// OS, and other details ushastry@ushastry:~/mybuilds$ ushastry@ushastry:~/mybuilds$ cat /etc/*release PRETTY_NAME="Debian GNU/Linux 7 (wheezy)" NAME="Debian GNU/Linux" VERSION_ID="7" VERSION="7 (wheezy)" ID=debian ANSI_COLOR="1;31" HOME_URL="http://www.debian.org/" SUPPORT_URL="http://www.debian.org/support/" BUG_REPORT_URL="http://bugs.debian.org/" ushastry@ushastry:~/mybuilds$ ushastry@ushastry:~/mybuilds$ gdb --version GNU gdb (GDB) 7.8 Copyright (C) 2014 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. Type "show copying" and "show warranty" for details. This GDB was configured as "x86_64-unknown-linux-gnu". Type "show configuration" for configuration details. For bug reporting instructions, please see: . Find the GDB manual and other documentation resources online at: . For help, type "help". Type "apropos word" to search for commands related to "word". ushastry@ushastry:~/mybuilds$ valgrind --version valgrind-3.10.0 ushastry@ushastry:~/mybuilds$ cmake --version cmake version 2.8.9 ushastry@ushastry:~/mybuilds$ // Downloaded source ushastry@ushastry:~/mybuilds$ md5sum mysql-5.6.21.tar.gz e47c3a70b8d89db3199a349204b2ae4e mysql-5.6.21.tar.gz Followed steps from - https://github.com/Tokutek/tokudb-engine/wiki/MySQL-leaks-memory-for-str-type-thread-varia... // Modified ushastry@ushastry:~/mybuilds/mysql-5.6.21$ diff storage/example/ha_example.cc /tmp/ha_example.cc 882d881 < static MYSQL_THDVAR_STR(last_create, PLUGIN_VAR_MEMALLOC, "last_create", NULL /*check*/, NULL /*update*/, NULL /*default*/); 910,916d908 < < THD *thd = ha_thd(); < my_free(THDVAR(thd, last_create)); < char *sp = (char *) my_malloc(100000000, MYF(MY_FAE)); // allocate 100MB so that it is easily seen with valgrind < sprintf(sp, "%p %s:%u %s my_malloc 100MB at %p", (void *) &ha_example::create, __FILE__, __LINE__, name, sp); < sql_print_information("%s", sp); < THDVAR(thd, last_create) = sp; 988d979 < MYSQL_SYSVAR(last_create), root@ushastry:/home/ushastry/mybuilds/mysql-5.6.21# pwd /home/ushastry/mybuilds/mysql-5.6.21 root@ushastry:/home/ushastry/mybuilds/mysql-5.6.21# root@ushastry:/home/ushastry/mybuilds/mysql-5.6.21# cmake -D CMAKE_BUILD_TYPE=Debug -D CMAKE_INSTALL_PREFIX=../mysql-5.6.21-debug-install -DWITH_EXAMPLE_STORAGE_ENGINE=1 ../mysql-5.6.21 . root@ushastry:/home/ushastry/mybuilds/mysql-5.6.21# make root@ushastry:/home/ushastry/mybuilds/mysql-5.6.21# make install root@ushastry:/home/ushastry/mybuilds/mysql-5.6.21# cd .. root@ushastry:/home/ushastry/mybuilds# ls -l total 32244 drwxr-xr-x 35 ushastry ushastry 4096 Oct 30 13:37 mysql-5.6.21 drwxr-xr-x 13 root root 4096 Oct 30 13:33 mysql-5.6.21-debug-install -rw-r--r-- 1 root root 33009070 Oct 30 10:19 mysql-5.6.21.tar.gz root@ushastry:/home/ushastry/mybuilds# cd mysql-5.6.21-debug-install/ root@ushastry:/home/ushastry/mybuilds/mysql-5.6.21-debug-install# chmod 755 scripts/mysql_install_db root@ushastry:/home/ushastry/mybuilds/mysql-5.6.21-debug-install# /home/ushastry/mybuilds/mysql-5.6.21-debug-install/scripts/mysql_install_db --basedir=/home/ushastry/mybuilds/mysql-5.6.21-debug-install/ --datadir=/tmp/bug // started mysqld using valgrind root@ushastry:/home/ushastry/mybuilds/mysql-5.6.21-debug-install# valgrind --show-reachable=yes --leak-check=full /home/ushastry/mybuilds/mysql-5.6.21-debug-install/bin/mysqld --basedir=/home/ushastry/mybuilds/mysql-5.6.21-debug-install/ --datadir=/tmp/bug --user=root ==20587== Memcheck, a memory error detector ==20587== Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al. ==20587== Using Valgrind-3.10.0 and LibVEX; rerun with -h for copyright info ==20587== Command: /home/ushastry/mybuilds/mysql-5.6.21-debug-install/bin/mysqld --basedir=/home/ushastry/mybuilds/mysql-5.6.21-debug-install/ --datadir=/tmp/bug --user=root ==20587== // Created required schema ushastry@ushastry:~/mybuilds/mysql-5.6.21-debug-install$ for i in {1..50}; do `bin/mysql -u root -e "drop database if exists test;create database test;use test;create table test.t$i (id int) engine=example;"`; done // Shutdown ushastry@ushastry:~/mybuilds/mysql-5.6.21-debug-install$ bin/mysqladmin -uroot -p shutdown Enter password: // Valgrind summary ==20587== 5,300,000,000 bytes in 53 blocks are definitely lost in loss record 250 of 250 ==20587== at 0x4C29554: malloc (vg_replace_malloc.c:296) ==20587== by 0xA9B951: my_malloc (my_malloc.c:38) ==20587== by 0xB81056E: ??? ==20587== by 0x66525D: handler::ha_create(char const*, TABLE*, st_ha_create_information*) (handler.cc:4524) ==20587== by 0x665AEF: ha_create_table(THD*, char const*, char const*, char const*, st_ha_create_information*, bool, bool) (handler.cc:4762) ==20587== by 0x8BBB21: rea_create_table(THD*, char const*, char const*, char const*, st_ha_create_information*, List&, unsigned int, st_key*, handler*, bool) (unireg.cc:527) ==20587== by 0x855E0C: create_table_impl(THD*, char const*, char const*, char const*, st_ha_create_information*, Alter_info*, bool, unsigned int, bool, bool*, st_key**, unsigned int*) (sql_table.cc:4919) ==20587== by 0x8562C8: mysql_create_table_no_lock(THD*, char const*, char const*, st_ha_create_information*, Alter_info*, unsigned int, bool*) (sql_table.cc:5029) ==20587== by 0x8563C8: mysql_create_table(THD*, TABLE_LIST*, st_ha_create_information*, Alter_info*) (sql_table.cc:5078) ==20587== by 0x7EE099: mysql_execute_command(THD*) (sql_parse.cc:3061) ==20587== by 0x7F68DB: mysql_parse(THD*, char*, unsigned int, Parser_state*) (sql_parse.cc:6245) ==20587== by 0x7EA35D: dispatch_command(enum_server_command, THD*, char*, unsigned int) (sql_parse.cc:1332) ==20587== ==20587== LEAK SUMMARY: ==20587== definitely lost: 5,300,000,000 bytes in 53 blocks ==20587== indirectly lost: 0 bytes in 0 blocks ==20587== possibly lost: 4,200,248,704 bytes in 1,230 blocks ==20587== still reachable: 75,100,728 bytes in 379 blocks ==20587== suppressed: 0 bytes in 0 blocks ==20587== ==20587== For counts of detected and suppressed errors, rerun with: -v ==20587== ERROR SUMMARY: 182 errors from 182 contexts (suppressed: 6 from 6) root@ushastry:/home/ushastry/mybuilds/mysql-5.6.21-debug-install# // Second attempt ==20897== 3,800,000,000 bytes in 38 blocks are possibly lost in loss record 245 of 245 ==20897== at 0x4C29554: malloc (vg_replace_malloc.c:296) ==20897== by 0xA9B951: my_malloc (my_malloc.c:38) ==20897== by 0xB81056E: ??? ==20897== by 0x66525D: handler::ha_create(char const*, TABLE*, st_ha_create_information*) (handler.cc:4524) ==20897== by 0x665AEF: ha_create_table(THD*, char const*, char const*, char const*, st_ha_create_information*, bool, bool) (handler.cc:4762) ==20897== by 0x8BBB21: rea_create_table(THD*, char const*, char const*, char const*, st_ha_create_information*, List&, unsigned int, st_key*, handler*, bool) (unireg.cc:527) ==20897== by 0x855E0C: create_table_impl(THD*, char const*, char const*, char const*, st_ha_create_information*, Alter_info*, bool, unsigned int, bool, bool*, st_key**, unsigned int*) (sql_table.cc:4919) ==20897== by 0x8562C8: mysql_create_table_no_lock(THD*, char const*, char const*, st_ha_create_information*, Alter_info*, unsigned int, bool*) (sql_table.cc:5029) ==20897== by 0x8563C8: mysql_create_table(THD*, TABLE_LIST*, st_ha_create_information*, Alter_info*) (sql_table.cc:5078) ==20897== by 0x7EE099: mysql_execute_command(THD*) (sql_parse.cc:3061) ==20897== by 0x7F68DB: mysql_parse(THD*, char*, unsigned int, Parser_state*) (sql_parse.cc:6245) ==20897== by 0x7EA35D: dispatch_command(enum_server_command, THD*, char*, unsigned int) (sql_parse.cc:1332) ==20897== ==20897== LEAK SUMMARY: ==20897== definitely lost: 1,200,000,000 bytes in 12 blocks ==20897== indirectly lost: 0 bytes in 0 blocks ==20897== possibly lost: 3,800,248,024 bytes in 1,211 blocks ==20897== still reachable: 75,089,328 bytes in 54 blocks ==20897== suppressed: 0 bytes in 0 blocks ==20897== ==20897== For counts of detected and suppressed errors, rerun with: -v ==20897== ERROR SUMMARY: 191 errors from 191 contexts (suppressed: 6 from 6) ## Modified storage/ha_example.cc /* Copyright (c) 2004, 2013, Oracle and/or its affiliates. All rights reserved. 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 02110-1301 USA */ /** @file ha_example.cc @brief The ha_example engine is a stubbed storage engine for example purposes only; it does 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. @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). 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:
./configure --with-example-storage-engine Once this is done, MySQL will let you create tables with:
CREATE TABLE (...) 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!
-Brian */ #include "sql_priv.h" #include "sql_class.h" // MYSQL_HANDLERTON_INTERFACE_VERSION #include "ha_example.h" #include "probes_mysql.h" #include "sql_plugin.h" static handler *example_create_handler(handlerton *hton, TABLE_SHARE *table, MEM_ROOT *mem_root); handlerton *example_hton; /* Interface to mysqld, to check system tables supported by SE */ static const char* example_system_database(); static bool example_is_supported_system_table(const char *db, const char *table_name, bool is_sql_layer_system_table); #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); } #endif 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"); #ifdef HAVE_PSI_INTERFACE init_example_psi_keys(); #endif example_hton= (handlerton *)p; example_hton->state= SHOW_OPTION_YES; example_hton->create= example_create_handler; example_hton->flags= HTON_CAN_RECREATE; example_hton->system_database= example_system_database; example_hton->is_supported_system_table= example_is_supported_system_table; 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(get_ha_share_ptr()))) { tmp_share= new Example_share; if (!tmp_share) goto err; set_ha_share_ptr(static_cast(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 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. For engines that have two file name extentions (separate meta/index file and data file), the order of elements is relevant. First element of engine file name extentions 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 }; const char **ha_example::bas_ext() const { return ha_example_exts; } /* Following handler function provides access to system database specific to SE. This interface is optional, so every SE need not implement it. */ const char* ha_example_system_database= NULL; const char* example_system_database() { return ha_example_system_database; } /* List of all system tables specific to the SE. Array element would look like below, { "", "" }, The last element MUST be, { (const char*)NULL, (const char*)NULL } This array is optional, so every SE need not implement it. */ static st_system_tablename ha_example_system_tables[]= { {(const char*)NULL, (const char*)NULL} }; /** @brief Check if the given db.tablename is a system table for this SE. @param db Database name to check. @param table_name table name to check. @param is_sql_layer_system_table if the supplied db.table_name is a SQL layer system table. @return @retval TRUE Given db.table_name is supported system table. @retval FALSE Given db.table_name is not a supported system table. */ static bool example_is_supported_system_table(const char *db, const char *table_name, bool is_sql_layer_system_table) { st_system_tablename *systab; // Does this SE support "ALL" SQL layer system tables ? if (is_sql_layer_system_table) return false; // Check if this is SE layer system tables systab= ha_example_system_tables; while (systab && systab->db) { if (systab->db == db && strcmp(systab->tablename, table_name) == 0) return true; systab++; } return false; } /** @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); 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. 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(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. You can do this 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, 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"); MYSQL_INDEX_READ_ROW_START(table_share->db.str, table_share->table_name.str); rc= HA_ERR_WRONG_COMMAND; MYSQL_INDEX_READ_ROW_DONE(rc); 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"); MYSQL_INDEX_READ_ROW_START(table_share->db.str, table_share->table_name.str); rc= HA_ERR_WRONG_COMMAND; MYSQL_INDEX_READ_ROW_DONE(rc); 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"); MYSQL_INDEX_READ_ROW_START(table_share->db.str, table_share->table_name.str); rc= HA_ERR_WRONG_COMMAND; MYSQL_INDEX_READ_ROW_DONE(rc); 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"); MYSQL_INDEX_READ_ROW_START(table_share->db.str, table_share->table_name.str); rc= HA_ERR_WRONG_COMMAND; MYSQL_INDEX_READ_ROW_DONE(rc); 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"); MYSQL_INDEX_READ_ROW_START(table_share->db.str, table_share->table_name.str); rc= HA_ERR_WRONG_COMMAND; MYSQL_INDEX_READ_ROW_DONE(rc); 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"); MYSQL_READ_ROW_START(table_share->db.str, table_share->table_name.str, TRUE); rc= HA_ERR_END_OF_FILE; MYSQL_READ_ROW_DONE(rc); 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"); MYSQL_READ_ROW_START(table_share->db.str, table_share->table_name.str, TRUE); rc= HA_ERR_WRONG_COMMAND; MYSQL_READ_ROW_DONE(rc); 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 Used for handler specific truncate table. The table is locked in exclusive mode and handler is responsible for reseting the auto- increment counter. @details Called from Truncate_statement::handler_truncate. Not used if the handlerton supports HTON_CAN_RECREATE, unless this engine can be used as a partition. In this case, it is invoked when a particular partition is to be truncated. @see Truncate_statement in sql_truncate.cc Remarks in handler::truncate. */ int ha_example::truncate() { DBUG_ENTER("ha_example::truncate"); 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 Renames a table from one name to another via an alter table call. @details If you do not implement this, the default rename_table() is called from handler.cc and it will delete all files with the file extensions returned by bas_ext(). Called from sql_table.cc by mysql_rename_table(). @see mysql_rename_table() in sql_table.cc */ int ha_example::rename_table(const char * from, const char * to) { DBUG_ENTER("ha_example::rename_table "); DBUG_RETURN(HA_ERR_WRONG_COMMAND); } /** @brief Given a starting key and an ending key, estimate the number of rows that will exist between the two keys. @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, key_range *min_key, key_range *max_key) { DBUG_ENTER("ha_example::records_in_range"); DBUG_RETURN(10); // low number to force index usage } static MYSQL_THDVAR_STR(last_create, PLUGIN_VAR_MEMALLOC, "last_create", NULL /*check*/, NULL /*update*/, NULL /*default*/); /** @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) { DBUG_ENTER("ha_example::create"); /* This is not implemented but we want someone to be able to see that it works. */ THD *thd = ha_thd(); my_free(THDVAR(thd, last_create)); char *sp = (char *) my_malloc(100000000, MYF(MY_FAE)); // allocate 100MB so that it is easily seen with valgrind sprintf(sp, "%p %s:%u %s my_malloc 100MB at %p", (void *) &ha_example::create, __FILE__, __LINE__, name, sp); sql_print_information("%s", sp); THDVAR(thd, last_create) = sp; DBUG_RETURN(0); } 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_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 struct st_mysql_sys_var* example_system_variables[]= { MYSQL_SYSVAR(enum_var), MYSQL_SYSVAR(ulong_var), MYSQL_SYSVAR(double_var), MYSQL_SYSVAR(last_create), MYSQL_SYSVAR(double_thdvar), NULL }; // this is an example of SHOW_FUNC and of my_snprintf() service 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, " "double_var is %f, %.6b", // %b is a MySQL extension srv_enum_var, srv_ulong_var, srv_double_var, "really"); return 0; } static struct st_mysql_show_var func_status[]= { {"example_func_example", (char *)show_func_example, SHOW_FUNC}, {0,0,SHOW_UNDEF} }; mysql_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 /* 0.1 */, func_status, /* status variables */ example_system_variables, /* system variables */ NULL, /* config options */ 0, /* flags */ } mysql_declare_plugin_end;