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Re: RIGHT/FULL OUTER hash joins (was Re: small table left outer join big table)

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Jie Li <jay23jack(at)gmail(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: RIGHT/FULL OUTER hash joins (was Re: small table left outer join big table)
Date: 2010-12-30 16:35:05
Message-ID: 18600.1293726905@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Thu, Dec 30, 2010 at 10:45 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> ... But we only need one bit, so what about commandeering
>> an infomask bit in the tuple itself? For the initial implementation
>> I'd be inclined to take one of the free bits in t_infomask2. We could
>> actually get away with overlaying the flag bit with one of the tuple
>> visibility bits, since it will only be used in tuples that are in the
>> in-memory hash table, which don't need visibility info anymore. But
>> that seems like a kluge that could wait until we really need the flag
>> space.

> I think that's a reasonable approach, although I might be inclined to
> do the overlay sooner rather than later if it doesn't add too much
> complexity.

Well, there's no "complexity" involved, it's just which bit do we define
the macro as.  Any complexity is conceptual.

			regards, tom lane

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