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  1. MariaDB Server
  2. MDEV-2898

LP:860553 - Crash in create_ref_for_key with semijoin + materialization

    Details

    • Type: Bug
    • Status: Closed
    • Priority: Major
    • Resolution: Fixed
    • Affects Version/s: None
    • Fix Version/s: None
    • Component/s: None
    • Labels:

      Description

      #5 0x0832c786 in create_ref_for_key (join=0xae63add8, j=0xae645994, org_keyuse=0xae633ff8, used_tables=4611686018427387907) at sql_select.cc:7307
      #6 0x0832c029 in get_best_combination (join=0xae63add8) at sql_select.cc:7122
      #7 0x0832448c in make_join_statistics (join=0xae63add8, tables_list=..., conds=0xae6334e8, keyuse_array=0xae63ff18) at sql_select.cc:3548
      #8 0x0831c038 in JOIN::optimize (this=0xae63add8) at sql_select.cc:1112
      #9 0x081b67f2 in st_select_lex::optimize_unflattened_subqueries (this=0xb336120) at sql_lex.cc:3126
      #10 0x083e4a35 in JOIN::optimize_unflattened_subqueries (this=0xae635b50) at opt_subselect.cc:4334
      #11 0x0831dc0a in JOIN::optimize (this=0xae635b50) at sql_select.cc:1621
      #12 0x08321e11 in mysql_select (thd=0xb3346e0, rref_pointer_array=0xb33625c, tables=0xae6130c0, wild_num=1, fields=..., conds=0x0, og_num=0, order=0x0,
      group=0x0, having=0x0, proc_param=0x0, select_options=2147764736, result=0xae632020, unit=0xb335e40, select_lex=0xb336120) at sql_select.cc:2886
      #13 0x08319c67 in handle_select (thd=0xb3346e0, lex=0xb335de4, result=0xae632020, setup_tables_done_option=0) at sql_select.cc:283
      #14 0x082b4434 in execute_sqlcom_select (thd=0xb3346e0, all_tables=0xae6130c0) at sql_parse.cc:5110
      #15 0x082ab1f1 in mysql_execute_command (thd=0xb3346e0) at sql_parse.cc:2250
      #16 0x082b6a63 in mysql_parse (thd=0xb3346e0,
      rawbuf=0xae612ec0 "SELECT *\nFROM t1\nJOIN t2\nON ( t2.f5 ) IN (\nSELECT t3.f4 \nFROM t3\nWHERE ( 1 ) IN (\nSELECT t4.f3 \nFROM t4 , t5\n)\n)",
      length=112, found_semicolon=0xae9e1228) at sql_parse.cc:6110
      #17 0x082a8e40 in dispatch_command (command=COM_QUERY, thd=0xb3346e0,
      packet=0xb38d321 "SELECT *\nFROM t1\nJOIN t2\nON ( t2.f5 ) IN (\nSELECT t3.f4 \nFROM t3\nWHERE ( 1 ) IN (\nSELECT t4.f3 \nFROM t4 , t5\n)\n)",
      packet_length=112) at sql_parse.cc:1221
      #18 0x082a829b in do_command (thd=0xb3346e0) at sql_parse.cc:916
      #19 0x082a527f in handle_one_connection (arg=0xb3346e0) at sql_connect.cc:1191
      #20 0x00821919 in start_thread () from /lib/libpthread.so.0
      #21 0x0076acce in clone () from /lib/libc.so.6

      minimal switch: semijoin=on,materialization=on

      full 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=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=off,mrr=off,mrr_cost_based=off,mrr_sort_keys=off,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on,optimize_join_buffer_size=off,table_elimination=on

      EXPLAIN crashes

      test case:

      CREATE TABLE t1 ( f1 int ) ;

      CREATE TABLE t2 ( f5 varchar(52) NOT NULL ) ;

      CREATE TABLE t3 ( f1 varchar(3), f4 varchar(52) , KEY (f4), PRIMARY KEY (f1)) ;

      CREATE TABLE t4 ( f3 int, KEY (f3));
      INSERT INTO t4 VALUES (17),(20);

      CREATE TABLE t5 ( f2 int);
      INSERT INTO t5 VALUES (0),(0);

      SET SESSION optimizer_switch='semijoin=ON,materialization=ON';

      SELECT *
      FROM t1
      JOIN t2
      ON ( t2.f5 ) IN (
      SELECT t3.f4
      FROM t3
      WHERE ( 1 ) IN (
      SELECT t4.f3
      FROM t4 , t5
      )
      );

      revision-id: <email address hidden>
      date: 2011-09-26 23:54:00 +0300
      build-date: 2011-09-27 16:15:50 +0300
      revno: 3196
      branch-nick: maria-5.3

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            Hide
            psergey Sergei Petrunia added a comment -

            Re: Crash in create_ref_for_key with semijoin + materialization
            The crash happens because create_ref_for_key() is invoked with a keyuse that does not match the table:

            Breakpoint 17, create_ref_for_key (join=0xb29d690, j=0xb2a8db4, org_keyuse=0xb2abf70, used_tables=4611686018427387907) at sql_select.cc:7264
            (gdb) p j->table->alias->Ptr
            $170 = 0xb291230 "t4"
            (gdb) p org_keyuse->table->alias->Ptr
            $171 = 0xb28ce58 "t3"

            Show
            psergey Sergei Petrunia added a comment - Re: Crash in create_ref_for_key with semijoin + materialization The crash happens because create_ref_for_key() is invoked with a keyuse that does not match the table: Breakpoint 17, create_ref_for_key (join=0xb29d690, j=0xb2a8db4, org_keyuse=0xb2abf70, used_tables=4611686018427387907) at sql_select.cc:7264 (gdb) p j->table->alias->Ptr $170 = 0xb291230 "t4" (gdb) p org_keyuse->table->alias->Ptr $171 = 0xb28ce58 "t3"
            Hide
            psergey Sergei Petrunia added a comment -

            Re: Crash in create_ref_for_key with semijoin + materialization
            The mismatch between JOIN_TAB and its KEYUSE is created in fix_semijoin_strategies_for_picked_join_order(), here:

            if (pos->sj_strategy == SJ_OPT_MATERIALIZE)
            {
            SJ_MATERIALIZATION_INFO *sjm= s->emb_sj_nest->sj_mat_info;
            sjm->is_used= TRUE;
            sjm->is_sj_scan= FALSE;
            memcpy(pos - sjm->tables + 1, sjm->positions,
            sizeof(POSITION) * sjm->tables);

            The mismatch is caused by this scenario:

            • "(1) IN (SELECT t4.f3 FROM t4 , t5)" is converted into a semi-join nest
            • JOIN::optimize is invoked for '(SELECT t3.f4 FROM t3 WHERE ... )')
            • optimize_semijoin_nests() remembers SJ-Materialization plan for "(SELECT t4.f3 FROM t4 , t5)"
            • join->choose_subquery_plan() is invoked
            • it adds another keyuse elements
            • it re-runs choose_plan() which choses a different query plan.
            • fix_semijoin_strategies() is called, it executes the above code that copies over POSITION elements that has "old" keyuse pointers which now refer to the wrong tables.

            that fair choice between IN->EXISTS and Materialization modifi

            Show
            psergey Sergei Petrunia added a comment - Re: Crash in create_ref_for_key with semijoin + materialization The mismatch between JOIN_TAB and its KEYUSE is created in fix_semijoin_strategies_for_picked_join_order(), here: if (pos->sj_strategy == SJ_OPT_MATERIALIZE) { SJ_MATERIALIZATION_INFO *sjm= s->emb_sj_nest->sj_mat_info; sjm->is_used= TRUE; sjm->is_sj_scan= FALSE; memcpy(pos - sjm->tables + 1, sjm->positions, sizeof(POSITION) * sjm->tables); The mismatch is caused by this scenario: "(1) IN (SELECT t4.f3 FROM t4 , t5)" is converted into a semi-join nest JOIN::optimize is invoked for '(SELECT t3.f4 FROM t3 WHERE ... )') optimize_semijoin_nests() remembers SJ-Materialization plan for "(SELECT t4.f3 FROM t4 , t5)" join->choose_subquery_plan() is invoked it adds another keyuse elements it re-runs choose_plan() which choses a different query plan. fix_semijoin_strategies() is called, it executes the above code that copies over POSITION elements that has "old" keyuse pointers which now refer to the wrong tables. that fair choice between IN->EXISTS and Materialization modifi
            Hide
            psergey Sergei Petrunia added a comment -

            Re: Crash in create_ref_for_key with semijoin + materialization
            Results of discussion with Timour: Need to save/restore SJM nest query subplans, and re-optimize them in JOIN::reoptimize()

            Show
            psergey Sergei Petrunia added a comment - Re: Crash in create_ref_for_key with semijoin + materialization Results of discussion with Timour: Need to save/restore SJM nest query subplans, and re-optimize them in JOIN::reoptimize()
            Hide
            ratzpo Rasmus Johansson added a comment -

            Launchpad bug id: 860553

            Show
            ratzpo Rasmus Johansson added a comment - Launchpad bug id: 860553

              People

              • Assignee:
                psergey Sergei Petrunia
                Reporter:
                philipstoev Philip Stoev
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                Dates

                • Created:
                  Updated:
                  Resolved: