| From: | Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at> |
|---|---|
| To: | Radoslav Nedyalkov <rnedyalkov(at)gmail(dot)com>, pgsql-general <pgsql-general(at)postgresql(dot)org> |
| Subject: | Re: logical replication initial copy and WAL generation |
| Date: | 2021-05-19 12:56:36 |
| Message-ID: | 2281ae132dfaca6932f69a9faddf893f16287683.camel@cybertec.at |
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| Lists: | pgsql-general |
On Wed, 2021-05-19 at 14:16 +0300, Radoslav Nedyalkov wrote:
> Hello Forum,
> I know it sounds weird but we have faced it a couple of times already and have no idea.
> We're trying to establish logical replication from RDS(10.9) to RDS(12.5).
> We're adding tables to the publication one by one.
> During the initial copy for some tables we experience huge WAL generation on the source db.
> From 0.5mb/s it jumps to 15MB/s.
> This happens when a copy just started or in the middle or at the end.
> WAL generation causes service statements to wait on WALWriteLock causing high response time.
>
> Any idea how the initial copy can cause WAL generation ?!
I don't know how much RDS is like PostgreSQL, but on PostgreSQL this could be
the setting of hint bits for new rows that have never been read before.
Yours,
Laurenz Albe
--
Cybertec | https://www.cybertec-postgresql.com
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