This seems to be peculuar to our operational database which is version
7.2.x. Version 7.4 gives the index scan.
Cheers,
Randall
On 8 Apr 2004, at 14:28, Randall Skelton wrote:
[color=blue]
> Can someone explain why the latter query uses an index scan while the
> former uses a sequence scan? I have tried all sorts of casting in the
> first case but I cannot get the index scan.
>
> Cheers,
> Randall
>
> ==
> data=> EXPLAIN ANALYZE SELECT acqtimestamp FROM aux_datarecord where
> acqtimestamp between (extract(epoch from timestamp '2004-02-21
> 22:39:57+00') - 50716800)::double precision and (extract(epoch from
> timestamp '2004-02-21 22:43:52+00'::timestamp) - 50716800.0)::double
> precision;
> NOTICE:
> QUERY PLAN:
>
> Seq Scan on aux_datarecord (cost=100000000.00..100548707.00
> rows=477476 width=8) (actual time=114670.09..114670.09 rows=0 loops=1)
> Total runtime: 114670.23 msec
>
> EXPLAIN
>
> data=> EXPLAIN ANALYZE SELECT acqtimestamp FROM aux_datarecord where
> acqtimestamp between '1026686397'::double precision and
> '1026686632'::double precision;
> NOTICE:
> QUERY PLAN:
>
> Index Scan using aux_datarecord_acqtimestamp on aux_datarecord
> (cost=0.00..3.54 rows=1 width=8) (actual time=0.66..0.66 rows=0
> loops=1)
> Total runtime: 0.83 msec
>
> EXPLAIN
> ==
>
>
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extract epoch and index scanning 
