Re: Patch for removng unused targets

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Etsuro Fujita" <fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp>
Cc: "'Alexander Korotkov'" <aekorotkov(at)gmail(dot)com>, "'pgsql-hackers'" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Patch for removng unused targets
Date: 2012-12-03 16:31:32
Message-ID: 14993.1354552292@sss.pgh.pa.us
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"Etsuro Fujita" <fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp> writes:
> Sorry for the delay. I've reviewed the patch. It was applied
> successfully, and it worked well for tests I did including the example
> you showed. I think it's worth the work, but I'm not sure you go
> about it in the right way. (I feel the patch decreases code
> readability more than it gives an advantage.)

One thought here is that I don't particularly like adding a field like
"resorderbyonly" to TargetEntry in the first place. That makes this
optimization the business of the parser, which it should not be; and
furthermore makes it incumbent on the rewriter, as well as anything else
that manipulates parsetrees, to maintain the flag correctly while
rearranging queries. It would be better if this were strictly the
business of the planner.

But having said that, I'm wondering (without having read the patch)
why you need anything more than the existing "resjunk" field.

regards, tom lane

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