Skip site navigation (1) Skip section navigation (2)

Re: [QUESTIONS] How fully will subselects be implemented?

From: Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us>
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 (view raw or flat)
Thread:
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
  +  If your life is a hard drive,     |  (610) 353-9879(w)
  +  Christ can be your backup.        |  (610) 853-3000(h)

Responses

pgsql-hackers by date

Next:From: Jan WieckDate: 1998-02-25 14:28:26
Subject: Re: [HACKERS] Re: [PATCHES] pg_shadow
Previous:From: Bruce MomjianDate: 1998-02-25 14:24:13
Subject: Re: [HACKERS] Cannot compile postgresql 6.3

Privacy Policy | About PostgreSQL
Copyright © 1996-2014 The PostgreSQL Global Development Group