From: Tom Lane <tgl@sss.pgh.pa.us>
To: Aleksander Alekseev <aleksander@tigerdata.com>
cc: pgsql-bugs@lists.postgresql.org, exclusion@gmail.com
Subject: Re: BUG #18984: Empty prepared statement from psql \parse triggers
 assert in PortalRunMulti
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References: <18984-0f4778a6599ac3ae@postgresql.org>
 <715434.1752521761@sss.pgh.pa.us>
 <CAJ7c6TOoGUosKwdXt1LwJpThvP2-ZNpuv0H=owYdp6omwQ=keA@mail.gmail.com>
Comments: In-reply-to Aleksander Alekseev <aleksander@tigerdata.com>
	message dated "Tue, 15 Jul 2025 00:11:31 +0300"
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Date: Mon, 14 Jul 2025 17:40:22 -0400
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Aleksander Alekseev <aleksander@tigerdata.com> writes:
>> That being the case, maybe we should band-aid this by returning
>> EXECUTE if the prepared statement is empty.

> This sounds pretty straightforward and seems to solve the problem.
> Patch attached.

Hmm, throwing an error is exactly not what I was suggesting above.
The attached quick draft (needs attention to comments) results in

regression=# \parse s

regression=# execute s;
EXECUTE

which matches the behavior of pre-v12 servers.

(BTW, I wonder why psql is emitting an extra newline after \parse.)

			regards, tom lane


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diff --git a/src/backend/tcop/pquery.c b/src/backend/tcop/pquery.c
index d1593f38b35..2d998e87846 100644
--- a/src/backend/tcop/pquery.c
+++ b/src/backend/tcop/pquery.c
@@ -1365,8 +1365,8 @@ PortalRunMulti(Portal portal,
 	{
 		if (portal->qc.commandTag != CMDTAG_UNKNOWN)
 			CopyQueryCompletion(qc, &portal->qc);
-		/* If the caller supplied a qc, we should have set it by now. */
-		Assert(qc->commandTag != CMDTAG_UNKNOWN);
+		else
+			qc->commandTag = CMDTAG_EXECUTE;
 	}
 }
 

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