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

Class DefaultNode

  • All Implemented Interfaces:
    Visitable
    public class DefaultNode
extends ValueNode
    DefaultNode represents a column/parameter default.

    • Field Detail

      • columnName

        private java.lang.String columnName

      • defaultText

        private java.lang.String defaultText

    • Constructor Detail

      • DefaultNode

        DefaultNode​(ContextManager cm)
        Constructor for a generated by default as identity column.
        Parameters:
        cm - The context manager

      • DefaultNode

        DefaultNode​(ValueNode defaultTree,
            java.lang.String defaultText,
            ContextManager cm)
        Constructor for a column/parameter default.
        Parameters:
        defaultTree - Query tree for default
        defaultText - The text of the default.
        cm - The context manager

      • DefaultNode

        DefaultNode​(java.lang.String columnName,
            ContextManager cm)
        Constructor for insert/update
        Parameters:
        columnName - The column name for which a default is to be applied

    • Method Detail

      • getDefaultText

        public java.lang.String getDefaultText()
        Get the text of the default.

      • getDefaultTree

        ValueNode getDefaultTree()
        Get the query tree for the default.
        Returns:
        The query tree for the default.

      • 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

      • printSubNodes

        void printSubNodes​(int depth)
        Prints the sub-nodes of this object. See QueryTreeNode.java for how tree printing is supposed to work.
        Overrides:
        printSubNodes in class QueryTreeNode
        Parameters:
        depth - The depth of this node in the tree

      • 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 failure

      • isEquivalent

        boolean isEquivalent​(ValueNode other)
        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.