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Date: Tue, 21 Jan 2025 09:56:49 -0800
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Subject: Re: Records count mismatch with logical replication
To: Durgamahesh Manne <maheshpostgres9@gmail.com>
Cc: pgsql-general <pgsql-general@lists.postgresql.org>
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From: Adrian Klaver <adrian.klaver@aklaver.com>
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On 1/21/25 09:38, Durgamahesh Manne wrote:
> 
> 

> 
> Hi Adrian Klaver
> 
> Really Thanks for your quick response
> 
> This happened during repack lag went to more than 350Gb then gradually 
> decreased to minimal lag after running pg_repack

I don't use pg_repack so I don't know what effect it would have on the 
process.
> 

> 3) Define how lag is being calculated and what 'minimal' is.
> 
> postgres=> select 
> slot_name,pg_wal_lsn_diff(pg_current_wal_lsn(),restart_lsn) as bytes_behind,
> pg_size_pretty(pg_wal_lsn_diff(pg_current_wal_lsn(), restart_lsn)) as 
> behind_size, active from pg_replication_slots;
>    slot_name  | bytes_behind | behind_size | active
> -------------+--------------+-------------+--------
>   cls_eva_msa |     22906216 | 22 MB       | t
> 
> 4) Define how the record counts are being derived.
>    Source : archiving=> select count(*) from archiving.events_archive ;
>    count
> ---------
>   1262908
> (1 row)
> 
> Destination : archiving=> select count(*) from archiving.events_archive ;
>    count
> ---------
>   1252062
> (1 row)

22,906,216 bytes/10,846 rows  works out to 2112 bytes per row.

Is that a reasonable per row estimate?

> 
> 5) The network distance between the servers.
> 
>   Both are under same vpc security groups
> 
> Regards
> Durga Mahesh

-- 
Adrian Klaver
adrian.klaver@aklaver.com