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https://issues.apache.org/jira/browse/DERBY-3732?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12608741#action_12608741
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Knut Anders Hatlen commented on DERBY-3732:
-------------------------------------------
The setting of derby.storage.pageCacheSize will only be respected if the
database is booted by that test. I see it is set to 100 when it's run as a
separate test, but not when it's run as part of a larger suite.
It would be good to document in a comment why the optimizer override is needed.
I was going to suggest that we should call skip(Long.MAX_VALUE) instead of
skip(Integer.MAX_VALUE), but then I saw that it would probably trigger a bug in
ArrayInputStream.skip() (will log a separate bug for that).
Tiny nit: testBlobLength(boolean) should be private so that it's clearer that
it's not a top-level test case.
> 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_diff.txt, derby-3732_proto_diff.txt,
> derby-3732_skip2_diff.txt, derby-3732_skip_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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