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  1. MariaDB Server
  2. MDEV-3658

LP:874035 - Wrong result with merge view , derived table, first execution of a prepared statement

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Details

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

    Description

      The following query:

      SELECT * FROM (
      SELECT *
      FROM t2
      LEFT JOIN v1
      ON (t2.a = v1.b)
      ) AS derived

      returns the following incorrect result when run the first time as a prepared statement:

      a b
      6 0

      The second run, as well as non-prepared execution, return the correct result:

      a b
      6 NULL

      explain:

      id select_type table type possible_keys key key_len ref rows Extra
      1 PRIMARY <derived2> ALL NULL NULL NULL NULL 2
      2 DERIVED t2 system NULL NULL NULL NULL 1
      2 DERIVED t1 ALL NULL NULL NULL NULL 0 Using where

      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

      repeatable on maria-5.3. Not repeatable on maria-5.2, mysql-5.5

      bzr version-info:

      revision-id: <email address hidden>
      date: 2011-10-13 13:44:50 +0200
      build-date: 2011-10-14 13:08:11 +0300
      revno: 3233
      branch-nick: maria-5.3

      test case:

      CREATE TABLE t2 (a int NOT NULL);
      INSERT INTO t2 VALUES (6);

      CREATE TABLE t1 (b int NOT NULL);
      CREATE ALGORITHM=MERGE VIEW v1 AS SELECT * FROM t1;

      PREPARE st1 FROM '
      SELECT * FROM (
      SELECT *
      FROM t2
      LEFT JOIN v1
      ON (t2.a = v1.b)
      ) AS derived
      ';

      EXECUTE st1;
      EXECUTE st1;

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            igor Igor Babaev (Inactive)
            philipstoev Philip Stoev (Inactive)
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            Dates

              Created:
              Updated:
              Resolved:

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