Class UnionNode

java.lang.Object
org.apache.derby.impl.sql.compile.QueryTreeNode
org.apache.derby.impl.sql.compile.ResultSetNode
org.apache.derby.impl.sql.compile.FromTable
org.apache.derby.impl.sql.compile.TableOperatorNode
org.apache.derby.impl.sql.compile.SetOperatorNode
org.apache.derby.impl.sql.compile.UnionNode
All Implemented Interfaces:
Optimizable, Visitable
class UnionNode extends SetOperatorNode
A UnionNode represents a UNION in a DML statement. It contains a boolean telling whether the union operation should eliminate duplicate rows.

  • Field Details

    • addNewNodesCalled

      private boolean addNewNodesCalled

    • tableConstructor

      boolean tableConstructor

    • topTableConstructor

      boolean topTableConstructor

  • Constructor Details

    • UnionNode

      UnionNode(ResultSetNode leftResult, ResultSetNode rightResult, boolean all, boolean tableConstructor, Properties tableProperties, ContextManager cm) throws StandardException
      Constructor for a UnionNode.
      Parameters:
      leftResult - The ResultSetNode on the left side of this union
      rightResult - The ResultSetNode on the right side of this union
      all - Whether or not this is a UNION ALL.
      tableConstructor - Whether or not this is from a table constructor.
      tableProperties - Properties list associated with the table
      Throws:
      StandardException - Thrown on error

  • Method Details

    • markTopTableConstructor

      void markTopTableConstructor()
      Mark this as the top node of a table constructor.

    • tableConstructor

      boolean tableConstructor()
      Tell whether this is a UNION for a table constructor.

    • rejectParameters

      void rejectParameters() throws StandardException
      Check for (and reject) ? parameters directly under the ResultColumns. This is done for SELECT statements. Don't reject parameters that are in a table constructor - these are allowed, as long as the table constructor is in an INSERT statement or each column of the table constructor has at least one non-? column. The latter case is checked below, in bindExpressions().
      Overrides:
      rejectParameters in class TableOperatorNode
      Throws:
      StandardException - Thrown if a ? parameter found directly under a ResultColumn

    • setTableConstructorTypes

      void setTableConstructorTypes(ResultColumnList typeColumns) throws StandardException
      Set the type of column in the result column lists of each source of this union tree to the type in the given result column list (which represents the result columns for an insert). This is only for table constructors that appear in insert statements.
      Overrides:
      setTableConstructorTypes in class ResultSetNode
      Parameters:
      typeColumns - The ResultColumnList containing the desired result types.
      Throws:
      StandardException - Thrown on error

    • enhanceRCLForInsert

      ResultSetNode enhanceRCLForInsert(InsertNode target, boolean inOrder, int[] colMap) throws StandardException
      Make the RCL of this node match the target node for the insert. If this node represents a table constructor (a VALUES clause), we replace the RCL with an enhanced one if necessary, and recursively enhance the RCL of each child node. For table constructors, we also need to check that we don't attempt to override auto-increment columns in each child node (checking the top-level RCL isn't sufficient since a table constructor may contain the DEFAULT keyword, which makes it possible to specify a column without overriding its value). If this node represents a regular UNION, put a ProjectRestrictNode on top of this node and enhance the RCL in that node.
      Overrides:
      enhanceRCLForInsert in class ResultSetNode
      Parameters:
      target - the target node for the insert
      inOrder - are source cols in same order as target cols?
      colMap - int array representation of correspondence between RCLs - colmap[i] = -1 -> missing in current RCL colmap[i] = j -> targetRCL(i) <-> thisRCL(j+1)
      Returns:
      a node that replaces this node and whose RCL matches the target RCL. May return this node if no changes to the RCL are needed, or if the RCL is modified in-place.
      Throws:
      StandardException - Thrown on error

    • optimizeIt

      public CostEstimate optimizeIt(Optimizer optimizer, OptimizablePredicateList predList, CostEstimate outerCost, RowOrdering rowOrdering) throws StandardException
      Description copied from interface: Optimizable
      Choose the best access path for this Optimizable.
      Specified by:
      optimizeIt in interface Optimizable
      Overrides:
      optimizeIt in class FromTable
      Parameters:
      optimizer - Optimizer to use.
      predList - The predicate list to optimize against
      outerCost - The CostEstimate for the outer tables in the join order, telling how many times this Optimizable will be scanned.
      rowOrdering - The row ordering for all the tables in the join order, including this one.
      Returns:
      The optimizer's estimated cost of the best access path.
      Throws:
      StandardException - Thrown on error
      See Also:

    • pushExpressions

      void pushExpressions(PredicateList predicateList) throws StandardException
      DERBY-649: Handle pushing predicates into UnionNodes. It is possible to push single table predicates that are binaryOperations or inListOperations. Predicates of the form or IN are currently handled. Since these predicates would allow optimizer to pick available indices, pushing them provides maximum benifit. It should be possible to expand this logic to cover more cases. Even pushing expressions (like a+b = 10) into SELECTs would improve performance, even if they don't allow use of index. It would mean evaluating expressions closer to data and hence could avoid sorting or other overheads that UNION may require. Note that the predicates are not removed after pushing. This is to ensure if pushing is not possible or only partially feasible.
      Overrides:
      pushExpressions in class FromTable
      Parameters:
      predicateList - List of single table predicates to push
      Throws:
      StandardException - Thrown on error

    • modifyAccessPath

      public Optimizable modifyAccessPath(JBitSet outerTables) throws StandardException
      Description copied from interface: Optimizable
      Modify the access path for this Optimizable, as necessary. This includes things like adding a result set to translate from index rows to base rows
      Specified by:
      modifyAccessPath in interface Optimizable
      Overrides:
      modifyAccessPath in class TableOperatorNode
      Parameters:
      outerTables - Bit map of the tables that are outer to this one in the join order.
      Returns:
      The (potentially new) Optimizable at the top of the tree.
      Throws:
      StandardException - Thrown on error
      See Also:

    • modifyAccessPaths

      ResultSetNode modifyAccessPaths() throws StandardException
      Description copied from class: ResultSetNode
      Modify the access paths according to the decisions the optimizer made. This can include adding project/restrict nodes, index-to-base-row nodes, etc.
      Overrides:
      modifyAccessPaths in class TableOperatorNode
      Returns:
      The modified query tree
      Throws:
      StandardException - Thrown on error
      See Also:

    • addNewNodes

      private ResultSetNode addNewNodes() throws StandardException
      Add any new ResultSetNodes that are necessary to the tree. We wait until after optimization to do this in order to make it easier on the optimizer.
      Returns:
      (Potentially new) head of the ResultSetNode tree.
      Throws:
      StandardException - Thrown on error

    • 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 SetOperatorNode
      Returns:
      This object as a String

    • bindExpressions

      public void bindExpressions(FromList fromListParam) throws StandardException
      Bind the expressions under this TableOperatorNode. This means binding the sub-expressions, as well as figuring out what the return type is for each expression.
      Overrides:
      bindExpressions in class SetOperatorNode
      Parameters:
      fromListParam - FromList to use/append to.
      Throws:
      StandardException - Thrown on error

    • generate

      void generate(ActivationClassBuilder acb, MethodBuilder mb) throws StandardException
      Generate the code for this UnionNode.
      Overrides:
      generate in class QueryTreeNode
      Parameters:
      acb - The ActivationClassBuilder for the class being built
      mb - The method for the generated code to go into
      Throws:
      StandardException - Thrown on error

    • getFinalCostEstimate

      CostEstimate getFinalCostEstimate() throws StandardException
      Description copied from class: FromTable
      Get the final CostEstimate for this FromTable.
      Overrides:
      getFinalCostEstimate in class FromTable
      Returns:
      The final CostEstimate for this UnionNode, which is the sum of the two child costs.
      Throws:
      StandardException
      See Also:

    • getOperatorName

      String getOperatorName()
      Specified by:
      getOperatorName in class SetOperatorNode
      Returns:
      the operator name: "UNION", "INTERSECT", or "EXCEPT"