update, truncate and vacuum - Mailing list pgsql-performance

From Scott Feldstein
Subject update, truncate and vacuum
Date
Msg-id B195EEA2-7B5D-444F-8F48-46BB88FCFFA8@hyperic.com
Whole thread Raw
Responses Re: update, truncate and vacuum  ("Dave Dutcher" <dave@tridecap.com>)
List pgsql-performance
Hi,
I have a couple questions about how update, truncate and vacuum would
work together.

1) If I update a table foo (id int, value numeric (20, 6))
with
update foo set value = 100 where id = 1

Would a vacuum be necessary after this type of operation since the
updated value is a numeric? (as opposed to a sql type where its size
could potentially change i.e varchar)

2) After several updates/deletes to a table, if I truncate it, would
it be necessary to run vacuum in order to reclaim the space?

thanks,
Scott

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