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BUG#16590: Optimized does not do right "const" table pre-read

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st_table::const_key_parts member is used in determining if
 certain key has a prefix that is compared to constant(s) in
 the query predicates.
 If there's such prefix the index can be used to get the data
 from the remaining suffix columns in sorted order.
 However if a field is compared to another field from a "const"
 table the const_key_parts is not amended.
 This makes the optimizer unable to detect that the key can be 
 used for sorting and adds an extra filesort.
 Fixed by updating const_key_parts after reading in the "const"
 table.


mysql-test/r/order_by.result:
  BUG#16590: Optimized does not do right "const" table pre-read
   - test case
mysql-test/t/order_by.test:
  BUG#16590: Optimized does not do right "const" table pre-read
   - test case
sql/sql_select.cc:
  BUG#16590: Optimized does not do right "const" table pre-read
   - fill up the const_key_parts structure
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unknown
2007-01-22 12:51:21 +02:00
parent e84b4600b8
commit 2c6e678dd9
3 changed files with 38 additions and 0 deletions
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9
mysql-test/r/order_by.result
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@ -918,3 +918,12 @@ NULL
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DROP TABLE t1,t2,t3,t4;
CREATE TABLE t1 (a INT, b INT, PRIMARY KEY (a), UNIQUE KEY b (b));
INSERT INTO t1 VALUES (1,1),(2,2);
CREATE TABLE t2 (a INT, b INT, KEY a (a,b));
INSERT INTO t2 VALUES (1,1),(1,2),(2,1),(2,2);
EXPLAIN SELECT 1 FROM t1,t2 WHERE t1.b=2 AND t1.a=t2.a ORDER BY t2.b;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 const PRIMARY,b b 5 const 1
1 SIMPLE t2 ref a a 5 const 2 Using where; Using index
DROP TABLE t1,t2;