From: | Arseny Sher <a(dot)sher(at)postgrespro(dot)ru> |
---|---|
To: | Masahiko Sawada <masahiko(dot)sawada(at)2ndquadrant(dot)com> |
Cc: | PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> |
Subject: | Re: logical copy_replication_slot issues |
Date: | 2020-03-09 12:46:39 |
Message-ID: | 87h7yx7l1s.fsf@ars-thinkpad |
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Lists: | pgsql-hackers |
Masahiko Sawada <masahiko(dot)sawada(at)2ndquadrant(dot)com> writes:
> /*
> - * Create logical decoding context, to build the initial snapshot.
> + * Create logical decoding context to find start point or, if we don't
> + * need it, to 1) bump slot's restart_lsn and xmin 2) check plugin sanity.
> */
>
> Do we need to numbering that despite not referring them?
No, it just seemed clearer to me this way. I don't mind removing the
numbers if you feel this is better.
> ctx = CreateInitDecodingContext(plugin, NIL,
> - false, /* do not build snapshot */
> + false, /* do not build data snapshot */
> restart_lsn,
> logical_read_local_xlog_page, NULL, NULL,
> NULL);
> I'm not sure this change makes the comment better. Could you elaborate
> on the motivation of this change?
Well, DecodingContextFindStartpoint always builds a snapshot allowing
historical *catalog* lookups. This bool controls whether the snapshot
should additionally be suitable for looking at the actual data, this is
e.g. used by initial data sync in the native logical replication.
-- cheers, arseny
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