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From "Knut Anders Hatlen (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (DERBY-6096) OutOfMemoryError with Clob or Blob hash join: DataTypeDescriptor.estimatedMemoryUsage() has no case for BLOB or CLOB so would underestimate memory usage for those types at zero
Date Thu, 04 Apr 2013 11:47:15 GMT

     [ https://issues.apache.org/jira/browse/DERBY-6096?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Knut Anders Hatlen updated DERBY-6096:
--------------------------------------

    Attachment: less-gc.diff

Attaching less-gc.diff which makes a small change in the tests so that they only run System.gc()
if the memory statistics are actually going to be printed. (The call to gc() doesn't seem
to slow down the test when it's run separately, but I suppose it could take longer if it runs
as part of a larger test suite and there's more data on the heap.)

Committed revision 1464470.
                
> OutOfMemoryError with Clob or Blob hash join: DataTypeDescriptor.estimatedMemoryUsage()
 has no case for BLOB or CLOB so would underestimate memory usage for those types at zero
> ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: DERBY-6096
>                 URL: https://issues.apache.org/jira/browse/DERBY-6096
>             Project: Derby
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 10.1.3.1, 10.2.2.0, 10.3.3.0, 10.4.2.0, 10.5.3.0, 10.6.2.1, 10.7.1.1,
10.9.1.0, 10.10.1.1, 10.8.3.0
>            Reporter: Kathey Marsden
>            Assignee: Kathey Marsden
>         Attachments: D6096.java, derby-6096_code_diff.txt, derby-6096_diff2.txt, derby-6096_diff.txt,
less-gc.diff, releaseNote.html
>
>
> In discussion on derby-dev regarding how much memory is used for hash joins, Knut noted:
> I haven't verified, but I think HashJoinStrategy uses
> DataTypeDescriptor.estimatedMemoryUsage() to estimate how much memory
> the hash table will consume. That method has no case for BLOB or CLOB,
> so it looks as if it will return zero for LOB columns. If that's so, it
> will definitely overestimate how many rows fits in maxMemoryPerTable
> kilobytes if the rows contain LOBs.
> DataTypeDescriptor.estimatedMemoryUsage() should be updated to include BLOB and CLOB
and we should try verify if this theory is correct with a reproduction.

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