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From "ASF GitHub Bot (JIRA)" <>
Subject [jira] [Work logged] (BEAM-3714) should create a forward-only, read-only result set
Date Mon, 12 Mar 2018 16:42:00 GMT


ASF GitHub Bot logged work on BEAM-3714:

                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
   @evindj Any updates here?

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Issue Time Tracking

    Worklog Id:     (was: 79517)
    Time Spent: 1h  (was: 50m)

> should create a forward-only, read-only result set
> ----------------------------------------------------------------
>                 Key: BEAM-3714
>                 URL:
>             Project: Beam
>          Issue Type: Bug
>          Components: io-java-jdbc
>            Reporter: Eugene Kirpichov
>            Assignee: Innocent
>            Priority: Major
>          Time Spent: 1h
>  Remaining Estimate: 0h
> [] -
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)"
- 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."
. 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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