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Fixed MDEV-14994 Assertion `join->best_read < double(1.79...15e+308L)' or

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server crash in JOIN::fix_all_splittings_in_plan

Cost formulas must take into account the case when a splittable table
has now rows.
This commit is contained in:
Igor Babaev
2018-01-30 21:12:11 -08:00
parent a1e0e64a47
commit 7a9611aee2
3 changed files with 37 additions and 2 deletions
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17
mysql-test/r/derived_cond_pushdown.result
View File

@ -14928,3 +14928,20 @@ SELECT * FROM t1 LEFT JOIN v2 ON (a = pk);
a pk MIN(b)
DROP VIEW v2;
DROP TABLE t1,t2;
#
# MDEV-14994: splittable table with no rows
#
CREATE TABLE t1 (f INT PRIMARY KEY) ENGINE=MyISAM;
CREATE VIEW v1 AS SELECT a.* FROM t1 AS a STRAIGHT_JOIN t1 AS b;
CREATE VIEW v2 AS SELECT f FROM v1 GROUP BY f;
SELECT * FROM v1 JOIN v2 ON v1.f = v2.f;
f f
EXPLAIN EXTENDED
SELECT * FROM v1 JOIN v2 ON v1.f = v2.f;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 PRIMARY NULL NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
3 LATERAL DERIVED NULL NULL NULL NULL NULL NULL NULL NULL no matching row in const table
Warnings:
Note 1003 /* select#1 */ select NULL AS `f`,`v2`.`f` AS `f` from `test`.`t1` `a` straight_join `test`.`t1` `b` join `test`.`v2` where 0
DROP VIEW v1,v2;
DROP TABLE t1;

15
mysql-test/t/derived_cond_pushdown.test
View File

@ -2598,3 +2598,18 @@ SELECT * FROM t1 LEFT JOIN v2 ON (a = pk);
DROP VIEW v2;
DROP TABLE t1,t2;
--echo #
--echo # MDEV-14994: splittable table with no rows
--echo #
CREATE TABLE t1 (f INT PRIMARY KEY) ENGINE=MyISAM;
CREATE VIEW v1 AS SELECT a.* FROM t1 AS a STRAIGHT_JOIN t1 AS b;
CREATE VIEW v2 AS SELECT f FROM v1 GROUP BY f;
SELECT * FROM v1 JOIN v2 ON v1.f = v2.f;
EXPLAIN EXTENDED
SELECT * FROM v1 JOIN v2 ON v1.f = v2.f;
DROP VIEW v1,v2;
DROP TABLE t1;

7
sql/opt_split.cc
View File

@ -645,7 +645,8 @@ double spl_postjoin_oper_cost(THD *thd, double join_record_count, uint rec_len)
cost+= get_tmp_table_lookup_cost(thd, join_record_count,rec_len) *
join_record_count; // cost to perform post join operation used here
cost+= get_tmp_table_lookup_cost(thd, join_record_count, rec_len) +
join_record_count * log2 (join_record_count) *
(join_record_count == 0 ? 0 :
join_record_count * log2 (join_record_count)) *
SORT_INDEX_CMP_COST; // cost to perform sorting
return cost;
}
@ -948,7 +949,9 @@ SplM_plan_info * JOIN_TAB::choose_best_splitting(double record_count,
spl_plan->table= best_table;
spl_plan->key= best_key;
spl_plan->parts= best_key_parts;
spl_plan->split_sel= best_rec_per_key / spl_opt_info->unsplit_card;
spl_plan->split_sel= best_rec_per_key /
(spl_opt_info->unsplit_card ?
spl_opt_info->unsplit_card : 1);
uint rec_len= table->s->rec_buff_length;