On 08/22/2012 12:27 PM, Wells Oliver wrote:
We have a lot of tables which store numeric data. These tables all use
the numeric type, where the values are 95% integer values. We used
numeric because it eliminated the need for casting during division to
yield a floating point value.
I'm curious as to whether this would have performance and/or disk size
implications.
Yes, and yes, though the gap seems to have shrunk a lot since I first
started using Pg.
It's easy to concoct fairly meaningless micro-benchmarks, but you should
really try it with some real queries you run on your real schema. Take a
copy of your data, convert it, and run some tests. Use
`pg_total_relation_size` to compare the numeric and int versions of the
relations after `CLUSTER`ing them to debloat and reindex them.
Would converting these columns to integer (or double
precision on the handful that require the precision) and forcing
developers to use explicit casting be worth the time?
Without knowing your workload and your constraints, that's a "how blue
is the sky" question.
--
Craig Ringer
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