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Re: Does PG cache results of an aggregate function, (and results of non-volatile functions)? - Mailing list pgsql-general

From 纪晓曦
Subject Re: Does PG cache results of an aggregate function, (and results of non-volatile functions)?
Date
Msg-id 37a11ce00909190606vd4200daw3ea97431f866e52e@mail.gmail.com
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In response to Does PG cache results of an aggregate function, (and results of non-volatile functions)?  (Allan Kamau <kamauallan@gmail.com>)
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Well I don't think the result would keep if you run a "hot" test. However, in  one SELECT clause, maybe it can be optimised .

2009/9/3 Allan Kamau <kamauallan@gmail.com>
Hi,
I do have a query which make use of the results of an aggregate
function (for example bit_or) several times in the output column list
of the SELECT clause, does PostgreSQL simply execute the aggregate
function only once and provide the output to the other calls to the
same aggregate function.
How about the case of non volatile functions? Do they get executed as
many times as they occur in the select clause?

Allan.

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