| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Andrew Gierth <andrew(at)tao11(dot)riddles(dot)org(dot)uk> |
| Cc: | Andreas Karlsson <andreas(at)proxel(dot)se>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Merlin Moncure <mmoncure(at)gmail(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, Michael Paquier <michael(at)paquier(dot)xyz>, Robert Haas <robertmhaas(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com>, David Fetter <david(at)fetter(dot)org>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Early WIP/PoC for inlining CTEs |
| Date: | 2019-04-09 19:50:49 |
| Message-ID: | 22900.1554839449@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
I wrote:
> Andrew Gierth <andrew(at)tao11(dot)riddles(dot)org(dot)uk> writes:
>> So what I think we need to do here is to forbid inlining if (a) the
>> refcount is greater than 1 and (b) the CTE in question contains,
>> recursively anywhere inside its rtable or the rtables of any of its
>> nested CTEs, a "self_reference" RTE.
> That's kind of "ugh" too: it sounds expensive, and doing it in a way
> that doesn't produce false positives would be even more complicated.
After further investigation, I concluded that that wasn't that awful,
so done that way.
I'm still not entirely convinced about the behavior for nested WITHs
with different materialization specifications, but that seems like
a separate topic.
regards, tom lane
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