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 Details

    • 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 Details

    • 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 Details

    • 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, 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, 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
    • bindCaseOperand

      private ValueNodeList bindCaseOperand(CompilerContext cc, FromList fromList, SubqueryList subqueryList, List<AggregateNode> aggregates) throws StandardException

      Bind the case operand, if there is one, and check that it doesn't contain anything that's illegal in a case operand (such as calls to routines that are non-deterministic or modify SQL).

      Also, if the type of the case operand needs to be inferred, insert dummy parameter nodes into testConditions instead of the case operand, so that the type can be inferred individually for each test condition. Later, bindExpression(org.apache.derby.impl.sql.compile.FromList, org.apache.derby.impl.sql.compile.SubqueryList, java.util.List<org.apache.derby.impl.sql.compile.AggregateNode>) will find a common type for all of them, use that type for the case operand, and reinsert the case operand into the test conditions.

      Returns:
      a list of dummy parameter nodes that have been inserted into the tree instead of the case operand, if such a replacement has happened; otherwise, null is returned
      Throws:
      StandardException
    • 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
    • remapColumnReferencesToExpressions

      ValueNode remapColumnReferencesToExpressions() throws StandardException
      Remap all ColumnReferences in this tree to be clones of the underlying expression.
      Overrides:
      remapColumnReferencesToExpressions in class ValueNode
      Returns:
      ValueNode The remapped expression tree.
      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.
    • 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:
    • 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
    • generateExpression

      void generateExpression(ExpressionClassBuilder acb, MethodBuilder mb) throws StandardException
      Do code generation for this conditional expression.
      Overrides:
      generateExpression in class ValueNode
      Parameters:
      acb - The ExpressionClassBuilder for the class we're generating
      mb - The method the expression will go into
      Throws:
      StandardException - Thrown on error
    • acceptChildren

      void acceptChildren(Visitor v) throws StandardException
      Accept the visitor for all visitable children of this node.
      Overrides:
      acceptChildren in class QueryTreeNode
      Parameters:
      v - the visitor
      Throws:
      StandardException - 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