test_sql_discovery storage engine

use it to test main test cases with need_full_discover_for_existence > 0

sql/sql_base.cc

@@ -713,15 +713,6 @@ end:
     */
     share= (TABLE_SHARE*) 1;
   }
-  else
-  {
-    /*
-      To be able perform any operation on table we should own
-      some kind of metadata lock on it.
-    */
-    DBUG_ASSERT(thd->mdl_context.is_lock_owner(MDL_key::TABLE, db, table_name,
-                                               MDL_SHARED));
-  }
 
   mysql_mutex_unlock(&LOCK_open);
   DBUG_RETURN(share);

sql/sql_rename.cc

@@ -32,6 +32,9 @@
 
 static TABLE_LIST *rename_tables(THD *thd, TABLE_LIST *table_list,
 				 bool skip_error);
+static bool do_rename(THD *thd, TABLE_LIST *ren_table, char *new_db,
+                      char *new_table_name, char *new_table_alias,
+                      bool skip_error);
 
 static TABLE_LIST *reverse_table_list(TABLE_LIST *table_list);
 
@@ -144,10 +147,6 @@ bool mysql_rename_tables(THD *thd, TABLE_LIST *table_list, bool silent)
                        MYSQL_OPEN_SKIP_TEMPORARY))
     goto err;
 
-  for (ren_table= table_list; ren_table; ren_table= ren_table->next_local)
-    tdc_remove_table(thd, TDC_RT_REMOVE_ALL, ren_table->db,
-                     ren_table->table_name, FALSE);
-
   error=0;
   /*
     An exclusive lock on table names is satisfactory to ensure
@@ -235,7 +234,7 @@ static TABLE_LIST *reverse_table_list(TABLE_LIST *table_list)
     true      rename failed
 */
 
-bool
+static bool
 do_rename(THD *thd, TABLE_LIST *ren_table, char *new_db, char *new_table_name,
           char *new_table_alias, bool skip_error)
 {
@@ -269,6 +268,10 @@ do_rename(THD *thd, TABLE_LIST *ren_table, char *new_db, char *new_table_name,
 
   if (old_exists)
   {
+    DBUG_ASSERT(!thd->locked_tables_mode);
+    tdc_remove_table(thd, TDC_RT_REMOVE_ALL,
+                     ren_table->db, ren_table->table_name, false);
+
     if (hton != view_pseudo_hton)
     {
       if (!(rc= mysql_rename_table(hton, ren_table->db, old_alias,

sql/sql_rename.h

@@ -20,8 +20,5 @@ class THD;
 struct TABLE_LIST;
 
 bool mysql_rename_tables(THD *thd, TABLE_LIST *table_list, bool silent);
-bool do_rename(THD *thd, TABLE_LIST *ren_table, char *new_db,
-               char *new_table_name, char *new_table_alias,
-               bool skip_error);
 
 #endif /* SQL_RENAME_INCLUDED */

sql/sql_table.cc

@@ -22,7 +22,6 @@
 #include "unireg.h"
 #include "debug_sync.h"
 #include "sql_table.h"
-#include "sql_rename.h" // do_rename
 #include "sql_parse.h"                        // test_if_data_home_dir
 #include "sql_cache.h"                          // query_cache_*
 #include "sql_base.h"   // open_table_uncached, lock_table_names

storage/test_sql_discovery/CMakeLists.txt

@@ -0,0 +1,2 @@
+MYSQL_ADD_PLUGIN(test_sql_discovery test_sql_discovery.cc STORAGE_ENGINE
+  COMPONENT Test)

storage/test_sql_discovery/mysql-test/archive/discover.test

@@ -0,0 +1,3 @@
+# run the normal test file with need_full_discover_for_existence>0
+--source ../sql_discovery/inc.inc
+--source discover.test

storage/test_sql_discovery/mysql-test/main/r/partition_disabled.rdiff

@@ -0,0 +1,11 @@
+--- r/partition_disabled.result	2013-04-07 12:36:57.000000000 +0200
++++ /usr/home/serg/Abk/mysql/10.0-serg/storage/test_sql_discovery/mysql-test/main/r/partition_disabled.reject	2013-04-07 23:19:14.000000000 +0200
+@@ -3,7 +3,7 @@
+ SELECT * FROM t1;
+ ERROR HY000: The MariaDB server is running with the --skip-partition option so it cannot execute this statement
+ TRUNCATE TABLE t1;
+-ERROR 42S02: Table 'test.t1' doesn't exist
++ERROR HY000: The MariaDB server is running with the --skip-partition option so it cannot execute this statement
+ ANALYZE TABLE t1;
+ Table	Op	Msg_type	Msg_text
+ test.t1	analyze	Error	The MariaDB server is running with the --skip-partition option so it cannot execute this statement

storage/test_sql_discovery/mysql-test/main/r/plugin.rdiff

@@ -0,0 +1,11 @@
+--- r/plugin.result	2013-02-21 19:46:59.000000000 +0100
++++ r/plugin.reject	2013-02-27 11:13:22.000000000 +0100
+@@ -71,6 +71,8 @@
+ SELECT * FROM t2;
+ ERROR 42000: Unknown storage engine 'EXAMPLE'
+ DROP TABLE t2;
++Warnings:
++Error	1286	Unknown storage engine 'EXAMPLE'
+ UNINSTALL PLUGIN EXAMPLE;
+ ERROR 42000: PLUGIN EXAMPLE does not exist
+ UNINSTALL PLUGIN non_exist;

storage/test_sql_discovery/mysql-test/main/t/create.test

@@ -0,0 +1,3 @@
+# run the normal test file with need_full_discover_for_existence>0
+--source ../sql_discovery/inc.inc
+--source create.test

storage/test_sql_discovery/mysql-test/main/t/drop.test

@@ -0,0 +1,3 @@
+# run the normal test file with need_full_discover_for_existence>0
+--source ../sql_discovery/inc.inc
+--source drop.test

storage/test_sql_discovery/mysql-test/main/t/mdl_sync.test

@@ -0,0 +1,3 @@
+# run the normal test file with need_full_discover_for_existence>0
+--source ../sql_discovery/inc.inc
+--source mdl_sync.test

storage/test_sql_discovery/mysql-test/main/t/partition_disabled.test

@@ -0,0 +1,3 @@
+# run the normal test file with need_full_discover_for_existence>0
+--source ../sql_discovery/inc.inc
+--source partition_disabled.test

storage/test_sql_discovery/mysql-test/main/t/plugin.test

@@ -0,0 +1,3 @@
+# run the normal test file with need_full_discover_for_existence>0
+--source ../sql_discovery/inc.inc
+--source plugin.test

storage/test_sql_discovery/mysql-test/main/t/rename.test

@@ -0,0 +1,3 @@
+# run the normal test file with need_full_discover_for_existence>0
+--source ../sql_discovery/inc.inc
+--source rename.test

storage/test_sql_discovery/mysql-test/sql_discovery/inc.inc

@@ -0,0 +1,4 @@
+if (`SELECT COUNT(*) = 0 FROM INFORMATION_SCHEMA.ENGINES WHERE engine = 'test_sql_discovery' AND support='YES'`)
+{
+  --skip Test requires test_sql_discovery engine
+}

storage/test_sql_discovery/mysql-test/sql_discovery/inc.opt

@@ -0,0 +1 @@
+--plugin-load=$HA_TEST_SQL_DISCOVERY_SO

storage/test_sql_discovery/mysql-test/sql_discovery/simple.result

@@ -0,0 +1,199 @@
+show variables like 'test_sql_discovery%';
+Variable_name	Value
+test_sql_discovery_statement	
+test_sql_discovery_write_frm	ON
+set sql_quote_show_create=0;
+create table t1 (a int) engine=test_sql_discovery;
+ERROR HY000: Can't create table 'test.t1' (errno: 131 "Command not supported by database")
+select * from t1;
+ERROR 42S02: Table 'test.t1' doesn't exist
+set @@test_sql_discovery_statement='t1:foobar bwa-ha-ha';
+select * from t0;
+ERROR 42S02: Table 'test.t0' doesn't exist
+select * from t1;
+ERROR 42S02: Table 'test.t1' doesn't exist
+show warnings;
+Level	Code	Message
+Error	1064	You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'foobar bwa-ha-ha' at line 1
+Error	1146	Table 'test.t1' doesn't exist
+Error	1030	Got error 130 "Incorrect file format" from storage engine
+set @@test_sql_discovery_statement='t1:select 1';
+select * from t1;
+ERROR 42S02: Table 'test.t1' doesn't exist
+show warnings;
+Level	Code	Message
+Error	1939	Engine TEST_SQL_DISCOVERY failed to discover table `test`.`t1` with 'select 1'
+Error	1146	Table 'test.t1' doesn't exist
+Error	1030	Got error 130 "Incorrect file format" from storage engine
+set @@test_sql_discovery_statement='t1:create table t1 (a int primary key) partition by hash(id) partitions 2';
+select * from t1;
+ERROR 42S02: Table 'test.t1' doesn't exist
+show warnings;
+Level	Code	Message
+Error	1290	The MariaDB server is running with the --skip-partition option so it cannot execute this statement
+Error	1146	Table 'test.t1' doesn't exist
+Error	1030	Got error 130 "Incorrect file format" from storage engine
+set @@test_sql_discovery_statement='t1:create table t1 (a int) union=(t3,t4)';
+select * from t1;
+ERROR 42S02: Table 'test.t1' doesn't exist
+show warnings;
+Level	Code	Message
+Error	1939	Engine TEST_SQL_DISCOVERY failed to discover table `test`.`t1` with 'create table t1 (a int) union=(t3,t4)'
+Error	1146	Table 'test.t1' doesn't exist
+Error	1030	Got error 130 "Incorrect file format" from storage engine
+set @@test_sql_discovery_statement='t1:create table t1 like t2';
+select * from t1;
+ERROR 42S02: Table 'test.t1' doesn't exist
+show warnings;
+Level	Code	Message
+Error	1939	Engine TEST_SQL_DISCOVERY failed to discover table `test`.`t1` with 'create table t1 like t2'
+Error	1146	Table 'test.t1' doesn't exist
+Error	1030	Got error 130 "Incorrect file format" from storage engine
+set @@test_sql_discovery_statement='t1:create table t1 select * from t2';
+select * from t1;
+ERROR 42S02: Table 'test.t1' doesn't exist
+show warnings;
+Level	Code	Message
+Error	1939	Engine TEST_SQL_DISCOVERY failed to discover table `test`.`t1` with 'create table t1 select * from t2'
+Error	1146	Table 'test.t1' doesn't exist
+Error	1030	Got error 130 "Incorrect file format" from storage engine
+set @@test_sql_discovery_statement='t1:create table t1 (a int) index directory="/tmp"';
+select * from t1;
+ERROR 42S02: Table 'test.t1' doesn't exist
+show warnings;
+Level	Code	Message
+Error	1939	Engine TEST_SQL_DISCOVERY failed to discover table `test`.`t1` with 'create table t1 (a int) index directory="/tmp"'
+Error	1146	Table 'test.t1' doesn't exist
+Error	1030	Got error 130 "Incorrect file format" from storage engine
+set @@test_sql_discovery_statement='t1:create table t1 (a int) data directory="/tmp"';
+select * from t1;
+ERROR 42S02: Table 'test.t1' doesn't exist
+show warnings;
+Level	Code	Message
+Error	1939	Engine TEST_SQL_DISCOVERY failed to discover table `test`.`t1` with 'create table t1 (a int) data directory="/tmp"'
+Error	1146	Table 'test.t1' doesn't exist
+Error	1030	Got error 130 "Incorrect file format" from storage engine
+set @@test_sql_discovery_statement='t1:create table t1 (a int) engine=myisam';
+select * from t1;
+ERROR 42S02: Table 'test.t1' doesn't exist
+show warnings;
+Level	Code	Message
+Error	1939	Engine TEST_SQL_DISCOVERY failed to discover table `test`.`t1` with 'create table t1 (a int) engine=myisam'
+Error	1146	Table 'test.t1' doesn't exist
+Error	1030	Got error 130 "Incorrect file format" from storage engine
+set @@test_sql_discovery_statement='t1:create temporary table t1 (a int)';
+select * from t1;
+ERROR 42S02: Table 'test.t1' doesn't exist
+show warnings;
+Level	Code	Message
+Error	1939	Engine TEST_SQL_DISCOVERY failed to discover table `test`.`t1` with 'create temporary table t1 (a int)'
+Error	1146	Table 'test.t1' doesn't exist
+Error	1030	Got error 130 "Incorrect file format" from storage engine
+set @@test_sql_discovery_statement='t1:create table if not exists t1 (a int)';
+select * from t1;
+ERROR 42S02: Table 'test.t1' doesn't exist
+show warnings;
+Level	Code	Message
+Error	1939	Engine TEST_SQL_DISCOVERY failed to discover table `test`.`t1` with 'create table if not exists t1 (a int)'
+Error	1146	Table 'test.t1' doesn't exist
+Error	1030	Got error 130 "Incorrect file format" from storage engine
+set @@test_sql_discovery_statement='t1:create table t1 (a int)';
+select * from t1;
+a
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE t1 (
+  a int(11) DEFAULT NULL
+) ENGINE=TEST_SQL_DISCOVERY DEFAULT CHARSET=latin1
+drop table t1;
+set @@test_sql_discovery_statement='t1:create table t2 (a int)';
+select * from t1;
+a
+select * from t2;
+ERROR 42S02: Table 'test.t2' doesn't exist
+drop table t1;
+set @@test_sql_discovery_statement='t1:
+create table t1 (
+  a int not null default 5 primary key,
+  b timestamp,
+  c tinyblob,
+  d decimal(5,2),
+  e varchar(30) character set ascii,
+  f geometry not null,
+  index (d,b),
+  unique index (c(10)),
+  fulltext (e),
+  spatial (f)
+) comment="abc" default character set utf8 max_rows=100 min_rows=10 checksum=1';
+show status like 'handler_discover';
+Variable_name	Value
+Handler_discover	13
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE t1 (
+  a int(11) NOT NULL DEFAULT '5',
+  b timestamp NOT NULL DEFAULT '0000-00-00 00:00:00',
+  c tinyblob,
+  d decimal(5,2) DEFAULT NULL,
+  e varchar(30) CHARACTER SET ascii DEFAULT NULL,
+  f geometry NOT NULL,
+  PRIMARY KEY (a),
+  UNIQUE KEY c (c(10)),
+  KEY d (d,b),
+  SPATIAL KEY f (f),
+  FULLTEXT KEY e (e)
+) ENGINE=TEST_SQL_DISCOVERY DEFAULT CHARSET=utf8 MIN_ROWS=10 MAX_ROWS=100 CHECKSUM=1 COMMENT='abc'
+show status like 'handler_discover';
+Variable_name	Value
+Handler_discover	14
+----
+t1.frm
+----
+show open tables from test;
+Database	Table	In_use	Name_locked
+test	t1	0	0
+select * from t1;
+a	b	c	d	e	f
+show status like 'handler_discover';
+Variable_name	Value
+Handler_discover	14
+flush tables;
+select * from t1;
+a	b	c	d	e	f
+show status like 'handler_discover';
+Variable_name	Value
+Handler_discover	14
+drop table t1;
+set @@test_sql_discovery_write_frm=0;
+set @@test_sql_discovery_statement='t1:create table t1 (a int)';
+show status like 'handler_discover';
+Variable_name	Value
+Handler_discover	14
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE t1 (
+  a int(11) DEFAULT NULL
+) ENGINE=TEST_SQL_DISCOVERY DEFAULT CHARSET=latin1
+show status like 'handler_discover';
+Variable_name	Value
+Handler_discover	15
+----
+----
+show open tables from test;
+Database	Table	In_use	Name_locked
+test	t1	0	0
+select * from t1;
+a
+show status like 'handler_discover';
+Variable_name	Value
+Handler_discover	15
+flush tables;
+select * from t1;
+a
+show status like 'handler_discover';
+Variable_name	Value
+Handler_discover	16
+drop table t1;
+show status like 'handler_discover';
+Variable_name	Value
+Handler_discover	16

storage/test_sql_discovery/mysql-test/sql_discovery/simple.test

@@ -0,0 +1,133 @@
+--source inc.inc
+
+show variables like 'test_sql_discovery%';
+set sql_quote_show_create=0;
+let $mysqld_datadir= `select @@datadir`;
+
+--error ER_CANT_CREATE_TABLE
+create table t1 (a int) engine=test_sql_discovery;
+
+--error ER_NO_SUCH_TABLE
+select * from t1;
+
+set @@test_sql_discovery_statement='t1:foobar bwa-ha-ha';
+--error ER_NO_SUCH_TABLE
+select * from t0;
+--error ER_NO_SUCH_TABLE
+select * from t1;
+show warnings;
+
+#
+# test different invalid discovering statements
+#
+
+set @@test_sql_discovery_statement='t1:select 1';
+--error ER_NO_SUCH_TABLE
+select * from t1;
+show warnings;
+
+set @@test_sql_discovery_statement='t1:create table t1 (a int primary key) partition by hash(id) partitions 2';
+--error ER_NO_SUCH_TABLE
+select * from t1;
+show warnings;
+
+set @@test_sql_discovery_statement='t1:create table t1 (a int) union=(t3,t4)';
+--error ER_NO_SUCH_TABLE
+select * from t1;
+show warnings;
+
+set @@test_sql_discovery_statement='t1:create table t1 like t2';
+--error ER_NO_SUCH_TABLE
+select * from t1;
+show warnings;
+
+set @@test_sql_discovery_statement='t1:create table t1 select * from t2';
+--error ER_NO_SUCH_TABLE
+select * from t1;
+show warnings;
+
+set @@test_sql_discovery_statement='t1:create table t1 (a int) index directory="/tmp"';
+--error ER_NO_SUCH_TABLE
+select * from t1;
+show warnings;
+
+set @@test_sql_discovery_statement='t1:create table t1 (a int) data directory="/tmp"';
+--error ER_NO_SUCH_TABLE
+select * from t1;
+show warnings;
+
+set @@test_sql_discovery_statement='t1:create table t1 (a int) engine=myisam';
+--error ER_NO_SUCH_TABLE
+select * from t1;
+show warnings;
+
+set @@test_sql_discovery_statement='t1:create temporary table t1 (a int)';
+--error ER_NO_SUCH_TABLE
+select * from t1;
+show warnings;
+
+set @@test_sql_discovery_statement='t1:create table if not exists t1 (a int)';
+--error ER_NO_SUCH_TABLE
+select * from t1;
+show warnings;
+
+#
+# this should work:
+#
+set @@test_sql_discovery_statement='t1:create table t1 (a int)';
+select * from t1;
+show create table t1;
+drop table t1;
+
+# table name in the create table statement is ignored
+set @@test_sql_discovery_statement='t1:create table t2 (a int)';
+select * from t1;
+--error ER_NO_SUCH_TABLE
+select * from t2;
+drop table t1;
+
+# and something more complex
+set @@test_sql_discovery_statement='t1:
+create table t1 (
+  a int not null default 5 primary key,
+  b timestamp,
+  c tinyblob,
+  d decimal(5,2),
+  e varchar(30) character set ascii,
+  f geometry not null,
+  index (d,b),
+  unique index (c(10)),
+  fulltext (e),
+  spatial (f)
+) comment="abc" default character set utf8 max_rows=100 min_rows=10 checksum=1';
+show status like 'handler_discover';
+show create table t1;
+show status like 'handler_discover';
+--echo ----
+--list_files $mysqld_datadir/test t*
+--echo ----
+show open tables from test;
+select * from t1;
+show status like 'handler_discover';
+flush tables;
+select * from t1;
+show status like 'handler_discover';
+drop table t1;
+
+set @@test_sql_discovery_write_frm=0;
+set @@test_sql_discovery_statement='t1:create table t1 (a int)';
+show status like 'handler_discover';
+show create table t1;
+show status like 'handler_discover';
+--echo ----
+--list_files $mysqld_datadir/test t*
+--echo ----
+show open tables from test;
+select * from t1;
+show status like 'handler_discover';
+flush tables;
+select * from t1;
+show status like 'handler_discover';
+drop table t1;
+show status like 'handler_discover';
+

storage/test_sql_discovery/test_sql_discovery.cc

@@ -0,0 +1,175 @@
+/*
+   Copyright (c) 2013 Monty Program 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 02110-1301  USA
+*/
+
+/*
+  a really minimal engine to test table discovery via sql statements.
+  See the archive engine if you're interested in real-life usable engine that
+  uses discovery via frm shipping.
+*/
+
+#include <mysql_version.h>
+#include <handler.h>
+#include <table.h>
+
+static MYSQL_THDVAR_STR(statement, PLUGIN_VAR_MEMALLOC,
+  "The table name and the SQL statement to discover the next table",
+  NULL, NULL, 0);
+
+static MYSQL_THDVAR_BOOL(write_frm, 0,
+  "Whether to cache discovered table metadata in frm files",
+  NULL, NULL, TRUE);
+
+static struct st_mysql_sys_var *sysvars[] = {
+  MYSQL_SYSVAR(statement),
+  MYSQL_SYSVAR(write_frm),
+  NULL
+};
+
+typedef struct st_share {
+  const char *name;
+  THR_LOCK lock;
+  uint use_count;
+  struct st_share *next;
+} SHARE;
+
+class ha_tsd: public handler
+{
+private:
+  THR_LOCK_DATA lock;
+  SHARE *share;
+
+public:
+  ha_tsd(handlerton *hton, TABLE_SHARE *table_arg)
+    : handler(hton, table_arg) { }
+  ulonglong table_flags() const
+  { // NO_TRANSACTIONS and everything that affects CREATE TABLE
+    return HA_NO_TRANSACTIONS | HA_CAN_GEOMETRY | HA_NULL_IN_KEY |
+           HA_CAN_INDEX_BLOBS | HA_AUTO_PART_KEY | HA_CAN_RTREEKEYS |
+           HA_CAN_FULLTEXT;
+  }
+
+  ulong index_flags(uint inx, uint part, bool all_parts) const { return 0; }
+
+  THR_LOCK_DATA **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;
+  }
+
+  int rnd_init(bool scan) { return 0; }
+  int rnd_next(unsigned char *buf) { return HA_ERR_END_OF_FILE; }
+  void position(const uchar *record) { }
+  int rnd_pos(uchar *buf, uchar *pos) { return HA_ERR_END_OF_FILE; }
+  int info(uint flag) { return 0; }
+  uint max_supported_keys() const { return 16; }
+  int create(const char *name, TABLE *table_arg,
+             HA_CREATE_INFO *create_info) { return HA_ERR_WRONG_COMMAND; }
+
+  int open(const char *name, int mode, uint test_if_locked);
+  int close(void);
+};
+
+static SHARE *find_or_create_share(const char *table_name, TABLE *table)
+{
+  SHARE *share;
+  for (share = (SHARE*)table->s->ha_data; share; share = share->next)
+    if (my_strcasecmp(table_alias_charset, table_name, share->name) == 0)
+      return share;
+
+  share = (SHARE*)alloc_root(&table->s->mem_root, sizeof(*share));
+  bzero(share, sizeof(*share));
+  share->name = strdup_root(&table->s->mem_root, table_name);
+  share->next = (SHARE*)table->s->ha_data;
+  table->s->ha_data = share;
+  return share;
+}
+
+int ha_tsd::open(const char *name, int mode, uint test_if_locked)
+{
+  mysql_mutex_lock(&table->s->LOCK_ha_data);
+  share = find_or_create_share(name, table);
+  if (share->use_count++ == 0)
+    thr_lock_init(&share->lock);
+  mysql_mutex_unlock(&table->s->LOCK_ha_data);
+  thr_lock_data_init(&share->lock,&lock,NULL);
+
+  return 0;
+}
+
+int ha_tsd::close(void)
+{
+  mysql_mutex_lock(&table->s->LOCK_ha_data);
+  if (--share->use_count == 0)
+    thr_lock_delete(&share->lock);
+  mysql_mutex_unlock(&table->s->LOCK_ha_data);
+  return 0;
+}
+
+static handler *create_handler(handlerton *hton, TABLE_SHARE *table,
+                               MEM_ROOT *mem_root)
+{
+  return new (mem_root) ha_tsd(hton, table);
+}
+
+static int discover_table(handlerton *hton, THD* thd, TABLE_SHARE *share)
+{
+  const char *sql= THDVAR(thd, statement);
+
+  // the table is discovered if sql starts from "table_name:"
+  if (!sql ||
+      strncmp(sql, share->table_name.str, share->table_name.length) ||
+      sql[share->table_name.length] != ':')
+    return HA_ERR_NO_SUCH_TABLE;
+
+  sql+= share->table_name.length + 1;
+  return share->init_from_sql_statement_string(thd, THDVAR(thd, write_frm),
+                                               sql, strlen(sql));
+}
+
+static int init(void *p)
+{
+  handlerton *hton = (handlerton *)p;
+  hton->create = create_handler;
+  hton->discover_table = discover_table;
+  return 0;
+}
+
+struct st_mysql_storage_engine descriptor =
+{ MYSQL_HANDLERTON_INTERFACE_VERSION };
+
+maria_declare_plugin(tsd)
+{
+  MYSQL_STORAGE_ENGINE_PLUGIN,
+  &descriptor,
+  "TEST_SQL_DISCOVERY",
+  "Sergei Golubchik",
+  "Minimal engine to test table discovery via sql statements",
+  PLUGIN_LICENSE_GPL,
+  init,
+  NULL,
+  0x0001,
+  NULL,
+  sysvars,
+  "0.1",
+  MariaDB_PLUGIN_MATURITY_EXPERIMENTAL
+}
+maria_declare_plugin_end;
+