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Posted to commits@beam.apache.org by "ASF GitHub Bot (JIRA)" <ji...@apache.org> on 2018/03/12 16:42:00 UTC
[jira] [Work logged] (BEAM-3714) JdbcIO.read() should create a
forward-only, read-only result set
[ https://issues.apache.org/jira/browse/BEAM-3714?focusedWorklogId=79517&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-79517 ]
ASF GitHub Bot logged work on BEAM-3714:
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Author: ASF GitHub Bot
Created on: 12/Mar/18 16:41
Start Date: 12/Mar/18 16:41
Worklog Time Spent: 10m
Work Description: jkff commented on issue #4786: [BEAM-3714]modified result set to be forward only and read only
URL: https://github.com/apache/beam/pull/4786#issuecomment-372377397
@evindj Any updates here?
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Issue Time Tracking
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Worklog Id: (was: 79517)
Time Spent: 1h (was: 50m)
> 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: 1h
> 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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