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MDEV-6480: Remove conditions for which range optimizer returned SEL_ARG::IMPOSSIBLE

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Let range optimizer remove parts of OR-clauses for which range analysis
produced SEL_TREE(IMPOSSIBLE).
There is no need to remove parts of AND-clauses: either they are inside
of OR (and the whole AND-clause will be removed), or the AND-clause is
at the top level, in which case the whole WHERE (or ON) is always FALSE
and this is a degenerate case which receives special treatment.

The removal process takes care not to produce 1-way ORs (in that case
we substitute the OR for its remaining member).
This commit is contained in:
Sergei Petrunia
2014-08-27 18:47:33 +04:00
parent 9534fd83ce
commit be00e279c6
9 changed files with 241 additions and 38 deletions
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45
mysql-test/r/range.result
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@ -2196,3 +2196,48 @@ id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t3 const PRIMARY PRIMARY 4 const 1
1 SIMPLE t2 range a a 5 NULL 1 Using where; Using index
drop table t1,t2,t3;
#
# MDEV-6480: Remove conditions for which range optimizer returned SEL_ARG::IMPOSSIBLE.
#
create table t1(a int);
insert into t1 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
create table t2 (a int, b int, c int, key(a), key(b));
insert into t2
select
A.a + B.a* 10 + C.a * 100,
A.a + B.a* 10 + C.a * 100,
12345
from
t1 A, t1 B, t1 C;
# EXPLAIN EXTENDED should show that 'b > 25 and b < 15' is removed from the WHERE:
explain extended select * from t2 where (b > 25 and b < 15) or a<44;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE t2 range a,b a 5 NULL 43 100.00 Using index condition
Warnings:
Note 1003 select `test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b`,`test`.`t2`.`c` AS `c` from `test`.`t2` where (`test`.`t2`.`a` < 44)
# EXPLAIN EXTENDED should show that 'b > 25 and b < 15' is removed from the WHERE:
explain extended select * from t2 where a < 44 or (b > 25 and b < 15);
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE t2 range a,b a 5 NULL 43 100.00 Using index condition
Warnings:
Note 1003 select `test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b`,`test`.`t2`.`c` AS `c` from `test`.`t2` where (`test`.`t2`.`a` < 44)
# Here, conditions b will not be removed, because "c<44" is not sargable
# and hence (b.. and .. b) part is not analyzed at all:
explain extended select * from t2 where c < 44 or (b > 25 and b < 15);
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE t2 ALL b NULL NULL NULL 1000 100.00 Using where
Warnings:
Note 1003 select `test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b`,`test`.`t2`.`c` AS `c` from `test`.`t2` where ((`test`.`t2`.`c` < 44) or ((`test`.`t2`.`b` > 25) and (`test`.`t2`.`b` < 15)))
# EXPLAIN EXTENDED should show that 'b > 25 and b < 15' is removed from the WHERE:
explain extended select * from t2 where (b > 25 and b < 15) or c < 44;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE t2 ALL b NULL NULL NULL 1000 100.00 Using where
Warnings:
Note 1003 select `test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b`,`test`.`t2`.`c` AS `c` from `test`.`t2` where ((`test`.`t2`.`c` < 44))
# Try a case where both OR parts produce SEL_ARG::IMPOSSIBLE:
explain extended select * from t2 where (b > 25 and b < 15) or (a>55 and a<44);
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
Warnings:
Note 1003 select `test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b`,`test`.`t2`.`c` AS `c` from `test`.`t2` where 0
drop table t1,t2;