From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: jian he <jian.universality@gmail.com>
Cc: Pg Hackers <pgsql-hackers@lists.postgresql.org>
Cc: Tender Wang <tndrwang@gmail.com>
Subject: Re: not null constraints, again
Date: Sat, 9 Nov 2024 13:29:12 +0100
Message-ID: <202411091229.k6wy32lley63@alvherre.pgsql> (raw)
In-Reply-To: <3649828.1731083171@sss.pgh.pa.us>
On 2024-Nov-08, Tom Lane wrote:
> Alvaro Herrera <alvherre@alvh.no-ip.org> writes:
> > But we'll see what else the buildfarm has to say now that I pushed it ...
>
> A lot of the buildfarm is saying
>
> adder | 2024-11-08 13:04:39 | ../pgsql/src/backend/catalog/pg_constraint.c:708:37: warning: comparison is always true due to limited range of data type [-Wtype-limits]
>
> which evidently is about this:
>
> Assert(colnum > 0 && colnum <= MaxAttrNumber);
Hah.
> The memcpy right before that doesn't seem like project style either.
> Most other places that are doing similar things just cast the
> ARR_DATA_PTR to the right pointer type and dereference it.
Hmm, yeah, that's easily removed,
inline patch 1: src/backend/catalog/pg_constraint.c (+1/-5 lines) download inline-1.patchdiff --git a/src/backend/catalog/pg_constraint.c b/src/backend/catalog/pg_constraint.cindex e953000c01d..043bf7c24dd 100644--- a/src/backend/catalog/pg_constraint.c+++ b/src/backend/catalog/pg_constraint.c@@ -704,11 +704,7 @@ extractNotNullColumn(HeapTuple constrTup)
ARR_DIMS(arr)[0] != 1)
elog(ERROR, "conkey is not a 1-D smallint array");
- memcpy(&colnum, ARR_DATA_PTR(arr), sizeof(AttrNumber));- Assert(colnum > 0 && colnum <= MaxAttrNumber);-- if ((Pointer) arr != DatumGetPointer(adatum))- pfree(arr); /* free de-toasted copy, if any */+ colnum = ((AttrNumber *) ARR_DATA_PTR(arr))[0];
return colnum;
}
I notice I cargo-culted a "free de-toasted copy", but I think it's
impossible to end up with a toasted datum here, because the column is
guaranteed to have only one element, so not a candidate for toasting.
But also, if we don't free it (in case somebody does an UPDATE to the
catalog with a large array), nothing happens, because memory is going to
be released soon anyway, by the error that results by conkey not being
one element long.
--
Álvaro Herrera 48°01'N 7°57'E — https://www.EnterpriseDB.com/
"Si quieres ser creativo, aprende el arte de perder el tiempo"
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Cc: alvherre@alvh.no-ip.org, tgl@sss.pgh.pa.us, jian.universality@gmail.com, pgsql-hackers@lists.postgresql.org, tndrwang@gmail.com
Subject: Re: not null constraints, again
In-Reply-To: <202411091229.k6wy32lley63@alvherre.pgsql>
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