Class UserTypeConstantNode

  • All Implemented Interfaces:
    Visitable

    class UserTypeConstantNode
    extends ConstantNode
    User type constants. These are created by built-in types that use user types as their implementation. This could also potentially be used by an optimizer that wanted to store plans for frequently-used parameter values. This is also used to represent nulls in user types, which occurs when NULL is inserted into or supplied as the update value for a user type column.
    • Field Detail

      • val

        java.lang.Object val
    • Method Detail

      • getObjectValue

        public java.lang.Object getObjectValue()
        Return the object value of this user defined type.
        Returns:
        the value of this constant. can't use getValue() for this. getValue() returns the DataValueDescriptor for the built-in types that are implemented as user types (date, time, timestamp)
      • isNull

        boolean isNull()
        Return whether or not this node represents a typed null constant.
        Overrides:
        isNull in class ConstantNode
      • getConstantValueAsObject

        java.lang.Object getConstantValueAsObject()
        Return an Object representing the bind time value of this expression tree. If the expression tree does not evaluate to a constant at bind time then we return null. This is useful for bind time resolution of VTIs. RESOLVE: What do we do for primitives?
        Overrides:
        getConstantValueAsObject in class ValueNode
        Returns:
        An Object representing the bind time value of this expression tree. (null if not a bind time constant.)
      • generateExpression

        void generateExpression​(ExpressionClassBuilder acb,
                                MethodBuilder mb)
                         throws StandardException
        For a UserTypeConstantNode, we have to store away the object somewhere and have a way to get it back at runtime. These objects are serializable. This gives us at least two options: 1) serialize it out into a byte array field, and serialize it back in when needed, from the field. 2) have an array of objects in the prepared statement and a #, to find the object directly. Because it is serializable, it will store with the rest of the executable just fine. Choice 2 gives better performance -- the ser/deser cost is paid on database access for the statement, not for each execution of it. However, it requires some infrastructure support from prepared statements. For now, we take choice 3, and make some assumptions about available methods on the user type. This choice has the shortcoming that it will not work for arbitrary user types. REVISIT and implement choice 2 when a general solution is needed.

        A null is generated as a Null value cast to the type of the constant node.

        Overrides:
        generateExpression in class ConstantNode
        Parameters:
        acb - The ExpressionClassBuilder for the class being built
        mb - The method the expression will go into
        Throws:
        StandardException - Thrown on error