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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Alexander Korotkov <aekorotkov@gmail.com>
Cc: Alena Rybakina <a.rybakina@postgrespro.ru>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Cc: Andrei Lepikhov <lepihov@gmail.com>
Cc: Robert Haas <robertmhaas@gmail.com>
Cc: Richard Guo <guofenglinux@gmail.com>
Cc: Alexander Lakhin <exclusion@gmail.com>
Cc: Gregory Stark (as CFM) <stark.cfm@gmail.com>
Cc: Michał Kłeczek <michal@kleczek.org>
Cc: Dean Rasheed <dean.a.rasheed@gmail.com>
Subject: Re: Removing unneeded self joins
Date: Sun, 23 Feb 2025 12:02:49 -0500
Message-ID: <914330.1740330169@sss.pgh.pa.us> (raw)
In-Reply-To: <CAPpHfdseDr02BT+kFfW1ORWd0xnf9B=OUNmYkDxF2x-bE32UOw@mail.gmail.com>
References: <64486b0b-0404-e39e-322d-0801154901f3@postgrespro.ru>
	<2422119.1714691974@sss.pgh.pa.us>
	<CAPpHfdv6B8HCLdj8WidBryRrX0+X3F1rrR8uAuMQmp6rvPdscg@mail.gmail.com>
	<24e93efd-eeac-43a6-a75a-ad68eacb32ee@postgrespro.ru>
	<CA+TgmoZ66x=uWasH+O40a=G=fpbXN1ANEdGVunvR8BKuekqa2g@mail.gmail.com>
	<3622801.1715010885@sss.pgh.pa.us>
	<CAPpHfduRB9oW3YRDpvPGcDSAbH4iu0LSRhxpRRAzBh7euC9amQ@mail.gmail.com>
	<CAEZATCUeJ93gWCEzK1eRxyZakvv5PVG9LfF3PkSGMsNBC7h9kA@mail.gmail.com>
	<CAPpHfdsj1WdqoCg+g4oq1XQ_=KOj0U4pXqhauBc7e+0msHu66A@mail.gmail.com>
	<CAPpHfds16a7bjQHv-jCLMNzwdukJ_i3da2e0OJFB9L5rTCWEEg@mail.gmail.com>
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	<d6319b0c-b186-472f-8b64-41dfa4! 1e7b5f@postgrespro.ru>
	<CAPpHfdsFcde5VWCxSup7x_12ig6uynrFaOms62-M_c8DM-FTBQ@mail.gmail.com>
	<CAPpHfdseDr02BT+kFfW1ORWd0xnf9B=OUNmYkDxF2x-bE32UOw@mail.gmail.com>

Alexander Korotkov <aekorotkov@gmail.com> writes:
> I've corrected some spelling error reported by Alexander Lakhin
> privately to me.  Also, I've revised comments around ChangeVarNodes()
> and ChangeVarNodesExtended().  I'm going to continue nitpicking this
> patch during next couple days then push it if no objections.

Coverity has another nit-pick:

/srv/coverity/git/pgsql-git/postgresql/src/backend/optimizer/plan/analyzejoins.c: 327 in remove_rel_from_query()
321     static void
322     remove_rel_from_query(PlannerInfo *root, RelOptInfo *rel,
323     					  int subst, SpecialJoinInfo *sjinfo,
324     					  Relids joinrelids)
325     {
326     	int			relid = rel->relid;
>>>     CID 1643155:  Integer handling issues  (INTEGER_OVERFLOW)
>>>     Expression "ojrelid", which is equal to 4294967295, where "(sjinfo != NULL) ? sjinfo->ojrelid : 4294967295U" is known to be equal to 4294967295, overflows the type that receives it, a signed integer 32 bits wide.
327     	int			ojrelid = (sjinfo != NULL) ? sjinfo->ojrelid : -1;
328     	Index		rti;
329     	ListCell   *l;
330     
331     	/*
332     	 * Update all_baserels and related relid sets.

This is unhappy because sjinfo->ojrelid, which is declared Index
(that is, unsigned int) is being converted to int.  Admittedly
there are plenty of other places that do likewise, but the additional
load of assuming that -1 isn't a possible value of sjinfo->ojrelid
seems to be enough to draw its ire.

I suggest finding another way to code this function that doesn't
depend on that type pun.  I think it's fairly accidental that
adjust_relid_set doesn't misbehave on -1 anyway, so personally I'd
get rid of that local variable entirely in favor of something like

    if (sjinfo != NULL)
    {
        root->outer_join_rels = adjust_relid_set(root->outer_join_rels,
                                                 sjinfo->ojrelid, subst);
        root->all_query_rels = adjust_relid_set(root->all_query_rels,
                                                sjinfo->ojrelid, subst);
    }

			regards, tom lane





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  Cc: tgl@sss.pgh.pa.us, aekorotkov@gmail.com, a.rybakina@postgrespro.ru, pgsql-hackers@lists.postgresql.org, lepihov@gmail.com, robertmhaas@gmail.com, guofenglinux@gmail.com, exclusion@gmail.com, stark.cfm@gmail.com, michal@kleczek.org, dean.a.rasheed@gmail.com
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