Re: [BUG] Logical replication failure "ERROR: could not map filenode "base/13237/442428" to relation OID" with catalog modifying txns

On Mon, Jul 25, 2022 at 7:57 PM shiy(dot)fnst(at)fujitsu(dot)com
<shiy(dot)fnst(at)fujitsu(dot)com> wrote:
>
> Hi,
>
> I did some performance test for the master branch patch (based on v6 patch) to
> see if the bsearch() added by this patch will cause any overhead.

Thank you for doing performance tests!

>
> I tested them three times and took the average.
>
> The results are as follows, and attach the bar chart.
>
> case 1
> ---------
> No catalog modifying transaction.
> Decode 800k pgbench transactions. (8 clients, 100k transactions per client)
>
> master 7.5417
> patched 7.4107
>
> case 2
> ---------
> There's one catalog modifying transaction.
> Decode 100k/500k/1M transactions.
>
> 100k 500k 1M
> master 0.0576 0.1491 0.4346
> patched 0.0586 0.1500 0.4344
>
> case 3
> ---------
> There are 64 catalog modifying transactions.
> Decode 100k/500k/1M transactions.
>
> 100k 500k 1M
> master 0.0600 0.1666 0.4876
> patched 0.0620 0.1653 0.4795
>
> (Because the result of case 3 shows that there is a overhead of about 3% in the
> case decoding 100k transactions with 64 catalog modifying transactions, I
> tested the next run of 100k xacts with or without catalog modifying
> transactions, to see if it affects subsequent decoding.)
>
> case 4.1
> ---------
> After the test steps in case 3 (64 catalog modifying transactions, decode 100k
> transactions), run 100k xacts and then decode.
>
> master 0.3699
> patched 0.3701
>
> case 4.2
> ---------
> After the test steps in case 3 (64 catalog modifying transactions, decode 100k
> transactions), run 64 DDLs(without checkpoint) and 100k xacts, then decode.
>
> master 0.3687
> patched 0.3696
>
> Summary of the tests:
> After applying this patch, there is a overhead of about 3% in the case decoding
> 100k transactions with 64 catalog modifying transactions. This is an extreme
> case, so maybe it's okay.

Yes. If we're worried about the overhead and doing bsearch() is the
cause, probably we can try simplehash instead of the array.

An improvement idea is that we pass the parsed->xinfo down to
SnapBuildXidHasCatalogChanges(), and then return from that function
before doing bearch() if the parsed->xinfo doesn't have
XACT_XINFO_HAS_INVALS. That would save calling bsearch() for
non-catalog-modifying transactions. Is it worth trying?

Regards,

--
Masahiko Sawada
EDB: https://www.enterprisedb.com/