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https://issues.apache.org/jira/browse/BEAM-12044?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17308322#comment-17308322
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Eugene Kirpichov commented on BEAM-12044:
-----------------------------------------
When glancing over the code it seems like the setDefaultAutoCommit line in beam
JdbcIO actually is not executed - it's used only when you use
PoolableDataSourceProvider, it's not used by default, and the scio JdbcIO isn't
using it either.
I think your proposed patch makes sense, please send a PR, thanks! Just please
add a comment explaining why the connection must not be in autocommit mode. A
link to the Postgres documentation might be good enough, as long as there are
no other database engines requiring the connection to be *in* autocommit mode
to allow streaming, which seems unlikely.
> JdbcIO should explicitly setAutoCommit to false
> -----------------------------------------------
>
> Key: BEAM-12044
> URL: https://issues.apache.org/jira/browse/BEAM-12044
> Project: Beam
> Issue Type: Bug
> Components: sdk-java-core
> Affects Versions: 2.28.0
> Reporter: Sylvain Veyrié
> Priority: P2
>
> Hello,
> Per [PostgreSQL JDBC
> documentation|https://jdbc.postgresql.org/documentation/head/query.html#query-with-cursor],
> autocommit must be explicitly disabled on the connection to allow cursor
> streaming.
> [~jkff] mentionned it [on the mailing
> list|https://www.mail-archive.com/[email protected]/msg16808.html], however
> even if there is:
> {code:java}
> poolableConnectionFactory.setDefaultAutoCommit(false);
> {code}
> in JdbcIO:1555, currently, at least with JDBC driver 42.2.16, any read with
> JdbcIO will memoize the whole dataset (which leads to OOM), since
> {code:java}
> connection.getAutoCommit()
> {code}
> returns true in JdbcIO#ReadFn#processElement.
> I can provide a PR — the patch is pretty simple (and solves the problem for
> us in 2.28.0):
> {code:java}
> if (connection == null) {
> connection = dataSource.getConnection();
> }
> connection.setAutoCommit(false); // line added
> {code}
> Thanks!
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