com.akiban.sql.parser
Class CastNode

java.lang.Object
  com.akiban.sql.parser.QueryTreeNode
      com.akiban.sql.parser.ValueNode
          com.akiban.sql.parser.CastNode

All Implemented Interfaces:

Visitable

public class CastNode
extends ValueNode

An CastNode represents a cast expressionr.

Field Summary

Fields inherited from class com.akiban.sql.parser.QueryTreeNode

AUTOINCREMENT_CREATE_MODIFY, AUTOINCREMENT_INC_INDEX, AUTOINCREMENT_IS_AUTOINCREMENT_INDEX, AUTOINCREMENT_START_INDEX

Constructor Summary

CastNode()

Method Summary

void	copyFrom(QueryTreeNode node) Fill this node with a deep copy of the given node.
ValueNode	getCastOperand()
void	init(Object castOperand, Object castTarget) Initializer for a CastNode
void	init(Object castOperand, Object charType, Object charLength) Initializer for a CastNode
boolean	isConstantExpression() Return whether or not this expression tree represents a constant expression.
protected boolean	isEquivalent(ValueNode o) Tests if this node is equivalent to the specified ValueNode.
void	printSubNodes(int depth) Prints the sub-nodes of this object.
String	toString() Convert this object to a String.

Methods inherited from class com.akiban.sql.parser.ValueNode

getColumnName, getSchemaName, getSourceResultColumn, getTableName, getType, getTypeId, init, isBinaryEqualsOperatorNode, isBooleanFalse, isBooleanTrue, isInListProbeNode, isParameterNode, isRelationalOperator, isSameNodeType, setNullability, setType

Methods inherited from class com.akiban.sql.parser.QueryTreeNode

accept, convertDefaultNode, debugFlush, debugPrint, formatNodeString, getBeginOffset, getDebugOutput, getEndOffset, getNodeFactory, getNodeType, getNullNode, getParserContext, getStatementType, getUserData, init, init, init, init, init, init, init, init, init, init, init, isInstanceOf, makeTableName, makeTableName, nodeHeader, printLabel, setBeginOffset, setDebugOutput, setEndOffset, setNodeType, setParserContext, setUserData, stackPrint, treePrint, treePrint, treePrint

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

CastNode

public CastNode()

Method Detail

init

public void init(Object castOperand,
                 Object castTarget)
          throws StandardException

Initializer for a CastNode

Overrides:

init in class QueryTreeNode

Parameters:

castOperand - The operand of the node

castTarget - DataTypeDescriptor (target type of cast)

Throws:

StandardException - Thrown on error

init

public void init(Object castOperand,
                 Object charType,
                 Object charLength)
          throws StandardException

Initializer for a CastNode

Overrides:

init in class QueryTreeNode

Parameters:

castOperand - The operand of the node

charType - CHAR or VARCHAR JDBC type as target

charLength - target type length

Throws:

StandardException - Thrown on error

copyFrom

public void copyFrom(QueryTreeNode node)
              throws StandardException

Fill this node with a deep copy of the given node.

Overrides:

copyFrom in class ValueNode

Throws:

StandardException

getCastOperand

public ValueNode getCastOperand()

toString

public 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

public 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

isConstantExpression

public 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.

isEquivalent

protected 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