I tried it out. It did not make any difference.
On 01.10.2013 23:30, Alejandro Brust wrote:
Did U perform any vacuumdb / reindexdb before the Pg_dump?
El 01/10/2013 09:49, Magnus Hagander escribió:
On Tue, Oct 1, 2013 at 11:07 AM, Sergey Klochkov <kloch...@iqbuzz.ru> wrote:
Hello All,
While trying to backup a database of relatively modest size (160 Gb) I ran
into the following issue:
When I run
$ pg_dump -f /path/to/mydb.dmp -C -Z 9 mydb
File /path/to/mydb.dmp does not appear (yes, I've checked permissions and so
on). pg_dump just begins to consume memory until it eats up all avaliable
RAM (96 Gb total on server, >64 Gb available) and is killed by the oom
killer.
According to pg_stat_activity, pg_dump runs the following query
SELECT oid, (SELECT rolname FROM pg_catalog.pg_roles WHERE oid = lomowner)
AS rolname, lomacl FROM pg_largeobject_metadata
until it is killed.
strace shows that pg_dump is constantly reading a large amount of data from
a UNIX socket. I suspect that it is the result of the above query.
There are >300000000 large objects in the database. Please don't ask me why.
I tried googling on this, and found mentions of pg_dump being killed by oom
killer, but I failed to find anything related to the huge large objects
number.
Is there any method of working around this issue?
I think this problem comes from the fact that pg_dump treats each
large object as it's own item. See getBlobs() which allocates a
BlobInfo struct for each LO (and a DumpableObject if there are any,
but that's just one).
I assume the query (from that file):
SELECT oid, lomacl FROM pg_largeobject_metadata
returns 300000000 rows, which are then looped over?
I ran into a similar issue a few years ago with a client using a
32-bit version of pg_dump, and got it worked around by moving to
64-bit. Did unfortunately not have time to look at the underlying
issue.
--
Sergey Klochkov
kloch...@iqbuzz.ru
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