| From: | Andreas Karlsson <andreas(at)proxel(dot)se> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Andrew Gierth <andrew(at)tao11(dot)riddles(dot)org(dot)uk> |
| Cc: | David Fetter <david(at)fetter(dot)org>, Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Early WIP/PoC for inlining CTEs |
| Date: | 2019-01-27 17:24:21 |
| Message-ID: | 88d21b0d-4c5c-df4c-c94f-9fabcdd03906@proxel.se |
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| Lists: | pgsql-hackers |
On 1/27/19 4:21 PM, Tom Lane wrote:
> Andrew Gierth <andrew(at)tao11(dot)riddles(dot)org(dot)uk> writes:
>> I'm not sure we should nail down the rule that the absence of NOT
>> MATERIALIZED will mean a multiply-referenced CTE is evaluated once. One
>> would hope that in the future the planner might be taught to inline or
>> not in that case depending on cost. I think it makes more sense to say
>> that we never inline if MATERIALIZED is specified, that we always inline
>> if NOT MATERIALIZED is specified, and that if neither is specified the
>> planner will choose (but perhaps note that currently it always chooses
>> only based on refcount).
>
> I have no objection to documenting it like that; I just don't want us
> to go off into the weeds trying to actually implement something smarter
> for v12.
+1
Andreas
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