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  1. MariaDB Server
  2. MDEV-2908

LP:806504 - Wrong result with semijoin=off,derived_merge=on , right join and subquery

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Details

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

    Description

      The following query

      SELECT *
      FROM t2
      RIGHT JOIN ( SELECT * FROM t1 ) AS alias2
      ON alias2.f10 != 0
      WHERE alias2.f10 IN ( SELECT f11 FROM t1 );

      returns no rows when executed with derived_merge=on,semijoin=off and 1 row in all other cases (e.g. when run with other switches or by manually in-lining the derived table, or inlining the subquery, rotating the join to be LEFT JOIN).

      Explain:

      1 PRIMARY t1 system NULL NULL NULL NULL 1  
      1 PRIMARY t2 ALL NULL NULL NULL NULL 2  
      3 SUBQUERY t1 system NULL NULL NULL NULL 1  

      minimal optimizer switch:derived_merge=on,semijoin=off

      full 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=on,derived_merge=on,derived_with_keys=on,firstmatch=off,loosescan=off,materialization=on,in_to_exists=on,semijoin=off,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr=on,mrr_cost_based=off,mrr_sort_keys=on,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=on,table_elimination=on

      test case:

      CREATE TABLE t1 ( f10 int, f11 int) ;
      INSERT IGNORE INTO t1 VALUES (0,0);

      CREATE TABLE t2 ( f11 int) ;
      INSERT INTO t2 VALUES (0),(0);

      SELECT *
      FROM t2
      RIGHT JOIN ( SELECT * FROM t1 ) AS alias2
      ON alias2.f10 != 0
      WHERE alias2.f10 IN ( SELECT f11 FROM t1 );

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            igor Igor Babaev
            philipstoev Philip Stoev (Inactive)
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            Dates

              Created:
              Updated:
              Resolved:

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