index with LIKE

hello all,

on my master-db-server i'm running postgres 7.4.1,
and I have got two slave-servers running postgres 7.4.2

running the following query on the master-server (7.4.1) delivers:

explain analyze select * from foo where bar like '0101%' and foobar like
'top%';

Index Scan using foo_foobar_idx on foo (cost...)
  Index Cond: ((foobar>='top::text) and (firma < 'toq'::text))
  Filter: ((bar ~~ '0101%'::text) and (firma ~~ 'top%'::text))
Total runtime: 1.519 ms

the same query on both slaves (7.4.2)(mirrored from master, same
structure of table etc.) yields:

Seq Scan on foo (cost ....)
  Filter: ((bar ~~ '0101%'::text) AND (foobar ~~ 'top%'::text))
Total runtime: 722.331 ms


Is there such a difference in 7.4.1 to 7.4.2 ?

A retardation of 722 ms is not acceptable for me, and I don't see why
the indexes are not used.
Do you have an idea? I have run VACUUM ANALYZE several times, and
REINDEX TABLE foo and even
DROPped and reCREATEd the index. Didn't help.

BTW if I run:
explain analyze select * from foo where bar like '0101%' and
foobar>='top'::text and foobar<'toq'::text;
the index is utilized as it is supposed to

Any hint appreciated,

thank you


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