Re: Early WIP/PoC for inlining CTEs

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Andres Freund <andres(at)anarazel(dot)de>
Cc: Jeremy Finzel <finzelj(at)gmail(dot)com>, Andrew Gierth <andrew(at)tao11(dot)riddles(dot)org(dot)uk>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Early WIP/PoC for inlining CTEs
Date: 2018-07-24 23:57:49
Message-ID: 21958.1532476669@sss.pgh.pa.us
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Andres Freund <andres(at)anarazel(dot)de> writes:
> On 2018-07-24 19:49:19 -0400, Tom Lane wrote:
>> However, a singly-referenced SELECT CTE could reasonably be treated as
>> equivalent to a sub-select-in-FROM, and then you would have the same
>> mechanisms for preventing inlining as you do for those cases,
>> e.g. OFFSET 0. And sticking in OFFSET 0 would be backwards-compatible
>> too: your code would still work the same in older releases, unlike if
>> we invent new syntax for this.

> I still think this is just doubling down on prior mistakes.

Not following what you think a better alternative is? I'd be the
first to agree that OFFSET 0 is a hack, but people are used to it.

Assuming that we go for inline-by-default for at least some cases,
there's a separate discussion to be had about whether it's worth
making a planner-control GUC to force the old behavior. I'm not
very excited about that, but I bet some people will be.

regards, tom lane

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