db-derby-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Kathey Marsden (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-3732) SQL Length function materializes lob into memory
Date Tue, 24 Jun 2008 17:46:45 GMT

    [ https://issues.apache.org/jira/browse/DERBY-3732?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12607697#action_12607697
] 

Kathey Marsden commented on DERBY-3732:
---------------------------------------

I'm not really sure the best way to test this.  Should I create a new LowMemTest and run it
with 16M heap via the top level junit-all ant target?  This would mean it wouldn't get run
 in suites.All.  Alternately I can just add tests to existing tests in suites.All and make
sure we have coverage of the new code, but then it won't test for the memory usage explicitly.

We have an existing test derbyStress.java which runs in the old suite which runs with 64MB
but I want to run with less memory than that.


> SQL Length function materializes lob into memory
> ------------------------------------------------
>
>                 Key: DERBY-3732
>                 URL: https://issues.apache.org/jira/browse/DERBY-3732
>             Project: Derby
>          Issue Type: Improvement
>          Components: SQL
>    Affects Versions: 10.3.3.0, 10.4.1.3, 10.5.0.0
>            Reporter: Kathey Marsden
>            Priority: Minor
>         Attachments: derby-3732_proto_diff.txt, LengthLargeLob.zip, LengthThruBlob.java
>
>
> Currently the SQL length function materializes the entire lob into memory. In SQLBinary.getLength()
we have 
> public final int	getLength() throws StandardException
> 	{
> 		if (stream != null) {
> 			if (streamValueLength != -1)
> 				return streamValueLength;
> 		}
> 		return (getBytes() == null) ? 0 : getBytes().length;
> 	}
> Which actually is doubly bad because we call getBytes twice and materialize it twice.
> It would be good to read the length from the stream if available and otherwise stream
the value to get the length, rather than materializing it into memory.
> To reproduce, run the attached repro.
> java -Xmx16M  LengthLargeLob
> It gives an out of memory exception
> Caused by: java.lang.OutOfMemoryError: Java heap space
>         at org.apache.derby.iapi.types.SQLBinary.readFromStream(SQLBinary.java:415)
>         at org.apache.derby.iapi.types.SQLBinary.readExternal(SQLBinary.java:318)
>         at org.apache.derby.iapi.types.SQLBinary.getValue(SQLBinary.java:220)
>         at org.apache.derby.iapi.types.SQLBinary.getBytes(SQLBinary.java:210)
>         at org.apache.derby.iapi.types.SQLBinary.getLength(SQLBinary.java:250)
>         at org.apache.derby.impl.sql.execute.BaseActivation.getDB2Length(BaseActivation.java:1684)
>         at org.apache.derby.exe.acf81e0010x011axa317x5db8x0000003d9dc81.e1(Unknown Source)
>         at org.apache.derby.impl.services.reflect.DirectCall.invoke(ReflectGeneratedClass.java:141)
>         at org.apache.derby.impl.sql.execute.ProjectRestrictResultSet.doProjection(ProjectRestrictResultSet.java:497)
>         at org.apache.derby.impl.sql.execute.ProjectRestrictResultSet.getNextRowCore(ProjectRestrictResultSet.java:291)
>         at org.apache.derby.impl.sql.execute.BasicNoPutResultSetImpl.getNextRow(BasicNoPutResultSetImpl.java:460)
>         at org.apache.derby.impl.jdbc.EmbedResultSet.movePosition(EmbedResultSet.java:423)
>         ... 2 more
> [
>  

-- 
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.


Mime
View raw message