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From "Mamta A. Satoor (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-3872) NullPoinerException thrown when INTEGER function used as a predicate in a WHERE clause of a SELECT .. GROUP BY .. HAVING statement
Date Mon, 22 Sep 2008 16:50:44 GMT

    [ https://issues.apache.org/jira/browse/DERBY-3872?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12633378#action_12633378
] 

Mamta A. Satoor commented on DERBY-3872:
----------------------------------------

While trying to run through the 10.2 codeline and trunk, one of the things I noticed is that
impl.sql.compile.SelectNode:preprocess method has code around line number 1000 that looks
like following in 10.2 codeline
	/* A valid group by without any aggregates is equivalent to 
	 * a distinct without the group by.  We do the transformation
	 * in order to simplify the group by code.
	 */
	if (groupByList != null &&
		selectAggregates.size() == 0 &&
		whereAggregates.size() == 0)
	{
		isDistinct = true;
		groupByList = null;
	}

The corresponding code in trunk has additional check in the if condition as shown below
	/* A valid group by without any aggregates or a having clause
	 * is equivalent to a distinct without the group by.  We do the transformation
	 * in order to simplify the group by code.
	 */
	if (groupByList != null &&
		havingClause == null &&
		selectAggregates.size() == 0 &&
		whereAggregates.size() == 0)
	{
		isDistinct = true;
		groupByList = null;
		wasGroupBy = true;
	}

Just to see what would happen I removed the (havingClause == null &&) check in the
trunk codeline and ran our queries that are running in NPE in this jira entry and they ran
fine with no NPE. But of course, the solution couldn't be this easy because this change causes
existing tests in junit suite to fail. I will try to undestand what was the logic behind the
changes that went in for DERBY-681 but any other tips at all to make progress on this jira
entry will be greatly appreciated. I am not sure if the queries in question in this jira entry
should follow the new code path introduced by DERBY-681.

I am wondering if anyone who has looked at other regressions caused by DERBY-681 know why
removing the havingClause == null && check makes the queries in this jira entry run
with no NPE. 

> 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
>            Assignee: Mamta A. Satoor
>         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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