From: | Oliver Jowett <oliver(at)opencloud(dot)com> |
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To: | Rich Cullingford <rculling(at)sysd(dot)com> |
Cc: | pgsql-jdbc(at)postgresql(dot)org |
Subject: | Re: AbstractJdbc2Statement.setFetchSize() |
Date: | 2003-10-17 01:14:13 |
Message-ID: | 20031017011411.GA433@opencloud.com |
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Thread: | |
Lists: | pgsql-jdbc |
On Thu, Oct 16, 2003 at 06:09:47PM -0400, Rich Cullingford wrote:
> All,
> I had hoped to use this method, which is implemented in PG 7.4, to limit
> the number of rows retrieved (for display purposes) out of some massive
> datasets we have. I know the JDBC spec says that this is just a hint,
> but calling the method on a Statement doesn't seem to have any effect on
> the SELECT. It still seesm to try to load the whole dataset.
>
> Is there any way to avoid cursored FETCH approaches to this problem?
Recent drivers should transparently transform queries into a cursor-based
form if you set a non-zero fetchsize. However there are a few gotchas:
- it doesn't do this if (JDBC-level) autocommit is on
- it doesn't do this if you use a PreparedStatement with parameters
- it tries to do this even if the statement is something other than a
SELECT statement, and gets horribly confused in the process.
I have patches for the second two if needed; they probably won't reach CVS
until after 7.4 is out, though, since they're a bit invasive.
-O
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