bzr commit into mysql-6.0 branch (davi:2746) Bug#989 WL#4284

[Davi Arnaut]

# At a local mysql-6.0 repository of davi

 2746 Davi Arnaut	2009-03-23
      Bug#989: If DROP TABLE while there's an active transaction, wrong binlog order
      WL#4284: Transactional DDL locking
      
      After some discussions with stakeholders it has been decided that
      metadata locks acquired during a PREPARE statement must be released
      once the statement is prepared even if it is prepared within a multi
      statement transaction.
     @ mysql-test/r/ps.result
        Add test case result.
     @ mysql-test/t/ps.test
        Add test case.
     @ sql/sql_prepare.cc
        Release metdata locks acquired while the prepared statement is being
        checked.

    modified:
      mysql-test/r/ps.result
      mysql-test/t/ps.test
      sql/sql_prepare.cc
=== modified file 'mysql-test/r/ps.result'
--- a/mysql-test/r/ps.result	2009-03-18 12:49:07 +0000
+++ b/mysql-test/r/ps.result	2009-03-23 18:17:10 +0000
@@ -3096,6 +3096,16 @@ EXECUTE stmt1;
 ERROR 42S01: Table 't1' already exists
 DEALLOCATE PREPARE stmt1;
 DROP TABLE t1;
+#
+# WL#4284: Transactional DDL locking
+#
+# Test that metadata locks taken during prepare are released.
+#
+DROP TABLE IF EXISTS t1;
+CREATE TABLE t1 (a INT);
+BEGIN;
+PREPARE stmt1 FROM "SELECT * FROM t1";
+DROP TABLE t1;
 
 # End of WL#4435.
 

=== modified file 'mysql-test/t/ps.test'
--- a/mysql-test/t/ps.test	2009-03-18 12:49:07 +0000
+++ b/mysql-test/t/ps.test	2009-03-23 18:17:10 +0000
@@ -3212,6 +3212,25 @@ EXECUTE stmt1;
 DEALLOCATE PREPARE stmt1;
 DROP TABLE t1;
 
+--echo #
+--echo # WL#4284: Transactional DDL locking
+--echo #
+--echo # Test that metadata locks taken during prepare are released.
+--echo #
+
+connect(con1,localhost,root,,);
+connection default;
+--disable_warnings
+DROP TABLE IF EXISTS t1;
+--enable_warnings
+CREATE TABLE t1 (a INT);
+connection con1;
+BEGIN;
+PREPARE stmt1 FROM "SELECT * FROM t1";
+connection default;
+DROP TABLE t1;
+disconnect con1;
+
 #
 # Additional cleanup.
 #

=== modified file 'sql/sql_prepare.cc'
--- a/sql/sql_prepare.cc	2009-03-18 12:49:07 +0000
+++ b/sql/sql_prepare.cc	2009-03-23 18:17:10 +0000
@@ -3147,6 +3147,7 @@ bool Prepared_statement::prepare(const c
   bool error;
   Statement stmt_backup;
   Query_arena *old_stmt_arena;
+  MDL_ticket *mdl_savepoint= NULL;
   DBUG_ENTER("Prepared_statement::prepare");
   /*
     If this is an SQLCOM_PREPARE, we also increase Com_prepare_sql.
@@ -3205,6 +3206,13 @@ bool Prepared_statement::prepare(const c
   */
   DBUG_ASSERT(thd->change_list.is_empty());
 
+  /*
+    Marker used to release metadata locks acquired while the prepared
+    statement is being checked.
+  */
+  if (thd->in_multi_stmt_transaction())
+    mdl_savepoint= thd->mdl_context.mdl_savepoint();
+
   /* 
    The only case where we should have items in the thd->free_list is
    after stmt->set_params_from_vars(), which may in some cases create
@@ -3228,6 +3236,15 @@ bool Prepared_statement::prepare(const c
 
   lex_end(lex);
   cleanup_stmt();
+  /*
+    If not inside a multi-statement transaction, the metadata locks have
+    already been released and the rollback_to_savepoint is a nop.
+    Otherwise, release acquired locks -- a NULL mdl_savepoint means that
+    all locks are going to be released or that the transaction didn't
+    own any locks.
+  */
+  if (!thd->locked_tables_mode)
+    thd->mdl_context.rollback_to_savepoint(mdl_savepoint);
   thd->restore_backup_statement(this, &stmt_backup);
   thd->stmt_arena= old_stmt_arena;
 


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