/*

   Derby - Class org.apache.derby.impl.sql.compile.HalfOuterJoinNode

   Licensed to the Apache Software Foundation (ASF) under one or more
   contributor license agreements.  See the NOTICE file distributed with
   this work for additional information regarding copyright ownership.
   The ASF licenses this file to you under the Apache License, Version 2.0
   (the "License"); you may not use this file except in compliance with
   the License.  You may obtain a copy of the License at

      http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.

 */

package	org.apache.derby.impl.sql.compile;

import java.util.Properties;
import org.apache.derby.iapi.error.StandardException;
import org.apache.derby.iapi.services.compiler.MethodBuilder;
import org.apache.derby.iapi.services.context.ContextManager;
import org.apache.derby.shared.common.sanity.SanityManager;
import org.apache.derby.iapi.sql.compile.CostEstimate;
import org.apache.derby.iapi.sql.compile.Optimizable;
import org.apache.derby.iapi.sql.compile.OptimizablePredicate;
import org.apache.derby.iapi.util.JBitSet;

/**
 * An HalfOuterJoinNode represents a left or a right outer join result set.
 * Right outer joins are always transformed into left outer joins during
 * preprocessing for simplicity.
 *
 */

class HalfOuterJoinNode extends JoinNode
{
	private boolean rightOuterJoin;
	private boolean transformed = false;

	/**
     * Constructor for a HalfOuterJoinNode.
	 *
	 * @param leftResult		The ResultSetNode on the left side of this join
	 * @param rightResult		The ResultSetNode on the right side of this join
	 * @param onClause			The ON clause
	 * @param usingClause		The USING clause
	 * @param rightOuterJoin	Whether or not this node represents a user
	 *							specified right outer join
	 * @param tableProperties	Properties list associated with the table
     * @param cm                The context manager
	 *
	 * @exception StandardException		Thrown on error
	 */
    HalfOuterJoinNode(ResultSetNode leftResult,
                      ResultSetNode rightResult,
                      ValueNode onClause,
                      ResultColumnList usingClause,
                      boolean rightOuterJoin,
                      Properties tableProperties,
                      ContextManager cm)
		throws StandardException
	{
        super(  leftResult,
                rightResult,
                onClause,
                usingClause,
                null,
				tableProperties,
                null,
                cm);
        this.rightOuterJoin = rightOuterJoin;

		/* We can only flatten an outer join
		 * using the null intolerant predicate xform.
		 * In that case, we will return an InnerJoin.
		 */
		flattenableJoin = false;
	}

	/*
	 *  Optimizable interface
	 */

	/**
	 * @see Optimizable#pushOptPredicate
	 *
	 * @exception StandardException		Thrown on error
	 */
    @Override
	public boolean pushOptPredicate(OptimizablePredicate optimizablePredicate)
			throws StandardException
	{
		/* We should never push the predicate to joinPredicates as in JoinNode.  joinPredicates
		 * should only be predicates relating the two joining tables.  In the case of half join,
		 * it is biased.  If the general predicate (not join predicate) contains refernce to right
		 * result set, and if doesn't qualify, we shouldn't return the row for the result to be
		 * correct, but half join will fill right side NULL and return the row.  So we can only
		 * push predicate to the left, as we do in "pushExpression".  bug 5055
		 */
		FromTable		leftFromTable = (FromTable) leftResultSet;
		if (leftFromTable.getReferencedTableMap().contains(optimizablePredicate.getReferencedMap()))
			return leftFromTable.pushOptPredicate(optimizablePredicate);
		return false;
	}

	/**
	 * Convert this object to a String.  See comments in QueryTreeNode.java
	 * for how this should be done for tree printing.
	 *
	 * @return	This object as a String
	 */
    @Override
	public String toString()
	{
		if (SanityManager.DEBUG)
		{
			return 	"rightOuterJoin: " + rightOuterJoin + "\n" +
				"transformed: " + transformed + "\n" + 
				super.toString();
		}
		else
		{
			return "";
		}
	}

	/** 
	 * Put a ProjectRestrictNode on top of each FromTable in the FromList.
	 * ColumnReferences must continue to point to the same ResultColumn, so
	 * that ResultColumn must percolate up to the new PRN.  However,
	 * that ResultColumn will point to a new expression, a VirtualColumnNode, 
	 * which points to the FromTable and the ResultColumn that is the source for
	 * the ColumnReference.  
	 * (The new PRN will have the original of the ResultColumnList and
	 * the ResultColumns from that list.  The FromTable will get shallow copies
	 * of the ResultColumnList and its ResultColumns.  ResultColumn.expression
	 * will remain at the FromTable, with the PRN getting a new 
	 * VirtualColumnNode for each ResultColumn.expression.)
	 * We then project out the non-referenced columns.  If there are no referenced
	 * columns, then the PRN's ResultColumnList will consist of a single ResultColumn
	 * whose expression is 1.
	 *
	 * @param numTables			Number of tables in the DML Statement
	 * @param gbl				The group by list, if any
	 * @param fromList			The from list, if any
	 *
	 * @return The generated ProjectRestrictNode atop the original FromTable.
	 *
	 * @exception StandardException		Thrown on error
	 */
    @Override
    ResultSetNode preprocess(int numTables,
									GroupByList gbl,
									FromList fromList)
								throws StandardException
	{
		ResultSetNode newTreeTop;

		/* Transform right outer joins to the equivalent left outer join */
		if (rightOuterJoin)
		{
			/* Verify that a user specifed right outer join is transformed into
			 * a left outer join exactly once.
			 */
			if (SanityManager.DEBUG)
			{
				SanityManager.ASSERT(! transformed,
					"Attempting to transform a right outer join multiple times");
			}

			ResultSetNode tmp = leftResultSet;

			leftResultSet = rightResultSet;
			rightResultSet = tmp;
			transformed = true;
		}
		
		newTreeTop = super.preprocess(numTables, gbl, fromList);

		return newTreeTop;
	}

	/**
	 * Push expressions down to the first ResultSetNode which can do expression
	 * evaluation and has the same referenced table map.
	 * RESOLVE - This means only pushing down single table expressions to
	 * DistinctNodes today.  Once we have a better understanding of how
	 * the optimizer will work, we can push down join clauses.
	 *
	 * @param outerPredicateList	The PredicateList from the outer RS.
	 *
	 * @exception StandardException		Thrown on error
	 */
    @Override
    void pushExpressions(PredicateList outerPredicateList)
					throws StandardException
	{
		FromTable		leftFromTable = (FromTable) leftResultSet;
		FromTable		rightFromTable = (FromTable) rightResultSet;

		/* We only try to push single table predicates to the left.
		 * Pushing them to the right would give incorrect semantics.
		 * We use the logic for pushing down single table predicates here.
		 */
		pushExpressionsToLeft(outerPredicateList);

		/* Push the pushable outer join predicates to the right.  This is done
		 * bottom up, hence at the end of this method, so that outer join
		 * conditions only get pushed down 1 level.
		 * We use the optimizer's logic for pushing down join clause here.
		 */
		// Walk joinPredicates backwards due to possible deletes
		for (int index = joinPredicates.size() - 1; index >= 0; index --)
		{
			Predicate predicate;

            predicate = joinPredicates.elementAt(index);
			if (! predicate.getPushable())
			{
				continue;
			}

			getRightPredicateList().addPredicate(predicate);

			/* Remove the matching predicate from the outer list */
			joinPredicates.removeElementAt(index);
		}

		/* Recurse down both sides of tree */
        PredicateList noPredicates = new PredicateList(getContextManager());
		leftFromTable.pushExpressions(getLeftPredicateList());
		rightFromTable.pushExpressions(noPredicates);
	}

    /**
     * This method recursively:
     * <ul>
     *    <li>determines if this part of the query tree is a compound OJ of
     *            the shape required for reordering and if so,</li>
     *    <li>does a reordering.</li>
     * </ul>
     * <pre>
     *
     *    OJ1  pT1T2                      OJ1  pT2T3
     *   /  \                             / \
     *  /    \                 can       /   t3
     * t1    OJ2 pT2T3       reorder    /
     *       /  \              to      OJ2  pT1T2
     *      /    \                    /   \
     *     t2    t3                  /     \
     *                             t1     t2
     *
     * where pR1R2 is a null-rejecting predicate which references the schema
     * of joinee R1 and R2, cf. terminology explanation in #isNullRejecting.
     * <p/>
     * OJ1 represents <em>this</em> before and after the reordering.
     * </pre>
     * <p/>
     * The join predicates are assumed to be in CNF form.
     * <p/>
     * <em>Note:</em> Present implementation limitations
     * <ul>
     *   <li>Only left outer joins are considered, i.e. both OJs in diagram
     *       above must be LOJ.</li>
     *   <li>Top left side must be a base table (t1 above). The bottow right
     *       side
*       (t3 above) may be another OJ, so reordering can happen
     *       recursively.</li>
     * </ul>
     *
     * @param numTables number of tables involved (needed to right size the
     *                  bitmaps)
     * @return boolean true if any reordering took place at this level or deeper
     *                 so caller can know whether rebinding may be necessary
     * @throws StandardException standard error policy
     */
    @Override
    boolean LOJ_reorderable(int numTables)
		throws StandardException
	{
		boolean anyChange = false;

		ResultSetNode logicalLeftResultSet;  // row-preserving side
		ResultSetNode logicalRightResultSet; // null-producing side

		// Figure out which is the row-preserving side and which is
		// null-producing side.
		if (rightOuterJoin)
		{ // right outer join
			logicalLeftResultSet  = rightResultSet;
			logicalRightResultSet = leftResultSet;
		}
		else 
		{
			logicalLeftResultSet  = leftResultSet;
			logicalRightResultSet = rightResultSet;
		}
		
		// Redundantly normalize the ON predicate (it will also be called in preprocess()).
		super.normExpressions();

        // This is a very simple OJ of base tables. Do nothing.
		if (logicalLeftResultSet instanceof FromBaseTable &&
			logicalRightResultSet instanceof FromBaseTable)
			return anyChange;

        // Recursively check if we can reordering OJ, and build the table
		// references. Note that joins may have been reordered and therefore the
		// table references need to be recomputed.
		if (logicalLeftResultSet instanceof HalfOuterJoinNode)
		{
			anyChange =	((HalfOuterJoinNode)logicalLeftResultSet).LOJ_reorderable(numTables) || anyChange;
		}
		else if (!(logicalLeftResultSet instanceof FromBaseTable))
        {// left operand must be either a base table or another OJ
			// In principle, we don't care about the left operand.  However, we
			// need to re-bind the resultColumns.  If the left operand is a
			// view, we may have to re-bind the where clause etc...
			// We ran into difficulty for the following query:
			//  create view v8 (cv, bv, av) as (select c, b, a from t union select f, e, d from s);
			//  select * from v8 left outer join (s left outer join r on (f = i)) on (e=v8.bv);
			return anyChange;
		}

		if (logicalRightResultSet instanceof HalfOuterJoinNode)
		{
			anyChange = ((HalfOuterJoinNode)logicalRightResultSet).LOJ_reorderable(numTables) || anyChange;
		}
		else if (!(logicalRightResultSet instanceof FromBaseTable))
        {// right operand must be either a base table or another OJ
			return anyChange;
		}

        // It is much easier to do OJ reordering if there is no ROJ.
		// However, we ran into some problem downstream when we transform an ROJ
		// into LOJ -- transformOuterJoin() didn't expect ROJ to be transformed
		// into LOJ alread.  So, we skip optimizing ROJ at the moment.
		if (rightOuterJoin || (logicalRightResultSet instanceof HalfOuterJoinNode && 
							   ((HalfOuterJoinNode)logicalRightResultSet).rightOuterJoin))
		{
			return LOJ_bindResultColumns(anyChange);
		}

        // Build the data structure for testing/doing OJ reordering.  Fill in
        // the table references on row-preserving and null-producing sides.  It
        // may be possible that either operand is a complex view.

        JBitSet RPReferencedTableMap; // Row-preserving
        JBitSet NPReferencedTableMap; // Null-producing

		RPReferencedTableMap = logicalLeftResultSet.LOJgetReferencedTables(numTables);
		NPReferencedTableMap = logicalRightResultSet.LOJgetReferencedTables(numTables);

		if ((RPReferencedTableMap == null || NPReferencedTableMap == null) &&
			anyChange)
		{
			return LOJ_bindResultColumns(anyChange);
		}


        // Check if logical right operand is another OJ... so we may be able
        // to push the join.
        if (logicalRightResultSet instanceof HalfOuterJoinNode)
		{
            // Get the row-preserving map of the  child OJ
            JBitSet  nestedChildOJRPRefTableMap =
                ((HalfOuterJoinNode)logicalRightResultSet).
                LOJgetRPReferencedTables(numTables);

            // Checks that top has p(t1,t2)
            if ( ! isNullRejecting(
                         joinClause,
                         RPReferencedTableMap,
                         nestedChildOJRPRefTableMap)) {
                // No, give up.
                return LOJ_bindResultColumns(anyChange);
            }

            // Get the null-producing map of the child OJ
            JBitSet  nestedChildOJNPRefTableMap =
                ((HalfOuterJoinNode)logicalRightResultSet).
                LOJgetNPReferencedTables(numTables);

            // Checks that right child has p(t2,t3)
            if ( isNullRejecting(
                         ((HalfOuterJoinNode)logicalRightResultSet).joinClause,
                         nestedChildOJRPRefTableMap,
                         nestedChildOJNPRefTableMap)) {
                // Push the current OJ into the next level For safety, check
                // the JoinNode data members: they should null or empty list
                // before we proceed.
                if (super.subqueryList.size() != 0 ||
                    ((JoinNode)logicalRightResultSet).
                        subqueryList.size() != 0 ||
                    super.joinPredicates.size() != 0 ||
                    ((JoinNode)logicalRightResultSet).
                        joinPredicates.size() != 0 ||
                    super.usingClause != null ||
                    ((JoinNode)logicalRightResultSet).
                        usingClause != null) {

                    return LOJ_bindResultColumns(anyChange); //  get out of here
                }
                anyChange = true; // we are reordering the OJs.

                ResultSetNode tmp = logicalLeftResultSet;
                ResultSetNode LChild, RChild;

                //            this OJ
                //            /      \
                //  logicalLeftRS   LogicalRightRS
                //                   /     \
                //                LChild  RChild
                // becomes
                //
                //               this OJ
                //               /      \
                //     LogicalRightRS   RChild
                //           /     \
                // logicalLeftRS LChild <<< we need to be careful about this
                //                          order as the "LogicalRightRS
                //                          may be a ROJ
                //

                // handle the lower level OJ node
                LChild = ((HalfOuterJoinNode)logicalRightResultSet).
                    leftResultSet;
                RChild = ((HalfOuterJoinNode)logicalRightResultSet).
                    rightResultSet;

                ((HalfOuterJoinNode)logicalRightResultSet).
                    rightResultSet = LChild;
                ((HalfOuterJoinNode)logicalRightResultSet).
                    leftResultSet  = tmp;

                // switch the ON clause
                {
                    ValueNode vn = joinClause;
                    joinClause =
                        ((HalfOuterJoinNode)logicalRightResultSet).joinClause;
                    ((HalfOuterJoinNode)logicalRightResultSet).joinClause = vn;
                }

                // No need to switch HalfOuterJoinNode data members for now
                // because we are handling only OJ.
                // boolean local_rightOuterJoin = rightOuterJoin;
                // boolean local_transformed    = transformed;
                // rightOuterJoin = ((HalfOuterJoinNode)logicalRightResultSet).
                //     rightOuterJoin;
                // transformed = ((HalfOuterJoinNode)logicalRightResultSet).
                //     transformed;
                // ((HalfOuterJoinNode)logicalRightResultSet).rightOuterJoin =
                //     local_rightOuterJoin;
                // ((HalfOuterJoinNode)logicalRightResultSet).transformed =
                //     local_transformed;

                FromList localFromList = new FromList(
                        getOptimizerFactory().doJoinOrderOptimization(),
                        getContextManager());

                // switch OJ nodes: by handling the current OJ node
                leftResultSet  = logicalRightResultSet;
                rightResultSet = RChild;

                // rebuild the result columns and re-bind column references
                ((HalfOuterJoinNode)leftResultSet).setResultColumns( null );
                 // localFromList is empty:
                ((JoinNode)leftResultSet).bindResultColumns(localFromList);

                // left operand must be another OJ, so recurse.
                boolean localChange = ((HalfOuterJoinNode)leftResultSet).
                    LOJ_reorderable(numTables);
            }
        }

        return LOJ_bindResultColumns(anyChange);
    }



    /**
     * Tests pRiRj in the sense of Galindo-Legaria et al: <em>Outerjoin
     * Simplification and Reordering for Query Optimization</em>, ACM
     * Transactions on Database Systems, Vol. 22, No. 1, March 1997, Pages
     * 43-74:
     * <quote>
     *  "The set of attributes referenced by a predicate p is called the schema
     *  of p, and denoted sch(p). As a notational convention, we annotate
     *  predicates to reflect their schema. If sch(p) includes attributes of
     *  both Ri, Rj and only those relations, we can write the predicate as
     *  pRiRj.
     * </quote>
     *
     * If a null-valued column is compared in a predicate that
     * contains no OR connectives, the predicate evaluates to undefined, and
     * the tuple is rejected. The relops satisfy this criterion.
     * <p/>
     * To simplify analysis, we only accept predicates of the form:
     * <pre>
     * X relop Y [and .. and X-n relop Y-n]
     * </pre>
     *
     * At least one of the relops should reference both {@code leftTableMap}
     * and {@code rightTableMap}, so that we know that sch(p) includes
     * attributes of both Ri, Rj. I.e.
     *
     * <p/>
     * {@code X} should be a table in {@code leftTableMap}, and
     * {@code Y} should be a table in {@code rightTableMap}.
     * <p/>
     * <b>or</b>
     * {@code X} should be a table in {@code rightTableMap}, and
     * {@code Y} should be a table in {@code leftTableMap}.
     *
     * @param joinClause The join clause (i.e. predicate) we want to check
     * @param leftTableMap a bit map representing the tables expected for the
     *                     predicate (logical left)
     * @param rightTableMap a bit map representing the tables expected for the
     *                      predicate (logical right)
     * @return true if the {@code joinClause} has at least one relop that
     *              references both {@code leftTableMap} and {@code
     *              rightTableMap}
     * @throws StandardException standard exception policy
     */

private boolean isNullRejecting (
        ValueNode joinClause,
        JBitSet leftTableMap,
        JBitSet rightTableMap)
        throws StandardException {

        ValueNode vn = joinClause;
        boolean foundPred = false;

        while (vn != null) {
            AndNode andNode = null;

            if (vn instanceof AndNode) {
                andNode = (AndNode)vn;
                vn = andNode.getLeftOperand();
            }

            if (vn instanceof BinaryRelationalOperatorNode) {

                BinaryRelationalOperatorNode relop =
                    (BinaryRelationalOperatorNode)vn;
                ValueNode leftCol = relop.getLeftOperand();
                ValueNode rightCol = relop.getRightOperand();

                boolean leftFound = false;
                boolean rightFound = false;

                if (leftCol instanceof ColumnReference) {
                    if (leftTableMap.get(
                                ((ColumnReference)leftCol).getTableNumber())) {

                        leftFound = true;

                    } else if (
                        rightTableMap.get(
                            ((ColumnReference)leftCol).getTableNumber())) {

                        rightFound = true;
                    } else {
                        // references unexpected table
                        return false;
                    }

                }

                if (rightCol instanceof ColumnReference) {
                    if (leftTableMap.get(
                                ((ColumnReference)rightCol).getTableNumber())) {
                        leftFound = true;

                    } else if (rightTableMap.get(
                                       ((ColumnReference)rightCol).
                                       getTableNumber())) {
                        rightFound = true;
                    } else {
                        // references unexpected table, sch(p) is wrong
                        return false;
                    }
                }


                if (leftFound && rightFound) {
                    foundPred = true; // sch(p) covers both R1 and R2
                }
            } else if ((vn instanceof BooleanConstantNode) && foundPred) {
                // OK, simple predicate which covers both R1 and R2 found
            } else {
                // reject other operators, e.g. OR
                return false;
            }

            if (andNode != null) {
                vn = andNode.getRightOperand();
            } else {
                vn = null;
            }
        }

        return foundPred;
    }



	// This method re-binds the result columns which may be referenced in the ON
	// clause in this node.
    boolean LOJ_bindResultColumns(boolean anyChange)
		throws StandardException
	{
		if (anyChange)
		{
			setResultColumns( null );
            FromList localFromList = new FromList(
                    getOptimizerFactory().doJoinOrderOptimization(),
                    getContextManager());
			((JoinNode)this).bindResultColumns(localFromList);
		}
		return anyChange;
	}
	

	/**
	 * Transform any Outer Join into an Inner Join where applicable.
	 * (Based on the existence of a null intolerant
	 * predicate on the inner table.)
	 *
	 * @param predicateTree	The predicate tree for the query block
	 *
	 * @return The new tree top (OuterJoin or InnerJoin).
	 *
	 * @exception StandardException		Thrown on error
	 */
    @Override
    FromTable transformOuterJoins(ValueNode predicateTree, int numTables)
		throws StandardException
	{
		ResultSetNode innerRS;

		if (predicateTree == null)
		{
			/* We can't transform this node, so tell both sides of the 
			 * outer join that they can't get flattened into outer query block.
			 */
			leftResultSet.notFlattenableJoin();
			rightResultSet.notFlattenableJoin();
			return this;
		}

		super.transformOuterJoins(predicateTree, numTables);

		if (rightOuterJoin)
		{
			if (SanityManager.DEBUG)
			{
				SanityManager.ASSERT(! transformed,
					"right OJ not expected to be transformed into left OJ yet");
			}
			innerRS = leftResultSet;
		}
		else
		{
			innerRS = rightResultSet;
		}

        // We a relooking for a null intolerant predicate on an inner table.
        // Collect base table numbers, also if they are located inside a join
        // (inner or outer), that is, the inner operand is itself a join,
        // recursively.
        JBitSet innerMap = innerRS.LOJgetReferencedTables(numTables);

		/* Walk predicates looking for 
		 * a null intolerant predicate on the inner table.
		 */
		ValueNode vn = predicateTree;
		while (vn instanceof AndNode)
		{
			AndNode and = (AndNode) vn;
			ValueNode left = and.getLeftOperand();

			/* Skip IS NULL predicates as they are not null intolerant */
            if (left.getClass().equals(IsNullNode.class) &&
                ((IsNullNode)left).isNullNode())
			{
				vn = and.getRightOperand();
				continue;
			}

			/* Only consider predicates that are relops */
			if (left instanceof RelationalOperator)
			{
				JBitSet refMap = new JBitSet(numTables);
				/* Do not consider method calls, 
				 * conditionals, field references, etc. */
				if (! (left.categorize(refMap, true)))
				{
					vn = and.getRightOperand();
					continue;
				}

				/* If the predicate is a null intolerant predicate
				 * on the right side then we can flatten to an
				 * inner join.  We do the xform here, flattening
				 * will happen later.
				 */
				for (int bit = 0; bit < numTables; bit++)
				{
					if (refMap.get(bit) && innerMap.get(bit))
					{
						// OJ -> IJ
                        JoinNode ij =  new JoinNode(
												leftResultSet,
												rightResultSet,
												joinClause,
												null,
												getResultColumns(),
												null,
												null,
												getContextManager());
						ij.setTableNumber(tableNumber);
						ij.setSubqueryList(subqueryList);
                        ij.setAggregates(aggregates);
						return ij;
					}
				}
			}

			vn = and.getRightOperand();
		}

		/* We can't transform this node, so tell both sides of the 
		 * outer join that they can't get flattened into outer query block.
		 */
		leftResultSet.notFlattenableJoin();
		rightResultSet.notFlattenableJoin();

		return this;
	}

	/** @see JoinNode#adjustNumberOfRowsReturned */
    @Override
	protected void adjustNumberOfRowsReturned(CostEstimate costEstimate)
	{
		/*
		** An outer join returns at least as many rows as in the outer
		** table. Even if this started as a right outer join, it will
		** have been transformed to a left outer join by this point.
		*/
		CostEstimate outerCost = getLeftResultSet().getCostEstimate();

		if (costEstimate.rowCount() < outerCost.rowCount())
		{
			costEstimate.setCost(costEstimate.getEstimatedCost(),
								 outerCost.rowCount(),
								 outerCost.rowCount());
		}
	}

    /**
     * Generate the code for an inner join node.
	 *
	 * @exception StandardException		Thrown on error
     */
    @Override
    void generate(ActivationClassBuilder acb, MethodBuilder mb)
						throws StandardException
	{
		/* Verify that a user specifed right outer join is transformed into
		 * a left outer join exactly once.
		 */
		if (SanityManager.DEBUG)
		{
			SanityManager.ASSERT(rightOuterJoin == transformed,
				"rightOuterJoin (" + rightOuterJoin +
				") is expected to equal transformed (" + transformed + ")");
		}
		super.generateCore(acb, mb, LEFTOUTERJOIN);
	}

	/**
	 * Generate	and add any arguments specifict to outer joins.
	 * Generate	the methods (and add them as parameters) for
	 * returning an empty row from 1 or more sides of an outer join,
	 * if required.  Pass whether or not this was originally a
	 * right outer join.
	 *
	 * @param acb		The ActivationClassBuilder
	 * @param mb the method the generate code is to go into
	 *
	 * return The args that have been added
	 *
	 * @exception StandardException		Thrown on error
	 */
    @Override
    int addOuterJoinArguments(ActivationClassBuilder acb, MethodBuilder mb)
		 throws StandardException
	 {
		/* Nulls always generated from the right */
		rightResultSet.getResultColumns().generateNulls(acb, mb);

		/* Was this originally a right outer join? */
		mb.push(rightOuterJoin);

		return 2;
	 }

	/**
	 * Return the number of arguments to the join result set.
	 */
    @Override
	protected int getNumJoinArguments()
	{
		/* We add two more arguments than the superclass does */
		return super.getNumJoinArguments() + 2;
	}

    @Override
    void oneRowRightSide(ActivationClassBuilder acb, MethodBuilder mb)
	{
		// always return false for now
		mb.push(false);
		mb.push(false);  //isNotExists?
	}

	/**
	 * Return the logical left result set for this qualified
	 * join node.
	 * (For RIGHT OUTER JOIN, the left is the right
	 * and the right is the left and the JOIN is the NIOJ).
	 */
    @Override
	ResultSetNode getLogicalLeftResultSet()
	{
		if (rightOuterJoin)
		{
			return rightResultSet;
		}
		else
		{
			return leftResultSet;
		}
	}

	/**
	 * Return the logical right result set for this qualified
	 * join node.
	 * (For RIGHT OUTER JOIN, the left is the right
	 * and the right is the left and the JOIN is the NIOJ).
	 */
    @Override
	ResultSetNode getLogicalRightResultSet()
	{
		if (rightOuterJoin)
		{
			return leftResultSet;
		}
		else
		{
			return rightResultSet;
		}
	}

	/**
	 * Return true if right outer join or false if left outer join
	 * Used to set Nullability correctly in JoinNode
	 */
    boolean isRightOuterJoin()
	{
		return rightOuterJoin;
	}
    
	/**
	 * If this is a right outer join node with USING/NATURAL clause, then
	 *  check if the passed ResultColumn is a join column. If yes, then 
	 *  ResultColumn should be marked such. DERBY-4631
	 */
    @Override
    void isJoinColumnForRightOuterJoin(ResultColumn rc)
	{
		if (isRightOuterJoin() && usingClause != null &&  
				usingClause.getResultColumn(rc.getUnderlyingOrAliasName()) != null) {
			rc.setRightOuterJoinUsingClause(true);
			rc.setJoinResultset(this);
		}
	}

	// return the Null-producing table references
    JBitSet LOJgetNPReferencedTables(int numTables)
				throws StandardException
	{
		if (rightOuterJoin && !transformed)
            return leftResultSet.LOJgetReferencedTables(numTables);
		else
            return rightResultSet.LOJgetReferencedTables(numTables);
	}

    // return the row-preserving table references
    public JBitSet LOJgetRPReferencedTables(int numTables)
                throws StandardException
    {
        if (rightOuterJoin && !transformed)
            return rightResultSet.LOJgetReferencedTables(numTables);
        else
            return leftResultSet.LOJgetReferencedTables(numTables);
    }
}
