Hi all,
I have a question.
I did the following.
Even though I accessed one partition table(test2 table), I also acquired locks on other partition tables(test1 table).
I expected to acquire locks on the parent table(test table) and the partition table to access(test2 table).
Why does this happen?
At the first execution, to create a generic plan, I thought it was accessing all partition tables.
However, the following event occur after second time too.
* Only occurs when plan_cache_mode = force_generic_plan.
postgres=# create table test(id int) partition by range (id);
CREATE TABLE
postgres=# create table test1 partition of test for values from (1) to (2);
CREATE TABLE
postgres=# create table test2 partition of test for values from (2) to (3);
CREATE TABLE
postgres=# prepare hoge(int) as select * from test where id = $1;
PREPARE
postgres=# set plan_cache_mode = force_generic_plan ;
SET
postgres=# begin;
BEGIN
postgres=# execute hoge(2);
id
----
(0 rows)
postgres=# SELECT l.pid,l.granted,d.datname,l.locktype,relation,relation::regclass,transactionid,l.mode FROM pg_locks l
LEFT JOIN pg_database d ON l.database = d.oid WHERE l.pid != pg_backend_pid() ORDER BY l.pid;
pid | granted | datname | locktype | relation | relation | transactionid | mode
-------+---------+----------+------------+----------+----------+---------------+-----------------
16921 | t | postgres | relation | 16562 | test2 | | AccessShareLock
16921 | t | postgres | relation | 16559 | test1 | | AccessShareLock
16921 | t | postgres | relation | 16556 | test | | AccessShareLock
16921 | t | | virtualxid | | | | ExclusiveLock
(4 rows)
Regards
Naoki Yotsunaga