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From "Derek Hulley (JIRA)" <j...@apache.org>
Subject [jira] Issue Comment Edited: (DBCP-352) Repeated calls to getMetadata in a transaction leads to performance degredation
Date Wed, 02 Feb 2011 12:05:29 GMT

    [ https://issues.apache.org/jira/browse/DBCP-352?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12989596#comment-12989596
] 

Derek Hulley edited comment on DBCP-352 at 2/2/11 12:03 PM:
------------------------------------------------------------

The table is deliberately simple, so use your database of choice.  I'm not convinced that
using an in-memory DB is the solution given that the test is designed to scale up to hundreds
of thousands of insertions; it's probably better just to piggy back off a real DB.

      was (Author: derekhulley):
    The table is deliberately simple, so use your database of choice.
  
> Repeated calls to getMetadata in a transaction leads to performance degredation
> -------------------------------------------------------------------------------
>
>                 Key: DBCP-352
>                 URL: https://issues.apache.org/jira/browse/DBCP-352
>             Project: Commons Dbcp
>          Issue Type: Bug
>    Affects Versions: 1.2.2, 1.3.1, 1.4
>         Environment: PostgreSQL, MySQL, JDK 1.6
>            Reporter: Derek Hulley
>            Priority: Critical
>             Fix For: 1.3.1, 1.4.1
>
>         Attachments: DBCPMetadataTest.zip
>
>
> During long-running transactions that utilize conditional logic based on the database
metadata, it is possible to get thousands of calls to Connection.getMetaData.  An ArrayList
is built up containing objects which are never removed (this is the cause of DBCP-330).  However,
the array is shared with all other PreparedStatements, so the array scan and modification
time keeps rising as the transaction progresses.
> I will attempt to attach an Eclipse project; profiling (or even a few JStacks) will show
that most of the time is spent scanning the cluttered and growing array for objects to remove.

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