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"Range Checked for Each Record" should be only employed when the other option would be cross-product join (i.e. the other option is so bad that we hardly risk anything). Previous logic was: use RCfER if there are no possible quick selects, or quick select would read > 100 rows. Also, it didn't always work as expected due to range optimizer changing table->quick_keys and us looking at sel->quick_keys. Another angle is that recent versions have enabled use of Join Buffering in e.g. outer joins. This further reduces the range of cases where RCfER should be used. We are still unable to estimate the cost of RCfER with any precision, so now changing the condition of "no quick select or quick->records> 100" to a hopefully better condition "no quick select or quick would cost more than full table scan".
40 lines
1.0 KiB
Plaintext
40 lines
1.0 KiB
Plaintext
#
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# Range optimizer (and related) tests that need InnoDB.
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#
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drop table if exists t0, t1, t2;
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#
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# MDEV-6735: Range checked for each record used with key
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#
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create table t0(a int);
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insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
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create table t1(a int);
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insert into t1 select A.a + B.a* 10 + C.a * 100 + D.a * 1000
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from t0 A, t0 B, t0 C, t0 D;
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create table t2 (
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a int,
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b int,
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filler1 char(100),
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filler2 char(100),
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filler3 char(100),
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filler4 char(100),
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key(a),
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key(b)
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) engine=innodb;
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insert into t2
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select
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a,a,
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repeat('0123456789', 10),
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repeat('0123456789', 10),
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repeat('0123456789', 10),
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repeat('0123456789', 10)
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from t1;
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analyze table t2;
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Table Op Msg_type Msg_text
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test.t2 analyze status OK
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# The following must not use "Range checked for each record":
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explain select * from t0 left join t2 on t2.a <t0.a and t2.b between 50 and 250;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t0 ALL NULL NULL NULL NULL 10
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1 SIMPLE t2 range a,b b 5 NULL 201 Using where; Using join buffer (flat, BNL join)
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drop table t0,t1,t2;
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