Package org.apache.derby.impl.sql.compile

Class CurrentDatetimeOperatorNode

  • All Implemented Interfaces:
    Visitable
    class CurrentDatetimeOperatorNode
extends ValueNode
    The CurrentDatetimeOperator operator is for the builtin CURRENT_DATE, CURRENT_TIME, and CURRENT_TIMESTAMP operations.

    • Field Detail

      • jdbcTypeId

        private static final int[] jdbcTypeId

      • methodName

        private static final java.lang.String[] methodName

      • whichType

        private int whichType

    • Constructor Detail

      • CurrentDatetimeOperatorNode

        CurrentDatetimeOperatorNode​(int whichType,
                            ContextManager cm)

    • Method Detail

      • bindExpression

        ValueNode bindExpression​(FromList fromList,
                         SubqueryList subqueryList,
                         java.util.List<AggregateNode> aggregates)
                  throws StandardException
        Binding this expression means setting the result DataTypeServices. In this case, the result type is based on the operation requested.
        Overrides:
        bindExpression in class ValueNode
        Parameters:
        fromList - The FROM list for the statement. This parameter is not used in this case.
        subqueryList - The subquery list being built as we find SubqueryNodes. Not used in this case.
        aggregates - The aggregate list being built as we find AggregateNodes. Not used in this case.
        Returns:
        The new top of the expression tree.
        Throws:
        StandardException - Thrown on error

      • 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 (constant expressions)
        Overrides:
        getOrderableVariantType in class ValueNode
        Returns:
        The variant type for the underlying expression.

      • generateExpression

        void generateExpression​(ExpressionClassBuilder acb,
                        MethodBuilder mb)
                 throws StandardException
        CurrentDatetimeOperatorNode is used in expressions. The expression generated for it invokes a static method on a special Derby type to get the system time and wrap it in the right java.sql type, and then wrap it into the right shape for an arbitrary value, i.e. a column holder. This is very similar to what constants do.
        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

      • toString

        public java.lang.String toString()
        Description copied from class: ValueNode
        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 o)
        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.