| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
| Cc: | Andrew Dunstan <andrew(dot)dunstan(at)2ndquadrant(dot)com>, "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com>, Serge Rielau <serge(at)rielau(dot)com>, Gavin Flower <GavinFlower(at)archidevsys(dot)co(dot)nz>, Craig Ringer <craig(dot)ringer(at)2ndquadrant(dot)com>, Ilya Shkuratov <motr(dot)ilya(at)ya(dot)ru>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>, Mario Becroft <mb(at)true(dot)group> |
| Subject: | Re: CTE inlining |
| Date: | 2017-05-04 18:37:46 |
| Message-ID: | 23652.1493923066@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> writes:
> I'm not sure what your point is. We know that for some cases the
> optimization barrier semantics are useful, which is why the proposal is
> to add a keyword to install one explicitely:
> with materialized r as
> (
> select json_populate_record(null::mytype, myjson) as x
> from mytable
> )
> select (x).*
> from r;
> this would preserve the current semantics.
Uh, no, it wouldn't, until you had changed your query (and made it
non-SQL-compliant, and unable to work at all on pre-v11 PG).
This might be a good design, but surely it does not provide backwards
compatibility.
regards, tom lane
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