| 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 |
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| 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
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