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From "Mamta A. Satoor (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (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 Tue, 02 Apr 2013 19:47:15 GMT

    [ https://issues.apache.org/jira/browse/DERBY-6096?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13620178#comment-13620178
] 

Mamta A. Satoor commented on DERBY-6096:
----------------------------------------

I reviewed the change too and it looks good to me. Just one minor comment, in the tests, should
we initialize the data to be inserted into clob and blob data types?
                
> 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
>         Attachments: D6096.java, derby-6096_code_diff.txt, derby-6096_diff.txt, 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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