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https://issues.apache.org/jira/browse/BEAM-3714?focusedWorklogId=92880&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-92880
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ASF GitHub Bot logged work on BEAM-3714:
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Author: ASF GitHub Bot
Created on: 19/Apr/18 22:21
Start Date: 19/Apr/18 22:21
Worklog Time Spent: 10m
Work Description: jkff commented on issue #5109: [BEAM-3714]modified
result set to be forward only and read only
URL: https://github.com/apache/beam/pull/5109#issuecomment-382898723
The Go precommit is a flake, but in Java there seems to be a couple of final
simple checkstyle errors (line too long) remaining.
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Issue Time Tracking
-------------------
Worklog Id: (was: 92880)
Time Spent: 3h 20m (was: 3h 10m)
> JdbcIO.read() should create a forward-only, read-only result set
> ----------------------------------------------------------------
>
> Key: BEAM-3714
> URL: https://issues.apache.org/jira/browse/BEAM-3714
> Project: Beam
> Issue Type: Bug
> Components: io-java-jdbc
> Reporter: Eugene Kirpichov
> Assignee: Innocent
> Priority: Major
> Time Spent: 3h 20m
> Remaining Estimate: 0h
>
> [https://stackoverflow.com/questions/48784889/streaming-data-from-cloudsql-into-dataflow/48819934#48819934]
> - a user is trying to load a large table from MySQL, and the MySQL JDBC
> driver requires special measures when loading large result sets.
> JdbcIO currently calls simply "connection.prepareStatement(query)"
> https://github.com/apache/beam/blob/bb8c12c4956cbe3c6f2e57113e7c0ce2a5c05009/sdks/java/io/jdbc/src/main/java/org/apache/beam/sdk/io/jdbc/JdbcIO.java#L508
> - it should specify type TYPE_FORWARD_ONLY and concurrency CONCUR_READ_ONLY
> - these values should always be used.
> Seems that different databases have different requirements for streaming
> result sets.
> E.g. MySQL requires setting fetch size; PostgreSQL says "The Connection must
> not be in autocommit mode."
> https://jdbc.postgresql.org/documentation/head/query.html#query-with-cursor .
> Oracle, I think, doesn't have any special requirements but I don't know.
> Fetch size should probably still be set to a reasonably large value.
> Seems that the common denominator of these requirements is: set fetch size to
> a reasonably large but not maximum value; disable autocommit (there's nothing
> to commit in read() anyway).
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