Re: [GENERAL] Question about indexes. - Mailing list pgsql-general

From jim@reptiles.org (Jim Mercer)
Subject Re: [GENERAL] Question about indexes.
Date
Msg-id m10pmrb-00080YC@mailbox.reptiles.org
Whole thread Raw
In response to Question about indexes.  ("Spolar Alejandro" <alejo@mecon.ar>)
List pgsql-general
> This table has no indexes at all. Each query made (using EXPLAIN) reveals a
> "Seq Scan".
> So far, everything is OK.
> Then I define 2 indexes, one affects a varchar field, for example 'lastname'
> an the other a float type field, let´s call it 'id'.
> When I perform a query such as SELECT * FROM table WHERE lastname =
> 'Douglas', EXPLAIN reveals that index is being used ("Index Scan").
> But when the query is like: SELECT * FROM table WHERE id = 10, no index is
> used, a "Seq Scan" is made. So it looks like if an index defined on a
> numeric type field, doesn't work. (same thing happens with an index on
> integer field).
> Finally I made the index on 'id' field CLUSTERED. Repeating the query using
> EXPLAIN I get a lower cost and "Index Scan".

i found a similar problem with 6.5beta, only i was using index fields of
int8, float8, datestamp and abstime.

be nice to know what the issue is.

jim (wandering off to look up "CLUSTERED")

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