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If a table had a primary_key index, non_primary_key index, and an extended index with primary key in desc order, then the query with where clause predicates containing these index fields was picking an index_merge plan which was causing a wrong result. The plan shouldn't have contained index_merge in the first place, because the rows produced by one index have rows ordered by rowid in ascending order, and the rows coming from the other index were in a different order. The solution is to not produce index_merge plan in such scenarios. is_key_scan_ror() would now return false, for non_primary_key indexes if any primary key part with a reverse sort is present in them.
90 lines
3 KiB
Text
90 lines
3 KiB
Text
--source include/have_innodb.inc
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--source include/have_sequence.inc
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--source include/not_embedded.inc
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--echo
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--echo # MDEV-36410 wrong result with index_merge on indexes having descending primary key
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--echo #
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set optimizer_trace='enabled=on';
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SET @save_sort_buffer_size=@@sort_buffer_size;
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SET SESSION sort_buffer_size = 1024*16;
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CREATE TABLE t1 (
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id bigint(20) NOT NULL,
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title varchar(255) NOT NULL,
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status tinyint(4) DEFAULT 0,
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country_code varchar(5) DEFAULT NULL,
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PRIMARY KEY (id),
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KEY idx_status (status),
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KEY idx_country_code_status_id (country_code,status,id DESC)
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) ENGINE=InnoDB;
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INSERT INTO t1(id,title,status,country_code)
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SELECT seq, CONCAT('abc', seq), seq%10, CONCAT('C', seq%5) FROM seq_1_to_500;
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--echo # This must not use index_merge:
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EXPLAIN
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SELECT * FROM t1 WHERE country_code ='C1' and `status` =1;
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set @trace= (select JSON_EXTRACT(trace, '$**.range_scan_alternatives[*]')
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from INFORMATION_SCHEMA.OPTIMIZER_TRACE);
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select json_detailed(json_extract(@trace, '$[*].index')) as INDEXES;
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select json_detailed(json_extract(@trace, '$[*].rowid_ordered')) as ROR;
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#select JSON_DETAILED(JSON_EXTRACT(trace, '$**.range_scan_alternatives[*].index')) AS JS from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
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DROP table t1;
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--echo # Now, try with indexes using ASC ordering and PK using DESC
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CREATE TABLE t1 (
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id bigint(20) NOT NULL,
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title varchar(255) NOT NULL,
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status tinyint(4) DEFAULT 0,
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country_code varchar(5) DEFAULT NULL,
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PRIMARY KEY (id DESC),
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KEY idx_status (status),
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KEY idx_country_code_status_id (country_code,status,id)
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) ENGINE=InnoDB;
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INSERT INTO t1(id,title,status,country_code)
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SELECT seq, CONCAT('abc', seq), seq%10, CONCAT('C', seq%5) FROM seq_1_to_500;
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--echo # Must not use index_merge:
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EXPLAIN
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SELECT * FROM t1 WHERE country_code ='C1' and status = 1;
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set @trace= (select JSON_EXTRACT(trace, '$**.range_scan_alternatives[*]')
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from INFORMATION_SCHEMA.OPTIMIZER_TRACE);
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select json_detailed(json_extract(@trace, '$[*].index')) as INDEXES;
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select json_detailed(json_extract(@trace, '$[*].rowid_ordered')) as ROR;
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DROP TABLE t1;
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--echo # Now, try with indexes using DESC ordering and PK using DESC
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CREATE TABLE t1 (
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id bigint(20) NOT NULL,
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title varchar(255) NOT NULL,
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status tinyint(4) DEFAULT 0,
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country_code varchar(5) DEFAULT NULL,
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PRIMARY KEY (id DESC),
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KEY idx_status (status),
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KEY idx_country_code_status_id (country_code,status,id DESC)
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) ENGINE=InnoDB;
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INSERT INTO t1(id,title,status,country_code)
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SELECT seq, CONCAT('abc', seq), seq%10, CONCAT('C', seq%5) FROM seq_1_to_500;
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--echo # Must not use index_merge:
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EXPLAIN
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SELECT * FROM t1 WHERE country_code ='C1' and status = 1;
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set @trace= (select JSON_EXTRACT(trace, '$**.range_scan_alternatives[*]')
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from INFORMATION_SCHEMA.OPTIMIZER_TRACE);
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select json_detailed(json_extract(@trace, '$[*].index')) as INDEXES;
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select json_detailed(json_extract(@trace, '$[*].rowid_ordered')) as ROR;
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DROP TABLE t1;
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SET sort_buffer_size= @save_sort_buffer_size;
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