From: | Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us> |
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To: | vadim(at)sable(dot)krasnoyarsk(dot)su (Vadim B(dot) Mikheev) |
Cc: | herouth(at)oumail(dot)openu(dot)ac(dot)il, hackers(at)postgreSQL(dot)org (PostgreSQL-development) |
Subject: | Re: [QUESTIONS] How fully will subselects be implemented? |
Date: | 1998-02-25 14:28:10 |
Message-ID: | 199802251428.JAA01718@candle.pha.pa.us |
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Lists: | pgsql-hackers |
>
> First, this list is not right place to ask about 6.3 features :)
> 2nd, subselects within UPDATE are supported.
They are? I thought he wanted to do:
update test set x = (select y from taby)
I didn't think we supported that. Can you confirm that?
> 3rd, there will be separate select (better say - separate re-scan of
> subquery' plan) for each parent row (I assume that you talk about
> correlated subqueries) but this will be more efficient than using
> SQL-funcs which do _initialization_, scannig, _closing_ of query' plan
> for each parent row. When using subqueries performance will be
> near the same as for performing Nestloop join.
Good.
--
Bruce Momjian | 830 Blythe Avenue
maillist(at)candle(dot)pha(dot)pa(dot)us | Drexel Hill, Pennsylvania 19026
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