Field Detail

• value

  DataValueDescriptor value

Constructor Detail

• ConstantNode

  ConstantNode​(TypeId typeId,
               boolean nullable,
               int maximumWidth,
               ContextManager cm)
        throws StandardException

  Throws:

  StandardException

• ConstantNode

  ConstantNode​(ContextManager cm)

Method Detail

• setValue

  void setValue​(DataValueDescriptor value)

  Set the value in this ConstantNode.

• getValue

  DataValueDescriptor getValue()

  Get the value in this ConstantNode

• toString

  public java.lang.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

• isCloneable

  boolean isCloneable()

  Return whether or not this expression tree is cloneable.

  Overrides:

  isCloneable in class ValueNode

  Returns:

  boolean Whether or not this expression tree is cloneable.

• getClone

  ValueNode getClone()

  Return a clone of this node.

  Overrides:

  getClone in class ValueNode

  Returns:

  ValueNode A clone of this node.

• bindExpression

  ValueNode bindExpression​(FromList fromList,
                           SubqueryList subqueryList,
                           java.util.List<AggregateNode> aggregates)
                    throws StandardException

  Bind this expression. This means binding the sub-expressions, as well as figuring out what the return type is for this expression. In this case, there are no sub-expressions, and the return type is already known, so this is just a stub.

  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. Although this class doesn't throw this exception, it's subclasses do and hence this method signature here needs to have throws StandardException

• isConstantExpression

  boolean isConstantExpression()

  Return whether or not this expression tree represents a constant expression.

  Overrides:

  isConstantExpression in class ValueNode

  Returns:

  Whether or not this expression tree represents a constant expression.

• constantExpression

  boolean constantExpression​(PredicateList whereClause)

  Description copied from class: ValueNode
  Return whether or not this expression tree represents a constant value. In this case, "constant" means that it will always evaluate to the same thing, even if it includes columns. A column is constant if it is compared to a constant expression.

  Overrides:

  constantExpression in class ValueNode

  Returns:

  True means this expression tree represents a constant value.

  See Also:

  ValueNode.constantExpression(org.apache.derby.impl.sql.compile.PredicateList)

• generateExpression

  void generateExpression​(ExpressionClassBuilder acb,
                          MethodBuilder mb)
                   throws StandardException

  For a ConstantNode, we generate the equivalent literal value. A null is generated as a Null value cast to the type of the constant node. The subtypes of ConstantNode generate literal expressions for non-null values.

  Overrides:

  generateExpression in class ValueNode

  Parameters:

  acb - The ExpressionClassBuilder for the class being built

  mb - The method the code to place the code

  Throws:

  StandardException - Thrown on error

• generateConstant

  abstract void generateConstant​(ExpressionClassBuilder acb,
                                 MethodBuilder mb)
                          throws StandardException

  This generates the proper constant. It is implemented by every specific constant node (e.g. IntConstantNode).

  Parameters:

  acb - The ExpressionClassBuilder for the class being built

  mb - The method the code to place the code

  Throws:

  StandardException - Thrown on error

• isNull

  boolean isNull()

  Return whether or not this node represents a typed null constant.

• getOrderableVariantType

  protected int getOrderableVariantType()

  Return the variant type for the underlying expression. The variant type can be: VARIANT - variant within a scan (method calls and non-static field access) SCAN_INVARIANT - invariant within a scan (column references from outer tables) QUERY_INVARIANT - invariant within the life of a query VARIANT - immutable

  Overrides:

  getOrderableVariantType in class ValueNode

  Returns:

  The variant type for the underlying expression.

• isEquivalent

  boolean isEquivalent​(ValueNode o)
                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:

  o - the node to compare this ValueNode against.

  Returns:

  true if the two nodes are equivalent, false otherwise.

  Throws:

  StandardException