/* Copyright (c) 2004, 2015, Oracle and/or its affiliates. Copyright (c) 2017, 2020, MariaDB Corporation. This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; version 2 of the License. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1335 USA */ /* MySQL Federated Storage Engine ha_federated.cc - MySQL Federated Storage Engine Patrick Galbraith and Brian Aker, 2004 This is a handler which uses a foreign database as the data file, as opposed to a handler like MyISAM, which uses .MYD files locally. How this handler works ---------------------------------- Normal database files are local and as such: You create a table called 'users', a file such as 'users.MYD' is created. A handler reads, inserts, deletes, updates data in this file. The data is stored in particular format, so to read, that data has to be parsed into fields, to write, fields have to be stored in this format to write to this data file. With MySQL Federated storage engine, there will be no local files for each table's data (such as .MYD). A foreign database will store the data that would normally be in this file. This will necessitate the use of MySQL client API to read, delete, update, insert this data. The data will have to be retrieve via an SQL call "SELECT * FROM users". Then, to read this data, it will have to be retrieved via mysql_fetch_row one row at a time, then converted from the column in this select into the format that the handler expects. The create table will simply create the .frm file, and within the "CREATE TABLE" SQL, there SHALL be any of the following : connection=scheme://username:password@hostname:port/database/tablename connection=scheme://username@hostname/database/tablename connection=scheme://username:password@hostname/database/tablename connection=scheme://username:password@hostname/database/tablename - OR - As of 5.1 (See worklog #3031), federated now allows you to use a non-url format, taking advantage of mysql.servers: connection="connection_one" connection="connection_one/table_foo" An example would be: connection=mysql://username:password@hostname:port/database/tablename or, if we had: create server 'server_one' foreign data wrapper 'mysql' options (HOST '127.0.0.1', DATABASE 'db1', USER 'root', PASSWORD '', PORT 3306, SOCKET '', OWNER 'root'); CREATE TABLE federated.t1 ( `id` int(20) NOT NULL, `name` varchar(64) NOT NULL default '' ) ENGINE="FEDERATED" DEFAULT CHARSET=latin1 CONNECTION='server_one'; So, this will have been the equivalent of CONNECTION="mysql://root@127.0.0.1:3306/db1/t1" Then, we can also change the server to point to a new schema: ALTER SERVER 'server_one' options(DATABASE 'db2'); All subsequent calls will now be against db2.t1! Guess what? You don't have to perform an alter table! This connecton="connection string" is necessary for the handler to be able to connect to the foreign server, either by URL, or by server name. The basic flow is this: SQL calls issues locally -> mysql handler API (data in handler format) -> mysql client API (data converted to SQL calls) -> foreign database -> mysql client API -> convert result sets (if any) to handler format -> handler API -> results or rows affected to local What this handler does and doesn't support ------------------------------------------ * Tables MUST be created on the foreign server prior to any action on those tables via the handler, first version. IMPORTANT: IF you MUST use the federated storage engine type on the REMOTE end, MAKE SURE [ :) ] That the table you connect to IS NOT a table pointing BACK to your ORIGNAL table! You know and have heard the screaching of audio feedback? You know putting two mirror in front of each other how the reflection continues for eternity? Well, need I say more?! * There will not be support for transactions. * There is no way for the handler to know if the foreign database or table has changed. The reason for this is that this database has to work like a data file that would never be written to by anything other than the database. The integrity of the data in the local table could be breached if there was any change to the foreign database. * Support for SELECT, INSERT, UPDATE , DELETE, indexes. * No ALTER TABLE, DROP TABLE or any other Data Definition Language calls. * Prepared statements will not be used in the first implementation, it remains to to be seen whether the limited subset of the client API for the server supports this. * This uses SELECT, INSERT, UPDATE, DELETE and not HANDLER for its implementation. * This will not work with the query cache. Method calls A two column table, with one record: (SELECT) "SELECT * FROM foo" ha_federated::info ha_federated::scan_time: ha_federated::rnd_init: share->select_query SELECT * FROM foo ha_federated::extra ha_federated::rnd_next ha_federated::convert_row_to_internal_format ha_federated::rnd_next ha_federated::rnd_end ha_federated::extra ha_federated::reset (INSERT) "INSERT INTO foo (id, ts) VALUES (2, now());" ha_federated::write_row ha_federated::reset (UPDATE) "UPDATE foo SET ts = now() WHERE id = 1;" ha_federated::index_init ha_federated::index_read ha_federated::index_read_idx ha_federated::rnd_next ha_federated::convert_row_to_internal_format ha_federated::update_row ha_federated::extra ha_federated::extra ha_federated::extra ha_federated::external_lock ha_federated::reset How do I use this handler? -------------------------- First of all, you need to build this storage engine: ./configure --with-federated-storage-engine make Next, to use this handler, it's very simple. You must have two databases running, either both on the same host, or on different hosts. One the server that will be connecting to the foreign host (client), you create your table as such: CREATE TABLE test_table ( id int(20) NOT NULL auto_increment, name varchar(32) NOT NULL default '', other int(20) NOT NULL default '0', PRIMARY KEY (id), KEY name (name), KEY other_key (other)) ENGINE="FEDERATED" DEFAULT CHARSET=latin1 CONNECTION='mysql://root@127.0.0.1:9306/federated/test_federated'; Notice the "COMMENT" and "ENGINE" field? This is where you respectively set the engine type, "FEDERATED" and foreign host information, this being the database your 'client' database will connect to and use as the "data file". Obviously, the foreign database is running on port 9306, so you want to start up your other database so that it is indeed on port 9306, and your federated database on a port other than that. In my setup, I use port 5554 for federated, and port 5555 for the foreign database. Then, on the foreign database: CREATE TABLE test_table ( id int(20) NOT NULL auto_increment, name varchar(32) NOT NULL default '', other int(20) NOT NULL default '0', PRIMARY KEY (id), KEY name (name), KEY other_key (other)) ENGINE="" <-- whatever you want, or not specify DEFAULT CHARSET=latin1 ; This table is exactly the same (and must be exactly the same), except that it is not using the federated handler and does not need the URL. How to see the handler in action -------------------------------- When developing this handler, I compiled the federated database with debugging: ./configure --with-federated-storage-engine --prefix=/home/mysql/mysql-build/federated/ --with-debug Once compiled, I did a 'make install' (not for the purpose of installing the binary, but to install all the files the binary expects to see in the diretory I specified in the build with --prefix, "/home/mysql/mysql-build/federated". Then, I started the foreign server: /usr/local/mysql/bin/mysqld_safe --user=mysql --log=/tmp/mysqld.5555.log -P 5555 Then, I went back to the directory containing the newly compiled mysqld, /sql/, started up gdb: gdb ./mysqld Then, withn the (gdb) prompt: (gdb) run --gdb --port=5554 --socket=/tmp/mysqld.5554 --skip-innodb --debug-dbug Next, I open several windows for each: 1. Tail the debug trace: tail -f /tmp/mysqld.trace|grep ha_fed 2. Tail the SQL calls to the foreign database: tail -f /tmp/mysqld.5555.log 3. A window with a client open to the federated server on port 5554 4. A window with a client open to the federated server on port 5555 I would create a table on the client to the foreign server on port 5555, and then to the federated server on port 5554. At this point, I would run whatever queries I wanted to on the federated server, just always remembering that whatever changes I wanted to make on the table, or if I created new tables, that I would have to do that on the foreign server. Another thing to look for is 'show variables' to show you that you have support for federated handler support: show variables like '%federat%' and: show storage engines; Both should display the federated storage handler. Testing ------- There is a test for MySQL Federated Storage Handler in ./mysql-test/t, federatedd.test It starts both a slave and master database using the same setup that the replication tests use, with the exception that it turns off replication, and sets replication to ignore the test tables. After ensuring that you actually do have support for the federated storage handler, numerous queries/inserts/updates/deletes are run, many derived from the MyISAM tests, plus som other tests which were meant to reveal any issues that would be most likely to affect this handler. All tests should work! ;) To run these tests, go into ./mysql-test (based in the directory you built the server in) ./mysql-test-run federated To run the test, or if you want to run the test and have debug info: ./mysql-test-run --debug federated This will run the test in debug mode, and you can view the trace and log files in the ./mysql-test/var/log directory ls -l mysql-test/var/log/ -rw-r--r-- 1 patg patg 17 4 Dec 12:27 current_test -rw-r--r-- 1 patg patg 692 4 Dec 12:52 manager.log -rw-rw---- 1 patg patg 21246 4 Dec 12:51 master-bin.000001 -rw-rw---- 1 patg patg 68 4 Dec 12:28 master-bin.index -rw-r--r-- 1 patg patg 1620 4 Dec 12:51 master.err -rw-rw---- 1 patg patg 23179 4 Dec 12:51 master.log -rw-rw---- 1 patg patg 16696550 4 Dec 12:51 master.trace -rw-r--r-- 1 patg patg 0 4 Dec 12:28 mysqltest-time -rw-r--r-- 1 patg patg 2024051 4 Dec 12:51 mysqltest.trace -rw-rw---- 1 patg patg 94992 4 Dec 12:51 slave-bin.000001 -rw-rw---- 1 patg patg 67 4 Dec 12:28 slave-bin.index -rw-rw---- 1 patg patg 249 4 Dec 12:52 slave-relay-bin.000003 -rw-rw---- 1 patg patg 73 4 Dec 12:28 slave-relay-bin.index -rw-r--r-- 1 patg patg 1349 4 Dec 12:51 slave.err -rw-rw---- 1 patg patg 96206 4 Dec 12:52 slave.log -rw-rw---- 1 patg patg 15706355 4 Dec 12:51 slave.trace -rw-r--r-- 1 patg patg 0 4 Dec 12:51 warnings Of course, again, you can tail the trace log: tail -f mysql-test/var/log/master.trace |grep ha_fed As well as the slave query log: tail -f mysql-test/var/log/slave.log Files that comprise the test suit --------------------------------- mysql-test/t/federated.test mysql-test/r/federated.result mysql-test/r/have_federated_db.require mysql-test/include/have_federated_db.inc Other tidbits ------------- These were the files that were modified or created for this Federated handler to work, in 5.0: ./configure.in ./sql/Makefile.am ./config/ac_macros/ha_federated.m4 ./sql/handler.cc ./sql/mysqld.cc ./sql/set_var.cc ./sql/field.h ./sql/sql_string.h ./mysql-test/mysql-test-run(.sh) ./mysql-test/t/federated.test ./mysql-test/r/federated.result ./mysql-test/r/have_federated_db.require ./mysql-test/include/have_federated_db.inc ./sql/ha_federated.cc ./sql/ha_federated.h In 5.1 my:~/mysql-build/mysql-5.1-bkbits patg$ ls storage/federated/ CMakeLists.txt Makefile.in ha_federated.h plug.in Makefile SCCS libfederated.a Makefile.am ha_federated.cc libfederated_a-ha_federated.o */ #define MYSQL_SERVER 1 #include #include "sql_priv.h" #include "sql_servers.h" // FOREIGN_SERVER, get_server_by_name #include "sql_class.h" // SSV #include "sql_analyse.h" // append_escaped #include #ifdef USE_PRAGMA_IMPLEMENTATION #pragma implementation // gcc: Class implementation #endif #include "ha_federated.h" #include "m_string.h" #include "key.h" // key_copy #include #ifdef I_AM_PARANOID #define MIN_PORT 1023 #else #define MIN_PORT 0 #endif /* Variables for federated share methods */ static HASH federated_open_tables; // To track open tables mysql_mutex_t federated_mutex; // To init the hash static char ident_quote_char= '`'; // Character for quoting // identifiers static char value_quote_char= '\''; // Character for quoting // literals static const int bulk_padding= 64; // bytes "overhead" in packet /* Variables used when chopping off trailing characters */ static const uint sizeof_trailing_comma= sizeof(", ") - 1; static const uint sizeof_trailing_and= sizeof(" AND ") - 1; static const uint sizeof_trailing_where= sizeof(" WHERE ") - 1; /* Static declaration for handerton */ static handler *federated_create_handler(handlerton *hton, TABLE_SHARE *table, MEM_ROOT *mem_root); static int federated_commit(handlerton *hton, THD *thd, bool all); static int federated_rollback(handlerton *hton, THD *thd, bool all); /* Federated storage engine handlerton */ static handler *federated_create_handler(handlerton *hton, TABLE_SHARE *table, MEM_ROOT *mem_root) { return new (mem_root) ha_federated(hton, table); } /* Function we use in the creation of our hash to get key */ static uchar *federated_get_key(FEDERATED_SHARE *share, size_t *length, my_bool not_used __attribute__ ((unused))) { *length= share->share_key_length; return (uchar*) share->share_key; } #ifdef HAVE_PSI_INTERFACE static PSI_mutex_key fe_key_mutex_federated, fe_key_mutex_FEDERATED_SHARE_mutex; static PSI_mutex_info all_federated_mutexes[]= { { &fe_key_mutex_federated, "federated", PSI_FLAG_GLOBAL}, { &fe_key_mutex_FEDERATED_SHARE_mutex, "FEDERATED_SHARE::mutex", 0} }; static void init_federated_psi_keys(void) { const char* category= "federated"; int count; if (PSI_server == NULL) return; count= array_elements(all_federated_mutexes); PSI_server->register_mutex(category, all_federated_mutexes, count); } #endif /* HAVE_PSI_INTERFACE */ /* Initialize the federated handler. SYNOPSIS federated_db_init() p Handlerton RETURN FALSE OK TRUE Error */ int federated_db_init(void *p) { DBUG_ENTER("federated_db_init"); #ifdef HAVE_PSI_INTERFACE init_federated_psi_keys(); #endif /* HAVE_PSI_INTERFACE */ handlerton *federated_hton= (handlerton *)p; federated_hton->db_type= DB_TYPE_FEDERATED_DB; federated_hton->commit= federated_commit; federated_hton->rollback= federated_rollback; federated_hton->create= federated_create_handler; federated_hton->drop_table= [](handlerton *, const char*) { return -1; }; federated_hton->flags= HTON_ALTER_NOT_SUPPORTED | HTON_NO_PARTITION; /* Support for transactions disabled until WL#2952 fixes it. We do it like this to avoid "defined but not used" compiler warnings. */ federated_hton->commit= 0; federated_hton->rollback= 0; if (mysql_mutex_init(fe_key_mutex_federated, &federated_mutex, MY_MUTEX_INIT_FAST)) goto error; if (!my_hash_init(PSI_INSTRUMENT_ME, &federated_open_tables, &my_charset_bin, 32, 0, 0, (my_hash_get_key) federated_get_key, 0, 0)) { DBUG_RETURN(FALSE); } mysql_mutex_destroy(&federated_mutex); error: DBUG_RETURN(TRUE); } /* Release the federated handler. SYNOPSIS federated_db_end() RETURN FALSE OK */ int federated_done(void *p) { my_hash_free(&federated_open_tables); mysql_mutex_destroy(&federated_mutex); return 0; } /** @brief Append identifiers to the string. @param[in,out] string The target string. @param[in] name Identifier name @param[in] length Length of identifier name in bytes @param[in] quote_char Quote char to use for quoting identifier. @return Operation Status @retval FALSE OK @retval TRUE There was an error appending to the string. @note This function is based upon the append_identifier() function in sql_show.cc except that quoting always occurs. */ static bool append_ident(String *string, const char *name, size_t length, const char quote_char) { bool result; uint clen; const char *name_end; DBUG_ENTER("append_ident"); if (quote_char) { string->reserve((uint) length * 2 + 2); if ((result= string->append("e_char, 1, system_charset_info))) goto err; for (name_end= name+length; name < name_end; name+= clen) { uchar c= *(uchar *) name; clen= system_charset_info->charlen_fix(name, name_end); if (clen == 1 && c == (uchar) quote_char && (result= string->append("e_char, 1, system_charset_info))) goto err; if ((result= string->append(name, clen, string->charset()))) goto err; } result= string->append("e_char, 1, system_charset_info); } else result= string->append(name, (uint) length, system_charset_info); err: DBUG_RETURN(result); } static int parse_url_error(FEDERATED_SHARE *share, TABLE *table, int error_num) { char buf[FEDERATED_QUERY_BUFFER_SIZE]; size_t buf_len; DBUG_ENTER("ha_federated parse_url_error"); buf_len= MY_MIN(table->s->connect_string.length, FEDERATED_QUERY_BUFFER_SIZE-1); strmake(buf, table->s->connect_string.str, buf_len); my_error(error_num, MYF(0), buf, 14); DBUG_RETURN(error_num); } /* retrieve server object which contains server meta-data from the system table given a server's name, set share connection parameter members */ int get_connection(MEM_ROOT *mem_root, FEDERATED_SHARE *share) { int error_num= ER_FOREIGN_SERVER_DOESNT_EXIST; FOREIGN_SERVER *server, server_buffer; DBUG_ENTER("ha_federated::get_connection"); /* get_server_by_name() clones the server if exists and allocates copies of strings in the supplied mem_root */ if (!(server= get_server_by_name(mem_root, share->connection_string, &server_buffer))) { DBUG_PRINT("info", ("get_server_by_name returned > 0 error condition!")); /* need to come up with error handling */ error_num=1; goto error; } DBUG_PRINT("info", ("get_server_by_name returned server at %p", server)); /* Most of these should never be empty strings, error handling will need to be implemented. Also, is this the best way to set the share members? Is there some allocation needed? In running this code, it works except there are errors in the trace file of the share being overrun at the address of the share. */ share->server_name_length= server->server_name_length; share->server_name= const_cast(server->server_name); share->username= const_cast(server->username); share->password= const_cast(server->password); share->database= const_cast(server->db); share->port= server->port > MIN_PORT && server->port < 65536 ? (ushort) server->port : MYSQL_PORT; share->hostname= const_cast(server->host); if (!(share->socket= const_cast(server->socket)) && !strcmp(share->hostname, my_localhost)) share->socket= (char *) MYSQL_UNIX_ADDR; share->scheme= const_cast(server->scheme); DBUG_PRINT("info", ("share->username %s", share->username)); DBUG_PRINT("info", ("share->password %s", share->password)); DBUG_PRINT("info", ("share->hostname %s", share->hostname)); DBUG_PRINT("info", ("share->database %s", share->database)); DBUG_PRINT("info", ("share->port %d", share->port)); DBUG_PRINT("info", ("share->socket %s", share->socket)); DBUG_RETURN(0); error: my_printf_error(error_num, "server name: '%s' doesn't exist!", MYF(0), share->connection_string); DBUG_RETURN(error_num); } /* Parse connection info from table->s->connect_string SYNOPSIS parse_url() mem_root MEM_ROOT pointer for memory allocation share pointer to FEDERATED share table pointer to current TABLE class table_create_flag determines what error to throw DESCRIPTION Populates the share with information about the connection to the foreign database that will serve as the data source. This string must be specified (currently) in the "CONNECTION" field, listed in the CREATE TABLE statement. This string MUST be in the format of any of these: CONNECTION="scheme://username:password@hostname:port/database/table" CONNECTION="scheme://username@hostname/database/table" CONNECTION="scheme://username@hostname:port/database/table" CONNECTION="scheme://username:password@hostname/database/table" _OR_ CONNECTION="connection name" An Example: CREATE TABLE t1 (id int(32)) ENGINE="FEDERATED" CONNECTION="mysql://joe:joespass@192.168.1.111:9308/federated/testtable"; CREATE TABLE t2 ( id int(4) NOT NULL auto_increment, name varchar(32) NOT NULL, PRIMARY KEY(id) ) ENGINE="FEDERATED" CONNECTION="my_conn"; ***IMPORTANT*** Currently, the Federated Storage Engine only supports connecting to another MySQL Database ("scheme" of "mysql"). Connections using JDBC as well as other connectors are in the planning stage. 'password' and 'port' are both optional. RETURN VALUE 0 success error_num particular error code */ static int parse_url(MEM_ROOT *mem_root, FEDERATED_SHARE *share, TABLE *table, uint table_create_flag) { uint error_num= (table_create_flag ? ER_FOREIGN_DATA_STRING_INVALID_CANT_CREATE : ER_FOREIGN_DATA_STRING_INVALID); DBUG_ENTER("ha_federated::parse_url"); share->port= 0; share->socket= 0; DBUG_PRINT("info", ("share at %p", share)); DBUG_PRINT("info", ("Length: %u", (uint) table->s->connect_string.length)); DBUG_PRINT("info", ("String: '%.*s'", (int) table->s->connect_string.length, table->s->connect_string.str)); share->connection_string= strmake_root(mem_root, table->s->connect_string.str, table->s->connect_string.length); DBUG_PRINT("info",("parse_url alloced share->connection_string %p", share->connection_string)); DBUG_PRINT("info",("share->connection_string %s",share->connection_string)); /* No :// or @ in connection string. Must be a straight connection name of either "servername" or "servername/tablename" */ if ( (!strstr(share->connection_string, "://") && (!strchr(share->connection_string, '@')))) { DBUG_PRINT("info", ("share->connection_string %s internal format \ share->connection_string %p", share->connection_string, share->connection_string)); /* ok, so we do a little parsing, but not completely! */ share->parsed= FALSE; /* If there is a single '/' in the connection string, this means the user is specifying a table name */ if ((share->table_name= strchr(share->connection_string, '/'))) { share->connection_string[share->table_name - share->connection_string]= '\0'; share->table_name++; share->table_name_length= (uint) strlen(share->table_name); DBUG_PRINT("info", ("internal format, parsed table_name share->connection_string \ %s share->table_name %s", share->connection_string, share->table_name)); /* there better not be any more '/'s ! */ if (strchr(share->table_name, '/')) goto error; } /* otherwise, straight server name, use tablename of federated table as remote table name */ else { /* connection specifies everything but, resort to expecting remote and foreign table names to match */ share->table_name= strmake_root(mem_root, table->s->table_name.str, (share->table_name_length= table->s->table_name.length)); DBUG_PRINT("info", ("internal format, default table_name share->connection_string \ %s share->table_name %s", share->connection_string, share->table_name)); } if ((error_num= get_connection(mem_root, share))) goto error; } else { share->parsed= TRUE; // Add a null for later termination of table name share->connection_string[table->s->connect_string.length]= 0; share->scheme= share->connection_string; DBUG_PRINT("info",("parse_url alloced share->scheme %p", share->scheme)); /* remove addition of null terminator and store length for each string in share */ if (!(share->username= strstr(share->scheme, "://"))) goto error; share->scheme[share->username - share->scheme]= '\0'; if (strcmp(share->scheme, "mysql") != 0) goto error; share->username+= 3; if (!(share->hostname= strchr(share->username, '@'))) goto error; share->username[share->hostname - share->username]= '\0'; share->hostname++; if ((share->password= strchr(share->username, ':'))) { share->username[share->password - share->username]= '\0'; share->password++; share->username= share->username; /* make sure there isn't an extra / or @ */ if ((strchr(share->password, '/') || strchr(share->hostname, '@'))) goto error; /* Found that if the string is: user:@hostname:port/db/table Then password is a null string, so set to NULL */ if (share->password[0] == '\0') share->password= NULL; } else share->username= share->username; /* make sure there isn't an extra / or @ */ if ((strchr(share->username, '/')) || (strchr(share->hostname, '@'))) goto error; if (!(share->database= strchr(share->hostname, '/'))) goto error; share->hostname[share->database - share->hostname]= '\0'; share->database++; if ((share->sport= strchr(share->hostname, ':'))) { share->hostname[share->sport - share->hostname]= '\0'; share->sport++; if (share->sport[0] == '\0') share->sport= NULL; else share->port= atoi(share->sport); } if (!(share->table_name= strchr(share->database, '/'))) goto error; share->database[share->table_name - share->database]= '\0'; share->table_name++; share->table_name_length= strlen(share->table_name); /* make sure there's not an extra / */ if ((strchr(share->table_name, '/'))) goto error; /* If hostname is omitted, we set it to NULL. According to mysql_real_connect() manual: The value of host may be either a hostname or an IP address. If host is NULL or the string "localhost", a connection to the local host is assumed. */ if (share->hostname[0] == '\0') share->hostname= NULL; } if (!share->port) { if (!share->hostname || strcmp(share->hostname, my_localhost) == 0) share->socket= (char*) MYSQL_UNIX_ADDR; else share->port= MYSQL_PORT; } DBUG_PRINT("info", ("scheme: %s username: %s password: %s \ hostname: %s port: %d db: %s tablename: %s", share->scheme, share->username, share->password, share->hostname, share->port, share->database, share->table_name)); DBUG_RETURN(0); error: DBUG_RETURN(parse_url_error(share, table, error_num)); } /***************************************************************************** ** FEDERATED tables *****************************************************************************/ ha_federated::ha_federated(handlerton *hton, TABLE_SHARE *table_arg) :handler(hton, table_arg), mysql(0), stored_result(0) { trx_next= 0; bzero(&bulk_insert, sizeof(bulk_insert)); } /* Convert MySQL result set row to handler internal format SYNOPSIS convert_row_to_internal_format() record Byte pointer to record row MySQL result set row from fetchrow() result Result set to use DESCRIPTION This method simply iterates through a row returned via fetchrow with values from a successful SELECT , and then stores each column's value in the field object via the field object pointer (pointing to the table's array of field object pointers). This is how the handler needs the data to be stored to then return results back to the user RETURN VALUE 0 After fields have had field values stored from record */ uint ha_federated::convert_row_to_internal_format(uchar *record, MYSQL_ROW row, MYSQL_RES *result) { ulong *lengths; Field **field; MY_BITMAP *old_map= dbug_tmp_use_all_columns(table, &table->write_set); DBUG_ENTER("ha_federated::convert_row_to_internal_format"); lengths= mysql_fetch_lengths(result); for (field= table->field; *field; field++, row++, lengths++) { /* index variable to move us through the row at the same iterative step as the field */ my_ptrdiff_t old_ptr; old_ptr= (my_ptrdiff_t) (record - table->record[0]); (*field)->move_field_offset(old_ptr); if (!*row) { (*field)->set_null(); (*field)->reset(); } else { if (bitmap_is_set(table->read_set, (*field)->field_index)) { (*field)->set_notnull(); (*field)->store_text(*row, *lengths, &my_charset_bin); } } (*field)->move_field_offset(-old_ptr); } dbug_tmp_restore_column_map(&table->write_set, old_map); DBUG_RETURN(0); } static bool emit_key_part_name(String *to, KEY_PART_INFO *part) { DBUG_ENTER("emit_key_part_name"); if (append_ident(to, part->field->field_name.str, part->field->field_name.length, ident_quote_char)) DBUG_RETURN(1); // Out of memory DBUG_RETURN(0); } static bool emit_key_part_element(String *to, KEY_PART_INFO *part, bool needs_quotes, bool is_like, const uchar *ptr, uint len) { Field *field= part->field; DBUG_ENTER("emit_key_part_element"); if (needs_quotes && to->append(STRING_WITH_LEN("'"))) DBUG_RETURN(1); if (part->type == HA_KEYTYPE_BIT) { char buff[STRING_BUFFER_USUAL_SIZE], *buf= buff; *buf++= '0'; *buf++= 'x'; buf= octet2hex(buf, (char*) ptr, len); if (to->append((char*) buff, (uint)(buf - buff))) DBUG_RETURN(1); } else if (part->key_part_flag & HA_BLOB_PART) { uint blob_length= uint2korr(ptr); String blob((char*) ptr+HA_KEY_BLOB_LENGTH, blob_length, &my_charset_bin); if (to->append_for_single_quote(&blob)) DBUG_RETURN(1); } else if (part->key_part_flag & HA_VAR_LENGTH_PART) { uint var_length= uint2korr(ptr); String varchar((char*) ptr+HA_KEY_BLOB_LENGTH, var_length, &my_charset_bin); if (to->append_for_single_quote(&varchar)) DBUG_RETURN(1); } else { char strbuff[MAX_FIELD_WIDTH]; String str(strbuff, sizeof(strbuff), part->field->charset()), *res; res= field->val_str(&str, ptr); if (field->result_type() == STRING_RESULT) { if (to->append_for_single_quote(res)) DBUG_RETURN(1); } else if (to->append(res->ptr(), res->length())) DBUG_RETURN(1); } if (is_like && to->append(STRING_WITH_LEN("%"))) DBUG_RETURN(1); if (needs_quotes && to->append(STRING_WITH_LEN("'"))) DBUG_RETURN(1); DBUG_RETURN(0); } /* Create a WHERE clause based off of values in keys Note: This code was inspired by key_copy from key.cc SYNOPSIS create_where_from_key () to String object to store WHERE clause key_info KEY struct pointer key byte pointer containing key key_length length of key range_type 0 - no range, 1 - min range, 2 - max range (see enum range_operation) DESCRIPTION Using iteration through all the keys via a KEY_PART_INFO pointer, This method 'extracts' the value of each key in the byte pointer *key, and for each key found, constructs an appropriate WHERE clause RETURN VALUE 0 After all keys have been accounted for to create the WHERE clause 1 No keys found Range flags Table per Timour: ----------------- - start_key: * ">" -> HA_READ_AFTER_KEY * ">=" -> HA_READ_KEY_OR_NEXT * "=" -> HA_READ_KEY_EXACT - end_key: * "<" -> HA_READ_BEFORE_KEY * "<=" -> HA_READ_AFTER_KEY records_in_range: ----------------- - start_key: * ">" -> HA_READ_AFTER_KEY * ">=" -> HA_READ_KEY_EXACT * "=" -> HA_READ_KEY_EXACT - end_key: * "<" -> HA_READ_BEFORE_KEY * "<=" -> HA_READ_AFTER_KEY * "=" -> HA_READ_AFTER_KEY 0 HA_READ_KEY_EXACT, Find first record else error 1 HA_READ_KEY_OR_NEXT, Record or next record 2 HA_READ_KEY_OR_PREV, Record or previous 3 HA_READ_AFTER_KEY, Find next rec. after key-record 4 HA_READ_BEFORE_KEY, Find next rec. before key-record 5 HA_READ_PREFIX, Key which as same prefix 6 HA_READ_PREFIX_LAST, Last key with the same prefix 7 HA_READ_PREFIX_LAST_OR_PREV, Last or prev key with the same prefix Flags that I've found: id, primary key, varchar id = 'ccccc' records_in_range: start_key 0 end_key 3 read_range_first: start_key 0 end_key NULL id > 'ccccc' records_in_range: start_key 3 end_key NULL read_range_first: start_key 3 end_key NULL id < 'ccccc' records_in_range: start_key NULL end_key 4 read_range_first: start_key NULL end_key 4 id <= 'ccccc' records_in_range: start_key NULL end_key 3 read_range_first: start_key NULL end_key 3 id >= 'ccccc' records_in_range: start_key 0 end_key NULL read_range_first: start_key 1 end_key NULL id like 'cc%cc' records_in_range: start_key 0 end_key 3 read_range_first: start_key 1 end_key 3 id > 'aaaaa' and id < 'ccccc' records_in_range: start_key 3 end_key 4 read_range_first: start_key 3 end_key 4 id >= 'aaaaa' and id < 'ccccc'; records_in_range: start_key 0 end_key 4 read_range_first: start_key 1 end_key 4 id >= 'aaaaa' and id <= 'ccccc'; records_in_range: start_key 0 end_key 3 read_range_first: start_key 1 end_key 3 id > 'aaaaa' and id <= 'ccccc'; records_in_range: start_key 3 end_key 3 read_range_first: start_key 3 end_key 3 numeric keys: id = 4 index_read_idx: start_key 0 end_key NULL id > 4 records_in_range: start_key 3 end_key NULL read_range_first: start_key 3 end_key NULL id >= 4 records_in_range: start_key 0 end_key NULL read_range_first: start_key 1 end_key NULL id < 4 records_in_range: start_key NULL end_key 4 read_range_first: start_key NULL end_key 4 id <= 4 records_in_range: start_key NULL end_key 3 read_range_first: start_key NULL end_key 3 id like 4 full table scan, select * from id > 2 and id < 8 records_in_range: start_key 3 end_key 4 read_range_first: start_key 3 end_key 4 id >= 2 and id < 8 records_in_range: start_key 0 end_key 4 read_range_first: start_key 1 end_key 4 id >= 2 and id <= 8 records_in_range: start_key 0 end_key 3 read_range_first: start_key 1 end_key 3 id > 2 and id <= 8 records_in_range: start_key 3 end_key 3 read_range_first: start_key 3 end_key 3 multi keys (id int, name varchar, other varchar) id = 1; records_in_range: start_key 0 end_key 3 read_range_first: start_key 0 end_key NULL id > 4; id > 2 and name = '333'; remote: id > 2 id > 2 and name > '333'; remote: id > 2 id > 2 and name > '333' and other < 'ddd'; remote: id > 2 no results id > 2 and name >= '333' and other < 'ddd'; remote: id > 2 1 result id >= 4 and name = 'eric was here' and other > 'eeee'; records_in_range: start_key 3 end_key NULL read_range_first: start_key 3 end_key NULL id >= 4; id >= 2 and name = '333' and other < 'ddd'; remote: `id` >= 2 AND `name` >= '333'; records_in_range: start_key 0 end_key NULL read_range_first: start_key 1 end_key NULL id < 4; id < 3 and name = '222' and other <= 'ccc'; remote: id < 3 records_in_range: start_key NULL end_key 4 read_range_first: start_key NULL end_key 4 id <= 4; records_in_range: start_key NULL end_key 3 read_range_first: start_key NULL end_key 3 id like 4; full table scan id > 2 and id < 4; records_in_range: start_key 3 end_key 4 read_range_first: start_key 3 end_key 4 id >= 2 and id < 4; records_in_range: start_key 0 end_key 4 read_range_first: start_key 1 end_key 4 id >= 2 and id <= 4; records_in_range: start_key 0 end_key 3 read_range_first: start_key 1 end_key 3 id > 2 and id <= 4; id = 6 and name = 'eric was here' and other > 'eeee'; remote: (`id` > 6 AND `name` > 'eric was here' AND `other` > 'eeee') AND (`id` <= 6) AND ( AND `name` <= 'eric was here') no results records_in_range: start_key 3 end_key 3 read_range_first: start_key 3 end_key 3 Summary: * If the start key flag is 0 the max key flag shouldn't even be set, and if it is, the query produced would be invalid. * Multipart keys, even if containing some or all numeric columns, are treated the same as non-numeric keys If the query is " = " (quotes or not): - records in range start key flag HA_READ_KEY_EXACT, end key flag HA_READ_AFTER_KEY (incorrect) - any other: start key flag HA_READ_KEY_OR_NEXT, end key flag HA_READ_AFTER_KEY (correct) * 'like' queries (of key) - Numeric, full table scan - Non-numeric records_in_range: start_key 0 end_key 3 other : start_key 1 end_key 3 * If the key flag is HA_READ_AFTER_KEY: if start_key, append > if end_key, append <= * If create_where_key was called by records_in_range: - if the key is numeric: start key flag is 0 when end key is NULL, end key flag is 3 or 4 - if create_where_key was called by any other function: start key flag is 1 when end key is NULL, end key flag is 3 or 4 - if the key is non-numeric, or multipart When the query is an exact match, the start key flag is 0, end key flag is 3 for what should be a no-range condition where you should have 0 and max key NULL, which it is if called by read_range_first Conclusion: 1. Need logic to determin if a key is min or max when the flag is HA_READ_AFTER_KEY, and handle appending correct operator accordingly 2. Need a boolean flag to pass to create_where_from_key, used in the switch statement. Add 1 to the flag if: - start key flag is HA_READ_KEY_EXACT and the end key is NULL */ bool ha_federated::create_where_from_key(String *to, KEY *key_info, const key_range *start_key, const key_range *end_key, bool from_records_in_range, bool eq_range_arg) { bool both_not_null= (start_key != NULL && end_key != NULL) ? TRUE : FALSE; const uchar *ptr; uint remainder, length; char tmpbuff[FEDERATED_QUERY_BUFFER_SIZE]; String tmp(tmpbuff, sizeof(tmpbuff), system_charset_info); const key_range *ranges[2]= { start_key, end_key }; DBUG_ENTER("ha_federated::create_where_from_key"); tmp.length(0); if (start_key == NULL && end_key == NULL) DBUG_RETURN(1); MY_BITMAP *old_map= dbug_tmp_use_all_columns(table, &table->write_set); for (uint i= 0; i <= 1; i++) { bool needs_quotes; KEY_PART_INFO *key_part; if (ranges[i] == NULL) continue; if (both_not_null) { if (i > 0) tmp.append(STRING_WITH_LEN(") AND (")); else tmp.append(STRING_WITH_LEN(" (")); } for (key_part= key_info->key_part, remainder= key_info->user_defined_key_parts, length= ranges[i]->length, ptr= ranges[i]->key; ; remainder--, key_part++) { Field *field= key_part->field; uint store_length= key_part->store_length; uint part_length= MY_MIN(store_length, length); needs_quotes= field->str_needs_quotes(); DBUG_DUMP("key, start of loop", ptr, length); if (key_part->null_bit) { if (*ptr++) { /* We got "IS [NOT] NULL" condition against nullable column. We distinguish between "IS NOT NULL" and "IS NULL" by flag. For "IS NULL", flag is set to HA_READ_KEY_EXACT. */ if (emit_key_part_name(&tmp, key_part) || (ranges[i]->flag == HA_READ_KEY_EXACT ? tmp.append(STRING_WITH_LEN(" IS NULL ")) : tmp.append(STRING_WITH_LEN(" IS NOT NULL ")))) goto err; /* We need to adjust pointer and length to be prepared for next key part. As well as check if this was last key part. */ goto prepare_for_next_key_part; } } if (tmp.append(STRING_WITH_LEN(" ("))) goto err; switch (ranges[i]->flag) { case HA_READ_KEY_EXACT: DBUG_PRINT("info", ("federated HA_READ_KEY_EXACT %d", i)); if (store_length >= length || !needs_quotes || key_part->type == HA_KEYTYPE_BIT || field->result_type() != STRING_RESULT) { if (emit_key_part_name(&tmp, key_part)) goto err; if (from_records_in_range) { if (tmp.append(STRING_WITH_LEN(" >= "))) goto err; } else { if (tmp.append(STRING_WITH_LEN(" = "))) goto err; } if (emit_key_part_element(&tmp, key_part, needs_quotes, 0, ptr, part_length)) goto err; } else { /* LIKE */ if (emit_key_part_name(&tmp, key_part) || tmp.append(STRING_WITH_LEN(" LIKE ")) || emit_key_part_element(&tmp, key_part, needs_quotes, 1, ptr, part_length)) goto err; } break; case HA_READ_AFTER_KEY: if (eq_range_arg) { if (tmp.append(STRING_WITH_LEN("1=1"))) // Dummy goto err; break; } DBUG_PRINT("info", ("federated HA_READ_AFTER_KEY %d", i)); if ((store_length >= length) || (i > 0)) /* for all parts of end key*/ { if (emit_key_part_name(&tmp, key_part)) goto err; if (i > 0) /* end key */ { if (tmp.append(STRING_WITH_LEN(" <= "))) goto err; } else /* start key */ { if (tmp.append(STRING_WITH_LEN(" > "))) goto err; } if (emit_key_part_element(&tmp, key_part, needs_quotes, 0, ptr, part_length)) { goto err; } break; } /* fall through */ case HA_READ_KEY_OR_NEXT: DBUG_PRINT("info", ("federated HA_READ_KEY_OR_NEXT %d", i)); if (emit_key_part_name(&tmp, key_part) || tmp.append(STRING_WITH_LEN(" >= ")) || emit_key_part_element(&tmp, key_part, needs_quotes, 0, ptr, part_length)) goto err; break; case HA_READ_BEFORE_KEY: DBUG_PRINT("info", ("federated HA_READ_BEFORE_KEY %d", i)); if (store_length >= length) { if (emit_key_part_name(&tmp, key_part) || tmp.append(STRING_WITH_LEN(" < ")) || emit_key_part_element(&tmp, key_part, needs_quotes, 0, ptr, part_length)) goto err; break; } /* fall through */ case HA_READ_KEY_OR_PREV: DBUG_PRINT("info", ("federated HA_READ_KEY_OR_PREV %d", i)); if (emit_key_part_name(&tmp, key_part) || tmp.append(STRING_WITH_LEN(" <= ")) || emit_key_part_element(&tmp, key_part, needs_quotes, 0, ptr, part_length)) goto err; break; default: DBUG_PRINT("info",("cannot handle flag %d", ranges[i]->flag)); goto err; } if (tmp.append(STRING_WITH_LEN(") "))) goto err; prepare_for_next_key_part: if (store_length >= length) break; DBUG_PRINT("info", ("remainder %d", remainder)); DBUG_ASSERT(remainder > 1); length-= store_length; /* For nullable columns, null-byte is already skipped before, that is ptr was incremented by 1. Since store_length still counts null-byte, we need to subtract 1 from store_length. */ ptr+= store_length - MY_TEST(key_part->null_bit); if (tmp.append(STRING_WITH_LEN(" AND "))) goto err; DBUG_PRINT("info", ("create_where_from_key WHERE clause: %s", tmp.c_ptr_quick())); } } dbug_tmp_restore_column_map(&table->write_set, old_map); if (both_not_null) if (tmp.append(STRING_WITH_LEN(") "))) DBUG_RETURN(1); if (to->append(STRING_WITH_LEN(" WHERE "))) DBUG_RETURN(1); if (to->append(tmp)) DBUG_RETURN(1); DBUG_RETURN(0); err: dbug_tmp_restore_column_map(&table->write_set, old_map); DBUG_RETURN(1); } /* Example of simple lock controls. The "share" it creates is structure we will pass to each federated handler. Do you have to have one of these? Well, you have pieces that are used for locking, and they are needed to function. */ static FEDERATED_SHARE *get_share(const char *table_name, TABLE *table) { char query_buffer[FEDERATED_QUERY_BUFFER_SIZE]; Field **field; String query(query_buffer, sizeof(query_buffer), &my_charset_bin); FEDERATED_SHARE *share= NULL, tmp_share; MEM_ROOT mem_root; DBUG_ENTER("ha_federated.cc::get_share"); /* In order to use this string, we must first zero it's length, or it will contain garbage */ query.length(0); init_alloc_root(PSI_INSTRUMENT_ME, &mem_root, 256, 0, MYF(0)); mysql_mutex_lock(&federated_mutex); tmp_share.share_key= table_name; tmp_share.share_key_length= (uint) strlen(table_name); if (parse_url(&mem_root, &tmp_share, table, 0)) goto error; /* TODO: change tmp_share.scheme to LEX_STRING object */ if (!(share= (FEDERATED_SHARE *) my_hash_search(&federated_open_tables, (uchar*) tmp_share.share_key, tmp_share. share_key_length))) { query.set_charset(system_charset_info); query.append(STRING_WITH_LEN("SELECT ")); for (field= table->field; *field; field++) { append_ident(&query, (*field)->field_name.str, (*field)->field_name.length, ident_quote_char); query.append(STRING_WITH_LEN(", ")); } /* chops off trailing comma */ query.length(query.length() - sizeof_trailing_comma); query.append(STRING_WITH_LEN(" FROM ")); append_ident(&query, tmp_share.table_name, tmp_share.table_name_length, ident_quote_char); if (!(share= (FEDERATED_SHARE *) memdup_root(&mem_root, (char*)&tmp_share, sizeof(*share))) || !(share->select_query= (char*) strmake_root(&mem_root, query.ptr(), query.length()))) goto error; share->use_count= 0; share->mem_root= mem_root; DBUG_PRINT("info", ("share->select_query %s", share->select_query)); if (my_hash_insert(&federated_open_tables, (uchar*) share)) goto error; thr_lock_init(&share->lock); mysql_mutex_init(fe_key_mutex_FEDERATED_SHARE_mutex, &share->mutex, MY_MUTEX_INIT_FAST); } else free_root(&mem_root, MYF(0)); /* prevents memory leak */ share->use_count++; mysql_mutex_unlock(&federated_mutex); DBUG_RETURN(share); error: mysql_mutex_unlock(&federated_mutex); free_root(&mem_root, MYF(0)); DBUG_RETURN(NULL); } /* Free lock controls. We call this whenever we close a table. If the table had the last reference to the share then we free memory associated with it. */ static int free_share(FEDERATED_SHARE *share) { MEM_ROOT mem_root= share->mem_root; DBUG_ENTER("free_share"); mysql_mutex_lock(&federated_mutex); if (!--share->use_count) { my_hash_delete(&federated_open_tables, (uchar*) share); thr_lock_delete(&share->lock); mysql_mutex_destroy(&share->mutex); free_root(&mem_root, MYF(0)); } mysql_mutex_unlock(&federated_mutex); DBUG_RETURN(0); } ha_rows ha_federated::records_in_range(uint inx, const key_range *start_key, const key_range *end_key, page_range *pages) { /* We really want indexes to be used as often as possible, therefore we just need to hard-code the return value to a very low number to force the issue */ DBUG_ENTER("ha_federated::records_in_range"); DBUG_RETURN(FEDERATED_RECORDS_IN_RANGE); } /* Used for opening tables. The name will be the name of the file. A table is opened when it needs to be opened. For instance when a request comes in for a select on the table (tables are not open and closed for each request, they are cached). Called from handler.cc by handler::ha_open(). The server opens all tables by calling ha_open() which then calls the handler specific open(). */ int ha_federated::open(const char *name, int mode, uint test_if_locked) { DBUG_ENTER("ha_federated::open"); if (!(share= get_share(name, table))) DBUG_RETURN(1); thr_lock_data_init(&share->lock, &lock, NULL); DBUG_ASSERT(mysql == NULL); ref_length= sizeof(MYSQL_RES *) + sizeof(MYSQL_ROW_OFFSET); DBUG_PRINT("info", ("ref_length: %u", ref_length)); my_init_dynamic_array(PSI_INSTRUMENT_ME, &results, sizeof(MYSQL_RES *), 4, 4, MYF(0)); reset(); DBUG_RETURN(0); } class Net_error_handler : public Internal_error_handler { public: Net_error_handler() = default; public: bool handle_condition(THD *thd, uint sql_errno, const char* sqlstate, Sql_condition::enum_warning_level *level, const char* msg, Sql_condition ** cond_hdl) { return sql_errno >= ER_ABORTING_CONNECTION && sql_errno <= ER_NET_WRITE_INTERRUPTED; } }; /* Closes a table. We call the free_share() function to free any resources that we have allocated in the "shared" structure. Called from sql_base.cc, sql_select.cc, and table.cc. In sql_select.cc it is only used to close up temporary tables or during the process where a temporary table is converted over to being a myisam table. For sql_base.cc look at close_data_tables(). */ int ha_federated::close(void) { DBUG_ENTER("ha_federated::close"); free_result(); delete_dynamic(&results); /* Disconnect from mysql */ THD *thd= ha_thd(); Net_error_handler err_handler; if (thd) thd->push_internal_handler(&err_handler); mysql_close(mysql); if (thd) thd->pop_internal_handler(); mysql= NULL; DBUG_RETURN(free_share(share)); } /* Checks if a field in a record is SQL NULL. SYNOPSIS field_in_record_is_null() table TABLE pointer, MySQL table object field Field pointer, MySQL field object record char pointer, contains record DESCRIPTION This method uses the record format information in table to track the null bit in record. RETURN VALUE 1 if NULL 0 otherwise */ static inline uint field_in_record_is_null(TABLE *table, Field *field, char *record) { int null_offset; DBUG_ENTER("ha_federated::field_in_record_is_null"); if (!field->null_ptr) DBUG_RETURN(0); null_offset= (uint) ((char*)field->null_ptr - (char*)table->record[0]); if (record[null_offset] & field->null_bit) DBUG_RETURN(1); DBUG_RETURN(0); } /** @brief Construct the INSERT statement. @details This method will construct the INSERT statement and appends it to the supplied query string buffer. @return @retval FALSE No error @retval TRUE Failure */ bool ha_federated::append_stmt_insert(String *query) { char insert_buffer[FEDERATED_QUERY_BUFFER_SIZE]; Field **field; uint tmp_length; bool added_field= FALSE; /* The main insert query string */ String insert_string(insert_buffer, sizeof(insert_buffer), &my_charset_bin); DBUG_ENTER("ha_federated::append_stmt_insert"); insert_string.length(0); if (replace_duplicates) insert_string.append(STRING_WITH_LEN("REPLACE INTO ")); else if (ignore_duplicates && !insert_dup_update) insert_string.append(STRING_WITH_LEN("INSERT IGNORE INTO ")); else insert_string.append(STRING_WITH_LEN("INSERT INTO ")); append_ident(&insert_string, share->table_name, share->table_name_length, ident_quote_char); tmp_length= insert_string.length(); insert_string.append(STRING_WITH_LEN(" (")); /* loop through the field pointer array, add any fields to both the values list and the fields list that match the current query id */ for (field= table->field; *field; field++) { if (bitmap_is_set(table->write_set, (*field)->field_index)) { /* append the field name */ append_ident(&insert_string, (*field)->field_name.str, (*field)->field_name.length, ident_quote_char); /* append commas between both fields and fieldnames */ /* unfortunately, we can't use the logic if *(fields + 1) to make the following appends conditional as we don't know if the next field is in the write set */ insert_string.append(STRING_WITH_LEN(", ")); added_field= TRUE; } } if (added_field) { /* Remove trailing comma. */ insert_string.length(insert_string.length() - sizeof_trailing_comma); insert_string.append(STRING_WITH_LEN(") ")); } else { /* If there were no fields, we don't want to add a closing paren. */ insert_string.length(tmp_length); } insert_string.append(STRING_WITH_LEN(" VALUES ")); DBUG_RETURN(query->append(insert_string)); } /* write_row() inserts a row. No extra() hint is given currently if a bulk load is happeneding. buf() is a byte array of data. You can use the field information to extract the data from the native byte array type. Example of this would be: for (Field **field=table->field ; *field ; field++) { ... } Called from item_sum.cc, item_sum.cc, sql_acl.cc, sql_insert.cc, sql_insert.cc, sql_select.cc, sql_table.cc, sql_udf.cc, and sql_update.cc. */ int ha_federated::write_row(const uchar *buf) { char values_buffer[FEDERATED_QUERY_BUFFER_SIZE]; char insert_field_value_buffer[STRING_BUFFER_USUAL_SIZE]; Field **field; uint tmp_length; int error= 0; bool use_bulk_insert; bool auto_increment_update_required= (table->next_number_field != NULL); /* The string containing the values to be added to the insert */ String values_string(values_buffer, sizeof(values_buffer), &my_charset_bin); /* The actual value of the field, to be added to the values_string */ String insert_field_value_string(insert_field_value_buffer, sizeof(insert_field_value_buffer), &my_charset_bin); MY_BITMAP *old_map= dbug_tmp_use_all_columns(table, &table->read_set); DBUG_ENTER("ha_federated::write_row"); values_string.length(0); insert_field_value_string.length(0); /* start both our field and field values strings We must disable multi-row insert for "INSERT...ON DUPLICATE KEY UPDATE" Ignore duplicates is always true when insert_dup_update is true. When replace_duplicates == TRUE, we can safely enable multi-row insert. When performing multi-row insert, we only collect the columns values for the row. The start of the statement is only created when the first row is copied in to the bulk_insert string. */ if (!(use_bulk_insert= bulk_insert.str && (!insert_dup_update || replace_duplicates))) append_stmt_insert(&values_string); values_string.append(STRING_WITH_LEN(" (")); tmp_length= values_string.length(); /* loop through the field pointer array, add any fields to both the values list and the fields list that is part of the write set */ for (field= table->field; *field; field++) { if (bitmap_is_set(table->write_set, (*field)->field_index)) { if ((*field)->is_null()) values_string.append(STRING_WITH_LEN(" NULL ")); else { bool needs_quote= (*field)->str_needs_quotes(); (*field)->val_str(&insert_field_value_string); if (needs_quote) values_string.append(value_quote_char); insert_field_value_string.print(&values_string); if (needs_quote) values_string.append(value_quote_char); insert_field_value_string.length(0); } /* append commas between both fields and fieldnames */ /* unfortunately, we can't use the logic if *(fields + 1) to make the following appends conditional as we don't know if the next field is in the write set */ values_string.append(STRING_WITH_LEN(", ")); } } dbug_tmp_restore_column_map(&table->read_set, old_map); /* if there were no fields, we don't want to add a closing paren AND, we don't want to chop off the last char '(' insert will be "INSERT INTO t1 VALUES ();" */ if (values_string.length() > tmp_length) { /* chops off trailing comma */ values_string.length(values_string.length() - sizeof_trailing_comma); } /* we always want to append this, even if there aren't any fields */ values_string.append(STRING_WITH_LEN(") ")); if (use_bulk_insert) { /* Send the current bulk insert out if appending the current row would cause the statement to overflow the packet size, otherwise set auto_increment_update_required to FALSE as no query was executed. */ if (bulk_insert.length + values_string.length() + bulk_padding > mysql->net.max_packet_size && bulk_insert.length) { error= real_query(bulk_insert.str, bulk_insert.length); bulk_insert.length= 0; } else auto_increment_update_required= FALSE; if (bulk_insert.length == 0) { char insert_buffer[FEDERATED_QUERY_BUFFER_SIZE]; String insert_string(insert_buffer, sizeof(insert_buffer), &my_charset_bin); insert_string.length(0); append_stmt_insert(&insert_string); dynstr_append_mem(&bulk_insert, insert_string.ptr(), insert_string.length()); } else dynstr_append_mem(&bulk_insert, ",", 1); dynstr_append_mem(&bulk_insert, values_string.ptr(), values_string.length()); } else { error= real_query(values_string.ptr(), values_string.length()); } if (error) { DBUG_RETURN(stash_remote_error()); } /* If the table we've just written a record to contains an auto_increment field, then store the last_insert_id() value from the foreign server */ if (auto_increment_update_required) { update_auto_increment(); /* mysql_insert() uses this for protocol return value */ table->next_number_field->store(stats.auto_increment_value, 1); } DBUG_RETURN(0); } /** @brief Prepares the storage engine for bulk inserts. @param[in] rows estimated number of rows in bulk insert or 0 if unknown. @details Initializes memory structures required for bulk insert. */ void ha_federated::start_bulk_insert(ha_rows rows, uint flags) { uint page_size; DBUG_ENTER("ha_federated::start_bulk_insert"); dynstr_free(&bulk_insert); /** We don't bother with bulk-insert semantics when the estimated rows == 1 The rows value will be 0 if the server does not know how many rows would be inserted. This can occur when performing INSERT...SELECT */ if (rows == 1) DBUG_VOID_RETURN; /* Make sure we have an open connection so that we know the maximum packet size. */ if (!mysql && real_connect()) DBUG_VOID_RETURN; page_size= (uint) my_getpagesize(); if (init_dynamic_string(&bulk_insert, NULL, page_size, page_size)) DBUG_VOID_RETURN; bulk_insert.length= 0; DBUG_VOID_RETURN; } /** @brief End bulk insert. @details This method will send any remaining rows to the remote server. Finally, it will deinitialize the bulk insert data structure. @return Operation status @retval 0 No error @retval != 0 Error occurred at remote server. Also sets my_errno. */ int ha_federated::end_bulk_insert() { int error= 0; DBUG_ENTER("ha_federated::end_bulk_insert"); if (!table_will_be_deleted && bulk_insert.str && bulk_insert.length) { if (real_query(bulk_insert.str, bulk_insert.length)) error= stash_remote_error(); else if (table->next_number_field) update_auto_increment(); } dynstr_free(&bulk_insert); DBUG_RETURN(my_errno= error); } /* ha_federated::update_auto_increment This method ensures that last_insert_id() works properly. What it simply does is calls last_insert_id() on the foreign database immediately after insert (if the table has an auto_increment field) and sets the insert id via thd->insert_id(ID)). */ void ha_federated::update_auto_increment(void) { THD *thd= current_thd; DBUG_ENTER("ha_federated::update_auto_increment"); ha_federated::info(HA_STATUS_AUTO); thd->first_successful_insert_id_in_cur_stmt= stats.auto_increment_value; DBUG_PRINT("info",("last_insert_id: %ld", (long) stats.auto_increment_value)); DBUG_VOID_RETURN; } int ha_federated::optimize(THD* thd, HA_CHECK_OPT* check_opt) { char query_buffer[STRING_BUFFER_USUAL_SIZE]; String query(query_buffer, sizeof(query_buffer), &my_charset_bin); DBUG_ENTER("ha_federated::optimize"); query.length(0); query.set_charset(system_charset_info); query.append(STRING_WITH_LEN("OPTIMIZE TABLE ")); append_ident(&query, share->table_name, share->table_name_length, ident_quote_char); if (real_query(query.ptr(), query.length())) { DBUG_RETURN(stash_remote_error()); } DBUG_RETURN(0); } int ha_federated::repair(THD* thd, HA_CHECK_OPT* check_opt) { char query_buffer[STRING_BUFFER_USUAL_SIZE]; String query(query_buffer, sizeof(query_buffer), &my_charset_bin); DBUG_ENTER("ha_federated::repair"); query.length(0); query.set_charset(system_charset_info); query.append(STRING_WITH_LEN("REPAIR TABLE ")); append_ident(&query, share->table_name, share->table_name_length, ident_quote_char); if (check_opt->flags & T_QUICK) query.append(STRING_WITH_LEN(" QUICK")); if (check_opt->flags & T_EXTEND) query.append(STRING_WITH_LEN(" EXTENDED")); if (check_opt->sql_flags & TT_USEFRM) query.append(STRING_WITH_LEN(" USE_FRM")); if (real_query(query.ptr(), query.length())) { DBUG_RETURN(stash_remote_error()); } DBUG_RETURN(0); } /* Yes, update_row() does what you expect, it updates a row. old_data will have the previous row record in it, while new_data will have the newest data in it. Keep in mind that the server can do updates based on ordering if an ORDER BY clause was used. Consecutive ordering is not guaranteed. Currently new_data will not have an updated auto_increament record, or and updated timestamp field. You can do these for federated by doing these: if (table->timestamp_on_update_now) update_timestamp(new_row+table->timestamp_on_update_now-1); if (table->next_number_field && record == table->record[0]) update_auto_increment(); Called from sql_select.cc, sql_acl.cc, sql_update.cc, and sql_insert.cc. */ int ha_federated::update_row(const uchar *old_data, const uchar *new_data) { /* This used to control how the query was built. If there was a primary key, the query would be built such that there was a where clause with only that column as the condition. This is flawed, because if we have a multi-part primary key, it would only use the first part! We don't need to do this anyway, because read_range_first will retrieve the correct record, which is what is used to build the WHERE clause. We can however use this to append a LIMIT to the end if there is NOT a primary key. Why do this? Because we only are updating one record, and LIMIT enforces this. */ bool has_a_primary_key= MY_TEST(table->s->primary_key != MAX_KEY); /* buffers for following strings */ char field_value_buffer[STRING_BUFFER_USUAL_SIZE]; char update_buffer[FEDERATED_QUERY_BUFFER_SIZE]; char where_buffer[FEDERATED_QUERY_BUFFER_SIZE]; /* Work area for field values */ String field_value(field_value_buffer, sizeof(field_value_buffer), &my_charset_bin); /* stores the update query */ String update_string(update_buffer, sizeof(update_buffer), &my_charset_bin); /* stores the WHERE clause */ String where_string(where_buffer, sizeof(where_buffer), &my_charset_bin); uchar *record= table->record[0]; DBUG_ENTER("ha_federated::update_row"); /* set string lengths to 0 to avoid misc chars in string */ field_value.length(0); update_string.length(0); where_string.length(0); if (ignore_duplicates) update_string.append(STRING_WITH_LEN("UPDATE IGNORE ")); else update_string.append(STRING_WITH_LEN("UPDATE ")); append_ident(&update_string, share->table_name, share->table_name_length, ident_quote_char); update_string.append(STRING_WITH_LEN(" SET ")); /* In this loop, we want to match column names to values being inserted (while building INSERT statement). Iterate through table->field (new data) and share->old_field (old_data) using the same index to create an SQL UPDATE statement. New data is used to create SET field=value and old data is used to create WHERE field=oldvalue */ for (Field **field= table->field; *field; field++) { if (bitmap_is_set(table->write_set, (*field)->field_index)) { append_ident(&update_string, (*field)->field_name.str, (*field)->field_name.length, ident_quote_char); update_string.append(STRING_WITH_LEN(" = ")); if ((*field)->is_null()) update_string.append(STRING_WITH_LEN(" NULL ")); else { /* otherwise = */ MY_BITMAP *old_map= tmp_use_all_columns(table, &table->read_set); bool needs_quote= (*field)->str_needs_quotes(); (*field)->val_str(&field_value); if (needs_quote) update_string.append(value_quote_char); field_value.print(&update_string); if (needs_quote) update_string.append(value_quote_char); field_value.length(0); tmp_restore_column_map(&table->read_set, old_map); } update_string.append(STRING_WITH_LEN(", ")); } if (bitmap_is_set(table->read_set, (*field)->field_index)) { append_ident(&where_string, (*field)->field_name.str, (*field)->field_name.length, ident_quote_char); if (field_in_record_is_null(table, *field, (char*) old_data)) where_string.append(STRING_WITH_LEN(" IS NULL ")); else { bool needs_quote= (*field)->str_needs_quotes(); where_string.append(STRING_WITH_LEN(" = ")); (*field)->val_str(&field_value, (old_data + (*field)->offset(record))); if (needs_quote) where_string.append(value_quote_char); field_value.print(&where_string); if (needs_quote) where_string.append(value_quote_char); field_value.length(0); } where_string.append(STRING_WITH_LEN(" AND ")); } } /* Remove last ', '. This works as there must be at least on updated field */ update_string.length(update_string.length() - sizeof_trailing_comma); if (where_string.length()) { /* chop off trailing AND */ where_string.length(where_string.length() - sizeof_trailing_and); update_string.append(STRING_WITH_LEN(" WHERE ")); update_string.append(where_string); } /* If this table has not a primary key, then we could possibly update multiple rows. We want to make sure to only update one! */ if (!has_a_primary_key) update_string.append(STRING_WITH_LEN(" LIMIT 1")); if (real_query(update_string.ptr(), update_string.length())) { DBUG_RETURN(stash_remote_error()); } DBUG_RETURN(0); } /* This will delete a row. 'buf' will contain a copy of the row to be =deleted. The server will call this right after the current row has been called (from either a previous rnd_next() or index call). If you keep a pointer to the last row or can access a primary key it will make doing the deletion quite a bit easier. Keep in mind that the server does no guarentee consecutive deletions. ORDER BY clauses can be used. Called in sql_acl.cc and sql_udf.cc to manage internal table information. Called in sql_delete.cc, sql_insert.cc, and sql_select.cc. In sql_select it is used for removing duplicates while in insert it is used for REPLACE calls. */ int ha_federated::delete_row(const uchar *buf) { char delete_buffer[FEDERATED_QUERY_BUFFER_SIZE]; char data_buffer[FEDERATED_QUERY_BUFFER_SIZE]; String delete_string(delete_buffer, sizeof(delete_buffer), &my_charset_bin); String data_string(data_buffer, sizeof(data_buffer), &my_charset_bin); uint found= 0; DBUG_ENTER("ha_federated::delete_row"); delete_string.length(0); delete_string.append(STRING_WITH_LEN("DELETE FROM ")); append_ident(&delete_string, share->table_name, share->table_name_length, ident_quote_char); delete_string.append(STRING_WITH_LEN(" WHERE ")); for (Field **field= table->field; *field; field++) { Field *cur_field= *field; found++; if (bitmap_is_set(table->read_set, cur_field->field_index)) { append_ident(&delete_string, (*field)->field_name.str, (*field)->field_name.length, ident_quote_char); data_string.length(0); if (cur_field->is_null()) { delete_string.append(STRING_WITH_LEN(" IS NULL ")); } else { bool needs_quote= cur_field->str_needs_quotes(); delete_string.append(STRING_WITH_LEN(" = ")); cur_field->val_str(&data_string); if (needs_quote) delete_string.append(value_quote_char); data_string.print(&delete_string); if (needs_quote) delete_string.append(value_quote_char); } delete_string.append(STRING_WITH_LEN(" AND ")); } } // Remove trailing AND delete_string.length(delete_string.length() - sizeof_trailing_and); if (!found) delete_string.length(delete_string.length() - sizeof_trailing_where); delete_string.append(STRING_WITH_LEN(" LIMIT 1")); DBUG_PRINT("info", ("Delete sql: %s", delete_string.c_ptr_quick())); if (real_query(delete_string.ptr(), delete_string.length())) { DBUG_RETURN(stash_remote_error()); } stats.deleted+= (ha_rows) mysql->affected_rows; stats.records-= (ha_rows) mysql->affected_rows; DBUG_PRINT("info", ("rows deleted %ld rows deleted for all time %ld", (long) mysql->affected_rows, (long) stats.deleted)); DBUG_RETURN(0); } /* Positions an index cursor to the index specified in the handle. Fetches the row if available. If the key value is null, begin at the first key of the index. This method, which is called in the case of an SQL statement having a WHERE clause on a non-primary key index, simply calls index_read_idx. */ int ha_federated::index_read(uchar *buf, const uchar *key, uint key_len, ha_rkey_function find_flag) { int rc; DBUG_ENTER("ha_federated::index_read"); free_result(); rc= index_read_idx_with_result_set(buf, active_index, key, key_len, find_flag, &stored_result); DBUG_RETURN(rc); } /* Positions an index cursor to the index specified in key. Fetches the row if any. This is only used to read whole keys. This method is called via index_read in the case of a WHERE clause using a primary key index OR is called DIRECTLY when the WHERE clause uses a PRIMARY KEY index. NOTES This uses an internal result set that is deleted before function returns. We need to be able to be calable from ha_rnd_pos() */ int ha_federated::index_read_idx(uchar *buf, uint index, const uchar *key, uint key_len, enum ha_rkey_function find_flag) { int retval; MYSQL_RES *mysql_result; DBUG_ENTER("ha_federated::index_read_idx"); if ((retval= index_read_idx_with_result_set(buf, index, key, key_len, find_flag, &mysql_result))) DBUG_RETURN(retval); mysql_free_result(mysql_result); results.elements--; DBUG_RETURN(0); } /* Create result set for rows matching query and return first row RESULT 0 ok In this case *result will contain the result set # error In this case *result will contain 0 */ int ha_federated::index_read_idx_with_result_set(uchar *buf, uint index, const uchar *key, uint key_len, ha_rkey_function find_flag, MYSQL_RES **result) { int retval; char error_buffer[FEDERATED_QUERY_BUFFER_SIZE]; char index_value[STRING_BUFFER_USUAL_SIZE]; char sql_query_buffer[FEDERATED_QUERY_BUFFER_SIZE]; String index_string(index_value, sizeof(index_value), &my_charset_bin); String sql_query(sql_query_buffer, sizeof(sql_query_buffer), &my_charset_bin); key_range range; DBUG_ENTER("ha_federated::index_read_idx_with_result_set"); *result= 0; // In case of errors index_string.length(0); sql_query.length(0); sql_query.append(share->select_query, strlen(share->select_query)); range.key= key; range.length= key_len; range.flag= find_flag; create_where_from_key(&index_string, &table->key_info[index], &range, NULL, 0, 0); sql_query.append(index_string); if (real_query(sql_query.ptr(), sql_query.length())) { sprintf(error_buffer, "error: %d '%s'", mysql_errno(mysql), mysql_error(mysql)); retval= ER_QUERY_ON_FOREIGN_DATA_SOURCE; goto error; } if (!(*result= store_result(mysql))) { retval= HA_ERR_END_OF_FILE; goto error; } if ((retval= read_next(buf, *result))) { mysql_free_result(*result); results.elements--; *result= 0; DBUG_RETURN(retval); } DBUG_RETURN(0); error: my_error(retval, MYF(0), error_buffer); DBUG_RETURN(retval); } /* This method is used exlusevely by filesort() to check if we can create sorting buffers of necessary size. If the handler returns more records that it declares here server can just crash on filesort(). We cannot guarantee that's not going to happen with the FEDERATED engine, as we have records==0 always if the client is a VIEW, and for the table the number of records can inpredictably change during execution. So we return maximum possible value here. */ ha_rows ha_federated::estimate_rows_upper_bound() { return HA_POS_ERROR; } /* Initialized at each key walk (called multiple times unlike rnd_init()) */ int ha_federated::index_init(uint keynr, bool sorted) { DBUG_ENTER("ha_federated::index_init"); DBUG_PRINT("info", ("table: '%s' key: %u", table->s->table_name.str, keynr)); DBUG_RETURN(0); } /* Read first range */ int ha_federated::read_range_first(const key_range *start_key, const key_range *end_key, bool eq_range_arg, bool sorted) { char sql_query_buffer[FEDERATED_QUERY_BUFFER_SIZE]; int retval; String sql_query(sql_query_buffer, sizeof(sql_query_buffer), &my_charset_bin); DBUG_ENTER("ha_federated::read_range_first"); DBUG_ASSERT(!(start_key == NULL && end_key == NULL)); sql_query.length(0); sql_query.append(share->select_query, strlen(share->select_query)); create_where_from_key(&sql_query, &table->key_info[active_index], start_key, end_key, 0, eq_range_arg); if (real_query(sql_query.ptr(), sql_query.length())) { retval= ER_QUERY_ON_FOREIGN_DATA_SOURCE; goto error; } sql_query.length(0); if (!(stored_result= store_result(mysql))) { retval= HA_ERR_END_OF_FILE; goto error; } retval= read_next(table->record[0], stored_result); DBUG_RETURN(retval); error: DBUG_RETURN(retval); } int ha_federated::read_range_next() { int retval; DBUG_ENTER("ha_federated::read_range_next"); retval= rnd_next_int(table->record[0]); DBUG_RETURN(retval); } /* Used to read forward through the index. */ int ha_federated::index_next(uchar *buf) { int retval; DBUG_ENTER("ha_federated::index_next"); retval= read_next(buf, stored_result); DBUG_RETURN(retval); } /* rnd_init() is called when the system wants the storage engine to do a table scan. This is the method that gets data for the SELECT calls. See the federated in the introduction at the top of this file to see when rnd_init() is called. Called from filesort.cc, records.cc, sql_handler.cc, sql_select.cc, sql_table.cc, and sql_update.cc. */ int ha_federated::rnd_init(bool scan) { DBUG_ENTER("ha_federated::rnd_init"); /* The use of the 'scan' flag is incredibly important for this handler to work properly, especially with updates containing WHERE clauses using indexed columns. When the initial query contains a WHERE clause of the query using an indexed column, it's index_read_idx that selects the exact record from the foreign database. When there is NO index in the query, either due to not having a WHERE clause, or the WHERE clause is using columns that are not indexed, a 'full table scan' done by rnd_init, which in this situation simply means a 'select * from ...' on the foreign table. In other words, this 'scan' flag gives us the means to ensure that if there is an index involved in the query, we want index_read_idx to retrieve the exact record (scan flag is 0), and do not want rnd_init to do a 'full table scan' and wipe out that result set. Prior to using this flag, the problem was most apparent with updates. An initial query like 'UPDATE tablename SET anything = whatever WHERE indexedcol = someval', index_read_idx would get called, using a query constructed with a WHERE clause built from the values of index ('indexcol' in this case, having a value of 'someval'). mysql_store_result would then get called (this would be the result set we want to use). After this rnd_init (from sql_update.cc) would be called, it would then unecessarily call "select * from table" on the foreign table, then call mysql_store_result, which would wipe out the correct previous result set from the previous call of index_read_idx's that had the result set containing the correct record, hence update the wrong row! */ if (scan) { if (real_query(share->select_query, strlen(share->select_query)) || !(stored_result= store_result(mysql))) DBUG_RETURN(stash_remote_error()); } DBUG_RETURN(0); } int ha_federated::rnd_end() { DBUG_ENTER("ha_federated::rnd_end"); DBUG_RETURN(index_end()); } int ha_federated::index_end(void) { DBUG_ENTER("ha_federated::index_end"); free_result(); DBUG_RETURN(0); } /* This is called for each row of the table scan. When you run out of records you should return HA_ERR_END_OF_FILE. Fill buff up with the row information. The Field structure for the table is the key to getting data into buf in a manner that will allow the server to understand it. Called from filesort.cc, records.cc, sql_handler.cc, sql_select.cc, sql_table.cc, and sql_update.cc. */ int ha_federated::rnd_next(uchar *buf) { int rc; DBUG_ENTER("ha_federated::rnd_next"); rc= rnd_next_int(buf); DBUG_RETURN(rc); } int ha_federated::rnd_next_int(uchar *buf) { DBUG_ENTER("ha_federated::rnd_next_int"); if (stored_result == 0) { /* Return value of rnd_init is not always checked (see records.cc), so we can get here _even_ if there is _no_ pre-fetched result-set! TODO: fix it. We can delete this in 5.1 when rnd_init() is checked. */ DBUG_RETURN(1); } DBUG_RETURN(read_next(buf, stored_result)); } /* ha_federated::read_next reads from a result set and converts to mysql internal format SYNOPSIS field_in_record_is_null() buf byte pointer to record result mysql result set DESCRIPTION This method is a wrapper method that reads one record from a result set and converts it to the internal table format RETURN VALUE 1 error 0 no error */ int ha_federated::read_next(uchar *buf, MYSQL_RES *result) { int retval; MYSQL_ROW row; DBUG_ENTER("ha_federated::read_next"); /* Save current data cursor position. */ current_position= result->data_cursor; /* Fetch a row, insert it back in a row format. */ if (!(row= mysql_fetch_row(result))) DBUG_RETURN(HA_ERR_END_OF_FILE); if (!(retval= convert_row_to_internal_format(buf, row, result))) table->status= 0; DBUG_RETURN(retval); } /** @brief Store a reference to current row. @details During a query execution we may have different result sets (RS), e.g. for different ranges. All the RS's used are stored in memory and placed in @c results dynamic array. At the end of execution all stored RS's are freed at once in the @c ha_federated::reset(). So, in case of federated, a reference to current row is a stored result address and current data cursor position. As we keep all RS in memory during a query execution, we can get any record using the reference any time until @c ha_federated::reset() is called. TODO: we don't have to store all RS's rows but only those we call @c ha_federated::position() for, so we can free memory where we store other rows in the @c ha_federated::index_end(). @param[in] record record data (unused) */ void ha_federated::position(const uchar *record __attribute__ ((unused))) { DBUG_ENTER("ha_federated::position"); if (!stored_result) DBUG_VOID_RETURN; position_called= TRUE; /* Store result set address. */ memcpy(ref, &stored_result, sizeof(MYSQL_RES *)); /* Store data cursor position. */ memcpy(ref + sizeof(MYSQL_RES *), ¤t_position, sizeof(MYSQL_ROW_OFFSET)); DBUG_VOID_RETURN; } /* This is like rnd_next, but you are given a position to use to determine the row. The position will be of the type that you stored in ref. This method is required for an ORDER BY Called from filesort.cc records.cc sql_insert.cc sql_select.cc sql_update.cc. */ int ha_federated::rnd_pos(uchar *buf, uchar *pos) { MYSQL_RES *result; int ret_val; DBUG_ENTER("ha_federated::rnd_pos"); /* Get stored result set. */ memcpy(&result, pos, sizeof(MYSQL_RES *)); DBUG_ASSERT(result); /* Set data cursor position. */ memcpy(&result->data_cursor, pos + sizeof(MYSQL_RES *), sizeof(MYSQL_ROW_OFFSET)); /* Read a row. */ ret_val= read_next(buf, result); DBUG_RETURN(ret_val); } /* ::info() is used to return information to the optimizer. Currently this table handler doesn't implement most of the fields really needed. SHOW also makes use of this data Another note, you will probably want to have the following in your code: if (records < 2) records = 2; The reason is that the server will optimize for cases of only a single record. If in a table scan you don't know the number of records it will probably be better to set records to two so you can return as many records as you need. Along with records a few more variables you may wish to set are: records deleted data_file_length index_file_length delete_length check_time Take a look at the public variables in handler.h for more information. Called in: filesort.cc ha_heap.cc item_sum.cc opt_sum.cc sql_delete.cc sql_delete.cc sql_derived.cc sql_select.cc sql_select.cc sql_select.cc sql_select.cc sql_select.cc sql_show.cc sql_show.cc sql_show.cc sql_show.cc sql_table.cc sql_union.cc sql_update.cc */ int ha_federated::info(uint flag) { char status_buf[FEDERATED_QUERY_BUFFER_SIZE]; int error; uint error_code; MYSQL_RES *result= 0; MYSQL_ROW row; String status_query_string(status_buf, sizeof(status_buf), &my_charset_bin); DBUG_ENTER("ha_federated::info"); error_code= ER_QUERY_ON_FOREIGN_DATA_SOURCE; /* we want not to show table status if not needed to do so */ if (flag & (HA_STATUS_VARIABLE | HA_STATUS_CONST)) { status_query_string.length(0); status_query_string.append(STRING_WITH_LEN("SHOW TABLE STATUS LIKE ")); append_ident(&status_query_string, share->table_name, share->table_name_length, value_quote_char); if (real_query(status_query_string.ptr(), status_query_string.length())) goto error; status_query_string.length(0); result= mysql_store_result(mysql); /* We're going to use fields num. 4, 12 and 13 of the resultset, so make sure we have these fields. */ if (!result || (mysql_num_fields(result) < 14)) goto error; if (!mysql_num_rows(result)) goto error; if (!(row= mysql_fetch_row(result))) goto error; /* deleted is set in ha_federated::info */ /* need to figure out what this means as far as federated is concerned, since we don't have a "file" data_file_length = ? index_file_length = ? delete_length = ? */ if (row[4] != NULL) stats.records= (ha_rows) my_strtoll10(row[4], (char**) 0, &error); if (row[5] != NULL) stats.mean_rec_length= (ulong) my_strtoll10(row[5], (char**) 0, &error); stats.data_file_length= stats.records * stats.mean_rec_length; if (row[12] != NULL) stats.update_time= (ulong) my_strtoll10(row[12], (char**) 0, &error); if (row[13] != NULL) stats.check_time= (ulong) my_strtoll10(row[13], (char**) 0, &error); /* size of IO operations (This is based on a good guess, no high science involved) */ if (flag & HA_STATUS_CONST) stats.block_size= 4096; } if ((flag & HA_STATUS_AUTO) && mysql) stats.auto_increment_value= mysql->insert_id; mysql_free_result(result); DBUG_RETURN(0); error: mysql_free_result(result); if (mysql) { my_printf_error(error_code, ": %d : %s", MYF(0), mysql_errno(mysql), mysql_error(mysql)); } else if (remote_error_number != -1 /* error already reported */) { error_code= remote_error_number; my_error(error_code, MYF(0), ER(error_code)); } DBUG_RETURN(error_code); } /** @brief Handles extra signals from MySQL server @param[in] operation Hint for storage engine @return Operation Status @retval 0 OK */ int ha_federated::extra(ha_extra_function operation) { DBUG_ENTER("ha_federated::extra"); switch (operation) { case HA_EXTRA_IGNORE_DUP_KEY: ignore_duplicates= TRUE; break; case HA_EXTRA_NO_IGNORE_DUP_KEY: insert_dup_update= FALSE; ignore_duplicates= FALSE; break; case HA_EXTRA_WRITE_CAN_REPLACE: replace_duplicates= TRUE; break; case HA_EXTRA_WRITE_CANNOT_REPLACE: /* We use this flag to ensure that we do not create an "INSERT IGNORE" statement when inserting new rows into the remote table. */ replace_duplicates= FALSE; break; case HA_EXTRA_INSERT_WITH_UPDATE: insert_dup_update= TRUE; break; case HA_EXTRA_PREPARE_FOR_DROP: table_will_be_deleted = TRUE; break; default: /* do nothing */ DBUG_PRINT("info",("unhandled operation: %d", (uint) operation)); } DBUG_RETURN(0); } /** @brief Reset state of file to after 'open'. @detail This function is called after every statement for all tables used by that statement. @return Operation status @retval 0 OK */ int ha_federated::reset(void) { insert_dup_update= FALSE; ignore_duplicates= FALSE; replace_duplicates= FALSE; /* Free stored result sets. */ for (uint i= 0; i < results.elements; i++) { MYSQL_RES *result; get_dynamic(&results, (uchar *) &result, i); mysql_free_result(result); } reset_dynamic(&results); if (mysql) mysql->net.thd= NULL; return 0; } /* Used to delete all rows in a table. Both for cases of truncate and for cases where the optimizer realizes that all rows will be removed as a result of a SQL statement. Called from item_sum.cc by Item_func_group_concat::clear(), Item_sum_count_distinct::clear(), and Item_func_group_concat::clear(). Called from sql_delete.cc by mysql_delete(). Called from sql_select.cc by JOIN::reinit(). Called from sql_union.cc by st_select_lex_unit::exec(). */ int ha_federated::delete_all_rows() { char query_buffer[FEDERATED_QUERY_BUFFER_SIZE]; String query(query_buffer, sizeof(query_buffer), &my_charset_bin); DBUG_ENTER("ha_federated::delete_all_rows"); query.length(0); query.set_charset(system_charset_info); query.append(STRING_WITH_LEN("TRUNCATE ")); append_ident(&query, share->table_name, share->table_name_length, ident_quote_char); /* TRUNCATE won't return anything in mysql_affected_rows */ if (real_query(query.ptr(), query.length())) { DBUG_RETURN(stash_remote_error()); } stats.deleted+= stats.records; stats.records= 0; DBUG_RETURN(0); } /* Used to manually truncate the table via a delete of all rows in a table. */ int ha_federated::truncate() { return delete_all_rows(); } /* The idea with handler::store_lock() is the following: The statement decided which locks we should need for the table for updates/deletes/inserts we get WRITE locks, for SELECT... we get read locks. Before adding the lock into the table lock handler (see thr_lock.c) mysqld calls store lock with the requested locks. Store lock can now modify a write lock to a read lock (or some other lock), ignore the lock (if we don't want to use MySQL table locks at all) or add locks for many tables (like we do when we are using a MERGE handler). Berkeley DB for federated changes all WRITE locks to TL_WRITE_ALLOW_WRITE (which signals that we are doing WRITES, but we are still allowing other reader's and writer's. When releasing locks, store_lock() are also called. In this case one usually doesn't have to do anything. In some exceptional cases MySQL may send a request for a TL_IGNORE; This means that we are requesting the same lock as last time and this should also be ignored. (This may happen when someone does a flush table when we have opened a part of the tables, in which case mysqld closes and reopens the tables and tries to get the same locks at last time). In the future we will probably try to remove this. Called from lock.cc by get_lock_data(). */ THR_LOCK_DATA **ha_federated::store_lock(THD *thd, THR_LOCK_DATA **to, enum thr_lock_type lock_type) { DBUG_ENTER("ha_federated::store_lock"); if (lock_type != TL_IGNORE && lock.type == TL_UNLOCK) { /* Here is where we get into the guts of a row level lock. If TL_UNLOCK is set If we are not doing a LOCK TABLE or DISCARD/IMPORT TABLESPACE, then allow multiple writers */ if ((lock_type >= TL_WRITE_CONCURRENT_INSERT && lock_type <= TL_WRITE) && !thd->in_lock_tables) lock_type= TL_WRITE_ALLOW_WRITE; /* In queries of type INSERT INTO t1 SELECT ... FROM t2 ... MySQL would use the lock TL_READ_NO_INSERT on t2, and that would conflict with TL_WRITE_ALLOW_WRITE, blocking all inserts to t2. Convert the lock to a normal read lock to allow concurrent inserts to t2. */ if (lock_type == TL_READ_NO_INSERT && !thd->in_lock_tables) lock_type= TL_READ; lock.type= lock_type; } *to++= &lock; DBUG_RETURN(to); } /* create() does nothing, since we have no local setup of our own. FUTURE: We should potentially connect to the foreign database and */ int ha_federated::create(const char *name, TABLE *table_arg, HA_CREATE_INFO *create_info) { int retval; THD *thd= current_thd; FEDERATED_SHARE tmp_share; // Only a temporary share, to test the url DBUG_ENTER("ha_federated::create"); retval= parse_url(thd->mem_root, &tmp_share, table_arg, 1); DBUG_RETURN(retval); } int ha_federated::real_connect() { char buffer[FEDERATED_QUERY_BUFFER_SIZE]; String sql_query(buffer, sizeof(buffer), &my_charset_bin); DBUG_ENTER("ha_federated::real_connect"); DBUG_ASSERT(mysql == NULL); if (!(mysql= mysql_init(NULL))) { remote_error_number= HA_ERR_OUT_OF_MEM; DBUG_RETURN(-1); } /* BUG# 17044 Federated Storage Engine is not UTF8 clean Add set names to whatever charset the table is at open of table */ /* this sets the csname like 'set names utf8' */ mysql_options(mysql,MYSQL_SET_CHARSET_NAME, this->table->s->table_charset->cs_name.str); sql_query.length(0); if (!mysql_real_connect(mysql, share->hostname, share->username, share->password, share->database, share->port, share->socket, 0)) { stash_remote_error(); mysql_close(mysql); mysql= NULL; my_error(ER_CONNECT_TO_FOREIGN_DATA_SOURCE, MYF(0), remote_error_buf); remote_error_number= -1; DBUG_RETURN(-1); } /* We have established a connection, lets try a simple dummy query just to check that the table and expected columns are present. */ sql_query.append(share->select_query, strlen(share->select_query)); sql_query.append(STRING_WITH_LEN(" WHERE 1=0")); if (mysql_real_query(mysql, sql_query.ptr(), sql_query.length())) { sql_query.length(0); sql_query.append(STRING_WITH_LEN("error: ")); sql_query.qs_append(mysql_errno(mysql)); sql_query.append(STRING_WITH_LEN(" '")); const char *errmsg= mysql_error(mysql); sql_query.append(errmsg, strlen(errmsg)); sql_query.append('\''); mysql_close(mysql); mysql= NULL; my_error(ER_FOREIGN_DATA_SOURCE_DOESNT_EXIST, MYF(0), sql_query.c_ptr_safe()); remote_error_number= -1; DBUG_RETURN(-1); } /* Just throw away the result, no rows anyways but need to keep in sync */ mysql_free_result(mysql_store_result(mysql)); /* Since we do not support transactions at this version, we can let the client API silently reconnect. For future versions, we will need more logic to deal with transactions */ mysql->reconnect= 1; DBUG_RETURN(0); } int ha_federated::real_query(const char *query, size_t length) { int rc= 0; DBUG_ENTER("ha_federated::real_query"); if (!query || !length) goto end; if (!mysql && (rc= real_connect())) goto end; mysql->net.thd= table->in_use; rc= mysql_real_query(mysql, query, (uint) length); end: DBUG_RETURN(rc); } int ha_federated::stash_remote_error() { DBUG_ENTER("ha_federated::stash_remote_error()"); if (!mysql) DBUG_RETURN(remote_error_number); remote_error_number= mysql_errno(mysql); strmake_buf(remote_error_buf, mysql_error(mysql)); if (remote_error_number == ER_DUP_ENTRY || remote_error_number == ER_DUP_KEY) DBUG_RETURN(HA_ERR_FOUND_DUPP_KEY); DBUG_RETURN(HA_FEDERATED_ERROR_WITH_REMOTE_SYSTEM); } bool ha_federated::get_error_message(int error, String* buf) { DBUG_ENTER("ha_federated::get_error_message"); DBUG_PRINT("enter", ("error: %d", error)); if (error == HA_FEDERATED_ERROR_WITH_REMOTE_SYSTEM) { buf->append(STRING_WITH_LEN("Error on remote system: ")); buf->qs_append(remote_error_number); buf->append(STRING_WITH_LEN(": ")); buf->append(remote_error_buf, strlen(remote_error_buf)); remote_error_number= 0; remote_error_buf[0]= '\0'; } DBUG_PRINT("exit", ("message: %s", buf->ptr())); DBUG_RETURN(FALSE); } /** @brief Store a result set. @details Call @c mysql_store_result() to save a result set then append it to the stored results array. @param[in] mysql_arg MySLQ connection structure. @return Stored result set (MYSQL_RES object). */ MYSQL_RES *ha_federated::store_result(MYSQL *mysql_arg) { MYSQL_RES *result= mysql_store_result(mysql_arg); DBUG_ENTER("ha_federated::store_result"); if (result) { (void) insert_dynamic(&results, (uchar*) &result); } position_called= FALSE; DBUG_RETURN(result); } void ha_federated::free_result() { DBUG_ENTER("ha_federated::free_result"); if (stored_result && !position_called) { mysql_free_result(stored_result); stored_result= 0; if (results.elements > 0) results.elements--; } DBUG_VOID_RETURN; } int ha_federated::external_lock(THD *thd, int lock_type) { int error= 0; DBUG_ENTER("ha_federated::external_lock"); table_will_be_deleted = FALSE; DBUG_RETURN(error); } static int federated_commit(handlerton *hton, THD *thd, bool all) { int return_val= 0; ha_federated *trx= (ha_federated *) thd_get_ha_data(thd, hton); DBUG_ENTER("federated_commit"); if (all) { int error= 0; ha_federated *ptr, *old= NULL; for (ptr= trx; ptr; old= ptr, ptr= ptr->trx_next) { if (old) old->trx_next= NULL; error= ptr->connection_commit(); if (error && !return_val) return_val= error; } thd_set_ha_data(thd, hton, NULL); } DBUG_PRINT("info", ("error val: %d", return_val)); DBUG_RETURN(return_val); } static int federated_rollback(handlerton *hton, THD *thd, bool all) { int return_val= 0; ha_federated *trx= (ha_federated *)thd_get_ha_data(thd, hton); DBUG_ENTER("federated_rollback"); if (all) { int error= 0; ha_federated *ptr, *old= NULL; for (ptr= trx; ptr; old= ptr, ptr= ptr->trx_next) { if (old) old->trx_next= NULL; error= ptr->connection_rollback(); if (error && !return_val) return_val= error; } thd_set_ha_data(thd, hton, NULL); } DBUG_PRINT("info", ("error val: %d", return_val)); DBUG_RETURN(return_val); } int ha_federated::connection_commit() { DBUG_ENTER("ha_federated::connection_commit"); DBUG_RETURN(execute_simple_query("COMMIT", 6)); } int ha_federated::connection_rollback() { DBUG_ENTER("ha_federated::connection_rollback"); DBUG_RETURN(execute_simple_query("ROLLBACK", 8)); } int ha_federated::connection_autocommit(bool state) { const char *text; DBUG_ENTER("ha_federated::connection_autocommit"); text= (state == TRUE) ? "SET AUTOCOMMIT=1" : "SET AUTOCOMMIT=0"; DBUG_RETURN(execute_simple_query(text, 16)); } int ha_federated::execute_simple_query(const char *query, int len) { DBUG_ENTER("ha_federated::execute_simple_query"); if (mysql_real_query(mysql, query, len)) { DBUG_RETURN(stash_remote_error()); } DBUG_RETURN(0); } struct st_mysql_storage_engine federated_storage_engine= { MYSQL_HANDLERTON_INTERFACE_VERSION }; maria_declare_plugin(federated) { MYSQL_STORAGE_ENGINE_PLUGIN, &federated_storage_engine, "FEDERATED", "Patrick Galbraith and Brian Aker, MySQL AB", "Allows accessing tables on other MariaDB servers", PLUGIN_LICENSE_GPL, federated_db_init, /* Plugin Init */ federated_done, /* Plugin Deinit */ 0x0100 /* 1.0 */, NULL, /* status variables */ NULL, /* system variables */ "1.0", /* string version */ MariaDB_PLUGIN_MATURITY_GAMMA /* maturity */ } maria_declare_plugin_end;