public boolean matches(RelOptRuleCall call) {
   JoinRel join = (JoinRel) call.rels[0];
   switch (join.getJoinType()) {
     case INNER:
     case LEFT:
       return true;
     case FULL:
     case RIGHT:
       return false;
     default:
       throw Util.unexpected(join.getJoinType());
   }
 }
  /**
   * Combines the join filters from the left and right inputs (if they are MultiJoinRels) with the
   * join filter in the joinrel into a single AND'd join filter, unless the inputs correspond to
   * null generating inputs in an outer join
   *
   * @param joinRel join rel
   * @param left left child of the joinrel
   * @param right right child of the joinrel
   * @return combined join filters AND'd together
   */
  private RexNode combineJoinFilters(JoinRel joinRel, RelNode left, RelNode right) {
    RexBuilder rexBuilder = joinRel.getCluster().getRexBuilder();
    JoinRelType joinType = joinRel.getJoinType();

    // first need to adjust the RexInputs of the right child, since
    // those need to shift over to the right
    RexNode rightFilter = null;
    if (canCombine(right, joinType.generatesNullsOnRight())) {
      MultiJoinRel multiJoin = (MultiJoinRel) right;
      rightFilter = shiftRightFilter(joinRel, left, multiJoin, multiJoin.getJoinFilter());
    }

    // AND the join condition if this isn't a left or right outer join;
    // in those cases, the outer join condition is already tracked
    // separately
    RexNode newFilter = null;
    if ((joinType != JoinRelType.LEFT) && (joinType != JoinRelType.RIGHT)) {
      newFilter = joinRel.getCondition();
    }
    if (canCombine(left, joinType.generatesNullsOnLeft())) {
      RexNode leftFilter = ((MultiJoinRel) left).getJoinFilter();
      newFilter = RelOptUtil.andJoinFilters(rexBuilder, newFilter, leftFilter);
    }
    newFilter = RelOptUtil.andJoinFilters(rexBuilder, newFilter, rightFilter);

    return newFilter;
  }
  /**
   * Combines the outer join conditions and join types from the left and right join inputs. If the
   * join itself is either a left or right outer join, then the join condition corresponding to the
   * join is also set in the position corresponding to the null-generating input into the join. The
   * join type is also set.
   *
   * @param joinRel join rel
   * @param combinedInputs the combined inputs to the join
   * @param left left child of the joinrel
   * @param right right child of the joinrel
   * @param combinedConds the array containing the combined join conditions
   * @param joinTypes the array containing the combined join types
   * @return combined join filters AND'd together
   */
  private RexNode[] combineOuterJoins(
      JoinRel joinRel,
      RelNode[] combinedInputs,
      RelNode left,
      RelNode right,
      RexNode[] combinedConds,
      JoinRelType[] joinTypes) {
    JoinRelType joinType = joinRel.getJoinType();
    int nCombinedInputs = combinedInputs.length;
    boolean leftCombined = canCombine(left, joinType.generatesNullsOnLeft());
    boolean rightCombined = canCombine(right, joinType.generatesNullsOnRight());
    if (joinType == JoinRelType.LEFT) {
      if (leftCombined) {
        copyOuterJoinInfo((MultiJoinRel) left, combinedConds, joinTypes, 0, 0, null, null);
      } else {
        joinTypes[0] = JoinRelType.INNER;
      }
      combinedConds[nCombinedInputs - 1] = joinRel.getCondition();
      joinTypes[nCombinedInputs - 1] = joinType;
    } else if (joinType == JoinRelType.RIGHT) {
      if (rightCombined) {
        copyOuterJoinInfo(
            (MultiJoinRel) right,
            combinedConds,
            joinTypes,
            1,
            left.getRowType().getFieldCount(),
            right.getRowType().getFields(),
            joinRel.getRowType().getFields());
      } else {
        joinTypes[nCombinedInputs - 1] = JoinRelType.INNER;
      }
      combinedConds[0] = joinRel.getCondition();
      joinTypes[0] = joinType;
    } else {
      int nInputsLeft;
      if (leftCombined) {
        nInputsLeft = left.getInputs().length;
        copyOuterJoinInfo((MultiJoinRel) left, combinedConds, joinTypes, 0, 0, null, null);
      } else {
        nInputsLeft = 1;
        joinTypes[0] = JoinRelType.INNER;
      }
      if (rightCombined) {
        copyOuterJoinInfo(
            (MultiJoinRel) right,
            combinedConds,
            joinTypes,
            nInputsLeft,
            left.getRowType().getFieldCount(),
            right.getRowType().getFields(),
            joinRel.getRowType().getFields());
      } else {
        joinTypes[nInputsLeft] = JoinRelType.INNER;
      }
    }

    return combinedConds;
  }
  /**
   * Combines the inputs into a JoinRel into an array of inputs.
   *
   * @param join original join
   * @param left left input into join
   * @param right right input into join
   * @param projFieldsList returns a list of the new combined projection fields
   * @param joinFieldRefCountsList returns a list of the new combined join field reference counts
   * @return combined left and right inputs in an array
   */
  private RelNode[] combineInputs(
      JoinRel join,
      RelNode left,
      RelNode right,
      List<BitSet> projFieldsList,
      List<int[]> joinFieldRefCountsList) {
    // leave the null generating sides of an outer join intact; don't
    // pull up those children inputs into the array we're constructing
    int nInputs;
    int nInputsOnLeft;
    MultiJoinRel leftMultiJoin = null;
    JoinRelType joinType = join.getJoinType();
    boolean combineLeft = canCombine(left, joinType.generatesNullsOnLeft());
    if (combineLeft) {
      leftMultiJoin = (MultiJoinRel) left;
      nInputs = left.getInputs().length;
      nInputsOnLeft = nInputs;
    } else {
      nInputs = 1;
      nInputsOnLeft = 1;
    }
    MultiJoinRel rightMultiJoin = null;
    boolean combineRight = canCombine(right, joinType.generatesNullsOnRight());
    if (combineRight) {
      rightMultiJoin = (MultiJoinRel) right;
      nInputs += right.getInputs().length;
    } else {
      nInputs += 1;
    }

    RelNode[] newInputs = new RelNode[nInputs];
    int i = 0;
    if (combineLeft) {
      for (; i < left.getInputs().length; i++) {
        newInputs[i] = leftMultiJoin.getInput(i);
        projFieldsList.add(((MultiJoinRel) left).getProjFields()[i]);
        joinFieldRefCountsList.add(((MultiJoinRel) left).getJoinFieldRefCountsMap().get(i));
      }
    } else {
      newInputs[0] = left;
      i = 1;
      projFieldsList.add(null);
      joinFieldRefCountsList.add(new int[left.getRowType().getFieldCount()]);
    }
    if (combineRight) {
      for (; i < nInputs; i++) {
        newInputs[i] = rightMultiJoin.getInput(i - nInputsOnLeft);
        projFieldsList.add(((MultiJoinRel) right).getProjFields()[i - nInputsOnLeft]);
        joinFieldRefCountsList.add(
            ((MultiJoinRel) right).getJoinFieldRefCountsMap().get(i - nInputsOnLeft));
      }
    } else {
      newInputs[i] = right;
      projFieldsList.add(null);
      joinFieldRefCountsList.add(new int[right.getRowType().getFieldCount()]);
    }

    return newInputs;
  }
  public void onMatch(RelOptRuleCall call) {
    JoinRel origJoinRel = (JoinRel) call.rels[0];

    RelNode left = call.rels[1];
    RelNode right = call.rels[2];

    // combine the children MultiJoinRel inputs into an array of inputs
    // for the new MultiJoinRel
    List<BitSet> projFieldsList = new ArrayList<BitSet>();
    List<int[]> joinFieldRefCountsList = new ArrayList<int[]>();
    RelNode[] newInputs =
        combineInputs(origJoinRel, left, right, projFieldsList, joinFieldRefCountsList);

    // combine the outer join information from the left and right
    // inputs, and include the outer join information from the current
    // join, if it's a left/right outer join
    RexNode[] newOuterJoinConds = new RexNode[newInputs.length];
    JoinRelType[] joinTypes = new JoinRelType[newInputs.length];
    combineOuterJoins(origJoinRel, newInputs, left, right, newOuterJoinConds, joinTypes);

    // pull up the join filters from the children MultiJoinRels and
    // combine them with the join filter associated with this JoinRel to
    // form the join filter for the new MultiJoinRel
    RexNode newJoinFilter = combineJoinFilters(origJoinRel, left, right);

    // add on the join field reference counts for the join condition
    // associated with this JoinRel
    Map<Integer, int[]> newJoinFieldRefCountsMap = new HashMap<Integer, int[]>();
    addOnJoinFieldRefCounts(
        newInputs,
        origJoinRel.getRowType().getFieldCount(),
        origJoinRel.getCondition(),
        joinFieldRefCountsList,
        newJoinFieldRefCountsMap);

    RexNode newPostJoinFilter = combinePostJoinFilters(origJoinRel, left, right);

    RelNode multiJoin =
        new MultiJoinRel(
            origJoinRel.getCluster(),
            newInputs,
            newJoinFilter,
            origJoinRel.getRowType(),
            (origJoinRel.getJoinType() == JoinRelType.FULL),
            newOuterJoinConds,
            joinTypes,
            projFieldsList.toArray(new BitSet[projFieldsList.size()]),
            newJoinFieldRefCountsMap,
            newPostJoinFilter);

    call.transformTo(multiJoin);
  }
  // implement RelOptRule
  public void onMatch(RelOptRuleCall call) {
    ProjectRel origProj = call.rel(0);
    JoinRel joinRel = call.rel(1);

    // locate all fields referenced in the projection and join condition;
    // determine which inputs are referenced in the projection and
    // join condition; if all fields are being referenced and there are no
    // special expressions, no point in proceeding any further
    PushProjector pushProject =
        new PushProjector(origProj, joinRel.getCondition(), joinRel, preserveExprCondition);
    if (pushProject.locateAllRefs()) {
      return;
    }

    // create left and right projections, projecting only those
    // fields referenced on each side
    RelNode leftProjRel = pushProject.createProjectRefsAndExprs(joinRel.getLeft(), true, false);
    RelNode rightProjRel = pushProject.createProjectRefsAndExprs(joinRel.getRight(), true, true);

    // convert the join condition to reference the projected columns
    RexNode newJoinFilter = null;
    int[] adjustments = pushProject.getAdjustments();
    if (joinRel.getCondition() != null) {
      List<RelDataTypeField> projJoinFieldList = new ArrayList<RelDataTypeField>();
      projJoinFieldList.addAll(joinRel.getSystemFieldList());
      projJoinFieldList.addAll(leftProjRel.getRowType().getFieldList());
      projJoinFieldList.addAll(rightProjRel.getRowType().getFieldList());
      newJoinFilter =
          pushProject.convertRefsAndExprs(joinRel.getCondition(), projJoinFieldList, adjustments);
    }

    // create a new joinrel with the projected children
    JoinRel newJoinRel =
        new JoinRel(
            joinRel.getCluster(),
            leftProjRel,
            rightProjRel,
            newJoinFilter,
            joinRel.getJoinType(),
            Collections.<String>emptySet(),
            joinRel.isSemiJoinDone(),
            joinRel.getSystemFieldList());

    // put the original project on top of the join, converting it to
    // reference the modified projection list
    ProjectRel topProject = pushProject.createNewProject(newJoinRel, adjustments);

    call.transformTo(topProject);
  }
  public void onMatch(RelOptRuleCall call) {
    assert matches(call);
    final JoinRel join = (JoinRel) call.rels[0];
    final List<Integer> leftKeys = new ArrayList<Integer>();
    final List<Integer> rightKeys = new ArrayList<Integer>();
    RelNode right = join.getRight();
    final RelNode left = join.getLeft();
    RexNode remainingCondition =
        RelOptUtil.splitJoinCondition(left, right, join.getCondition(), leftKeys, rightKeys);
    assert leftKeys.size() == rightKeys.size();
    final List<CorrelatorRel.Correlation> correlationList =
        new ArrayList<CorrelatorRel.Correlation>();
    if (leftKeys.size() > 0) {
      final RelOptCluster cluster = join.getCluster();
      final RexBuilder rexBuilder = cluster.getRexBuilder();
      int k = 0;
      RexNode condition = null;
      for (Integer leftKey : leftKeys) {
        Integer rightKey = rightKeys.get(k++);
        final String dyn_inIdStr = cluster.getQuery().createCorrel();
        final int dyn_inId = RelOptQuery.getCorrelOrdinal(dyn_inIdStr);

        // Create correlation to say 'each row, set variable #id
        // to the value of column #leftKey'.
        correlationList.add(new CorrelatorRel.Correlation(dyn_inId, leftKey));
        condition =
            RelOptUtil.andJoinFilters(
                rexBuilder,
                condition,
                rexBuilder.makeCall(
                    SqlStdOperatorTable.equalsOperator,
                    rexBuilder.makeInputRef(
                        right.getRowType().getFieldList().get(rightKey).getType(), rightKey),
                    rexBuilder.makeCorrel(
                        left.getRowType().getFieldList().get(leftKey).getType(), dyn_inIdStr)));
      }
      right = CalcRel.createFilter(right, condition);
    }
    RelNode newRel =
        new CorrelatorRel(
            join.getCluster(),
            left,
            right,
            remainingCondition,
            correlationList,
            join.getJoinType());
    call.transformTo(newRel);
  }
        public void onMatch(RelOptRuleCall call) {
          JoinRel join = (JoinRel) call.rels[0];
          List<RexNode> expList = new ArrayList<RexNode>(Arrays.asList(join.getChildExps()));
          if (reduceExpressions(join, expList)) {
            call.transformTo(
                new JoinRel(
                    join.getCluster(),
                    join.getLeft(),
                    join.getRight(),
                    expList.get(0),
                    join.getJoinType(),
                    join.getVariablesStopped()));

            // New plan is absolutely better than old plan.
            call.getPlanner().setImportance(join, 0.0);
          }
        }