| From: | Petr Jelinek <petr(dot)jelinek(at)2ndquadrant(dot)com> |
|---|---|
| To: | Craig Ringer <craig(at)2ndquadrant(dot)com>, sanyam jain <sanyamjain22(at)live(dot)in> |
| Cc: | Pg Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Use of snapshot in logical replication |
| Date: | 2017-06-08 01:14:55 |
| Message-ID: | 24974dc4-8b1a-024a-cc6d-f628687ff9d9@2ndquadrant.com |
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| Lists: | pgsql-hackers |
On 08/06/17 03:08, Craig Ringer wrote:
> On 7 June 2017 at 18:16, sanyam jain <sanyamjain22(at)live(dot)in> wrote:
>> Hi,
>>
>> Can someone explain the usage of exporting snapshot when a logical
>> replication slot is created?
>
> It's used to pg_dump the schema at a consistent point in history where
> all xacts are known to be in the snapshot (and thus dumped) or known
> not to be (so they'll be streamed out on the slot).
>
Not just schema, it can also be used to get existing data at consistent
point in history so that changes will follow without gaps or duplicates.
That being said, the built-in logical replication isn't using the
exported snapshots at all.
--
Petr Jelinek http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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