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Re: Memory leak or client side caching?

From: Roland Walter <rwa(at)mosaic-ag(dot)com>
To: Kovács Péter <peter(dot)kovacs(at)chemaxon(dot)hu>
Cc: pgsql-jdbc(at)postgresql(dot)org
Subject: Re: Memory leak or client side caching?
Date: 2006-01-11 14:43:36
Message-ID: rc4ace2kep3.fsf@mosaic-ag.com (view raw or flat)
Thread:
Lists: pgsql-jdbc
Kovács Péter <peter(dot)kovacs(at)chemaxon(dot)hu> writes:

> Hi,
>
> Executing the following code results in an increase of 1GB in memory
> usage by the process.
>
> String sql = "SELECT
> cd_id,cd_fp1,cd_fp2,cd_fp3,cd_fp4,cd_fp5,cd_fp6,cd_fp7,cd_fp8,cd_fp9,cd_fp10,cd_fp11,cd_fp12,cd_fp13,cd_fp14,cd_fp15,cd_fp16,cd_smiles
> FROM editexample1";
> PreparedStatement ps = conn.prepareStatement(sql);
> try {
> 	ResultSet rs = ps.executeQuery();
> 	try {
> 		while (rs.next()) {
> 			int cdId = rs.getInt(1);
> 			for (int i = 0; i < 16; i++) {
> 				int fp = rs.getInt(i+2);
> 			}
> 			String cdSmiles = rs.getString(18);
> 		}
> 	} finally {
> 		rs.close();
> 	}
> } finally {
> 	ps.close();
> }
>
> The result set contains 1 250 000 rows.
>
> I am not sure if this is a memory leak or the driver just caches the
> result set on the client side. If this is the latter, is there a way
> to turn off client side caching? If the former, how should I proceed
> to find the problem?
>

If you do not use a cursor, the ResultSet tries to load all rows
into the memory.

Before executing the query you should set autocommit to false and
set the fetchsize on the PreparedStatement to the maximal count
of rows that are loaded into the memory:

   con.setAutoCommit(false);
   ps.setFetchSize(1000);


-- 
Roland Walter                   mailto: rwa (at) mosaic-ag (dot) com
MOSAIC SOFTWARE AG               phone: +49 (0) 22 25 / 88 2-41 1
Am Pannacker 3                     fax: +49 (0) 22 25 / 88 2-20 1
D-53340 Meckenheim                http://www.mosaic-ag.com


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Next:From: Kris JurkaDate: 2006-01-11 16:58:55
Subject: Re: cannot dollar-quote $$?$$ in PreparedStatements
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Subject: Memory leak or client side caching?

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