Re: [QUESTIONS] How fully will subselects be implemented?
Bruce Momjian <maillist@candle.pha.pa.us>
From: Bruce Momjian <maillist@candle.pha.pa.us>
To: vadim@sable.krasnoyarsk.su (Vadim B. Mikheev)
Cc: herouth@oumail.openu.ac.il,
hackers@postgreSQL.org (PostgreSQL-development)
Date: 1998-02-25T14:28:10Z
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@candle.pha.pa.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)