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BUG#43768: Prepared query with nested subqueries core dumps on second execution

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Fix two problems:
1. Let optimize_semijoin_nests() reset sj_nest->sjmat_info irrespectively  
   of value of optimizer_flag. We need this in case somebody has turned optimization
   off between reexecutions of the same statement.

2. Do not pull out constant tables out of semi-join nests. The problem is that pullout 
   operation is not undoable, and if a table is constant because it is 1/0-row table it 
   may cease to be constant on the next execution. Note that tables that are constant
   because of possible eq_ref(const) access will still be pulled out as they are
   considered functionally-dependent.
This commit is contained in:
Sergey Petrunya 2010-03-14 20:54:12 +03:00
parent c2924e155e
commit 77e66c6985
5 changed files with 203 additions and 20 deletions
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53
mysql-test/r/subselect_sj.result
View file

@ -1,4 +1,4 @@
drop table if exists t0, t1, t2, t10, t11, t12;
drop table if exists t0, t1, t2, t3, t4, t10, t11, t12;
create table t0 (a int);
insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
create table t1(a int, b int);
@ -871,3 +871,54 @@ id select_type table type possible_keys key key_len ref rows Extra
DROP TABLE t1, t2, t3;
DROP VIEW v2, v3;
# End of Bug#49198
#
# BUG#43768: Prepared query with nested subqueries core dumps on second execution
#
create table t1 (
id int(11) unsigned not null primary key auto_increment,
partner_id varchar(35) not null,
t1_status_id int(10) unsigned
);
insert into t1 values ("1", "partner1", "10"), ("2", "partner2", "10"),
("3", "partner3", "10"), ("4", "partner4", "10");
create table t2 (
id int(11) unsigned not null default '0',
t1_line_id int(11) unsigned not null default '0',
article_id varchar(20),
sequence int(11) not null default '0',
primary key (id,t1_line_id)
);
insert into t2 values ("1", "1", "sup", "0"), ("2", "1", "sup", "1"),
("2", "2", "sup", "2"), ("2", "3", "sup", "3"),
("2", "4", "imp", "4"), ("3", "1", "sup", "0"),
("4", "1", "sup", "0");
create table t3 (
id int(11) not null default '0',
preceeding_id int(11) not null default '0',
primary key (id,preceeding_id)
);
create table t4 (
user_id varchar(50) not null,
article_id varchar(20) not null,
primary key (user_id,article_id)
);
insert into t4 values("nicke", "imp");
prepare stmt from
'select t1.partner_id
from t1
where
t1.id in (
select pl_inner.id
from t2 as pl_inner
where pl_inner.article_id in (
select t4.article_id from t4
where t4.user_id = \'nicke\'
)
)';
execute stmt;
partner_id
partner2
execute stmt;
partner_id
partner2
drop table t1,t2,t3,t4;

53
mysql-test/r/subselect_sj_jcl6.result
View file

@ -2,7 +2,7 @@ set join_cache_level=6;
show variables like 'join_cache_level';
Variable_name Value
join_cache_level 6
drop table if exists t0, t1, t2, t10, t11, t12;
drop table if exists t0, t1, t2, t3, t4, t10, t11, t12;
create table t0 (a int);
insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
create table t1(a int, b int);
@ -876,6 +876,57 @@ DROP TABLE t1, t2, t3;
DROP VIEW v2, v3;
# End of Bug#49198
#
# BUG#43768: Prepared query with nested subqueries core dumps on second execution
#
create table t1 (
id int(11) unsigned not null primary key auto_increment,
partner_id varchar(35) not null,
t1_status_id int(10) unsigned
);
insert into t1 values ("1", "partner1", "10"), ("2", "partner2", "10"),
("3", "partner3", "10"), ("4", "partner4", "10");
create table t2 (
id int(11) unsigned not null default '0',
t1_line_id int(11) unsigned not null default '0',
article_id varchar(20),
sequence int(11) not null default '0',
primary key (id,t1_line_id)
);
insert into t2 values ("1", "1", "sup", "0"), ("2", "1", "sup", "1"),
("2", "2", "sup", "2"), ("2", "3", "sup", "3"),
("2", "4", "imp", "4"), ("3", "1", "sup", "0"),
("4", "1", "sup", "0");
create table t3 (
id int(11) not null default '0',
preceeding_id int(11) not null default '0',
primary key (id,preceeding_id)
);
create table t4 (
user_id varchar(50) not null,
article_id varchar(20) not null,
primary key (user_id,article_id)
);
insert into t4 values("nicke", "imp");
prepare stmt from
'select t1.partner_id
from t1
where
t1.id in (
select pl_inner.id
from t2 as pl_inner
where pl_inner.article_id in (
select t4.article_id from t4
where t4.user_id = \'nicke\'
)
)';
execute stmt;
partner_id
partner2
execute stmt;
partner_id
partner2
drop table t1,t2,t3,t4;
#
# BUG#49129: Wrong result with IN-subquery with join_cache_level=6 and firstmatch=off
#
CREATE TABLE t0 (a INT);

59
mysql-test/t/subselect_sj.test
View file

@ -2,7 +2,7 @@
# Nested Loops semi-join subquery evaluation tests
#
--disable_warnings
drop table if exists t0, t1, t2, t10, t11, t12;
drop table if exists t0, t1, t2, t3, t4, t10, t11, t12;
--enable_warnings
#
@ -770,3 +770,60 @@ DROP TABLE t1, t2, t3;
DROP VIEW v2, v3;
--echo # End of Bug#49198
--echo #
--echo # BUG#43768: Prepared query with nested subqueries core dumps on second execution
--echo #
create table t1 (
id int(11) unsigned not null primary key auto_increment,
partner_id varchar(35) not null,
t1_status_id int(10) unsigned
);
insert into t1 values ("1", "partner1", "10"), ("2", "partner2", "10"),
("3", "partner3", "10"), ("4", "partner4", "10");
create table t2 (
id int(11) unsigned not null default '0',
t1_line_id int(11) unsigned not null default '0',
article_id varchar(20),
sequence int(11) not null default '0',
primary key (id,t1_line_id)
);
insert into t2 values ("1", "1", "sup", "0"), ("2", "1", "sup", "1"),
("2", "2", "sup", "2"), ("2", "3", "sup", "3"),
("2", "4", "imp", "4"), ("3", "1", "sup", "0"),
("4", "1", "sup", "0");
create table t3 (
id int(11) not null default '0',
preceeding_id int(11) not null default '0',
primary key (id,preceeding_id)
);
create table t4 (
user_id varchar(50) not null,
article_id varchar(20) not null,
primary key (user_id,article_id)
);
insert into t4 values("nicke", "imp");
prepare stmt from
'select t1.partner_id
from t1
where
t1.id in (
select pl_inner.id
from t2 as pl_inner
where pl_inner.article_id in (
select t4.article_id from t4
where t4.user_id = \'nicke\'
)
)';
execute stmt;
execute stmt;
drop table t1,t2,t3,t4;

52
sql/opt_subselect.cc
View file

@ -963,7 +963,6 @@ int pull_out_semijoin_tables(JOIN *join)
{
/* Action #1: Mark the constant tables to be pulled out */
table_map pulled_tables= 0;
List_iterator<TABLE_LIST> child_li(sj_nest->nested_join->join_list);
TABLE_LIST *tbl;
while ((tbl= child_li++))
@ -971,12 +970,34 @@ int pull_out_semijoin_tables(JOIN *join)
if (tbl->table)
{
tbl->table->reginfo.join_tab->emb_sj_nest= sj_nest;
#if 0
/*
Do not pull out tables because they are constant. This operation has
a problem:
- Some constant tables may become/cease to be constant across PS
re-executions
- Contrary to our initial assumption, it turned out that table pullout
operation is not easily undoable.
The solution is to leave constant tables where they are. This will
affect only constant tables that are 1-row or empty, tables that are
constant because they are accessed via eq_ref(const) access will
still be pulled out as functionally-dependent.
This will cause us to miss the chance to flatten some of the
subqueries, but since const tables do not generate many duplicates,
it really doesn't matter that much whether they were pulled out or
not.
All of this was done as fix for BUG#43768.
*/
if (tbl->table->map & join->const_table_map)
{
pulled_tables |= tbl->table->map;
DBUG_PRINT("info", ("Table %s pulled out (reason: constant)",
tbl->table->alias));
}
#endif
}
}
@ -1048,6 +1069,7 @@ int pull_out_semijoin_tables(JOIN *join)
pointers.
*/
child_li.remove();
sj_nest->nested_join->used_tables &= ~tbl->table->map;
upper_join_list->push_back(tbl);
tbl->join_list= upper_join_list;
tbl->embedding= sj_nest->embedding;
@ -1104,20 +1126,20 @@ bool optimize_semijoin_nests(JOIN *join, table_map all_table_map)
DBUG_ENTER("optimize_semijoin_nests");
List_iterator<TABLE_LIST> sj_list_it(join->select_lex->sj_nests);
TABLE_LIST *sj_nest;
/*
The statement may have been executed with 'semijoin=on' earlier.
We need to verify that 'semijoin=on' still holds.
*/
if (optimizer_flag(join->thd, OPTIMIZER_SWITCH_SEMIJOIN) &&
optimizer_flag(join->thd, OPTIMIZER_SWITCH_MATERIALIZATION))
while ((sj_nest= sj_list_it++))
{
while ((sj_nest= sj_list_it++))
{
/* semi-join nests with only constant tables are not valid */
DBUG_ASSERT(sj_nest->sj_inner_tables & ~join->const_table_map);
/* semi-join nests with only constant tables are not valid */
/// DBUG_ASSERT(sj_nest->sj_inner_tables & ~join->const_table_map);
sj_nest->sj_mat_info= NULL;
if (sj_nest->sj_inner_tables && /* not everything was pulled out */
sj_nest->sj_mat_info= NULL;
/*
The statement may have been executed with 'semijoin=on' earlier.
We need to verify that 'semijoin=on' still holds.
*/
if (optimizer_flag(join->thd, OPTIMIZER_SWITCH_SEMIJOIN) &&
optimizer_flag(join->thd, OPTIMIZER_SWITCH_MATERIALIZATION))
{
if ((sj_nest->sj_inner_tables & ~join->const_table_map) && /* not everything was pulled out */
!sj_nest->sj_subq_pred->is_correlated &&
sj_nest->sj_subq_pred->types_allow_materialization)
{
@ -1128,7 +1150,7 @@ bool optimize_semijoin_nests(JOIN *join, table_map all_table_map)
The best plan to run the subquery is now in join->best_positions,
save it.
*/
uint n_tables= my_count_bits(sj_nest->sj_inner_tables);
uint n_tables= my_count_bits(sj_nest->sj_inner_tables & ~join->const_table_map);
SJ_MATERIALIZATION_INFO* sjm;
if (!(sjm= new SJ_MATERIALIZATION_INFO) ||
!(sjm->positions= (POSITION*)join->thd->alloc(sizeof(POSITION)*
@ -1443,7 +1465,7 @@ void advance_sj_state(JOIN *join, table_map remaining_tables,
new_join_tab->emb_sj_nest->nested_join->sj_corr_tables |
new_join_tab->emb_sj_nest->nested_join->sj_depends_on;
const table_map sj_inner_tables=
new_join_tab->emb_sj_nest->sj_inner_tables;
new_join_tab->emb_sj_nest->sj_inner_tables & ~join->const_table_map;
/*
Enter condition:

6
sql/sql_select.cc
View file

@ -5127,7 +5127,9 @@ greedy_search(JOIN *join,
/* number of tables that remain to be optimized */
n_tables= size_remain= my_count_bits(remaining_tables &
(join->emb_sjm_nest?
join->emb_sjm_nest->sj_inner_tables :
(join->emb_sjm_nest->sj_inner_tables &
~join->const_table_map)
:
~(table_map)0));
do {
@ -5387,7 +5389,7 @@ best_extension_by_limited_search(JOIN *join,
table_map allowed_tables= ~(table_map)0;
if (join->emb_sjm_nest)
allowed_tables= join->emb_sjm_nest->sj_inner_tables;
allowed_tables= join->emb_sjm_nest->sj_inner_tables & ~join->const_table_map;
for (JOIN_TAB **pos= join->best_ref + idx ; (s= *pos) ; pos++)
{