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-- Copyright (c) 2015, 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
DROP PROCEDURE IF EXISTS table_exists;
DELIMITER $$
CREATE DEFINER='mariadb.sys'@'localhost' PROCEDURE table_exists (
IN in_db VARCHAR(64), IN in_table VARCHAR(64),
OUT out_exists ENUM('', 'BASE TABLE', 'VIEW', 'TEMPORARY', 'SEQUENCE')
)
COMMENT '
Description
-----------
Tests whether the table specified in in_db and in_table exists either as a regular
table, or as a temporary table. The returned value corresponds to the table that
will be used, so if there''s both a temporary and a permanent table with the given
name, then ''TEMPORARY'' will be returned.
Parameters
-----------
in_db (VARCHAR(64)):
The database name to check for the existence of the table in.
in_table (VARCHAR(64)):
The name of the table to check the existence of.
out_exists ENUM('''', ''BASE TABLE'', ''VIEW'', ''TEMPORARY''):
The return value: whether the table exists. The value is one of:
* '''' - the table does not exist neither as a base table, view, sequence nor temporary table.
* ''BASE TABLE'' - the table name exists as a permanent base table table.
* ''VIEW'' - the table name exists as a view.
* ''TEMPORARY'' - the table name exists as a temporary table.
* ''SEQUENCE'' - the table name exists as a sequence.
Example
--------
mysql> CREATE DATABASE db1;
Query OK, 1 row affected (0.07 sec)
mysql> use db1;
Database changed
mysql> CREATE TABLE t1 (id INT PRIMARY KEY);
Query OK, 0 rows affected (0.08 sec)
mysql> CREATE TABLE t2 (id INT PRIMARY KEY);
Query OK, 0 rows affected (0.08 sec)
mysql> CREATE view v_t1 AS SELECT * FROM t1;
Query OK, 0 rows affected (0.00 sec)
mysql> CREATE TEMPORARY TABLE t1 (id INT PRIMARY KEY);
Query OK, 0 rows affected (0.00 sec)
mysql> CALL sys.table_exists(''db1'', ''t1'', @exists); SELECT @exists;
Query OK, 0 rows affected (0.00 sec)
+------------+
| @exists |
+------------+
| TEMPORARY |
+------------+
1 row in set (0.00 sec)
mysql> CALL sys.table_exists(''db1'', ''t2'', @exists); SELECT @exists;
Query OK, 0 rows affected (0.00 sec)
+------------+
| @exists |
+------------+
| BASE TABLE |
+------------+
1 row in set (0.01 sec)
mysql> CALL sys.table_exists(''db1'', ''v_t1'', @exists); SELECT @exists;
Query OK, 0 rows affected (0.00 sec)
+---------+
| @exists |
+---------+
| VIEW |
+---------+
1 row in set (0.00 sec)
mysql> CALL sys.table_exists(''db1'', ''t3'', @exists); SELECT @exists;
Query OK, 0 rows affected (0.01 sec)
+---------+
| @exists |
+---------+
| |
+---------+
1 row in set (0.00 sec)
'
SQL SECURITY INVOKER
NOT DETERMINISTIC
CONTAINS SQL
BEGIN
DECLARE v_error BOOLEAN DEFAULT FALSE;
DECLARE CONTINUE HANDLER FOR 1050 SET v_error = TRUE;
DECLARE CONTINUE HANDLER FOR 1146 SET v_error = TRUE;
SET out_exists = '';
-- Verify whether the table name exists as a normal table
IF (EXISTS(SELECT 1 FROM information_schema.TABLES WHERE TABLE_SCHEMA = in_db AND TABLE_NAME = in_table)) THEN
-- Unfortunately the only way to determine whether there is also a temporary table is to try to create
-- a temporary table with the same name. If it succeeds the table didn't exist as a temporary table.
SET @sys.tmp.table_exists.SQL = CONCAT('CREATE TEMPORARY TABLE `', in_db, '`.`', in_table, '` (id INT PRIMARY KEY)');
PREPARE stmt_create_table FROM @sys.tmp.table_exists.SQL;
EXECUTE stmt_create_table;
DEALLOCATE PREPARE stmt_create_table;
IF (v_error) THEN
SET out_exists = 'TEMPORARY';
ELSE
-- The temporary table was created, i.e. it didn't exist. Remove it again so we don't leave garbage around.
SET @sys.tmp.table_exists.SQL = CONCAT('DROP TEMPORARY TABLE `', in_db, '`.`', in_table, '`');
PREPARE stmt_drop_table FROM @sys.tmp.table_exists.SQL;
EXECUTE stmt_drop_table;
DEALLOCATE PREPARE stmt_drop_table;
SET out_exists = (SELECT TABLE_TYPE FROM information_schema.TABLES WHERE TABLE_SCHEMA = in_db AND TABLE_NAME = in_table);
END IF;
ELSE
-- Check whether a temporary table exists with the same name.
-- If it does it's possible to SELECT from the table without causing an error.
-- If it does not exist even a PREPARE using the table will fail.
SET @sys.tmp.table_exists.SQL = CONCAT('SELECT COUNT(*) FROM `', in_db, '`.`', in_table, '`');
PREPARE stmt_select FROM @sys.tmp.table_exists.SQL;
IF (NOT v_error) THEN
DEALLOCATE PREPARE stmt_select;
SET out_exists = 'TEMPORARY';
END IF;
END IF;
END$$
DELIMITER ;
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