Hi Tom,

first of all thanks for your help! I really appreciate your fast response and if you ever have a question about WebObjects, just drop me line ;-)

Seq Scan on "KEY_VALUE_META_DATA" t0 (cost=0.00..2671.16 rows=931 width
=1068) (actual time=122.669..172.179 rows=25 loops=1)
Filter: (("ID_VALUE" = 21094) OR ("ID_VALUE" = 21103))

The problem is evidently that the row estimate is so far off (931 estimate vs 25 actual). Have you done ANALYZE or VACUUM ANALYZE on this table recently? If you have, I'd be interested to see the pg_stats row for ID_VALUE. It might be that you need to increase the statistics target for this table.

I am absolutely new to PostgreSQL. OK, after VACUUM ANALYZE i get:

Index Scan using key_value_meta_data__id_value__fk_index, key_value_meta _data__id_value__fk_index on "KEY_VALUE_META_DATA" t0  (cost=0.00..19.94  rows=14 width=75) (actual time=0.615..1.017 rows=25 loops=1)
  Index Cond: (("ID_VALUE" = 21094) OR ("ID_VALUE" = 21103))
Total runtime: 2.565 ms

and the second time i invoke this i get

Index Scan using key_value_meta_data__id_value__fk_index, key_value_meta _data__id_value__fk_index on "KEY_VALUE_META_DATA" t0  (cost=0.00..19.94  rows=14 width=75) (actual time=0.112..0.296 rows=25 loops=1)
  Index Cond: (("ID_VALUE" = 21094) OR ("ID_VALUE" = 21103))
Total runtime: 0.429 ms

Much better. So i think i will first read more about this optimization stuff and regular maintenance things. This is something i like very much from FrontBase: no need for such things, simply start and run. But other things were not so fine ;-).

Is there any hint where to start to understand more about this optimization problem?

regards David

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