Re: Upgrade from PG12 to PG

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It does a "--schema-only" dump.  The gianter the schema, the longer that "pg_dump --schema-only" takes.

Note also that there's a known issue with pg_upgrade and millions of Large Objects (not bytea or text, but lo_* columns).

On 7/20/23 12:05, Jef Mortelle wrote:
running /usr/lib/postgresql15/bin/pg_upgrade -v -p 5431 -P 5432 -k

gives you in the output :

"/usr/lib/postgresql15/bin/pg_dump" --host /pg/PG15 --port 5431 --username postgres --schema-only --quote-all-identifiers --binary-upgrade --format=custom --verbose --file="/pg/PG15/system/pg_upgrade_output.d/20230720T184333.610/dump/pg_upgrade_dump_16385.custom" 'dbname=dbname' >> "/pg/PG15/system/pg_upgrade_output.d/20230720T184333.610/log/pg_upgrade_dump_16385.log" 2>&1

so, yes pg_ugrade start a pg_dump session,

even a pg_restore at the end, runs about 7 hours

"/usr/lib/postgresql15/bin/pg_restore" --host /pg/PG15 --port 5432 --username postgres --create --exit-on-error --verbose --dbname template1 "/pg/PG15/system/pg_upgrade_output.d/20230720T184333.610/dump/pg_upgrade_dump_16385.custom" >> "/pg/PG15/system/pg_upgrade_output.d/20230720T184333.610/log/pg_upgrade_dump_16385.log" 2>&1

with a lot of lines in the logfiles  like:  pg_restore: executing BLOB 11108809

Server is a VM server, my VM has 64GB SuseSLES  attached to a SAN with SSD disk (Hp3Par)


lovacum -n =>  I have vacuumlo, running this:

vacuumlo  dbname  -v

postgres@dbfluxd02:/pg/data> vacuumlo  dflux -v
Connected to database "dflux"
Checking message_oid in fluxnaf.flux_message_content
Checking payload_oid in fluxnaf.bridge_payload_content
Successfully removed 0 large objects from database "dflux".

and again same issues

On 20/07/2023 16:51, Scott Ribe wrote:
On Jul 20, 2023, at 7:46 AM, Jef Mortelle <jefmortelle@xxxxxxxxx> wrote:

So: not possible to have very little downtime if you have a database with al lot rows containing text  as datatype, as pg_upgrade needs 12hr for 24 milj rows in pg_largeobject.
We need to get terminology straight, as at the moment your posts are very confusing. In PostgreSQL large objects and text are not the same. Text is basically varchar without a specified length limit. Large object is a blob (but not what SQL calls a BLOB)--it is kind of like a file stored outside the normal table mechanism, and provides facilities for partial reads, etc: There are a number of ways to wind up with references to large objects all deleted, but the orphaned large objects still in the database.

First thing you should do: run lovacuum -n to find out if you have orphaned large objects. If so, start cleaning those up, then see how long pg_upgrade takes.

Second, what's your hardware? I really don't see dump & restore of a 1TB database taking 6 hours.

Alsready tried to use --link and --jobs, but you cannot ommit the "select  lo_unlink ...."   for every rows containing datatype text in your database that the pg_* program creates in the export/dump file.
Terminology again, or are you conflating two different issues? pg_upgrade --link does not create a dump file.

Born in Arizona, moved to Babylonia.

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