From: | Richard Huxton <dev(at)archonet(dot)com> |
---|---|
To: | Chris Velevitch <chris(dot)velevitch(at)gmail(dot)com> |
Cc: | pgsql-general(at)postgresql(dot)org |
Subject: | Re: How efficient is select currval? |
Date: | 2005-12-09 07:53:59 |
Message-ID: | 43993817.40301@archonet.com |
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Thread: | |
Lists: | pgsql-general |
Chris Velevitch wrote:
> If I insert a record into a table with a serial primary key, does
> select currval fetch it from the database or does it get it from
> within memory?
>
> If it fetches it from the database, should I use a Serializable
> transaction or just a read committed transaction?
You can control the level of caching, but you'll have to be pushing it
for the serial to be a large part of your overheads. Each sequence is a
small table - you can do "SELECT * FROM my_seq" and see the "insides".
You don't need to worry about transaction isolation for sequences, you
are always guaranteed a new value. The price you pay for this is that
there might be gaps in the series of values you get.
--
Richard Huxton
Archonet Ltd
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