David Teran wrote:
Hi,

we have a table with about 6.000.000 rows. There is an index on a column with the name id which is an integer and serves as primary key.

When we execute select max(id) from theTable; it takes about 10 seconds. Explain analyze returns:

Due to the open-ended nature of PG's aggregate function system, it can't see inside the max() function to realise it doesn't need all the values.


Fortune favours the flexible however - the simple workaround is to use the equivalent:
SELECT id FROM theTable ORDER BY id DESC LIMIT 1;


--
  Richard Huxton
  Archonet Ltd

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