Re: ENABLE ROW LEVEL SECURITY cause huge produce of checkpoints

Hello,

thanks for reply, I investigated this and thanks to pg_xlog_dump i found:
/usr/pgsql-9.5/bin/pg_xlogdump 00000001000008700000007C
00000001000008700000007D | head -1
rmgr: Heap len (rec/tot): 7/ 53, tx: 284003096, lsn:
870/7C000030, prev 870/7BFFFFD0, desc: LOCK off 2: xid 284003096 LOCK_ONLY
EXCL_LOCK KEYS_UPDATED , blkref #0: rel 1663/16404/191292060 blk 15561

whole xlog file contains only this rows - its on table with enabled RLS
/usr/pgsql-9.5/bin/pg_xlogdump --stats=record 00000001000008700000007C
00000001000008700000007C
Type N (%) Record
size (%) FPI size (%) Combined size (%)
---- - ---
----------- --- -------- --- -------------
---
Transaction/COMMIT 5 ( 0.00)
160 ( 0.00) 0 ( 0.00) 160 ( 0.00)
Heap/INSERT 5 ( 0.00)
135 ( 0.00) 0 ( 0.00) 135 ( 0.00)
Heap/LOCK 298674 ( 99.99)
9258894 ( 99.99) 0 ( 0.00) 9258894
( 99.99)
Btree/INSERT_LEAF 20 ( 0.01)
520 ( 0.01) 0 ( 0.00) 520 ( 0.01)
Sequence/LOG 1 ( 0.00)
182 ( 0.00) 0 ( 0.00) 182 ( 0.00)
--------
-------- -------- --------
Total 298705

And thanks to xid i found transaction with
SELECT
/*lot joins*/
FOR UPDATE
there missed OF table name clause, but this not help much..., so i found i
made wrong POLICY on table ... something like:
CREATE POLICY some_policy ON projects FOR ALL TO role_name USING
(pg_has_role("current_user"(), 'some_role'::name, 'member'::text));
and made some subrole that have access without grant permisions to other
tables but better solution was create new role and grant access right and
in policy use true instead expression for role that have access to all
rows.
CREATE POLICY some_policy ON projects FOR ALL TO role_name USING (True);

So it was only bad idea, bad design.

Thanks not need solve this..., now not produce extra WAL records.

David

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Od: Michael Paquier <michael(dot)paquier(at)gmail(dot)com>
Komu: david(dot)turon(at)linuxbox(dot)cz
Kopie: PostgreSQL mailing lists <pgsql-general(at)postgresql(dot)org>
Datum: 09.11.2016 07:10
Předmět: Re: [GENERAL] ENABLE ROW LEVEL SECURITY cause huge produce of
checkpoints

On Wed, Nov 2, 2016 at 12:09 AM, <david(dot)turon(at)linuxbox(dot)cz> wrote:
> we tried new feature RLS - tested on postgres 9.5.3 / CentOS6. When we
turn
> on ENABLE RLS + FORCE RLS on normal workload cause huge produce
checkpoints
> (about 30x or more), our disk partition for xlog was full and log
shipping
> to replica maybe delayed removing old checkpoints. Have anybody same
> experiences after turn on RLS? Looks like more buffers set as dirty.
Yes,
> we can provide more space for xlog, but it will take much more space for
> xlog backups. We do not know if it's worth it. We had log_checkpoints ON
and
> I send log as attachment (RLS Turn ON at 13:26).

Interesting, I don't recall RLS generating a burst in activity. The
first heavier checkpoints happen 20 minutes after enabling RLS and
those are triggered by time. Then things cool down and 1 hour later
comes the real deal with a set of checkpoints triggered by volume. It
is difficult though to draw a conclusion without more idea about your
load, the WAL record generated, etc.
--
Michael