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7922fbf7b7
The problem affected queries in form: SELECT FROM (SELECT where Split Materialized is applicable) WHERE 1=0 The problem was caused by this: - The select in derived table uses two-phase optimization (due to a possible Split Materialized). - The primary select has "Impossible where" and so it short-cuts its optimization. - The optimization for the SELECT in the derived table is never finished, and EXPLAIN data structure has a dangling pointer to select #2. Fixed with this: make JOIN::optimize_stage2() invoke optimization of derived tables when it is handing a degenerate JOIN with zero tables. We will not execute the derived tables but we need their query plans for [SHOW]EXPLAIN.
20 lines
672 B
Text
20 lines
672 B
Text
#
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# MDEV-26249: Crash in in Explain_node::print_explain_for_children while writing to the slow query log
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#
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set @sql_tmp=@@slow_query_log;
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SET GLOBAL slow_query_log = 1;
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SET long_query_time = 0.000000;
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SET log_slow_verbosity = 'explain';
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CREATE TABLE t1 ( id varchar(50), KEY (id)) engine=innodb;
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SELECT * FROM (SELECT id FROM t1 GROUP BY id) dt WHERE 1=0;
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id
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select 1;
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1
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1
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explain
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SELECT * FROM (SELECT id FROM t1 GROUP BY id) dt WHERE 1=0;
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id select_type table type possible_keys key key_len ref rows Extra
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1 PRIMARY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE
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2 DERIVED t1 index NULL id 53 NULL 1 Using index
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SET GLOBAL slow_query_log = @sql_tmp;
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drop table t1;
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