Horton

RE: Slow catchup of 2PC (twophase) transactions on replica in LR

Zhijie Hou (Fujitsu) <houzj.fnst@fujitsu.com>

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From: "Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.com>
To: "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>, 'Amit Kapila' <amit.kapila16@gmail.com>
Cc: "pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>, Vitaly Davydov <v.davydov@postgrespro.ru>, Ajin Cherian <itsajin@gmail.com>
Date: 2024-07-17T00:58:51Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Fix random failure in 021_twophase.

  2. Allow altering of two_phase option of a SUBSCRIPTION.

  3. Doc: use true|false rather than on|off for "failover" option

  4. Support an optional asynchronous commit mode, in which we don't flush WAL

On Tuesday, July 16, 2024 1:17 PM Kuroda, Hayato/黒田 隼人 <kuroda.hayato@fujitsu.com> wrote
> 
> Dear Amit, Hou,
> 
> Thanks for giving comments! PSA new versions.
> What's new:
> 
> 0001: included Hou's patch [1] not to overwrite slot options.
>       Some other comments were also addressed.

Thanks for the patch!

One more issue I found is that:

+IsTwoPhaseTransactionGidForSubid(Oid subid, char *gid)
+{
+	int			ret;
+	Oid			subid_written;
+	TransactionId xid;
+
+	ret = sscanf(gid, "pg_gid_%u_%u", &subid_written, &xid);
+
+	return (ret == 2 && subid == subid_written);

I think it's not correct to use sscanf here, because it will return the same value
even if the gid is "pg_gid_123_123_123_123..." which isn't a
gid created by the apply worker. I think we should use TwoPhaseTransactionGid
to build the gid string and compare it with each existing gid(strcmp).

Best Regards,
Hou zj