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Fixed LP bug #754521.

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The function test_quick_select by mistake did not update the value
of table->quick_condition_rows for index intersection scans though
the specification explicitly required to do so from any table access
plan once the plan provided a better upper bound for the number of
rows selected from the table. It resulted in a bogus, usually very
big number saved as the cost of the table access. This, in its turn,
in many cases forced the optimizer to make a bad choice of the
execution plan for join queries.
This commit is contained in:
Igor Babaev
2011-04-27 15:29:46 -07:00
parent 24edac2211
commit 1556a136ac
4 changed files with 28 additions and 1 deletions
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7
mysql-test/r/index_intersect.result
View File

@ -998,6 +998,13 @@ ID Name Country Population
1898 Chengdu CHN 3361500 1898 Chengdu CHN 3361500
1900 Changchun CHN 2812000 1900 Changchun CHN 2812000
1910 Changsha CHN 1809800 1910 Changsha CHN 1809800
EXPLAIN
SELECT * FROM City, Country
WHERE City.Name LIKE 'C%' AND City.Population > 1000000 AND
Country.Code=City.Country;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE City index_merge Population,Name,CountryID,CountryName Name,Population 35,4 NULL # Using sort_intersect(Name,Population); Using where
1 SIMPLE Country eq_ref PRIMARY PRIMARY 3 world.City.Country #
DROP DATABASE world; DROP DATABASE world;
use test; use test;
CREATE TABLE t1 ( CREATE TABLE t1 (

7
mysql-test/r/index_intersect_innodb.result
View File

@ -999,6 +999,13 @@ ID Name Country Population
1898 Chengdu CHN 3361500 1898 Chengdu CHN 3361500
1900 Changchun CHN 2812000 1900 Changchun CHN 2812000
1910 Changsha CHN 1809800 1910 Changsha CHN 1809800
EXPLAIN
SELECT * FROM City, Country
WHERE City.Name LIKE 'C%' AND City.Population > 1000000 AND
Country.Code=City.Country;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE City index_merge Population,Name,CountryID,CountryName Population,Name 4,35 NULL # Using sort_intersect(Population,Name); Using where
1 SIMPLE Country eq_ref PRIMARY PRIMARY 3 world.City.Country #
DROP DATABASE world; DROP DATABASE world;
use test; use test;
CREATE TABLE t1 ( CREATE TABLE t1 (

11
mysql-test/t/index_intersect.test
View File

@ -396,6 +396,17 @@ SELECT * FROM City
WHERE Country='CHN' AND Population > 1500000 AND Name LIKE 'C%'; WHERE Country='CHN' AND Population > 1500000 AND Name LIKE 'C%';
#
# Bug #754521: wrong cost of index intersection leading
# to the choice of a suboptimal execution plan
#
--replace_column 9 #
EXPLAIN
SELECT * FROM City, Country
WHERE City.Name LIKE 'C%' AND City.Population > 1000000 AND
Country.Code=City.Country;
DROP DATABASE world; DROP DATABASE world;
use test; use test;

4
sql/opt_range.cc
View File

@ -3116,7 +3116,9 @@ int SQL_SELECT::test_quick_select(THD *thd, key_map keys_to_use,
best_read_time))) best_read_time)))
{ {
best_trp= intersect_trp; best_trp= intersect_trp;
best_read_time= best_trp->read_cost; best_read_time= best_trp->read_cost;
set_if_smaller(param.table->quick_condition_rows,
intersect_trp->records);
} }
} }