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https://issues.apache.org/jira/browse/DERBY-3872?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12631843#action_12631843
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Mamta A. Satoor commented on DERBY-3872:
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Thanks for verifying it, Bryan. I spent little more time on following 2 queries
to see how we generate the code for them
Query1
select q1."DEPTNO" from DEPTTAB q1, EMPTAB q2 -- DERBY-PROPERTIES
joinStrategy = HASH
where ( q2."DEPT_DEPTNO" = q1."DEPTNO")
GROUP BY q1."DEPTNO" HAVING 1 =
( select q3."SALARY" from EMPTAB q3 where ( q3."EMPID" = q1."DEPTNO") ) ;
Query2
select q1."DEPTNO" from DEPTTAB q1, EMPTAB q2
where ( q2."DEPT_DEPTNO" = q1."DEPTNO")
GROUP BY q1."DEPTNO" HAVING 1 =
( select q3."SALARY" from EMPTAB q3 where ( q3."EMPID" = q1."DEPTNO") ) ;
Query1 results in a NPE whereas Query2 runs fine. Notice that Query1 has
optimizer override to use hashjoin.
What I found during the code generation phase of the 2 queries is that
1)The number of resultsets generated for the 2 queries are not same. Query1 has
11 generated resultsets whereas Query2 has 10 generated resultsets.
2)For the outer query, in case of Query1, the DEPTTAB is the left operand of
the join node and EMPTAB is the right operand. The generated resultset for
DEPTTAB get resultset number 3 assigned to it and the generated resultset for
EMPTAB gets resultset number 4 assigned to it. For some reason, the order of
these resultsets are switched in case of Query2. So, EMPTAB is the left operand
for the join node and DEPTTAB is the right operand for the join node.
3)Another thing to note at code generation time is for subquery. In case of
Query1, we have 2 nodes associated with EMPTAB q3, namely IndexToBaseRowNode
and FromBaseTable. In case of Query2, we have only one node for EMPTAB q3 and
that is FromBaseTable.
Lastly, at runtime, right before we hit the NPE, activation object shows
following current rows associated with each of the 11 generated resultsets
[null, { 1 }, null, null, null, null, { 1 }, null, null, null, null]
Notice that current row for resultset number 3 is null and that is causing the
npe.
For Query2, the activation object shows following current rows associated with
each of it's 10 generated resultsets
[null, null, null, { 1 }, null, null, null, null, null, null]
Notice that current row for resultset number 3 is not null.
I am not sure how useful information is this, but I wanted to share what I
have. I will continue debugging more.
> NullPoinerException thrown when INTEGER function used as a predicate in a
> WHERE clause of a SELECT .. GROUP BY .. HAVING statement
> -----------------------------------------------------------------------------------------------------------------------------------
>
> Key: DERBY-3872
> URL: https://issues.apache.org/jira/browse/DERBY-3872
> Project: Derby
> Issue Type: Bug
> Affects Versions: 10.3.3.0
> Reporter: Stan Bradbury
> Attachments: NPE_Reproduction.sql, QueryWithoutTruePred.out,
> QueryWithTruePred.out
>
>
> Use attached SQL script to create two tables , execute the following SQL and
> throw the exception and stack trace below. NOTE: removing the 'always true'
> clause '.. ( integer (1.1) = 1) .." from the SQL and the query does not fail.
> Releated??
> select q1."DEPTNO" from DEPTTAB q1, EMPTAB q2 where ( integer (1.1) = 1)
> and ( q2."DEPT_DEPTNO" = q1."DEPTNO")
> GROUP BY q1."DEPTNO"
> HAVING max( q2."SALARY") >= ( select q3."SALARY" from EMPTAB q3 where (
> q3."EMPID" = q1."DEPTNO") )
> ERROR 38000: The exception 'java.lang.NullPointerException' was thrown while
> evaluating an expression.
> . . .derby.iapi.error.StandardException.newException
> . . .derby.iapi.error.StandardException.unexpectedUserException
> . . .derby.impl.services.reflect.DirectCall.invoke
> . . .derby.impl.sql.execute.ProjectRestrictResultSet.getNextRowCore
> . . .derby.impl.sql.execute.BasicNoPutResultSetImpl.getNextRow
> . . .derby.impl.jdbc.EmbedResultSet.movePosition
> . . .derby.impl.jdbc.EmbedResultSet.next
> . . .derby.tools.JDBCDisplayUtil.indent_DisplayResults
> . . .derby.tools.JDBCDisplayUtil.indent_DisplayResults
> . . .derby.tools.JDBCDisplayUtil.indent_DisplayResults
> . . .derby.tools.JDBCDisplayUtil.DisplayResults
> . . .derby.impl.tools.ij.utilMain.displayResult
> . . .derby.impl.tools.ij.utilMain.doCatch
> . . .derby.impl.tools.ij.utilMain.runScriptGuts
> . . .derby.impl.tools.ij.utilMain.go
> . . .derby.impl.tools.ij.Main.go
> . . .derby.impl.tools.ij.Main.mainCore
> . . .derby.impl.tools.ij.Main14.main
> . . .derby.tools.ij.main
> Caused by: java.lang.NullPointerException
> . . .derby.iapi.types.NumberDataType.compare
> . . .derby.impl.store.access.btree.ControlRow.compareIndexRowFromPageToKey
> . . .derby.impl.store.access.btree.ControlRow.searchForEntry
> . . .derby.impl.store.access.btree.LeafControlRow.search
> . . .derby.impl.store.access.btree.BTreeScan.positionAtStartForForwardScan
> . . .derby.impl.store.access.btree.BTreeForwardScan.positionAtStartPosition
> . . .derby.impl.store.access.btree.BTreeForwardScan.fetchRows
> . . .derby.impl.store.access.btree.BTreeScan.fetchNext
> . . .derby.impl.sql.execute.TableScanResultSet.getNextRowCore
> . . .derby.impl.sql.execute.IndexRowToBaseRowResultSet.getNextRowCore
> . . .derby.impl.sql.execute.ProjectRestrictResultSet.getNextRowCore
> . . .derby.impl.sql.execute.OnceResultSet.getNextRowCore
> . . .derby.exe.ac601a400fx011cx480cx5eacx00000010d8100.g0
> . . .derby.exe.ac601a400fx011cx480cx5eacx00000010d8100.e6
> ... 17 more
> ============= begin nested exception, level (1) ===========
> java.lang.NullPointerException
> . . .derby.iapi.types.NumberDataType.compare
> . . .derby.impl.store.access.btree.ControlRow.compareIndexRowFromPageToKey
> . . .derby.impl.store.access.btree.ControlRow.searchForEntry
> . . .derby.impl.store.access.btree.LeafControlRow.search
> . . .derby.impl.store.access.btree.BTreeScan.positionAtStartForForwardScan
> . . .derby.impl.store.access.btree.BTreeForwardScan.positionAtStartPosition
> . . .derby.impl.store.access.btree.BTreeForwardScan.fetchRows
> . . .derby.impl.store.access.btree.BTreeScan.fetchNext
> . . .derby.impl.sql.execute.TableScanResultSet.getNextRowCore
> . . .derby.impl.sql.execute.IndexRowToBaseRowResultSet.getNextRowCore
> . . .derby.impl.sql.execute.ProjectRestrictResultSet.getNextRowCore
> . . .derby.impl.sql.execute.OnceResultSet.getNextRowCore
> . . .derby.exe.ac601a400fx011cx480cx5eacx00000010d8100.g0
> . . .derby.exe.ac601a400fx011cx480cx5eacx00000010d8100.e6
> . . .derby.impl.services.reflect.DirectCall.invoke
> . . .derby.impl.sql.execute.ProjectRestrictResultSet.getNextRowCore
> . . .derby.impl.sql.execute.BasicNoPutResultSetImpl.getNextRow
> . . .derby.impl.jdbc.EmbedResultSet.movePosition
> . . .derby.impl.jdbc.EmbedResultSet.next
> . . .derby.tools.JDBCDisplayUtil.indent_DisplayResults
> . . .derby.tools.JDBCDisplayUtil.indent_DisplayResults
> . . .derby.tools.JDBCDisplayUtil.indent_DisplayResults
> . . .derby.tools.JDBCDisplayUtil.DisplayResults
> . . .derby.impl.tools.ij.utilMain.displayResult
> . . .derby.impl.tools.ij.utilMain.doCatch
> . . .derby.impl.tools.ij.utilMain.runScriptGuts
> . . .derby.impl.tools.ij.utilMain.go
> . . .derby.impl.tools.ij.Main.go
> . . .derby.impl.tools.ij.Main.mainCore
> . . .derby.impl.tools.ij.Main14.main
> . . .derby.tools.ij.main
> ============= end nested exception, level (1) ===========
> Cleanup action completed
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