Class NextSequenceNode

All Implemented Interfaces:
Visitable

class NextSequenceNode extends ValueNode
A class that represents a value obtained from a Sequence using 'NEXT VALUE'
  • Field Details

  • Constructor Details

    • NextSequenceNode

      NextSequenceNode(TableName sequenceName, ContextManager cm)
      Constructor for a NextSequenceNode
      Parameters:
      sequenceName - The name of the sequence being called
      cm - The context manager
  • Method Details

    • bindExpression

      ValueNode bindExpression(FromList fromList, SubqueryList subqueryList, List<AggregateNode> aggregates, boolean forQueryRewrite) throws StandardException
      Bind this expression. This means binding the sub-expressions, as well as figuring out what the return type is for this expression.
      Overrides:
      bindExpression in class ValueNode
      Parameters:
      fromList - The FROM list for the query this expression is in, for binding columns.
      subqueryList - The subquery list being built as we find SubqueryNodes
      aggregates - The aggregate list being built as we find AggregateNodes
      Returns:
      The new top of the expression tree.
      Throws:
      StandardException - Thrown on error
    • generateExpression

      void generateExpression(ExpressionClassBuilder acb, MethodBuilder mb) throws StandardException
      Description copied from class: ValueNode
      Generate code for this calculation. This is a place-holder method - it should not be called.
      Overrides:
      generateExpression in class ValueNode
      Parameters:
      acb - The ExpressionClassBuilder for the class being built
      mb - The method the expression will go into
      Throws:
      StandardException - Thrown on error
    • generateConstant

      void generateConstant(ExpressionClassBuilder ecb, MethodBuilder mb) throws StandardException
      Dummy implementation to return a constant. Will be replaced with actual NEXT VALUE logic.
      Parameters:
      ecb - The ExpressionClassBuilder for the class being built
      mb - The method the expression will go into
      Throws:
      StandardException - 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 ValueNode
      Returns:
      This object as a String
    • isEquivalent

      boolean isEquivalent(ValueNode other) throws StandardException
      Description copied from class: ValueNode
      Tests if this node is equivalent to the specified ValueNode. Two ValueNodes are considered equivalent if they will evaluate to the same value during query execution.

      This method provides basic expression matching facility for the derived class of ValueNode and it is used by the language layer to compare the node structural form of the two expressions for equivalence at bind phase.

      Note that it is not comparing the actual row values at runtime to produce a result; hence, when comparing SQL NULLs, they are considered to be equivalent and not unknown.

      One usage case of this method in this context is to compare the select column expression against the group by expression to check if they are equivalent. e.g.:

      SELECT c1+c2 FROM t1 GROUP BY c1+c2

      In general, node equivalence is determined by the derived class of ValueNode. But they generally abide to the rules below:

      • The two ValueNodes must be of the same node type to be considered equivalent. e.g.: CastNode vs. CastNode - equivalent (if their args also match), ColumnReference vs CastNode - not equivalent.
      • If node P contains other ValueNode(s) and so on, those node(s) must also be of the same node type to be considered equivalent.
      • If node P takes a parameter list, then the number of arguments and its arguments for the two nodes must also match to be considered equivalent. e.g.: CAST(c1 as INTEGER) vs CAST(c1 as SMALLINT), they are not equivalent.
      • When comparing SQL NULLs in this context, they are considered to be equivalent.
      • If this does not apply or it is determined that the two nodes are not equivalent then the derived class of this method should return false; otherwise, return true.
      Specified by:
      isEquivalent in class ValueNode
      Parameters:
      other - the node to compare this ValueNode against.
      Returns:
      true if the two nodes are equivalent, false otherwise.
      Throws:
      StandardException
    • acceptChildren

      void acceptChildren(Visitor v) throws StandardException
      Description copied from class: QueryTreeNode
      Accept a visitor on all child nodes. All sub-classes that add fields that should be visited, should override this method and call accept(v) on all visitable fields, as well as super.acceptChildren(v) to make sure all visitable fields defined by the super-class are accepted too.
      Overrides:
      acceptChildren in class QueryTreeNode
      Parameters:
      v - the visitor
      Throws:
      StandardException - on errors raised by the visitor