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https://issues.apache.org/jira/browse/BEAM-12044?focusedWorklogId=572173&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-572173
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ASF GitHub Bot logged work on BEAM-12044:
-----------------------------------------
Author: ASF GitHub Bot
Created on: 25/Mar/21 18:13
Start Date: 25/Mar/21 18:13
Worklog Time Spent: 10m
Work Description: jkff commented on pull request #14338:
URL: https://github.com/apache/beam/pull/14338#issuecomment-807215759
Actually this change might be mildly problematic for some users:
Imagine a user who was loading a moderately large dataset from Postgres, but
the dataset was fitting in memory.
Now with this change the dataset will be streamed incrementally in batches
of fetchSize, which will use less memory but more database roundtrips, so it
might perform worse. It might be OK though, because the default fetch size is
pretty large (50K). The problem will happen only if the user was setting a
small fetch size, which previously wasn't having any effect. In that case,
they'll need to set a larger fetchSize.
Now that I think of it, this probably is not a problem, but thought worth
mentioning.
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Issue Time Tracking
-------------------
Worklog Id: (was: 572173)
Time Spent: 1h (was: 50m)
> 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
> Time Spent: 1h
> Remaining Estimate: 0h
>
> 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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