Adding upstream version 1:10.11.6.upstream/1%10.11.6upstream

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

1 files changed, 1133 insertions, 0 deletions

diff --git a/storage/example/ha_example.cc b/storage/example/ha_example.cc
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+/* Copyright (c) 2004, 2013, Oracle and/or its affiliates.
+   Copyright (c) 2010, 2014, SkySQL Ab.
+
+  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 */
+
+/**
+  @file ha_example.cc
+
+  @brief
+  The ha_example engine is a stubbed storage engine for example purposes only;
+  it does almost nothing at this point. Its purpose is to provide a source
+  code illustration of how to begin writing new storage engines; see also
+  storage/example/ha_example.h.
+
+  Additionally, this file includes an example of a daemon plugin which does
+  nothing at all - absolutely nothing, even less than example storage engine.
+  But it shows that one dll/so can contain more than one plugin.
+
+  @details
+  ha_example will let you create/open/delete tables, but
+  nothing further (for example, indexes are not supported nor can data
+  be stored in the table). It also provides new status (example_func_example)
+  and system (example_ulong_var and example_enum_var) variables.
+
+  Use this example as a template for implementing the same functionality in
+  your own storage engine. You can enable the example storage engine in your
+  build by doing the following during your build process:<br> ./configure
+  --with-example-storage-engine
+
+  Once this is done, MySQL will let you create tables with:<br>
+  CREATE TABLE <table name> (...) ENGINE=EXAMPLE;
+
+  The example storage engine is set up to use table locks. It
+  implements an example "SHARE" that is inserted into a hash by table
+  name. You can use this to store information of state that any
+  example handler object will be able to see when it is using that
+  table.
+
+  Please read the object definition in ha_example.h before reading the rest
+  of this file.
+
+  @note
+  When you create an EXAMPLE table, the MySQL Server creates a table .frm
+  (format) file in the database directory, using the table name as the file
+  name as is customary with MySQL. No other files are created. To get an idea
+  of what occurs, here is an example select that would do a scan of an entire
+  table:
+
+  @code
+  ha_example::store_lock
+  ha_example::external_lock
+  ha_example::info
+  ha_example::rnd_init
+  ha_example::extra
+  ENUM HA_EXTRA_CACHE        Cache record in HA_rrnd()
+  ha_example::rnd_next
+  ha_example::rnd_next
+  ha_example::rnd_next
+  ha_example::rnd_next
+  ha_example::rnd_next
+  ha_example::rnd_next
+  ha_example::rnd_next
+  ha_example::rnd_next
+  ha_example::rnd_next
+  ha_example::extra
+  ENUM HA_EXTRA_NO_CACHE     End caching of records (def)
+  ha_example::external_lock
+  ha_example::extra
+  ENUM HA_EXTRA_RESET        Reset database to after open
+  @endcode
+
+  Here you see that the example storage engine has 9 rows called before
+  rnd_next signals that it has reached the end of its data. Also note that
+  the table in question was already opened; had it not been open, a call to
+  ha_example::open() would also have been necessary. Calls to
+  ha_example::extra() are hints as to what will be occuring to the request.
+
+  A Longer Example can be found called the "Skeleton Engine" which can be 
+  found on TangentOrg. It has both an engine and a full build environment
+  for building a pluggable storage engine.
+
+  Happy coding!<br>
+    -Brian
+*/
+
+#ifdef USE_PRAGMA_IMPLEMENTATION
+#pragma implementation        // gcc: Class implementation
+#endif
+
+#include <my_global.h>
+#include <mysql/plugin.h>
+#include "ha_example.h"
+#include "sql_class.h"
+
+static handler *example_create_handler(handlerton *hton,
+                                       TABLE_SHARE *table, 
+                                       MEM_ROOT *mem_root);
+
+handlerton *example_hton;
+
+static MYSQL_THDVAR_ULONG(varopt_default, PLUGIN_VAR_RQCMDARG,
+  "default value of the VAROPT table option", NULL, NULL, 5, 0, 100, 0);
+
+/**
+  Structure for CREATE TABLE options (table options).
+  It needs to be called ha_table_option_struct.
+
+  The option values can be specified in the CREATE TABLE at the end:
+  CREATE TABLE ( ... ) *here*
+*/
+
+struct ha_table_option_struct
+{
+  const char *strparam;
+  ulonglong ullparam;
+  uint enumparam;
+  bool boolparam;
+  ulonglong varparam;
+};
+
+
+/**
+  Structure for CREATE TABLE options (field options).
+  It needs to be called ha_field_option_struct.
+
+  The option values can be specified in the CREATE TABLE per field:
+  CREATE TABLE ( field ... *here*, ... )
+*/
+
+struct ha_field_option_struct
+{
+  const char *complex_param_to_parse_it_in_engine;
+};
+
+/*
+  no example here, but index options can be declared similarly
+  using the ha_index_option_struct structure.
+
+  Their values can be specified in the CREATE TABLE per index:
+  CREATE TABLE ( field ..., .., INDEX .... *here*, ... )
+*/
+
+ha_create_table_option example_table_option_list[]=
+{
+  /*
+    one numeric option, with the default of UINT_MAX32, valid
+    range of values 0..UINT_MAX32, and a "block size" of 10
+    (any value must be divisible by 10).
+  */
+  HA_TOPTION_NUMBER("ULL", ullparam, UINT_MAX32, 0, UINT_MAX32, 10),
+  /*
+    one option that takes an arbitrary string
+  */
+  HA_TOPTION_STRING("STR", strparam),
+  /*
+    one enum option. a valid values are strings ONE and TWO.
+    A default value is 0, that is "one".
+  */
+  HA_TOPTION_ENUM("one_or_two", enumparam, "one,two", 0),
+  /*
+    one boolean option, the valid values are YES/NO, ON/OFF, 1/0.
+    The default is 1, that is true, yes, on.
+  */
+  HA_TOPTION_BOOL("YESNO", boolparam, 1),
+  /*
+    one option defined by the system variable. The type, the range, or
+    a list of allowed values is the same as for the system variable.
+  */
+  HA_TOPTION_SYSVAR("VAROPT", varparam, varopt_default),
+
+  HA_TOPTION_END
+};
+
+ha_create_table_option example_field_option_list[]=
+{
+  /*
+    If the engine wants something more complex than a string, number, enum,
+    or boolean - for example a list - it needs to specify the option
+    as a string and parse it internally.
+  */
+  HA_FOPTION_STRING("COMPLEX", complex_param_to_parse_it_in_engine),
+  HA_FOPTION_END
+};
+
+
+/**
+  @brief
+  Function we use in the creation of our hash to get key.
+*/
+
+#ifdef HAVE_PSI_INTERFACE
+static PSI_mutex_key ex_key_mutex_Example_share_mutex;
+
+static PSI_mutex_info all_example_mutexes[]=
+{
+  { &ex_key_mutex_Example_share_mutex, "Example_share::mutex", 0}
+};
+
+static void init_example_psi_keys()
+{
+  const char* category= "example";
+  int count;
+
+  count= array_elements(all_example_mutexes);
+  mysql_mutex_register(category, all_example_mutexes, count);
+}
+#else
+static void init_example_psi_keys() { }
+#endif
+
+
+/**
+  @brief
+  If frm_error() is called then we will use this to determine
+  the file extensions that exist for the storage engine. This is also
+  used by the default rename_table and delete_table method in
+  handler.cc and by the default discover_many method.
+
+  For engines that have two file name extensions (separate meta/index file
+  and data file), the order of elements is relevant. First element of engine
+  file name extensions array should be meta/index file extention. Second
+  element - data file extention. This order is assumed by
+  prepare_for_repair() when REPAIR TABLE ... USE_FRM is issued.
+
+  @see
+  rename_table method in handler.cc and
+  delete_table method in handler.cc
+*/
+
+static const char *ha_example_exts[] = {
+  NullS
+};
+
+Example_share::Example_share()
+{
+  thr_lock_init(&lock);
+  mysql_mutex_init(ex_key_mutex_Example_share_mutex,
+                   &mutex, MY_MUTEX_INIT_FAST);
+}
+
+
+static int example_init_func(void *p)
+{
+  DBUG_ENTER("example_init_func");
+
+  init_example_psi_keys();
+
+  example_hton= (handlerton *)p;
+  example_hton->create=  example_create_handler;
+  example_hton->flags=   HTON_CAN_RECREATE;
+  example_hton->table_options= example_table_option_list;
+  example_hton->field_options= example_field_option_list;
+  example_hton->tablefile_extensions= ha_example_exts;
+  example_hton->drop_table= [](handlerton *, const char*) { return -1; };
+
+  DBUG_RETURN(0);
+}
+
+
+/**
+  @brief
+  Example of simple lock controls. The "share" it creates is a
+  structure we will pass to each example handler. Do you have to have
+  one of these? Well, you have pieces that are used for locking, and
+  they are needed to function.
+*/
+
+Example_share *ha_example::get_share()
+{
+  Example_share *tmp_share;
+
+  DBUG_ENTER("ha_example::get_share()");
+
+  lock_shared_ha_data();
+  if (!(tmp_share= static_cast<Example_share*>(get_ha_share_ptr())))
+  {
+    tmp_share= new Example_share;
+    if (!tmp_share)
+      goto err;
+
+    set_ha_share_ptr(static_cast<Handler_share*>(tmp_share));
+  }
+err:
+  unlock_shared_ha_data();
+  DBUG_RETURN(tmp_share);
+}
+
+static handler* example_create_handler(handlerton *hton,
+                                       TABLE_SHARE *table, 
+                                       MEM_ROOT *mem_root)
+{
+  return new (mem_root) ha_example(hton, table);
+}
+
+ha_example::ha_example(handlerton *hton, TABLE_SHARE *table_arg)
+  :handler(hton, table_arg)
+{}
+
+
+/**
+  @brief
+  Used for opening tables. The name will be the name of the file.
+
+  @details
+  A table is opened when it needs to be opened; e.g. 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().
+
+  @see
+  handler::ha_open() in handler.cc
+*/
+
+int ha_example::open(const char *name, int mode, uint test_if_locked)
+{
+  DBUG_ENTER("ha_example::open");
+
+  if (!(share = get_share()))
+    DBUG_RETURN(1);
+  thr_lock_data_init(&share->lock,&lock,NULL);
+
+#ifndef DBUG_OFF
+  ha_table_option_struct *options= table->s->option_struct;
+
+  DBUG_ASSERT(options);
+  DBUG_PRINT("info", ("strparam: '%-.64s'  ullparam: %llu  enumparam: %u  "\
+                      "boolparam: %u",
+                      (options->strparam ? options->strparam : "<NULL>"),
+                      options->ullparam, options->enumparam, options->boolparam));
+#endif
+
+  DBUG_RETURN(0);
+}
+
+
+/**
+  @brief
+  Closes a table.
+
+  @details
+  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().
+
+  @see
+  sql_base.cc, sql_select.cc and table.cc
+*/
+
+int ha_example::close(void)
+{
+  DBUG_ENTER("ha_example::close");
+  DBUG_RETURN(0);
+}
+
+
+/**
+  @brief
+  write_row() inserts a row. No extra() hint is given currently if a bulk load
+  is happening. buf() is a byte array of data. You can use the field
+  information to extract the data from the native byte array type.
+
+  @details
+  Example of this would be:
+  @code
+  for (Field **field=table->field ; *field ; field++)
+  {
+    ...
+  }
+  @endcode
+
+  See ha_tina.cc for an example of extracting all of the data as strings.
+  ha_berekly.cc has an example of how to store it intact by "packing" it
+  for ha_berkeley's own native storage type.
+
+  See the note for update_row() on auto_increments and timestamps. This
+  case also applies to write_row().
+
+  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.
+
+  @see
+  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_example::write_row(const uchar *buf)
+{
+  DBUG_ENTER("ha_example::write_row");
+  /*
+    Example of a successful write_row. We don't store the data
+    anywhere; they are thrown away. A real implementation will
+    probably need to do something with 'buf'. We report a success
+    here, to pretend that the insert was successful.
+  */
+  DBUG_RETURN(0);
+}
+
+
+/**
+  @brief
+  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.
+
+  @details
+  Currently new_data will not have an updated auto_increament record, or
+  and updated timestamp field. You can do these for example by doing:
+  @code
+  if (table->next_number_field && record == table->record[0])
+    update_auto_increment();
+  @endcode
+
+  Called from sql_select.cc, sql_acl.cc, sql_update.cc, and sql_insert.cc.
+
+  @see
+  sql_select.cc, sql_acl.cc, sql_update.cc and sql_insert.cc
+*/
+int ha_example::update_row(const uchar *old_data, const uchar *new_data)
+{
+
+  DBUG_ENTER("ha_example::update_row");
+  DBUG_RETURN(HA_ERR_WRONG_COMMAND);
+}
+
+
+/**
+  @brief
+  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).
+
+  @details
+  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
+  not guarantee 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.
+
+  @see
+  sql_acl.cc, sql_udf.cc, sql_delete.cc, sql_insert.cc and sql_select.cc
+*/
+
+int ha_example::delete_row(const uchar *buf)
+{
+  DBUG_ENTER("ha_example::delete_row");
+  DBUG_RETURN(HA_ERR_WRONG_COMMAND);
+}
+
+
+/**
+  @brief
+  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.
+*/
+
+int ha_example::index_read_map(uchar *buf, const uchar *key,
+                               key_part_map keypart_map __attribute__((unused)),
+                               enum ha_rkey_function find_flag
+                               __attribute__((unused)))
+{
+  int rc;
+  DBUG_ENTER("ha_example::index_read");
+  rc= HA_ERR_WRONG_COMMAND;
+  DBUG_RETURN(rc);
+}
+
+
+/**
+  @brief
+  Used to read forward through the index.
+*/
+
+int ha_example::index_next(uchar *buf)
+{
+  int rc;
+  DBUG_ENTER("ha_example::index_next");
+  rc= HA_ERR_WRONG_COMMAND;
+  DBUG_RETURN(rc);
+}
+
+
+/**
+  @brief
+  Used to read backwards through the index.
+*/
+
+int ha_example::index_prev(uchar *buf)
+{
+  int rc;
+  DBUG_ENTER("ha_example::index_prev");
+  rc= HA_ERR_WRONG_COMMAND;
+  DBUG_RETURN(rc);
+}
+
+
+/**
+  @brief
+  index_first() asks for the first key in the index.
+
+  @details
+  Called from opt_range.cc, opt_sum.cc, sql_handler.cc, and sql_select.cc.
+
+  @see
+  opt_range.cc, opt_sum.cc, sql_handler.cc and sql_select.cc
+*/
+int ha_example::index_first(uchar *buf)
+{
+  int rc;
+  DBUG_ENTER("ha_example::index_first");
+  rc= HA_ERR_WRONG_COMMAND;
+  DBUG_RETURN(rc);
+}
+
+
+/**
+  @brief
+  index_last() asks for the last key in the index.
+
+  @details
+  Called from opt_range.cc, opt_sum.cc, sql_handler.cc, and sql_select.cc.
+
+  @see
+  opt_range.cc, opt_sum.cc, sql_handler.cc and sql_select.cc
+*/
+int ha_example::index_last(uchar *buf)
+{
+  int rc;
+  DBUG_ENTER("ha_example::index_last");
+  rc= HA_ERR_WRONG_COMMAND;
+  DBUG_RETURN(rc);
+}
+
+
+/**
+  @brief
+  rnd_init() is called when the system wants the storage engine to do a table
+  scan. See the example in the introduction at the top of this file to see when
+  rnd_init() is called.
+
+  @details
+  Called from filesort.cc, records.cc, sql_handler.cc, sql_select.cc, sql_table.cc,
+  and sql_update.cc.
+
+  @see
+  filesort.cc, records.cc, sql_handler.cc, sql_select.cc, sql_table.cc and sql_update.cc
+*/
+int ha_example::rnd_init(bool scan)
+{
+  DBUG_ENTER("ha_example::rnd_init");
+  DBUG_RETURN(0);
+}
+
+int ha_example::rnd_end()
+{
+  DBUG_ENTER("ha_example::rnd_end");
+  DBUG_RETURN(0);
+}
+
+
+/**
+  @brief
+  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.
+
+  @details
+  Called from filesort.cc, records.cc, sql_handler.cc, sql_select.cc, sql_table.cc,
+  and sql_update.cc.
+
+  @see
+  filesort.cc, records.cc, sql_handler.cc, sql_select.cc, sql_table.cc and sql_update.cc
+*/
+int ha_example::rnd_next(uchar *buf)
+{
+  int rc;
+  DBUG_ENTER("ha_example::rnd_next");
+  rc= HA_ERR_END_OF_FILE;
+  DBUG_RETURN(rc);
+}
+
+
+/**
+  @brief
+  position() is called after each call to rnd_next() if the data needs
+  to be ordered. You can do something like the following to store
+  the position:
+  @code
+  my_store_ptr(ref, ref_length, current_position);
+  @endcode
+
+  @details
+  The server uses ref to store data. ref_length in the above case is
+  the size needed to store current_position. ref is just a byte array
+  that the server will maintain. If you are using offsets to mark rows, then
+  current_position should be the offset. If it is a primary key like in
+  BDB, then it needs to be a primary key.
+
+  Called from filesort.cc, sql_select.cc, sql_delete.cc, and sql_update.cc.
+
+  @see
+  filesort.cc, sql_select.cc, sql_delete.cc and sql_update.cc
+*/
+void ha_example::position(const uchar *record)
+{
+  DBUG_ENTER("ha_example::position");
+  DBUG_VOID_RETURN;
+}
+
+
+/**
+  @brief
+  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. You can use ha_get_ptr(pos,ref_length) to retrieve whatever key
+  or position you saved when position() was called.
+
+  @details
+  Called from filesort.cc, records.cc, sql_insert.cc, sql_select.cc, and sql_update.cc.
+
+  @see
+  filesort.cc, records.cc, sql_insert.cc, sql_select.cc and sql_update.cc
+*/
+int ha_example::rnd_pos(uchar *buf, uchar *pos)
+{
+  int rc;
+  DBUG_ENTER("ha_example::rnd_pos");
+  rc= HA_ERR_WRONG_COMMAND;
+  DBUG_RETURN(rc);
+}
+
+
+/**
+  @brief
+  ::info() is used to return information to the optimizer. See my_base.h for
+  the complete description.
+
+  @details
+  Currently this table handler doesn't implement most of the fields really needed.
+  SHOW also makes use of this data.
+
+  You will probably want to have the following in your code:
+  @code
+  if (records < 2)
+    records = 2;
+  @endcode
+  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, and sql_update.cc.
+
+  @see
+  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 and sql_update.cc
+*/
+int ha_example::info(uint flag)
+{
+  DBUG_ENTER("ha_example::info");
+  DBUG_RETURN(0);
+}
+
+
+/**
+  @brief
+  extra() is called whenever the server wishes to send a hint to
+  the storage engine. The myisam engine implements the most hints.
+  ha_innodb.cc has the most exhaustive list of these hints.
+
+    @see
+  ha_innodb.cc
+*/
+int ha_example::extra(enum ha_extra_function operation)
+{
+  DBUG_ENTER("ha_example::extra");
+  DBUG_RETURN(0);
+}
+
+
+/**
+  @brief
+  Used to delete all rows in a table, including cases of truncate and cases where
+  the optimizer realizes that all rows will be removed as a result of an SQL statement.
+
+  @details
+  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().
+
+  @see
+  Item_func_group_concat::clear(), Item_sum_count_distinct::clear() and
+  Item_func_group_concat::clear() in item_sum.cc;
+  mysql_delete() in sql_delete.cc;
+  JOIN::reinit() in sql_select.cc and
+  st_select_lex_unit::exec() in sql_union.cc.
+*/
+int ha_example::delete_all_rows()
+{
+  DBUG_ENTER("ha_example::delete_all_rows");
+  DBUG_RETURN(HA_ERR_WRONG_COMMAND);
+}
+
+
+/**
+  @brief
+  This create a lock on the table. If you are implementing a storage engine
+  that can handle transacations look at ha_berkely.cc to see how you will
+  want to go about doing this. Otherwise you should consider calling flock()
+  here. Hint: Read the section "locking functions for mysql" in lock.cc to understand
+  this.
+
+  @details
+  Called from lock.cc by lock_external() and unlock_external(). Also called
+  from sql_table.cc by copy_data_between_tables().
+
+  @see
+  lock.cc by lock_external() and unlock_external() in lock.cc;
+  the section "locking functions for mysql" in lock.cc;
+  copy_data_between_tables() in sql_table.cc.
+*/
+int ha_example::external_lock(THD *thd, int lock_type)
+{
+  DBUG_ENTER("ha_example::external_lock");
+  DBUG_RETURN(0);
+}
+
+
+/**
+  @brief
+  The idea with handler::store_lock() is: The statement decides which locks
+  should be needed for the table. For updates/deletes/inserts we get WRITE
+  locks, for SELECT... we get read locks.
+
+  @details
+  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 example, changes all WRITE locks to TL_WRITE_ALLOW_WRITE
+  (which signals that we are doing WRITES, but are still allowing other
+  readers and writers).
+
+  When releasing locks, store_lock() is 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().
+
+  @note
+  In this method one should NEVER rely on table->in_use, it may, in fact,
+  refer to a different thread! (this happens if get_lock_data() is called
+  from mysql_lock_abort_for_thread() function)
+
+  @see
+  get_lock_data() in lock.cc
+*/
+THR_LOCK_DATA **ha_example::store_lock(THD *thd,
+                                       THR_LOCK_DATA **to,
+                                       enum thr_lock_type lock_type)
+{
+  if (lock_type != TL_IGNORE && lock.type == TL_UNLOCK)
+    lock.type=lock_type;
+  *to++= &lock;
+  return to;
+}
+
+
+/**
+  @brief
+  Used to delete a table. By the time delete_table() has been called all
+  opened references to this table will have been closed (and your globally
+  shared references released). The variable name will just be the name of
+  the table. You will need to remove any files you have created at this point.
+
+  @details
+  If you do not implement this, the default delete_table() is called from
+  handler.cc and it will delete all files with the file extensions returned
+  by bas_ext().
+
+  Called from handler.cc by delete_table and ha_create_table(). Only used
+  during create if the table_flag HA_DROP_BEFORE_CREATE was specified for
+  the storage engine.
+
+  @see
+  delete_table and ha_create_table() in handler.cc
+*/
+int ha_example::delete_table(const char *name)
+{
+  DBUG_ENTER("ha_example::delete_table");
+  /* This is not implemented but we want someone to be able that it works. */
+  DBUG_RETURN(0);
+}
+
+
+/**
+  @brief
+  Given a starting key and an ending key, estimate the number of rows that
+  will exist between the two keys.
+  The handler can also optionally update the 'pages' parameter with the page
+  number that contains the min and max keys. This will help the optimizer
+  to know if two ranges are partly on the same pages and if the min and
+  max key are on the same page.
+
+  @details
+  end_key may be empty, in which case determine if start_key matches any rows.
+
+  Called from opt_range.cc by check_quick_keys().
+
+  @see
+  check_quick_keys() in opt_range.cc
+*/
+ha_rows ha_example::records_in_range(uint inx,
+                                     const key_range *min_key,
+                                     const key_range *max_key,
+                                     page_range *pages)
+{
+  DBUG_ENTER("ha_example::records_in_range");
+  DBUG_RETURN(10);                         // low number to force index usage
+}
+
+
+/**
+  @brief
+  create() is called to create a database. The variable name will have the name
+  of the table.
+
+  @details
+  When create() is called you do not need to worry about
+  opening the table. Also, the .frm file will have already been
+  created so adjusting create_info is not necessary. You can overwrite
+  the .frm file at this point if you wish to change the table
+  definition, but there are no methods currently provided for doing
+  so.
+
+  Called from handle.cc by ha_create_table().
+
+  @see
+  ha_create_table() in handle.cc
+*/
+
+int ha_example::create(const char *name, TABLE *table_arg,
+                       HA_CREATE_INFO *create_info)
+{
+#ifndef DBUG_OFF
+  ha_table_option_struct *options= table_arg->s->option_struct;
+  DBUG_ENTER("ha_example::create");
+  /*
+    This example shows how to support custom engine specific table and field
+    options.
+  */
+  DBUG_ASSERT(options);
+  DBUG_PRINT("info", ("strparam: '%-.64s'  ullparam: %llu  enumparam: %u  "\
+                      "boolparam: %u",
+                      (options->strparam ? options->strparam : "<NULL>"),
+                      options->ullparam, options->enumparam, options->boolparam));
+  for (Field **field= table_arg->s->field; *field; field++)
+  {
+    ha_field_option_struct *field_options= (*field)->option_struct;
+    DBUG_ASSERT(field_options);
+    DBUG_PRINT("info", ("field: %s  complex: '%-.64s'",
+                         (*field)->field_name.str,
+                         (field_options->complex_param_to_parse_it_in_engine ?
+                          field_options->complex_param_to_parse_it_in_engine :
+                          "<NULL>")));
+  }
+#endif
+  DBUG_RETURN(0);
+}
+
+
+/**
+  check_if_supported_inplace_alter() is used to ask the engine whether
+  it can execute this ALTER TABLE statement in place or the server needs to
+  create a new table and copy th data over.
+
+  The engine may answer that the inplace alter is not supported or,
+  if supported, whether the server should protect the table from concurrent
+  accesses. Return values are
+
+    HA_ALTER_INPLACE_NOT_SUPPORTED
+    HA_ALTER_INPLACE_EXCLUSIVE_LOCK
+    HA_ALTER_INPLACE_SHARED_LOCK
+    etc
+*/
+
+enum_alter_inplace_result
+ha_example::check_if_supported_inplace_alter(TABLE* altered_table,
+                                             Alter_inplace_info* ha_alter_info)
+{
+  HA_CREATE_INFO *info= ha_alter_info->create_info;
+  DBUG_ENTER("ha_example::check_if_supported_inplace_alter");
+
+  if (ha_alter_info->handler_flags & ALTER_CHANGE_CREATE_OPTION)
+  {
+    /*
+      This example shows how custom engine specific table and field
+      options can be accessed from this function to be compared.
+    */
+    ha_table_option_struct *param_new= info->option_struct;
+    ha_table_option_struct *param_old= table->s->option_struct;
+
+    /*
+      check important parameters:
+      for this example engine, we'll assume that changing ullparam or
+      boolparam requires a table to be rebuilt, while changing strparam
+      or enumparam - does not.
+
+      For debugging purposes we'll announce this to the user
+      (don't do it in production!)
+
+    */
+    if (param_new->ullparam != param_old->ullparam)
+    {
+      push_warning_printf(ha_thd(), Sql_condition::WARN_LEVEL_NOTE,
+                          ER_UNKNOWN_ERROR, "EXAMPLE DEBUG: ULL %llu -> %llu",
+                          param_old->ullparam, param_new->ullparam);
+      DBUG_RETURN(HA_ALTER_INPLACE_NOT_SUPPORTED);
+    }
+
+    if (param_new->boolparam != param_old->boolparam)
+    {
+      push_warning_printf(ha_thd(), Sql_condition::WARN_LEVEL_NOTE,
+                          ER_UNKNOWN_ERROR, "EXAMPLE DEBUG: YESNO %u -> %u",
+                          param_old->boolparam, param_new->boolparam);
+      DBUG_RETURN(HA_ALTER_INPLACE_NOT_SUPPORTED);
+    }
+  }
+
+  if (ha_alter_info->handler_flags & ALTER_COLUMN_OPTION)
+  {
+    for (uint i= 0; i < table->s->fields; i++)
+    {
+      ha_field_option_struct *f_old= table->s->field[i]->option_struct;
+      ha_field_option_struct *f_new= info->fields_option_struct[i];
+      DBUG_ASSERT(f_old);
+      if (f_new)
+      {
+        push_warning_printf(ha_thd(), Sql_condition::WARN_LEVEL_NOTE,
+                            ER_UNKNOWN_ERROR, "EXAMPLE DEBUG: Field %`s COMPLEX '%s' -> '%s'",
+                            table->s->field[i]->field_name.str,
+                            f_old->complex_param_to_parse_it_in_engine,
+                            f_new->complex_param_to_parse_it_in_engine);
+      }
+      else
+        DBUG_PRINT("info", ("old field %i did not changed", i));
+    }
+  }
+
+  DBUG_RETURN(HA_ALTER_INPLACE_EXCLUSIVE_LOCK);
+}
+
+
+struct st_mysql_storage_engine example_storage_engine=
+{ MYSQL_HANDLERTON_INTERFACE_VERSION };
+
+static ulong srv_enum_var= 0;
+static ulong srv_ulong_var= 0;
+static double srv_double_var= 0;
+
+const char *enum_var_names[]=
+{
+  "e1", "e2", NullS
+};
+
+TYPELIB enum_var_typelib=
+{
+  array_elements(enum_var_names) - 1, "enum_var_typelib",
+  enum_var_names, NULL
+};
+
+static MYSQL_SYSVAR_ENUM(
+  enum_var,                       // name
+  srv_enum_var,                   // varname
+  PLUGIN_VAR_RQCMDARG,            // opt
+  "Sample ENUM system variable.", // comment
+  NULL,                           // check
+  NULL,                           // update
+  0,                              // def
+  &enum_var_typelib);             // typelib
+
+static MYSQL_THDVAR_INT(int_var, PLUGIN_VAR_RQCMDARG, "-1..1",
+  NULL, NULL, 0, -1, 1, 0);
+
+static MYSQL_SYSVAR_ULONG(
+  ulong_var,
+  srv_ulong_var,
+  PLUGIN_VAR_RQCMDARG,
+  "0..1000",
+  NULL,
+  NULL,
+  8,
+  0,
+  1000,
+  0);
+
+static MYSQL_SYSVAR_DOUBLE(
+  double_var,
+  srv_double_var,
+  PLUGIN_VAR_RQCMDARG,
+  "0.500000..1000.500000",
+  NULL,
+  NULL,
+  8.5,
+  0.5,
+  1000.5,
+  0);                             // reserved always 0
+
+static MYSQL_THDVAR_DOUBLE(
+  double_thdvar,
+  PLUGIN_VAR_RQCMDARG,
+  "0.500000..1000.500000",
+  NULL,
+  NULL,
+  8.5,
+  0.5,
+  1000.5,
+  0);
+
+static MYSQL_THDVAR_INT(
+  deprecated_var, PLUGIN_VAR_RQCMDARG | PLUGIN_VAR_DEPRECATED, "-1..1",
+  NULL, NULL, 0, -1, 1, 0);
+
+static struct st_mysql_sys_var* example_system_variables[]= {
+  MYSQL_SYSVAR(enum_var),
+  MYSQL_SYSVAR(ulong_var),
+  MYSQL_SYSVAR(int_var),
+  MYSQL_SYSVAR(double_var),
+  MYSQL_SYSVAR(double_thdvar),
+  MYSQL_SYSVAR(deprecated_var),
+  MYSQL_SYSVAR(varopt_default),
+  NULL
+};
+
+// this is an example of SHOW_SIMPLE_FUNC and of my_snprintf() service
+// If this function would return an array, one should use SHOW_FUNC
+static int show_func_example(MYSQL_THD thd, struct st_mysql_show_var *var,
+                             char *buf)
+{
+  var->type= SHOW_CHAR;
+  var->value= buf; // it's of SHOW_VAR_FUNC_BUFF_SIZE bytes
+  my_snprintf(buf, SHOW_VAR_FUNC_BUFF_SIZE,
+              "enum_var is %lu, ulong_var is %lu, int_var is %d, "
+              "double_var is %f, %.6b", // %b is a MySQL extension
+              srv_enum_var, srv_ulong_var, THDVAR(thd, int_var),
+              srv_double_var, "really");
+  return 0;
+}
+
+static struct st_mysql_show_var func_status[]=
+{
+  {"func_example",  (char *)show_func_example, SHOW_SIMPLE_FUNC},
+  {0,0,SHOW_UNDEF}
+};
+
+struct st_mysql_daemon unusable_example=
+{ MYSQL_DAEMON_INTERFACE_VERSION };
+
+maria_declare_plugin(example)
+{
+  MYSQL_STORAGE_ENGINE_PLUGIN,
+  &example_storage_engine,
+  "EXAMPLE",
+  "Brian Aker, MySQL AB",
+  "Example storage engine",
+  PLUGIN_LICENSE_GPL,
+  example_init_func,                            /* Plugin Init */
+  NULL,                                         /* Plugin Deinit */
+  0x0001,                                       /* version number (0.1) */
+  func_status,                                  /* status variables */
+  example_system_variables,                     /* system variables */
+  "0.1",                                        /* string version */
+  MariaDB_PLUGIN_MATURITY_EXPERIMENTAL          /* maturity */
+},
+{
+  MYSQL_DAEMON_PLUGIN,
+  &unusable_example,
+  "UNUSABLE",
+  "Sergei Golubchik",
+  "Unusable Daemon",
+  PLUGIN_LICENSE_GPL,
+  NULL,                                         /* Plugin Init */
+  NULL,                                         /* Plugin Deinit */
+  0x030E,                                       /* version number (3.14) */
+  NULL,                                         /* status variables */
+  NULL,                                         /* system variables */
+  "3.14.15.926" ,                               /* version, as a string */
+  MariaDB_PLUGIN_MATURITY_EXPERIMENTAL          /* maturity */
+}
+maria_declare_plugin_end;