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Re: join removal

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Greg Stark <stark(at)mit(dot)edu>, "<pgsql-hackers(at)postgresql(dot)org>" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: join removal
Date: 2010-03-28 21:08:32
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Lists: pgsql-hackers
On Sun, Mar 28, 2010 at 4:12 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>> On Sun, Mar 28, 2010 at 2:10 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>>> joinremoval.c ?
>> Maybe, except as I mentioned in the email linked upthread, my plan for
>> implementing inner join removal would also include allowing join
>> reordering in cases where we currently don't.  So I don't want to
>> sandbox it too tightly as join removal, per se, though that's
>> certainly what we have on the table ATM.  It's more like advanced
>> open-heart join-tree surgery - like prepjointree, but much later in
>> the process.
> Hm.  At this point we're not really working with a join *tree* in any
> case --- the data structure we're mostly concerned with is the list of
> SpecialJoinInfo structs, and what we're trying to do is weaken the
> constraints described by that list.  So I'd rather stay away from "tree"
> terminology.
> planjoins.c would fit with other names in the plan/ directory but it
> seems like a misnomer because we're not really "planning" any joins
> at this stage.
> adjustjoins.c?  loosenjoins.c?  weakenjoins.c?

How about analyzejoins.c?  Loosen and weaken don't seem like quite the
right idea; adjust is a little generic and perhaps overused, but not
bad.  If you don't like analyzejoins then go with adjustjoins.


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