Partial index usage

[Laszlo Nagy <gandalf@xxxxxxxxxxxx>]

Hi All,

I have these indexes on a table:


CREATE INDEX uidx_product_partno_producer_id
 ON product
 USING btree
 (partno, producer_id);


CREATE INDEX idx_product_partno
 ON product
 USING btree
 (partno);

Can I safely delete the second one? Will postgresql use 
(partno,producer_id) when it only needs to order by partno? (partno is a 
text field, producer_id is int4). Index sizes: 172MB and 137MB. I guess 
if I only had one index, it would save memory and increase performance.

Another pair of incides, 144MB and 81MB respecively:


CREATE INDEX idx_product_producer_uploads
 ON product
 USING btree
 (producer_id, am_upload_status_id);


CREATE INDEX idx_product_producer_id
 ON product
 USING btree
 (producer_id);


am_upload_status_id is also an int4. Can I delete the second index 
without performance drawback?

Thanks,

  Laszlo


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