Details
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Bug
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Status: Closed (View Workflow)
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Major
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Resolution: Fixed
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10.2(EOL)
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None
Description
Found this while working on MDEV-14433:
Found an interesting mismatch between query plans that depends on the index number:
Upstream, MySQL 5.6
CREATE TABLE t3(
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pk int primary key,
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a varchar(10) NOT NULL,
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e int(11) DEFAULT 0,
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KEY (a)
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) ENGINE=ROCKSDB DEFAULT CHARSET=utf8;
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insert into t3 values (1,1,1),(2,2,2);
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explain select a from t3 where a <'zzz';
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+----+-------------+-------+-------+---------------+------+---------+------+------+-------------+
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| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
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+----+-------------+-------+-------+---------------+------+---------+------+------+-------------+
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| 1 | SIMPLE | t3 | range | a | a | 32 | NULL | 2 | Using where |
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+----+-------------+-------+-------+---------------+------+---------+------+------+-------------+
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CREATE TABLE t4(
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pk int,
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a varchar(10) NOT NULL,
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e int(11) DEFAULT 0,
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KEY (a)
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) ENGINE=ROCKSDB DEFAULT CHARSET=utf8;
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insert into t4 values (1,1,1),(2,2,2);
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explain select a from t4 where a <'zzz';
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+----+-------------+-------+-------+---------------+------+---------+------+------+-------------+
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| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
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+----+-------------+-------+-------+---------------+------+---------+------+------+-------------+
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| 1 | SIMPLE | t4 | range | a | a | 32 | NULL | 1 | Using where |
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+----+-------------+-------+-------+---------------+------+---------+------+------+-------------+
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MariaDB:
CREATE TABLE t3(
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pk int primary key,
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a varchar(10) NOT NULL,
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e int(11) DEFAULT 0,
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KEY (a)
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) ENGINE=ROCKSDB DEFAULT CHARSET=utf8;
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insert into t3 values (1,1,1),(2,2,2);
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explain select a from t3 where a <'zzz';
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+------+-------------+-------+-------+---------------+------+---------+------+------+-------------+
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| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
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+------+-------------+-------+-------+---------------+------+---------+------+------+-------------+
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| 1 | SIMPLE | t3 | range | a | a | 32 | NULL | 1 | Using where |
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+------+-------------+-------+-------+---------------+------+---------+------+------+-------------+
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CREATE TABLE t4(
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pk int,
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a varchar(10) NOT NULL,
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e int(11) DEFAULT 0,
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KEY (a)
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) ENGINE=ROCKSDB DEFAULT CHARSET=utf8;
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insert into t4 values (1,1,1),(2,2,2);
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explain select a from t4 where a <'zzz';
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+------+-------------+-------+-------+---------------+------+---------+------+------+--------------------------+
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| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
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+------+-------------+-------+-------+---------------+------+---------+------+------+--------------------------+
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| 1 | SIMPLE | t4 | index | a | a | 32 | NULL | 0 | Using where; Using index |
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+------+-------------+-------+-------+---------------+------+---------+------+------+--------------------------+
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Attachments
Issue Links
- includes
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- Closed
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- is part of
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- Closed
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Activity
table_share->primary_key is set in TABLE_SHARE::init_from_binary_frm_image but
the mentioned index_flags() call is made before that.
There is a local variable
uint primary_key= my_strcasecmp(system_charset_info, share->keynames.type_names[0],
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primary_key_name) ? MAX_KEY : 0;
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which is set before the index_flags() call.
Condition to set share->primary_key:
if (primary_key < MAX_KEY &&
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(share->keys_in_use.is_set(primary_key)))
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{
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share->primary_key= primary_key;
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Debugging
CREATE TABLE t4(pk int,a varchar(10) NOT NULL,e int(11) DEFAULT 0,KEY (a)) ENGINE=ROCKSDB DEFAULT CHARSET=utf8;in TABLE_SHARE::init_from_binary_frm_image, stepping into the
if (handler_file->index_flags(key, i, 0) & HA_KEYREAD_ONLY)call:
myrocks::ha_rocksdb::index_flags (this=0x7fff6c01b7e8, inx=0, part=0, all_parts=false)There, we have
(gdb) p table$33 = (TABLE *) 0x0(gdb) p table_share$34 = (TABLE_SHARE *) 0x7ffff41bd890(gdb) p table_share->primary_key$35 = 0That is,
if (inx == table_share->primary_key) {and returns an incorrect value.