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  1. MariaDB Server
  2. MDEV-273

SHOW EXPLAIN: server crashes in JOIN::print_explain on a query with impossible WHERE

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    Details

    • Type: Bug
    • Status: Closed (View Workflow)
    • Priority: Major
    • Resolution: Fixed
    • Affects Version/s: None
    • Fix Version/s: 10.0.0
    • Component/s: None
    • Labels:
      None

      Description

      #3  <signal handler called>
      #4  0x00000000007a86e2 in JOIN::print_explain (this=0x1d404b8, result=0x1cb3ab8, 
          explain_flags=0 '\000', on_the_fly=true, need_tmp_table=false, need_order=false, 
          distinct=false, message=0x0) at sql_select.cc:21264
      #5  0x00000000005d611d in st_select_lex::print_explain (this=0x1cf1100, 
          output=0x1cb3ab8, explain_flags=0 '\000') at sql_lex.cc:3769
      #6  0x00000000005d628f in st_select_lex_unit::print_explain (this=0x1cf1450, 
          output=0x1cb3ab8, explain_flags=0 '\000') at sql_lex.cc:3820
      #7  0x00000000005d6189 in st_select_lex::print_explain (this=0x1ce2098, 
          output=0x1cb3ab8, explain_flags=0 '\000') at sql_lex.cc:3784
      #8  0x00000000005d628f in st_select_lex_unit::print_explain (this=0x1ce1b90, 
          output=0x1cb3ab8, explain_flags=0 '\000') at sql_lex.cc:3820
      #9  0x00000000006ccbc5 in Show_explain_request::get_explain_data (arg=0x7f5ae1c5bba0)
          at sql_class.cc:3042
      #10 0x000000000095b335 in Apc_target::process_apc_requests (this=0x1ce1900)
          at my_apc.cc:255
      #11 0x00000000006c8a30 in THD::check_killed (this=0x1cdf5e8) at sql_class.cc:1904
      #12 0x0000000000744c9f in JOIN_CACHE::join_matching_records (this=0x1d4d658, 
          skip_last=false) at sql_join_cache.cc:2238
      #13 0x00000000007447fa in JOIN_CACHE::join_records (this=0x1d4d658, skip_last=false)
          at sql_join_cache.cc:2064
      #14 0x0000000000799de5 in sub_select_cache (join=0x1d3fe78, join_tab=0x1d4d158, 
          end_of_records=true) at sql_select.cc:15532
      #15 0x000000000079a004 in sub_select (join=0x1d3fe78, join_tab=0x1d4ce38, 
          end_of_records=true) at sql_select.cc:15694
      #16 0x0000000000799ab5 in do_select (join=0x1d3fe78, fields=0x1ce21a0, table=0x0, 
          procedure=0x0) at sql_select.cc:15416
      #17 0x000000000077aa4e in JOIN::exec_inner (this=0x1d3fe78) at sql_select.cc:2810
      #18 0x0000000000777e31 in JOIN::exec (this=0x1d3fe78) at sql_select.cc:2125
      #19 0x000000000077b2e7 in mysql_select (thd=0x1cdf5e8, rref_pointer_array=0x1ce22f0, 
          tables=0x1cf07a0, wild_num=0, fields=..., conds=0x1d3fcc8, og_num=0, order=0x0, 
          group=0x0, having=0x0, proc_param=0x0, select_options=2147764736, result=0x1d3fe58, 
          unit=0x1ce1b90, select_lex=0x1ce2098) at sql_select.cc:3031
      #20 0x0000000000771d62 in handle_select (thd=0x1cdf5e8, lex=0x1ce1af0, result=0x1d3fe58, 
          setup_tables_done_option=0) at sql_select.cc:332
      #21 0x00000000007002d9 in execute_sqlcom_select (thd=0x1cdf5e8, all_tables=0x1cf07a0)
          at sql_parse.cc:5178
      #22 0x00000000006f721f in mysql_execute_command (thd=0x1cdf5e8) at sql_parse.cc:2285
      #23 0x0000000000702cb4 in mysql_parse (thd=0x1cdf5e8, 
          rawbuf=0x1cf0520 "SELECT a1 FROM A, B \nWHERE a1 < ALL ( \nSELECT a1 FROM A \nWHERE a1 IN ( SELECT a1 FROM A, C ) \n)", length=95, found_semicolon=0x7f5ae1c14c98)
          at sql_parse.cc:6179
      #24 0x00000000006f49ce in dispatch_command (command=COM_QUERY, thd=0x1cdf5e8, 
          packet=0x1ce9bb9 "", packet_length=95) at sql_parse.cc:1229
      #25 0x00000000006f3d02 in do_command (thd=0x1cdf5e8) at sql_parse.cc:924
      #26 0x00000000006f0b46 in handle_one_connection (arg=0x1cdf5e8) at sql_connect.cc:1218

      Reproducible with the default optimizer switch as well as with all OFF values (except for in_to_exists which is required to execute the query).

      Default 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=on,loosescan=on,materialization=on,in_to_exists=on,semijoin=on,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=on,semijoin_with_cache=on,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on,optimize_join_buffer_size=off,table_elimination=on

      EXPLAIN (with default optimizer_switch):

      id      select_type     table   type    possible_keys   key     key_len ref     rows    filtered  Extra
      1       PRIMARY A       index   NULL    a1      5       NULL    20      100.00  Using where; Using index
      1       PRIMARY B       ALL     NULL    NULL    NULL    NULL    87      100.00  Using join buffer (flat, BNL join)
      2       SUBQUERY        NULL    NULL    NULL    NULL    NULL    NULL    NULL    NULL    Impossible WHERE noticed after reading const tables
      Warnings:
      Note    1003    select `test`.`A`.`a1` AS `a1` from `test`.`A` join `test`.`B` where <not>(<in_optimizer>(`test`.`A`.`a1`,(<min>(select `test`.`A`.`a1` from `test`.`A` semi join (`test`.`A` join `test`.`C`) where 0) <= <cache>(`test`.`A`.`a1`))))

      bzr version-info

      revision-id: psergey@askmonty.org-20120515115650-kqeip9cgxltgzx75
      date: 2012-05-15 15:56:50 +0400
      revno: 3511

      Test case:

      CREATE TABLE A (a1 INT, KEY(a1)) ENGINE=MyISAM;
      INSERT INTO A VALUES
        (4),(6),(7),(1),(0),(7),(7),(1),(7),(1),
        (5),(2),(0),(1),(8),(1),(1),(9),(1),(5);
       
      CREATE TABLE B (b1 INT) ENGINE=MyISAM;
      INSERT INTO B VALUES
        (4),(5),(8),(4),(8),(2),(9),(6),(4),(8),
        (3),(5),(9),(6),(8),(3),(2),(6),(3),(1),
        (4),(3),(1),(7),(0),(0),(9),(5),(9),(0),
        (2),(2),(5),(9),(1),(4),(8),(6),(5),(5),
        (1),(7),(2),(8),(9),(3),(2),(6),(6),(5),
        (4),(3),(2),(7),(4),(6),(0),(8),(5),(8),
        (2),(9),(7),(5),(7),(0),(4),(3),(1),(0),
        (6),(2),(8),(3),(7),(3),(5),(5),(1),(2),
        (1),(7),(1),(9),(9),(8),(3);
       
      CREATE TABLE C (c1 INT) ENGINE=MyISAM;
       
      --connect (con1,localhost,root,,)
      --let $con_id = `SELECT CONNECTION_ID()`
       
      --send
      SELECT a1 FROM A, B
      WHERE a1 < ALL ( 
        SELECT a1 FROM A
        WHERE a1 IN ( SELECT a1 FROM A, C )
      );
       
      --connection default
      --let $run = 100
      while ($run)
      {
        --error 0,1220
        --eval SHOW EXPLAIN FOR $con_id
        --dec $run
      }
       
      --connection con1
      --reap
       
      DROP TABLE A, B, C;
       

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              Assignee:
              psergei Sergei Petrunia
              Reporter:
              elenst Elena Stepanova
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                Created:
                Updated:
                Resolved:

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