IN lease_type TINYINT,
+    IN iaid INT UNSIGNED,
+    IN prefix_len TINYINT UNSIGNED,
+    IN fqdn_fwd TINYINT,
+    IN fqdn_rev TINYINT,
+    IN hostname VARCHAR(255),
+    IN hwaddr VARCHAR(64),
+    IN state INT UNSIGNED,
+    IN user_context TEXT,
+    IN hwtype SMALLINT,
+    IN hwaddr_source INT UNSIGNED,
+    IN pool_id INT UNSIGNED
+)
+BEGIN
+    INSERT INTO lease6 (
+        address,
+        duid,
+        valid_lifetime,
+        expire,
+        subnet_id,
+        pref_lifetime,
+        lease_type,
+        iaid,
+        prefix_len,
+        fqdn_fwd,
+        fqdn_rev,
+        hostname,
+        hwaddr,
+        state,
+        user_context,
+        hwtype,
+        hwaddr_source,
+        pool_id
+    ) VALUES (
+        INET6_ATON(address),
+        UNHEX(REPLACE(duid, ':', '')),
+        valid_lifetime,
+        FROM_UNIXTIME(expire),
+        subnet_id,
+        pref_lifetime,
+        lease_type,
+        iaid,
+        prefix_len,
+        fqdn_fwd,
+        fqdn_rev,
+        REPLACE(hostname, '&#x2c', ','),
+        UNHEX(REPLACE(hwaddr, ':', '')),
+        state,
+        REPLACE(user_context, '&#x2c', ','),
+        hwtype,
+        hwaddr_source,
+        pool_id
+    );
+END $$
+DELIMITER ;
+
+-- Update the schema version number.
+UPDATE schema_version
+    SET version = '19', minor = '0';
+
+-- This line concludes the schema upgrade to version 19.0.
+
+# Notes:
+#
+# Indexes
+# =======
+# It is likely that additional indexes will be needed.  However, the
+# increase in lookup performance from these will come at the expense
+# of a decrease in performance during insert operations due to the need
+# to update the indexes.  For this reason, the need for additional indexes
+# will be determined by experiment during performance tests.
+#
+# The most likely additional indexes will cover the following columns:
+#
+# hwaddr and client_id
+# For lease stability: if a client requests a new lease, try to find an
+# existing or recently expired lease for it so that it can keep using the
+# same IP address.
+#
+# Field Sizes
+# ===========
+# If any of the VARxxx field sizes are altered, the lengths in the MySQL
+# backend source file (mysql_lease_mgr.cc) must be correspondingly changed.
+#
+# Portability
+# ===========
+# The 'ENGINE = INNODB' on some tables is not portable to another database
+# and will need to be removed.
+#
+# Some columns contain binary data so are stored as VARBINARY instead of
+# VARCHAR.  This may be non-portable between databases: in this case, the
+# definition should be changed to VARCHAR.