From: Tom Lane <tgl@sss.pgh.pa.us>
To: Peter Geoghegan <pg@bowt.ie>
Cc: pgsql-committers@lists.postgresql.org
Subject: Re: pgsql: Add deduplication to nbtree.
Date: Sun, 01 Mar 2020 13:24:55 -0500
Message-ID: <27003.1583087095@sss.pgh.pa.us> (raw)
In-Reply-To: <E1j73sn-0003FQ-KO@gemulon.postgresql.org>
References: <E1j73sn-0003FQ-KO@gemulon.postgresql.org>
Peter Geoghegan <pg@bowt.ie> writes:
> Add deduplication to nbtree.
Coverity isn't very happy with the coding in _bt_update_posting():
*** CID 1460433: Memory - corruptions (ARRAY_VS_SINGLETON)
/srv/coverity/git/pgsql-git/postgresql/src/backend/access/nbtree/nbtdedup.c: 723 in _bt_update_posting()
717 {
718 if (d < vacposting->ndeletedtids && vacposting->deletetids[d] == i)
719 {
720 d++;
721 continue;
722 }
>>> CID 1460433: Memory - corruptions (ARRAY_VS_SINGLETON)
>>> Using "htids" as an array. This might corrupt or misinterpret adjacent memory locations.
723 htids[ui++] = *BTreeTupleGetPostingN(origtuple, i);
724 }
725 Assert(ui == nhtids);
726 Assert(d == vacposting->ndeletedtids);
727 Assert(nhtids == 1 || _bt_posting_valid(itup));
I can see its point: asserting after the fact that you didn't clobber
memory isn't a terribly safe coding method, especially in a production
build where you won't even have the asserts. Not sure if there's a
better way though.
regards, tom lane
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To: pgsql-committers@postgresql.org
Cc: tgl@sss.pgh.pa.us, pg@bowt.ie, pgsql-committers@lists.postgresql.org
Subject: Re: pgsql: Add deduplication to nbtree.
In-Reply-To: <27003.1583087095@sss.pgh.pa.us>
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