Στις 27/11/23 16:51, ο/η CG έγραψε:
On Wednesday, November 22, 2023 at 12:38:54 PM EST, Achilleas Mantzios
<a.mantz...@cloud.gatewaynet.com> wrote:
Στις 22/11/23 15:14, ο/η CG έγραψε:
On Wednesday, November 22, 2023 at 01:20:18 AM EST, Achilleas Mantzios
<a.mantz...@cloud.gatewaynet.com>
<mailto:a.mantz...@cloud.gatewaynet.com> wrote:
Στις 21/11/23 20:41, ο/η CG έγραψε:
I have a very large PostgreSQL 9.5 database that still has very large
tables with oids. I'm trying to get rid of the oids with as little
downtime as possible so I can prep the database for upgrade past
PostgreSQL 11. I had a wild idea to mod pg_repack to write a new table
without oids. I think it almost works.
To test out my idea I made a new table wipe_oid_test with oids. I
filled it with a few rows of data.
........
But PostgreSQL still thinks that the table has oids:
mydata=# \d+ wipe_oid_test
Table "public.wipe_oid_test"
Column | Type | Modifiers | Storage | Stats target | Description
--------+------+-----------+----------+--------------+-------------
k | text | not null | extended | |
v | text | | extended | |
Indexes:
"wipe_oid_test_pkey" PRIMARY KEY, btree (k)
Has OIDs: yes
Except where does it mention in the pg_repack docs (or source) that it
is meant to be used for NO OIDS conversion ?
It does not-- I was trying to leverage and tweak the base
functionality of pg_repack which sets up triggers and migrates data. I
figured if the target table was created without OIDs that when
pg_repack did the "swap" operation that the new table would take over
with the added bonus of not having oids.
I can modify pg_class and set relhasoids = false, but it isn't
actually eliminating the oid column. `\d+` will report not report
that it has oids, but the oid column is still present and returns the
same result before updating pg_class.
Just Dont!
Noted. ;)
So I'm definitely missing something. I really need a point in the
right direction.... Please help! ;)
There are a few of methods to get rid of OIDs :
- ALTER TABLE .. SET WITHOUT OIDS (just mentioning, you already
checked that)
This makes the database unusable for hours and hours and hours because
it locks the table entirely while it performs the operation. That's
just something that we can't afford.
- Use table copy + use of a trigger to log changes :
https://dba.stackexchange.com/questions/259359/eliminating-oids-while-upgrading-postgresql-from-9-4-to-12
<https://dba.stackexchange.com/questions/259359/eliminating-oids-while-upgrading-postgresql-from-9-4-to-12>
That SO is not quite the effect I'm going for. The poster of that SO
was using OIDS in their application and needed a solution to maintain
those values after conversion. I simply want to eliminate them without
the extraordinary downtime the database would experience during ALTER
operations.
Sorry I meant this one : Stripping OIDs from tables in preparation for
pg_upgrade
<https://dba.stackexchange.com/questions/286453/stripping-oids-from-tables-in-preparation-for-pg-upgrade>
Stripping OIDs from tables in preparation for pg_upgrade
I have a postgres database in RDS, file size approaching 1TB. We
started in 2005, using ruby/activerecord/rails...
<https://dba.stackexchange.com/questions/286453/stripping-oids-from-tables-in-preparation-for-pg-upgrade>
This is the same idea as the percona ETL strategy, and essentially 90%
of what pg_repack already does (creates new tables, sets up triggers,
locks the tables, and swaps new for old at the end of the process)
- Use of Inheritance (the most neat solution I have seen, this is
what I used for a 2TB table conversion) :
https://www.percona.com/blog/performing-etl-using-inheritance-in-postgresql/
<https://www.percona.com/blog/performing-etl-using-inheritance-in-postgresql/>
This is closest to the effect I was going for. pg_repack essentially
creates a second table and fills it with the data from the first
table while ensuring standard db operations against that table
continue to function while the data is being moved from the old table
to the new table. The process outlined in the Percona ETL strategy
has to be repeated per-table, which is work I was hoping to avoid by
leveraging 95% of the functionality of pg_repack while supplying my
own 5% as the resulting table would not have oids regardless of the
source table's configuration.
For my experiment, Table A did have oids. Table B (created by
pg_repack) did not (at least at creation). When the "swap" operation
happened in pg_repack, the metadata for Table A was assigned to Table
B. I'm just trying to figure out what metadata I need to change in
the system tables to reflect the actual table structure.
I have the fallback position for the Percona ETL strategy. But I feel
like I'm REALLY close with pg_repack and I just don't understand
enough about the system internals to nudge it to correctness and need
some expert assistance to tap it in the hole.
Why don't just inspect the code pg_repack ?
I have, and I have modified pg_repack (modification was shown in my
first post) to create and write to a new table without oids, the
problem is when the "swap" operation happens the old tabledefs with
all the old oid baggage gets mapped on top of the new table that
doesn't have oids in it. I need to know what PostgreSQL is seeing in
the tabledefs that makes it think this new table, swapped out with the
old table, has oids. My thought is if I correct those values in
pg_class and elsewhere, the tabledefs will match what is actually on
the filesystem after my modified pg_repack has finished processing the
tables.
Hi, I think pg_repack eventually calls :
src/backend/access/heap/heapam.c : heap_update , and this just makes
sure all cols of both old and new pg_class have same vals.
That's why, the new table ends up with hasoids = true.
CG
--
Achilleas Mantzios
IT DEV - HEAD
IT DEPT
Dynacom Tankers Mgmt
--
Achilleas Mantzios
IT DEV - HEAD
IT DEPT
Dynacom Tankers Mgmt
--
Achilleas Mantzios
IT DEV - HEAD
IT DEPT
Dynacom Tankers Mgmt
