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  1. MariaDB Server
  2. MDEV-2868

LP:877316 - Wrong result with view , derived EXISTS subquery, join_cache_level = 0

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Details

    • Bug
    • Status: Closed (View Workflow)
    • Critical
    • Resolution: Fixed
    • None
    • None
    • None

    Description

      The following query:

      SELECT v1.b
      FROM v1
      WHERE EXISTS (
      SELECT t2.b
      FROM t2
      WHERE t2.c < v1.c
      );

      returns no rows when executed with join_cache_level=0 and

      b

      ----

      19

      otherwise.

      explain:

      id select_type table type possible_keys key key_len ref rows Extra

      --------------------------------------------------------------------------------------------+

      1 PRIMARY t1 index NULL PRIMARY 4 NULL 2 Using where; Using index
      2 DEPENDENT SUBQUERY t2 system NULL NULL NULL NULL 1  

      optimizer switch: index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=off,derived_merge=off,derived_with_keys=off,firstmatch=off,loosescan=off,materialization=off,in_to_exists=on,semijoin=off,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr=off,mrr_cost_based=off,mrr_sort_keys=off,outer_join_with_cache=off,semijoin_with_cache=off,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on,optimize_join_buffer_size=off,table_elimination=on

      bzr version-info
      revision-id: <email address hidden>
      date: 2011-10-17 03:42:56 -0700
      build-date: 2011-10-18 13:36:56 +0300
      revno: 3239
      branch-nick: maria-5.3

      repeatable with 5.3 without derived_merge and derived_with_keys. Not repeatable on maria 5.2, mysql 5.5 or with join_cache_level=1. Not repeatable with SELECT * in place of SELECT v1.b

      test case:

      CREATE TABLE t1 ( b int(11) NOT NULL , c int(11), PRIMARY KEY (b)) ;
      INSERT INTO t1 VALUES (18,2),(19,9);

      CREATE TABLE t2 ( b int(11) NOT NULL , c int(11)) ;
      INSERT INTO t2 VALUES (10,8);

      SET SESSION join_cache_level=0;
      CREATE OR REPLACE VIEW v1 AS SELECT * FROM t1;

      SELECT v1.b
      FROM v1
      WHERE EXISTS (
      SELECT t2.b
      FROM t2
      WHERE t2.c < v1.c
      );

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            igor Igor Babaev
            philipstoev Philip Stoev (Inactive)
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            Dates

              Created:
              Updated:
              Resolved:

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