bzr commit into mysql-5.5-runtime branch (Dmitry.Lenev:3190)

[Dmitry Lenev]

#At file:///home/dlenev/src/bzr/mysql-5.5-rt-grl/ based on revid:dmitry.lenev@stripped

 3190 Dmitry Lenev	2010-11-08
      More changes to draft patch refactoring global read
      lock implementation. Makes GRL yet another type of
      metadata lock and thus exposes it to deadlock detector
      in MDL subsystem.
      
      Solves bugs #54673 "It takes too long to get readlock for
      'FLUSH TABLES WITH READ LOCK'" and #57006 "Deadlock between
      HANDLER and FLUSH TABLES WITH READ LOCK".
      
      Work-in-progress. Minor after review fixes.

    modified:
      sql/sql_base.cc
      sql/sql_parse.cc
=== modified file 'sql/sql_base.cc'
--- a/sql/sql_base.cc	2010-11-08 09:55:43 +0000
+++ b/sql/sql_base.cc	2010-11-08 14:10:47 +0000
@@ -2784,64 +2784,61 @@ bool open_table(THD *thd, TABLE_LIST *ta
     This is the normal use case.
   */
 
-  /*
-    We are not under LOCK TABLES and going to acquire write-lock/
-    modify the base table. We need to acquire protection against
-    global read lock until end of this statement in order to have
-    this statement blocked by active FLUSH TABLES WITH READ LOCK.
-
-    We don't block acquire this protection under LOCK TABLES as
-    such protection already acquired at LOCK TABLES time and
-    not released until UNLOCK TABLES.
-
-    We don't block statements which modify only temporary tables
-    as these tables are not preserved by backup by any form of
-    backup which uses FLUSH TABLES WITH READ LOCK.
-
-    TODO: The fact that we sometimes acquire protection against
-          GRL only when we encounter table to be write-locked
-          slightly increases probability of deadlock.
-          This problem will be solved once Alik pushes his
-          temporary table refactoring patch and we can start
-          pre-acquiring metadata locks at the beggining of
-          open_tables() call.
-
-    QQ: What about MYSQL_OPEN_HAS_MDL_LOCK flag?
-  */
-  if (table_list->mdl_request.type >= MDL_SHARED_WRITE &&
-      ! (flags & (MYSQL_OPEN_IGNORE_GLOBAL_READ_LOCK |
-                  MYSQL_OPEN_FORCE_SHARED_MDL |
-                  MYSQL_OPEN_FORCE_SHARED_HIGH_PRIO_MDL |
-                  MYSQL_OPEN_SKIP_SCOPED_MDL_LOCK)) &&
-      ! thd->locked_tables_mode &&
-      ! ot_ctx->has_protection_against_grl())
+  if (! (flags & MYSQL_OPEN_HAS_MDL_LOCK))
   {
-    MDL_request protection_request;
-    MDL_deadlock_handler mdl_deadlock_handler(ot_ctx);
+    /*
+      We are not under LOCK TABLES and going to acquire write-lock/
+      modify the base table. We need to acquire protection against
+      global read lock until end of this statement in order to have
+      this statement blocked by active FLUSH TABLES WITH READ LOCK.
+
+      We don't block acquire this protection under LOCK TABLES as
+      such protection already acquired at LOCK TABLES time and
+      not released until UNLOCK TABLES.
+
+      We don't block statements which modify only temporary tables
+      as these tables are not preserved by backup by any form of
+      backup which uses FLUSH TABLES WITH READ LOCK.
+
+      TODO: The fact that we sometimes acquire protection against
+            GRL only when we encounter table to be write-locked
+            slightly increases probability of deadlock.
+            This problem will be solved once Alik pushes his
+            temporary table refactoring patch and we can start
+            pre-acquiring metadata locks at the beggining of
+            open_tables() call.
+    */
+    if (table_list->mdl_request.type >= MDL_SHARED_WRITE &&
+        ! (flags & (MYSQL_OPEN_IGNORE_GLOBAL_READ_LOCK |
+                    MYSQL_OPEN_FORCE_SHARED_MDL |
+                    MYSQL_OPEN_FORCE_SHARED_HIGH_PRIO_MDL |
+                    MYSQL_OPEN_SKIP_SCOPED_MDL_LOCK)) &&
+        ! ot_ctx->has_protection_against_grl())
+    {
+      MDL_request protection_request;
+      MDL_deadlock_handler mdl_deadlock_handler(ot_ctx);
 
-    if (thd->global_read_lock.can_acquire_protection())
-      DBUG_RETURN(TRUE);
+      if (thd->global_read_lock.can_acquire_protection())
+        DBUG_RETURN(TRUE);
 
-    protection_request.init(MDL_key::GLOBAL, "", "", MDL_INTENTION_EXCLUSIVE,
-                            MDL_STATEMENT);
-    /*
-      Install error handler which if possible will convert deadlock error
-      into request to back-off and restart process of opening tables.
-    */
-    thd->push_internal_handler(&mdl_deadlock_handler);
-    bool result= thd->mdl_context.acquire_lock(&protection_request,
-                                               ot_ctx->get_timeout());
-    thd->pop_internal_handler();
+      protection_request.init(MDL_key::GLOBAL, "", "", MDL_INTENTION_EXCLUSIVE,
+                              MDL_STATEMENT);
 
-    if (result)
-      DBUG_RETURN(TRUE);
+      /*
+        Install error handler which if possible will convert deadlock error
+        into request to back-off and restart process of opening tables.
+      */
+      thd->push_internal_handler(&mdl_deadlock_handler);
+      bool result= thd->mdl_context.acquire_lock(&protection_request,
+                                                 ot_ctx->get_timeout());
+      thd->pop_internal_handler();
 
-    ot_ctx->set_has_protection_against_grl();
-  }
+      if (result)
+        DBUG_RETURN(TRUE);
 
+      ot_ctx->set_has_protection_against_grl();
+    }
 
-  if (! (flags & MYSQL_OPEN_HAS_MDL_LOCK))
-  {
     if (open_table_get_mdl_lock(thd, ot_ctx, &table_list->mdl_request,
                                 flags, &mdl_ticket) ||
         mdl_ticket == NULL)

=== modified file 'sql/sql_parse.cc'
--- a/sql/sql_parse.cc	2010-11-08 09:55:43 +0000
+++ b/sql/sql_parse.cc	2010-11-08 14:10:47 +0000
@@ -403,9 +403,7 @@ void init_update_queries(void)
   sql_command_flags[SQLCOM_FLUSH]=              CF_AUTO_COMMIT_TRANS;
   sql_command_flags[SQLCOM_RESET]=              CF_AUTO_COMMIT_TRANS;
   sql_command_flags[SQLCOM_CREATE_SERVER]=      CF_AUTO_COMMIT_TRANS;
-  // TODO/FIXME Investigate effect of implicit close_cached_tables.
   sql_command_flags[SQLCOM_ALTER_SERVER]=       CF_AUTO_COMMIT_TRANS;
-  // TODO/FIXME Investigate effect of implicit close_cached_tables.
   sql_command_flags[SQLCOM_DROP_SERVER]=        CF_AUTO_COMMIT_TRANS;
 }
 


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