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https://issues.apache.org/jira/browse/DERBY-6096?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13620154#comment-13620154
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Mike Matrigali commented on DERBY-6096:
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i reviewed the change, and seems a good change to me. some day we probably
should just raise the default internal maxMemoryPerTable on a major release
boundary to reflect increased default memory for most users, or maybe come up
with a better zero admin auto config for it. 1 meg seems pretty small.
> 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
>
>
> 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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