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  1. 27 May, 2011 1 commit
    • Igor Babaev's avatar
      Applied Sanja's patch to fix LP bug #784297 in the tree for mwl106. · 3e271b82
      Igor Babaev authored
      The patch imposes unconditional materialization for derived tables
      used in update and multi-update statements.
      Fixed a bug with a wrong order of processing derived tables/views
      at the prepare stage that caused a crash for the variant of the 
      query from test case for bug 52157.
      3e271b82
  2. 19 May, 2011 1 commit
  3. 09 Feb, 2011 1 commit
    • MySQL Build Team's avatar
      Backport into build-201102032246-5.1.52sp1 · 33e74cf1
      MySQL Build Team authored
      > ------------------------------------------------------------
      > revno: 3520
      > revision-id: sergey.glukhov@oracle.com-20101214093303-wmo9mqcb8rz0wv9f
      > parent: tor.didriksen@oracle.com-20101213161301-81lprlbune7r98dl
      > committer: Sergey Glukhov <sergey.glukhov@oracle.com>
      > branch nick: mysql-5.1-bugteam
      > timestamp: Tue 2010-12-14 12:33:03 +0300
      > message:
      >   Fixed following problems:
      >   --Bug#52157 various crashes and assertions with multi-table update, stored function
      >   --Bug#54475 improper error handling causes cascading crashing failures in innodb/ndb
      >   --Bug#57703 create view cause Assertion failed: 0, file .\item_subselect.cc, line 846
      >   --Bug#57352 valgrind warnings when creating view
      >   --Recently discovered problem when a nested materialized derived table is used
      >     before being populated and it leads to incorrect result
      >   
      >   We have several modes when we should disable subquery evaluation.
      >   The reasons for disabling are different. It could be
      >   uselessness of the evaluation as in case of 'CREATE VIEW'
      >   or 'PREPARE stmt', or we should disable subquery evaluation
      >   if tables are not locked yet as it happens in bug#54475, or
      >   too early evaluation of subqueries can lead to wrong result
      >   as it happened in Bug#19077.
      >   Main problem is that if subquery items are treated as const
      >   they are evaluated in ::fix_fields(), ::fix_length_and_dec()
      >   of the parental items as a lot of these methods have
      >   Item::val_...() calls inside.
      >   We have to make subqueries non-const to prevent unnecessary
      >   subquery evaluation. At the moment we have different methods
      >   for this. Here is a list of these modes:
      >   
      >   1. PREPARE stmt;
      >   We use UNCACHEABLE_PREPARE flag.
      >   It is set during parsing in sql_parse.cc, mysql_new_select() for
      >   each SELECT_LEX object and cleared at the end of PREPARE in
      >   sql_prepare.cc, init_stmt_after_parse(). If this flag is set
      >   subquery becomes non-const and evaluation does not happen.
      >   
      >   2. CREATE|ALTER VIEW, SHOW CREATE VIEW, I_S tables which
      >      process FRM files
      >   We use LEX::view_prepare_mode field. We set it before
      >   view preparation and check this flag in
      >   ::fix_fields(), ::fix_length_and_dec().
      >   Some bugs are fixed using this approach,
      >   some are not(Bug#57352, Bug#57703). The problem here is
      >   that we have a lot of ::fix_fields(), ::fix_length_and_dec()
      >   where we use Item::val_...() calls for const items.
      >   
      >   3. Derived tables with subquery = wrong result(Bug19077)
      >   The reason of this bug is too early subquery evaluation.
      >   It was fixed by adding Item::with_subselect field
      >   The check of this field in appropriate places prevents
      >   const item evaluation if the item have subquery.
      >   The fix for Bug19077 fixes only the problem with
      >   convert_constant_item() function and does not cover
      >   other places(::fix_fields(), ::fix_length_and_dec() again)
      >   where subqueries could be evaluated.
      >   
      >   Example:
      >   CREATE TABLE t1 (i INT, j BIGINT);
      >   INSERT INTO t1 VALUES (1, 2), (2, 2), (3, 2);
      >   SELECT * FROM (SELECT MIN(i) FROM t1
      >   WHERE j = SUBSTRING('12', (SELECT * FROM (SELECT MIN(j) FROM t1) t2))) t3;
      >   DROP TABLE t1;
      >   
      >   4. Derived tables with subquery where subquery
      >      is evaluated before table locking(Bug#54475, Bug#52157)
      >   
      >   Suggested solution is following:
      >   
      >   -Introduce new field LEX::context_analysis_only with the following
      >    possible flags:
      >    #define CONTEXT_ANALYSIS_ONLY_PREPARE 1
      >    #define CONTEXT_ANALYSIS_ONLY_VIEW    2
      >    #define CONTEXT_ANALYSIS_ONLY_DERIVED 4
      >   -Set/clean these flags when we perform
      >    context analysis operation
      >   -Item_subselect::const_item() returns
      >    result depending on LEX::context_analysis_only.
      >    If context_analysis_only is set then we return
      >    FALSE that means that subquery is non-const.
      >    As all subquery types are wrapped by Item_subselect
      >    it allow as to make subquery non-const when
      >    it's necessary.
      33e74cf1
  4. 14 Dec, 2010 1 commit
    • Sergey Glukhov's avatar
      Fixed following problems: · dda99909
      Sergey Glukhov authored
      --Bug#52157 various crashes and assertions with multi-table update, stored function
      --Bug#54475 improper error handling causes cascading crashing failures in innodb/ndb
      --Bug#57703 create view cause Assertion failed: 0, file .\item_subselect.cc, line 846
      --Bug#57352 valgrind warnings when creating view
      --Recently discovered problem when a nested materialized derived table is used
        before being populated and it leads to incorrect result
      
      We have several modes when we should disable subquery evaluation.
      The reasons for disabling are different. It could be
      uselessness of the evaluation as in case of 'CREATE VIEW'
      or 'PREPARE stmt', or we should disable subquery evaluation
      if tables are not locked yet as it happens in bug#54475, or
      too early evaluation of subqueries can lead to wrong result
      as it happened in Bug#19077.
      Main problem is that if subquery items are treated as const
      they are evaluated in ::fix_fields(), ::fix_length_and_dec()
      of the parental items as a lot of these methods have
      Item::val_...() calls inside.
      We have to make subqueries non-const to prevent unnecessary
      subquery evaluation. At the moment we have different methods
      for this. Here is a list of these modes:
      
      1. PREPARE stmt;
      We use UNCACHEABLE_PREPARE flag.
      It is set during parsing in sql_parse.cc, mysql_new_select() for
      each SELECT_LEX object and cleared at the end of PREPARE in
      sql_prepare.cc, init_stmt_after_parse(). If this flag is set
      subquery becomes non-const and evaluation does not happen.
      
      2. CREATE|ALTER VIEW, SHOW CREATE VIEW, I_S tables which
         process FRM files
      We use LEX::view_prepare_mode field. We set it before
      view preparation and check this flag in
      ::fix_fields(), ::fix_length_and_dec().
      Some bugs are fixed using this approach,
      some are not(Bug#57352, Bug#57703). The problem here is
      that we have a lot of ::fix_fields(), ::fix_length_and_dec()
      where we use Item::val_...() calls for const items.
      
      3. Derived tables with subquery = wrong result(Bug19077)
      The reason of this bug is too early subquery evaluation.
      It was fixed by adding Item::with_subselect field
      The check of this field in appropriate places prevents
      const item evaluation if the item have subquery.
      The fix for Bug19077 fixes only the problem with
      convert_constant_item() function and does not cover
      other places(::fix_fields(), ::fix_length_and_dec() again)
      where subqueries could be evaluated.
      
      Example:
      CREATE TABLE t1 (i INT, j BIGINT);
      INSERT INTO t1 VALUES (1, 2), (2, 2), (3, 2);
      SELECT * FROM (SELECT MIN(i) FROM t1
      WHERE j = SUBSTRING('12', (SELECT * FROM (SELECT MIN(j) FROM t1) t2))) t3;
      DROP TABLE t1;
      
      4. Derived tables with subquery where subquery
         is evaluated before table locking(Bug#54475, Bug#52157)
      
      Suggested solution is following:
      
      -Introduce new field LEX::context_analysis_only with the following
       possible flags:
       #define CONTEXT_ANALYSIS_ONLY_PREPARE 1
       #define CONTEXT_ANALYSIS_ONLY_VIEW    2
       #define CONTEXT_ANALYSIS_ONLY_DERIVED 4
      -Set/clean these flags when we perform
       context analysis operation
      -Item_subselect::const_item() returns
       result depending on LEX::context_analysis_only.
       If context_analysis_only is set then we return
       FALSE that means that subquery is non-const.
       As all subquery types are wrapped by Item_subselect
       it allow as to make subquery non-const when
       it's necessary.
      
      
      mysql-test/r/derived.result:
        test case
      mysql-test/r/multi_update.result:
        test case
      mysql-test/r/view.result:
        test case
      mysql-test/suite/innodb/r/innodb_multi_update.result:
        test case
      mysql-test/suite/innodb/t/innodb_multi_update.test:
        test case
      mysql-test/suite/innodb_plugin/r/innodb_multi_update.result:
        test case
      mysql-test/suite/innodb_plugin/t/innodb_multi_update.test:
        test case
      mysql-test/t/derived.test:
        test case
      mysql-test/t/multi_update.test:
        test case
      mysql-test/t/view.test:
        test case
      sql/item.cc:
        --removed unnecessary code
      sql/item_cmpfunc.cc:
        --removed unnecessary checks
        --THD::is_context_analysis_only() is replaced with LEX::is_ps_or_view_context_analysis()
      sql/item_func.cc:
        --refactored context analysis checks
      sql/item_row.cc:
        --removed unnecessary checks
      sql/item_subselect.cc:
        --removed unnecessary code
        --added DBUG_ASSERT into Item_subselect::exec()
          which asserts that subquery execution can not happen
          if LEX::context_analysis_only is set, i.e. at context
          analysis stage.
        --Item_subselect::const_item()
          Return FALSE if LEX::context_analysis_only is set.
          It prevents subquery evaluation in ::fix_fields &
          ::fix_length_and_dec at context analysis stage.
      sql/item_subselect.h:
        --removed unnecessary code
      sql/mysql_priv.h:
        --Added new set of flags.
      sql/sql_class.h:
        --removed unnecessary code
      sql/sql_derived.cc:
        --added LEX::context_analysis_only analysis intialization/cleanup
      sql/sql_lex.cc:
        --init LEX::context_analysis_only field
      sql/sql_lex.h:
        --New LEX::context_analysis_only field
      sql/sql_parse.cc:
        --removed unnecessary code
      sql/sql_prepare.cc:
        --removed unnecessary code
        --added LEX::context_analysis_only analysis intialization/cleanup
      sql/sql_select.cc:
        --refactored context analysis checks
      sql/sql_show.cc:
        --added LEX::context_analysis_only analysis intialization/cleanup
      sql/sql_view.cc:
        --added LEX::context_analysis_only analysis intialization/cleanup
      dda99909
  5. 05 May, 2010 1 commit