database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-07-15 19:21:59 +03:00
Code Activity

Add plan_cache_mode setting

Browse Source 
This allows overriding the choice of custom or generic plan.

Author: Pavel Stehule <pavel.stehule@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/CAFj8pRAGLaiEm8ur5DWEBo7qHRWTk9HxkuUAz00CZZtJj-LkCA%40mail.gmail.com
This commit is contained in:
Peter Eisentraut
2018-07-16 13:35:41 +02:00
parent a06e56b247
commit f7cb2842bf
7 changed files with 179 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

77
src/test/regress/expected/plancache.out
View File

@ -278,3 +278,80 @@ drop table pc_list_part_1;
execute pstmt_def_insert(1);
drop table pc_list_parted, pc_list_part_null;
deallocate pstmt_def_insert;
-- Test plan_cache_mode
create table test_mode (a int);
insert into test_mode select 1 from generate_series(1,1000) union all select 2;
create index on test_mode (a);
analyze test_mode;
prepare test_mode_pp (int) as select count(*) from test_mode where a = $1;
-- up to 5 executions, custom plan is used
explain (costs off) execute test_mode_pp(2);
QUERY PLAN
----------------------------------------------------------
Aggregate
-> Index Only Scan using test_mode_a_idx on test_mode
Index Cond: (a = 2)
(3 rows)
-- force generic plan
set plan_cache_mode to force_generic_plan;
explain (costs off) execute test_mode_pp(2);
QUERY PLAN
-----------------------------
Aggregate
-> Seq Scan on test_mode
Filter: (a = $1)
(3 rows)
-- get to generic plan by 5 executions
set plan_cache_mode to auto;
execute test_mode_pp(1); -- 1x
count
-------
1000
(1 row)
execute test_mode_pp(1); -- 2x
count
-------
1000
(1 row)
execute test_mode_pp(1); -- 3x
count
-------
1000
(1 row)
execute test_mode_pp(1); -- 4x
count
-------
1000
(1 row)
execute test_mode_pp(1); -- 5x
count
-------
1000
(1 row)
-- we should now get a really bad plan
explain (costs off) execute test_mode_pp(2);
QUERY PLAN
-----------------------------
Aggregate
-> Seq Scan on test_mode
Filter: (a = $1)
(3 rows)
-- but we can force a custom plan
set plan_cache_mode to force_custom_plan;
explain (costs off) execute test_mode_pp(2);
QUERY PLAN
----------------------------------------------------------
Aggregate
-> Index Only Scan using test_mode_a_idx on test_mode
Index Cond: (a = 2)
(3 rows)
drop table test_mode;

33
src/test/regress/sql/plancache.sql
View File

@ -177,3 +177,36 @@ drop table pc_list_part_1;
execute pstmt_def_insert(1);
drop table pc_list_parted, pc_list_part_null;
deallocate pstmt_def_insert;
-- Test plan_cache_mode
create table test_mode (a int);
insert into test_mode select 1 from generate_series(1,1000) union all select 2;
create index on test_mode (a);
analyze test_mode;
prepare test_mode_pp (int) as select count(*) from test_mode where a = $1;
-- up to 5 executions, custom plan is used
explain (costs off) execute test_mode_pp(2);
-- force generic plan
set plan_cache_mode to force_generic_plan;
explain (costs off) execute test_mode_pp(2);
-- get to generic plan by 5 executions
set plan_cache_mode to auto;
execute test_mode_pp(1); -- 1x
execute test_mode_pp(1); -- 2x
execute test_mode_pp(1); -- 3x
execute test_mode_pp(1); -- 4x
execute test_mode_pp(1); -- 5x
-- we should now get a really bad plan
explain (costs off) execute test_mode_pp(2);
-- but we can force a custom plan
set plan_cache_mode to force_custom_plan;
explain (costs off) execute test_mode_pp(2);
drop table test_mode;