Class ConditionalNode

  • All Implemented Interfaces:
    Visitable

    class ConditionalNode
    extends ValueNode
    A ConditionalNode represents an if/then/else operator with a single boolean expression on the "left" of the operator and a list of expressions on the "right". This is used to represent the java conditional (aka immediate if).
    • Field Detail

      • caseOperand

        private CachedValueNode caseOperand
        The case operand if this is a simple case expression. Otherwise, it is null.
      • testConditions

        private ValueNodeList testConditions
        The list of test conditions in the WHEN clauses.
      • thenElseList

        private ValueNodeList thenElseList
        The list of corresponding THEN expressions to the test conditions in testConditions. The last element represents the ELSE clause.
    • Constructor Detail

      • ConditionalNode

        ConditionalNode​(CachedValueNode caseOperand,
                        ValueNodeList testConditions,
                        ValueNodeList thenElseList,
                        ContextManager cm)
        Constructor for a ConditionalNode
        Parameters:
        caseOperand - The case operand if this is a simple case expression, or null otherwise
        testConditions - The boolean test conditions
        thenElseList - ValueNodeList with then and else expressions
        cm - The context manager
    • Method Detail

      • 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
      • recastNullNodes

        private void recastNullNodes​(DataTypeDescriptor castType,
                                     FromList fromList,
                                     SubqueryList subqueryList,
                                     java.util.List<AggregateNode> aggregates)
                              throws StandardException
        This method makes sure any SQL NULLs will be cast to the correct type.
        Parameters:
        castType - The type to cast SQL parsed NULL's too.
        fromList - FromList to pass on to bindExpression if recast is performed
        subqueryList - SubqueryList to pass on to bindExpression if recast is performed
        aggregates - List of aggregates to pass on to bindExpression if recast is performed
        Throws:
        StandardException - Thrown on error.
      • 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.
        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
      • preprocess

        ValueNode preprocess​(int numTables,
                             FromList outerFromList,
                             SubqueryList outerSubqueryList,
                             PredicateList outerPredicateList)
                      throws StandardException
        Preprocess an expression tree. We do a number of transformations here (including subqueries, IN lists, LIKE and BETWEEN) plus subquery flattening. NOTE: This is done before the outer ResultSetNode is preprocessed.
        Overrides:
        preprocess in class ValueNode
        Parameters:
        numTables - Number of tables in the DML Statement
        outerFromList - FromList from outer query block
        outerSubqueryList - SubqueryList from outer query block
        outerPredicateList - PredicateList from outer query block
        Returns:
        The modified expression
        Throws:
        StandardException - Thrown on error
      • categorize

        boolean categorize​(JBitSet referencedTabs,
                           boolean simplePredsOnly)
                    throws StandardException
        Categorize this predicate. Initially, this means building a bit map of the referenced tables for each predicate. If the source of this ColumnReference (at the next underlying level) is not a ColumnReference or a VirtualColumnNode then this predicate will not be pushed down. For example, in: select * from (select 1 from s) a (x) where x = 1 we will not push down x = 1. NOTE: It would be easy to handle the case of a constant, but if the inner SELECT returns an arbitrary expression, then we would have to copy that tree into the pushed predicate, and that tree could contain subqueries and method calls. RESOLVE - revisit this issue once we have views.
        Overrides:
        categorize in class ValueNode
        Parameters:
        referencedTabs - JBitSet with bit map of referenced FromTables
        simplePredsOnly - Whether or not to consider method calls, field references and conditional nodes when building bit map
        Returns:
        boolean Whether or not source.expression is a ColumnReference or a VirtualColumnNode.
        Throws:
        StandardException - Thrown on error
      • 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.
      • eliminateNots

        ValueNode eliminateNots​(boolean underNotNode)
                         throws StandardException
        Eliminate NotNodes in the current query block. We traverse the tree, inverting ANDs and ORs and eliminating NOTs as we go. We stop at ComparisonOperators and boolean expressions. We invert ComparisonOperators and replace boolean expressions with boolean expression = false. NOTE: Since we do not recurse under ComparisonOperators, there still could be NotNodes left in the tree.
        Overrides:
        eliminateNots in class ValueNode
        Parameters:
        underNotNode - Whether or not we are under a NotNode.
        Returns:
        The modified expression
        Throws:
        StandardException - Thrown on error
      • isEquivalent

        boolean isEquivalent​(ValueNode o)
                      throws StandardException
        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