From: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
---|---|
To: | Bryan White <bryan(at)arcamax(dot)com> |
Cc: | pgsql <pgsql-sql(at)postgresql(dot)org> |
Subject: | Re: Controlling Reuslts with Limit |
Date: | 2001-02-23 21:59:09 |
Message-ID: | 200102232159.QAA00396@candle.pha.pa.us |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-sql |
> I don't think it is actually random. It just that the order is not defined
> and other events may change the order. I believe that without an ORDER BY
> or other clauses that cause an index to be used that the database tends to
> return rows in the order stored on disk. This order tends to be the order
> in which rows were added. My observation is this ordering is faily stable
> and it seems to survive a database reload. Just don't rely on it. There is
> a CLUSTER command to change the physical ordering.
Yes, usually it is the heap order, but if you do "col > 12" you may get
it in index order by the column indexes, or you may not, depending on
the constant, the size of the table, vacuum, vacuum analyze, etc.
--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
+ If your life is a hard drive, | 830 Blythe Avenue
+ Christ can be your backup. | Drexel Hill, Pennsylvania 19026
From | Date | Subject | |
---|---|---|---|
Next Message | Stephan Richter | 2001-02-23 22:40:08 | Recursive Query (need of PL/pgSQL?) |
Previous Message | Stephan Szabo | 2001-02-23 21:46:50 | Re: Controlling Reuslts with Limit |