bzr push into mysql-5.5 branch (bjorn.munch:3490 to 3491)

[Bjorn Munch]

 3491 Bjorn Munch	2011-08-12
      Small followup fix to WL 5710:
        Test mysql_plugin failed if version string ended in -mN

    modified:
      mysql-test/t/mysql_plugin.test
 3490 Dmitry Lenev	2011-08-11
      Fix for bug #12828477 - "MDL SUBSYSTEM CREATES BIG OVERHEAD 
      FOR CERTAIN QUERIES TO INFORMATION_SCHEMA".
      
      The problem was that metadata locking subsystem introduced
      too much overhead for queries to I_S which were processed by
      opening only .FRM or .TRG files and had to scanned a lot of
      tables (e.g. SELECT COUNT(*) FROM I_S.TRIGGERS was affected). 
      The same effect was not observed for similar queries which 
      performed full-blown table open in order to fill I_S table.
      
      The problem stemmed from the fact that in case when I_S 
      implementation opened only .FRM or .TRG file for each table 
      processed it didn't release metadata lock it has acquired on 
      the table after finishing its processing. As result, list
      of acquired metadata locks were growing until the end of 
      statement. Since acquisition of each new lock required 
      search in the list of already acquired locks performance
      degraded.
      
      The same effect is not observed when I_S implementation
      performs full-blown table open for each table being
      processed, as in the latter cases metadata lock on the
      table is released right after table processing.
      
      This fix addressed the problem by ensuring that I_S 
      implementation releases metadata lock after processing
      the table in both cases of full-blown table open and in 
      case when only .FRM or .TRG file is read.
     @ mysql-test/r/information_schema.result
        Added coverage for bug #12828477 - "MDL SUBSYSTEM CREATES BIG
        OVERHEAD FOR CERTAIN QUERIES TO INFORMATION_SCHEMA".
     @ mysql-test/t/information_schema.test
        Added coverage for bug #12828477 - "MDL SUBSYSTEM CREATES BIG
        OVERHEAD FOR CERTAIN QUERIES TO INFORMATION_SCHEMA".
     @ sql/sql_show.cc
        Changed fill_schema_table_from_frm() to release metadata lock
        it has acquired after processing the .FRM or .TRG file for
        table. 
        Without this step metadata locks acquired for each table 
        processed will be accumulated. In situation when a lot of 
        tables are processed by I_S query this will result in
        transaction with too many metadata locks. As result
        performance of acquisition of new lock will degrade.

    modified:
      mysql-test/r/information_schema.result
      mysql-test/t/information_schema.test
      sql/sql_show.cc
=== modified file 'mysql-test/t/mysql_plugin.test'
--- a/mysql-test/t/mysql_plugin.test	2011-08-09 19:09:28 +0000
+++ b/mysql-test/t/mysql_plugin.test	2011-08-12 10:49:38 +0000
@@ -288,11 +288,11 @@ let $MYSQL_PLUGIN_CMD= $MYSQL_PLUGIN -n
 --echo # Show the help.
 --echo #
 replace_result $MYSQL_PLUGIN mysql_plugin;
---replace_regex /Ver [0-9.]+ Distrib [0-9.]+/Ver V.V.VV Distrib XX.XX.XX/
+--replace_regex /Ver [0-9.]+ Distrib [0-9.]+/Ver V.V.VV Distrib XX.XX.XX/ /XX-m[0-9]+/XX/
 --exec $MYSQL_PLUGIN --help
 
 replace_result $MYSQL_PLUGIN mysql_plugin;
---replace_regex /Ver [0-9.]+ Distrib [0-9.]+/Ver V.V.VV Distrib XX.XX.XX/
+--replace_regex /Ver [0-9.]+ Distrib [0-9.]+/Ver V.V.VV Distrib XX.XX.XX/ /XX-m[0-9]+/XX/
 --exec $MYSQL_PLUGIN --version
 
 #

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