MDEV-30014 Spider should not second guess server when locking / unlocking

This fixes MDEV-30014, MDEV-29456, MDEV-29667, and MDEV-30049.

The server may ask storage engines to unlock when the original sql
command is not UNLOCK. This patch makes sure that spider honours these
requests, so that the server has the correct idea which tables are
locked and which are not.

MDEV-29456, MDEV-29667, MDEV-30049: a later LOCK statement would, as
the first step, unlock locked tables and clear the OPTION_TABLE_LOCK
bit in thd->variables.option_bits, as well as locked_tables_list,
indicating no tables are locked. If Spider does not unlock because the
sql command is not UNLOCK, and if after this the LOCK statement fails
to lock any tables, these indications that no tables are locked
remains, so a later UNLOCK TABLES; statement would not try to unlock
any table. Causing later statements requiring mdl locks to hang on
waiting until lock_wait_timeout (default 1h) has passed.

MDEV-30014: when a LOCK statement tries to lock more than one tables,
say t2 and t3 as in mdev_30014.test, and t2 succeeds but t3 fails, the
sql layer would try to undo by unlocking t2, and again, if Spider does
not honour this request, the sql layer would assume t2 has been
unlocked, but later actions on t2 or t2's remote table could hang on
waiting for the mdl.

storage/spider/ha_spider.cc

@@ -1265,11 +1265,6 @@ int ha_spider::external_lock(
 #ifdef HA_CAN_BULK_ACCESS
   external_lock_cnt++;
 #endif
-  if (
-    lock_type == F_UNLCK &&
-    sql_command != SQLCOM_UNLOCK_TABLES
-  )
-    DBUG_RETURN(0);
   if (store_error_num)
     DBUG_RETURN(store_error_num);
 #if defined(HS_HAS_SQLCOM) && defined(HAVE_HANDLERSOCKET)
@@ -1306,7 +1301,7 @@ int ha_spider::external_lock(
     ) {
       if (sql_command == SQLCOM_TRUNCATE)
         DBUG_RETURN(0);
-      else if (sql_command != SQLCOM_UNLOCK_TABLES)
+      else if (lock_type != F_UNLCK)
       {
         DBUG_PRINT("info",("spider conns[%d]->join_trx=%u",
           roop_count, conns[roop_count]->join_trx));
@@ -1428,7 +1423,7 @@ int ha_spider::external_lock(
         }
         if (conns[roop_count]->table_lock == 2)
           conns[roop_count]->table_lock = 1;
-      } else if (sql_command == SQLCOM_UNLOCK_TABLES ||
+      } else if (lock_type == F_UNLCK ||
         spider_param_internal_unlock(thd) == 1)
       {
         if (conns[roop_count]->table_lock == 1)

storage/spider/mysql-test/spider/bugfix/r/mdev_29456.result

+#
+# MDEV-29456 Spider hangs in 'Waiting for table metadata lock' state on CREATE TABLE after LOCK TABLES
+#
+for master_1
+for child2
+for child3
+CREATE SERVER srv FOREIGN DATA WRAPPER mysql
+OPTIONS (SOCKET "$MASTER_1_MYSOCK", DATABASE 'test',user 'root');
+create table t1 (c int);
+create table t2 (c int) ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t1"';
+CREATE TABLE t3 (c INT KEY) ENGINE=Spider;
+LOCK TABLE t2 WRITE;
+LOCK TABLE t3 WRITE;
+ERROR HY000: Unable to connect to foreign data source: localhost
+UNLOCK TABLES;
+drop table t1, t2, t3;
+CREATE TABLE t (c INT) ENGINE=InnoDB;
+CREATE TABLE t1 (c INT) ENGINE=Spider;
+CREATE TABLE t2 (c INT) ENGINE=Spider COMMENT='WRAPPER "mysql",srv "srv",TABLE "t"';
+LOCK TABLES t2 WRITE;
+LOCK TABLES t1 READ;
+ERROR HY000: Unable to connect to foreign data source: localhost
+CREATE TABLE t (c INT) ENGINE=Spider;
+ERROR 42S01: Table 't' already exists
+drop table t, t1, t2;
+CREATE TABLE t (c INT) ENGINE=InnoDB;
+CREATE TABLE t2 (c INT) ENGINE=Spider COMMENT='WRAPPER "mysql",srv "srv",TABLE "t"';
+CREATE TABLE t3 (c INT) ENGINE=InnoDB;
+LOCK TABLES t2 WRITE;
+LOCK TABLES mysql.proc WRITE,mysql.user WRITE;
+ERROR HY000: You can't combine write-locking of system tables with other tables or lock types
+INSERT INTO t3 SELECT * FROM t;
+drop table t, t2, t3;
+drop server srv;
+for master_1
+for child2
+for child3
+#
+# end of test mdev_29456
+#

storage/spider/mysql-test/spider/bugfix/r/mdev_29667.result

+#
+# MDEV-29667 Server hangs on DROP DATABASE after failing LOCK TABLES on Spider table
+#
+for master_1
+for child2
+child2_1
+child2_2
+child2_3
+for child3
+connection child2_1;
+CREATE DATABASE auto_test_remote;
+USE auto_test_remote;
+CREATE TABLE tbl_a (
+a INT
+) ENGINE=InnoDB DEFAULT CHARSET=utf8;
+connection master_1;
+CREATE DATABASE auto_test_local;
+USE auto_test_local;
+CREATE TABLE tbl_a (
+a INT
+) ENGINE=Spider DEFAULT CHARSET=utf8 COMMENT='table "tbl_a", srv "s_2_1"';
+CREATE TABLE tbl_b (
+a INT
+) ENGINE=Spider DEFAULT CHARSET=utf8;
+LOCK TABLES tbl_a WRITE;
+LOCK TABLES tbl_b READ, tbl_a READ;
+ERROR HY000: Unable to connect to foreign data source: localhost
+connection master_1;
+DROP DATABASE IF EXISTS auto_test_local;
+connection child2_1;
+DROP DATABASE IF EXISTS auto_test_remote;
+for master_1
+for child2
+child2_1
+child2_2
+child2_3
+for child3
+#
+# end of test mdev_29667
+#

storage/spider/mysql-test/spider/bugfix/r/mdev_30014.result

+#
+# MDEV-30014 heap-use-after-free in  ha_spider::lock_tables(), highly sporadic SIGSEGV in intern_close_table
+#
+for master_1
+for child2
+for child3
+CREATE SERVER srv FOREIGN DATA WRAPPER mysql
+OPTIONS (SOCKET "$MASTER_1_MYSOCK", DATABASE 'test',user 'root');
+create table t1 (c int);
+create table t2 (c int) ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t1"';
+CREATE TABLE t3 (c INT KEY) ENGINE=Spider;
+LOCK TABLE t2 WRITE,t3 WRITE;
+ERROR HY000: Unable to connect to foreign data source: localhost
+CREATE TABLE t4 (c INT) ENGINE=Spider;
+FLUSH NO_WRITE_TO_BINLOG TABLES t4 WITH READ LOCK;
+Warnings:
+Error	1429	Unable to connect to foreign data source: localhost
+Error	1429	Unable to connect to foreign data source: localhost
+Error	1429	Unable to connect to foreign data source: localhost
+Error	1429	Unable to connect to foreign data source: localhost
+UNLOCK TABLES;
+drop table t1, t2, t3, t4;
+create table t1 (c int);
+create table t2 (c int) ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t1"';
+CREATE TABLE t3 (c INT KEY) ENGINE=Spider;
+LOCK TABLE t2 WRITE, t3 WRITE;
+ERROR HY000: Unable to connect to foreign data source: localhost
+UNLOCK TABLES;
+drop table t1, t2, t3;
+drop server srv;
+for master_1
+for child2
+for child3
+#
+# end of test mdev_30014
+#

storage/spider/mysql-test/spider/bugfix/t/mdev_29456.test

+--echo #
+--echo # MDEV-29456 Spider hangs in 'Waiting for table metadata lock' state on CREATE TABLE after LOCK TABLES
+--echo #
+--source include/have_innodb.inc
+--disable_query_log
+--disable_result_log
+--source ../../t/test_init.inc
+--enable_result_log
+--enable_query_log
+
+evalp CREATE SERVER srv FOREIGN DATA WRAPPER mysql
+OPTIONS (SOCKET "$MASTER_1_MYSOCK", DATABASE 'test',user 'root');
+
+create table t1 (c int);
+create table t2 (c int) ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t1"';
+CREATE TABLE t3 (c INT KEY) ENGINE=Spider;
+LOCK TABLE t2 WRITE;
+--error ER_CONNECT_TO_FOREIGN_DATA_SOURCE
+LOCK TABLE t3 WRITE;
+UNLOCK TABLES;
+drop table t1, t2, t3;
+
+CREATE TABLE t (c INT) ENGINE=InnoDB;
+CREATE TABLE t1 (c INT) ENGINE=Spider;
+CREATE TABLE t2 (c INT) ENGINE=Spider COMMENT='WRAPPER "mysql",srv "srv",TABLE "t"';
+LOCK TABLES t2 WRITE;
+--error ER_CONNECT_TO_FOREIGN_DATA_SOURCE
+LOCK TABLES t1 READ;
+--error ER_TABLE_EXISTS_ERROR
+CREATE TABLE t (c INT) ENGINE=Spider;
+drop table t, t1, t2;
+
+# MDEV-30049
+CREATE TABLE t (c INT) ENGINE=InnoDB;
+CREATE TABLE t2 (c INT) ENGINE=Spider COMMENT='WRAPPER "mysql",srv "srv",TABLE "t"';
+CREATE TABLE t3 (c INT) ENGINE=InnoDB;
+LOCK TABLES t2 WRITE;
+--error 1428
+LOCK TABLES mysql.proc WRITE,mysql.user WRITE;   # ERROR 1428 (HY000): You can't combine write-locking of system tables with other tables or lock types
+INSERT INTO t3 SELECT * FROM t;
+drop table t, t2, t3;
+
+drop server srv;
+--disable_query_log
+--disable_result_log
+--source ../../t/test_deinit.inc
+--enable_result_log
+--enable_query_log
+--echo #
+--echo # end of test mdev_29456
+--echo #

storage/spider/mysql-test/spider/bugfix/t/mdev_29667.cnf

+!include include/default_mysqld.cnf
+!include ../my_1_1.cnf
+!include ../my_2_1.cnf

storage/spider/mysql-test/spider/bugfix/t/mdev_29667.test

+--echo #
+--echo # MDEV-29667 Server hangs on DROP DATABASE after failing LOCK TABLES on Spider table
+--echo #
+--disable_query_log
+--disable_result_log
+--source ../../t/test_init.inc
+--enable_result_log
+--enable_query_log
+
+--connection child2_1
+CREATE DATABASE auto_test_remote;
+USE auto_test_remote;
+eval CREATE TABLE tbl_a (
+    a INT
+) $CHILD2_1_ENGINE $CHILD2_1_CHARSET;
+
+--connection master_1
+CREATE DATABASE auto_test_local;
+USE auto_test_local;
+eval CREATE TABLE tbl_a (
+    a INT
+) $MASTER_1_ENGINE $MASTER_1_CHARSET COMMENT='table "tbl_a", srv "s_2_1"';
+eval CREATE TABLE tbl_b (
+    a INT
+) $MASTER_1_ENGINE $MASTER_1_CHARSET;
+
+LOCK TABLES tbl_a WRITE;
+--error 1429
+LOCK TABLES tbl_b READ, tbl_a READ;
+
+--connection master_1
+DROP DATABASE IF EXISTS auto_test_local;
+
+--connection child2_1
+DROP DATABASE IF EXISTS auto_test_remote;
+
+--disable_query_log
+--disable_result_log
+--source ../t/test_deinit.inc
+--enable_query_log
+--enable_result_log
+--echo #
+--echo # end of test mdev_29667
+--echo #

storage/spider/mysql-test/spider/bugfix/t/mdev_30014.test

+--echo #
+--echo # MDEV-30014 heap-use-after-free in  ha_spider::lock_tables(), highly sporadic SIGSEGV in intern_close_table
+--echo #
+--disable_query_log
+--disable_result_log
+--source ../../t/test_init.inc
+--enable_result_log
+--enable_query_log
+
+evalp CREATE SERVER srv FOREIGN DATA WRAPPER mysql
+OPTIONS (SOCKET "$MASTER_1_MYSOCK", DATABASE 'test',user 'root');
+
+create table t1 (c int);
+create table t2 (c int) ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t1"';
+CREATE TABLE t3 (c INT KEY) ENGINE=Spider;
+--error ER_CONNECT_TO_FOREIGN_DATA_SOURCE
+LOCK TABLE t2 WRITE,t3 WRITE;
+CREATE TABLE t4 (c INT) ENGINE=Spider;
+FLUSH NO_WRITE_TO_BINLOG TABLES t4 WITH READ LOCK;
+UNLOCK TABLES;
+
+drop table t1, t2, t3, t4;
+
+# This is a test case in MDEV-29456 but it is more like the above
+# case.
+create table t1 (c int);
+create table t2 (c int) ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t1"';
+CREATE TABLE t3 (c INT KEY) ENGINE=Spider;
+--error ER_CONNECT_TO_FOREIGN_DATA_SOURCE
+LOCK TABLE t2 WRITE, t3 WRITE;
+UNLOCK TABLES;
+drop table t1, t2, t3;
+
+drop server srv;
+
+--disable_query_log
+--disable_result_log
+--source ../../t/test_deinit.inc
+--enable_result_log
+--enable_query_log
+--echo #
+--echo # end of test mdev_30014
+--echo #