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