MDEV-16980 Wrongly set tablename len while opening the

			table for purge thread

Problem:
=======
	Purge tries to fetch mdl lock for the whole table even though it tries
to open one of the partition. But table name length was wrongly set to indicate
the partition name too.

Solution:
========
- Table name length should identify the table name only not the partition name.

mysql-test/suite/gcol/r/gcol_partition_innodb.result

 SET @@session.default_storage_engine = 'InnoDB';
+SET @saved_frequency = @@GLOBAL.innodb_purge_rseg_truncate_frequency;
+SET GLOBAL innodb_purge_rseg_truncate_frequency = 1;
 drop table if exists t1;
 # Case 1. Partitioning by RANGE based on a non-stored generated column.
 CREATE TABLE t1 (
@@ -86,6 +88,20 @@ CHECK TABLE t EXTENDED;
 Table	Op	Msg_type	Msg_text
 test.t	check	status	OK
 DROP TABLE t;
+#
+# MDEV-16980 Wrongly set tablename len while opening the
+#                table for purge thread
+#
+CREATE TABLE t1(pk SERIAL, d DATE, vd DATE AS (d) VIRTUAL,
+PRIMARY KEY(pk), KEY (vd))ENGINE=InnoDB
+PARTITION BY HASH(pk) PARTITIONS 2;
+INSERT IGNORE INTO t1 (d) VALUES ('2015-04-14');
+SET sql_mode= '';
+REPLACE INTO t1 SELECT * FROM t1;
+Warnings:
+Warning	1906	The value specified for generated column 'vd' in table 't1' ignored
+DROP TABLE t1;
+InnoDB		0 transactions not purged
 DROP VIEW  IF EXISTS v1,v2;
 DROP TABLE IF EXISTS t1,t2,t3;
 DROP PROCEDURE IF EXISTS p1;
@@ -93,3 +109,4 @@ DROP FUNCTION IF EXISTS f1;
 DROP TRIGGER IF EXISTS trg1;
 DROP TRIGGER IF EXISTS trg2;
 set sql_warnings = 0;
+SET GLOBAL innodb_purge_rseg_truncate_frequency = @saved_frequency;

mysql-test/suite/gcol/t/gcol_partition_innodb.test

@@ -30,6 +30,8 @@
 # Set the session storage engine
 --source include/have_innodb.inc
 eval SET @@session.default_storage_engine = 'InnoDB';
+SET @saved_frequency = @@GLOBAL.innodb_purge_rseg_truncate_frequency;
+SET GLOBAL innodb_purge_rseg_truncate_frequency = 1;
 
 ##### Workarounds for known open engine specific bugs
 #     none
@@ -41,6 +43,24 @@ eval SET @@session.default_storage_engine = 'InnoDB';
 #------------------------------------------------------------------------------#
 # Execute storage engine specific tests
 
+--echo #
+--echo # MDEV-16980 Wrongly set tablename len while opening the
+--echo #                table for purge thread
+--echo #
+
+CREATE TABLE t1(pk SERIAL, d DATE, vd DATE AS (d) VIRTUAL,
+                PRIMARY KEY(pk), KEY (vd))ENGINE=InnoDB
+                PARTITION BY HASH(pk) PARTITIONS 2;
+
+INSERT IGNORE INTO t1 (d) VALUES ('2015-04-14');
+SET sql_mode= '';
+REPLACE INTO t1 SELECT * FROM t1;
+
+# Cleanup
+DROP TABLE t1;
+
+--source suite/innodb/include/wait_all_purged.inc
 #------------------------------------------------------------------------------#
 # Cleanup
 --source suite/gcol/inc/gcol_cleanup.inc
+SET GLOBAL innodb_purge_rseg_truncate_frequency = @saved_frequency;

sql/table.h

@@ -1765,6 +1765,8 @@ struct TABLE_LIST
       mdl_type= MDL_SHARED_READ;
 
     bzero((char*) this, sizeof(*this));
+    DBUG_ASSERT(!db_name_arg || strlen(db_name_arg) == db_length_arg);
+    DBUG_ASSERT(!table_name_arg || strlen(table_name_arg) == table_name_length_arg);
     db= (char*) db_name_arg;
     db_length= db_length_arg;
     table_name= (char*) table_name_arg;

storage/innobase/handler/ha_innodb.cc

@@ -21341,6 +21341,7 @@ static bool table_name_parse(
 
 	if (char *is_part = strchr(tbl_buf, '#')) {
 		*is_part = '\0';
+		tblnamelen = is_part - tbl_buf;
 	}
 
 	filename_to_tablename(tbl_buf, tblname, MAX_TABLE_NAME_LEN + 1, true);