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From "Knut Anders Hatlen (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-3571) LOB locators are not released if the LOB columns are not accessed by the client
Date Mon, 31 Mar 2008 19:58:25 GMT

    [ https://issues.apache.org/jira/browse/DERBY-3571?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12583812#action_12583812
] 

Knut Anders Hatlen commented on DERBY-3571:
-------------------------------------------

Just a quick control question:

The plan is to have three different mechanisms for releasing LOBs in the client driver?

  a) SingleReleaseLOBTracker if the server version is 10.3
  b) MultipleReleaseLOBTracker if the server version is 10.4
  c) some yet to be implemented piggybacking protocol if the server version is 10.5 or higher

Won't this add up to a fair amount of code that, once newer versions are released, ends up
being more or less dead and untested code? Or is there a way some of the mechanisms could
be consolidated or perhaps phased out later?

> LOB locators are not released if the LOB columns are not accessed by the client
> -------------------------------------------------------------------------------
>
>                 Key: DERBY-3571
>                 URL: https://issues.apache.org/jira/browse/DERBY-3571
>             Project: Derby
>          Issue Type: Bug
>          Components: JDBC, Network Client
>    Affects Versions: 10.3.2.1, 10.4.0.0, 10.5.0.0
>            Reporter: Kristian Waagan
>            Assignee: Kristian Waagan
>         Attachments: derby-3571-1a-client_track_lob_fix.diff, derby-3571-1a-client_track_lob_fix.stat,
derby-3571-1b-client_track_lob_fix.diff, derby-3571-1c-client_track_lob_fix.diff, derby-3571-1d-client_track_lob_fix.diff,
derby-3571-1e-client_track_lob_fix.diff
>
>
> If the client creates a result set containing LOB locator columns and iterates through
it without actually accessing the LOB columns, the locators are not released.
> The amount of locators and their associated LOB objects causes the server to consume
large amounts of memory and it eventually gets an OOME.
> There are a few workarounds for this bug:
>  a) Access and/or properly close the LOBs (i.e. Blob.free).
>     This is partly dependent on DERBY-2892.
>  b) Invoke Connection.commit (or rollback) periodically, which causes all locators on
the connection to be released.

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