Class HalfOuterJoinNode

All Implemented Interfaces:
Optimizable, Visitable

class HalfOuterJoinNode extends JoinNode
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.
  • Field Details

    • rightOuterJoin

      private boolean rightOuterJoin
    • transformed

      private boolean transformed
  • Constructor Details

    • HalfOuterJoinNode

      HalfOuterJoinNode(ResultSetNode leftResult, ResultSetNode rightResult, ValueNode onClause, ResultColumnList usingClause, boolean rightOuterJoin, Properties tableProperties, ContextManager cm) throws StandardException
      Constructor for a HalfOuterJoinNode.
      Parameters:
      leftResult - The ResultSetNode on the left side of this join
      rightResult - The ResultSetNode on the right side of this join
      onClause - The ON clause
      usingClause - The USING clause
      rightOuterJoin - Whether or not this node represents a user specified right outer join
      tableProperties - Properties list associated with the table
      cm - The context manager
      Throws:
      StandardException - Thrown on error
  • Method Details

    • pushOptPredicate

      public boolean pushOptPredicate(OptimizablePredicate optimizablePredicate) throws StandardException
      Description copied from interface: Optimizable
      Push an OptimizablePredicate down, if this node accepts it.
      Specified by:
      pushOptPredicate in interface Optimizable
      Overrides:
      pushOptPredicate in class JoinNode
      Parameters:
      optimizablePredicate - OptimizablePredicate to push down.
      Returns:
      Whether or not the predicate was pushed down.
      Throws:
      StandardException - Thrown on error
      See Also:
    • toString

      public String toString()
      Convert this object to a String. See comments in QueryTreeNode.java for how this should be done for tree printing.
      Overrides:
      toString in class TableOperatorNode
      Returns:
      This object as a String
    • preprocess

      ResultSetNode preprocess(int numTables, GroupByList gbl, FromList fromList) throws StandardException
      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.
      Overrides:
      preprocess in class JoinNode
      Parameters:
      numTables - Number of tables in the DML Statement
      gbl - The group by list, if any
      fromList - The from list, if any
      Returns:
      The generated ProjectRestrictNode atop the original FromTable.
      Throws:
      StandardException - Thrown on error
    • pushExpressions

      void pushExpressions(PredicateList outerPredicateList) throws StandardException
      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.
      Overrides:
      pushExpressions in class JoinNode
      Parameters:
      outerPredicateList - The PredicateList from the outer RS.
      Throws:
      StandardException - Thrown on error
    • LOJ_reorderable

      boolean LOJ_reorderable(int numTables) throws StandardException
      This method recursively:
      • determines if this part of the query tree is a compound OJ of the shape required for reordering and if so,
      • does a reordering.
      
          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.
       

      OJ1 represents this before and after the reordering.

      The join predicates are assumed to be in CNF form.

      Note: Present implementation limitations

      • Only left outer joins are considered, i.e. both OJs in diagram above must be LOJ.
      • 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.
      Overrides:
      LOJ_reorderable in class JoinNode
      Parameters:
      numTables - number of tables involved (needed to right size the bitmaps)
      Returns:
      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
    • isNullRejecting

      private boolean isNullRejecting(ValueNode joinClause, JBitSet leftTableMap, JBitSet rightTableMap) throws StandardException
      Tests pRiRj in the sense of Galindo-Legaria et al: Outerjoin Simplification and Reordering for Query Optimization, ACM Transactions on Database Systems, Vol. 22, No. 1, March 1997, Pages 43-74: "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. 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.

      To simplify analysis, we only accept predicates of the form:

       X relop Y [and .. and X-n relop Y-n]
       
      At least one of the relops should reference both leftTableMap and rightTableMap, so that we know that sch(p) includes attributes of both Ri, Rj. I.e.

      X should be a table in leftTableMap, and Y should be a table in rightTableMap.

      or X should be a table in rightTableMap, and Y should be a table in leftTableMap.

      Parameters:
      joinClause - The join clause (i.e. predicate) we want to check
      leftTableMap - a bit map representing the tables expected for the predicate (logical left)
      rightTableMap - a bit map representing the tables expected for the predicate (logical right)
      Returns:
      true if the joinClause has at least one relop that references both leftTableMap and rightTableMap
      Throws:
      StandardException - standard exception policy
    • LOJ_bindResultColumns

      boolean LOJ_bindResultColumns(boolean anyChange) throws StandardException
      Throws:
      StandardException
    • transformOuterJoins

      FromTable transformOuterJoins(ValueNode predicateTree, int numTables) throws StandardException
      Transform any Outer Join into an Inner Join where applicable. (Based on the existence of a null intolerant predicate on the inner table.)
      Overrides:
      transformOuterJoins in class JoinNode
      Parameters:
      predicateTree - The predicate tree for the query block
      Returns:
      The new tree top (OuterJoin or InnerJoin).
      Throws:
      StandardException - Thrown on error
    • adjustNumberOfRowsReturned

      protected void adjustNumberOfRowsReturned(CostEstimate costEstimate)
      Description copied from class: JoinNode
      Some types of joins (e.g. outer joins) will return a different number of rows than is predicted by optimizeIt() in JoinNode. So, adjust this value now. This method does nothing for most join types.
      Overrides:
      adjustNumberOfRowsReturned in class JoinNode
      See Also:
    • generate

      void generate(ActivationClassBuilder acb, MethodBuilder mb) throws StandardException
      Generate the code for an inner join node.
      Overrides:
      generate in class JoinNode
      Parameters:
      acb - The ActivationClassBuilder for the class being built
      mb - The method for the generated code to go into
      Throws:
      StandardException - Thrown on error
    • addOuterJoinArguments

      int addOuterJoinArguments(ActivationClassBuilder acb, MethodBuilder mb) throws StandardException
      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.
      Overrides:
      addOuterJoinArguments in class JoinNode
      Parameters:
      acb - The ActivationClassBuilder
      mb - the method the generate code is to go into return The args that have been added
      Throws:
      StandardException - Thrown on error
    • getNumJoinArguments

      protected int getNumJoinArguments()
      Return the number of arguments to the join result set.
      Overrides:
      getNumJoinArguments in class JoinNode
    • oneRowRightSide

      void oneRowRightSide(ActivationClassBuilder acb, MethodBuilder mb)
      Overrides:
      oneRowRightSide in class JoinNode
    • getLogicalLeftResultSet

      ResultSetNode getLogicalLeftResultSet()
      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).
      Overrides:
      getLogicalLeftResultSet in class JoinNode
    • getLogicalRightResultSet

      ResultSetNode getLogicalRightResultSet()
      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).
      Overrides:
      getLogicalRightResultSet in class JoinNode
    • isRightOuterJoin

      boolean isRightOuterJoin()
      Return true if right outer join or false if left outer join Used to set Nullability correctly in JoinNode
    • isJoinColumnForRightOuterJoin

      void isJoinColumnForRightOuterJoin(ResultColumn rc)
      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
      Overrides:
      isJoinColumnForRightOuterJoin in class FromTable
      See Also:
    • LOJgetNPReferencedTables

      JBitSet LOJgetNPReferencedTables(int numTables) throws StandardException
      Throws:
      StandardException
    • LOJgetRPReferencedTables

      public JBitSet LOJgetRPReferencedTables(int numTables) throws StandardException
      Throws:
      StandardException