org.apache.derby.impl.sql.compile
Class ConstantNode

java.lang.Object
  org.apache.derby.impl.sql.compile.QueryTreeNode
      org.apache.derby.impl.sql.compile.ValueNode
          org.apache.derby.impl.sql.compile.ConstantNode

All Implemented Interfaces:

Visitable

Direct Known Subclasses:

BitConstantNode, BooleanConstantNode, CharConstantNode, LOBConstantNode, NumericConstantNode, SQLBooleanConstantNode, UntypedNullConstantNode, UserTypeConstantNode, XMLConstantNode

abstract class ConstantNode

extends ValueNode

ConstantNode holds literal constants as well as nulls.

A NULL from the parser may not yet know its type; that must be set during binding, as it is for parameters.

the DataValueDescriptor methods want to throw exceptions when they are of the wrong type, but to do that they must check typeId when the value is null, rather than the instanceof check they do for returning a valid value.

For code generation, we generate a static field. Then we set the field be the proper constant expression (something like getDatavalueFactory().getCharDataValue("hello", ...)) ) in the constructor of the generated method. Ideally we would have just

Field Summary

protected DataValueDescriptor

value

Fields inherited from class org.apache.derby.impl.sql.compile.ValueNode

clause, dataTypeServices, IN_HAVING_CLAUSE, IN_SELECT_LIST, IN_UNKNOWN_CLAUSE, IN_WHERE_CLAUSE, transformed

Fields inherited from class org.apache.derby.impl.sql.compile.QueryTreeNode

AUTOINCREMENT_INC_INDEX, AUTOINCREMENT_IS_AUTOINCREMENT_INDEX, AUTOINCREMENT_START_INDEX, beginOffset, endOffset

Constructor Summary

(package private)

ConstantNode() Constructor for untyped nodes, which contain little information

Method Summary

ValueNode	bindExpression(FromList fromList, SubqueryList subqueryList, java.util.Vector aggregateVector) Bind this expression.
boolean	constantExpression(PredicateList whereClause) Return whether or not this expression tree represents a constant value.
(package private) abstract void	generateConstant(ExpressionClassBuilder acb, MethodBuilder mb) This generates the proper constant.
void	generateExpression(ExpressionClassBuilder acb, MethodBuilder mb) For a ConstantNode, we generate the equivalent literal value.
ValueNode	getClone() Return a clone of this node.
protected int	getOrderableVariantType() Return the variant type for the underlying expression.
DataValueDescriptor	getValue() Get the value in this ConstantNode
void	init(java.lang.Object typeId, java.lang.Object nullable, java.lang.Object maximumWidth) Initializer for non-numeric types
boolean	isCloneable() Return whether or not this expression tree is cloneable.
boolean	isConstantExpression() Return whether or not this expression tree represents a constant expression.
boolean	isNull() Return whether or not this node represents a typed null constant.
(package private) void	setValue(DataValueDescriptor value) Set the value in this ConstantNode.
java.lang.String	toString() Convert this object to a String.

Methods inherited from class org.apache.derby.impl.sql.compile.ValueNode

bindExpression, categorize, changeToCNF, checkIsBoolean, checkReliability, checkReliability, checkTopPredicatesForEqualsConditions, copyFields, eliminateNots, genEqualsFalseTree, generate, generateFilter, genIsNullTree, genSQLJavaSQLTree, getClause, getColumnName, getConstantValueAsObject, getDataValueFactory, getSchemaName, getSourceResultColumn, getTableName, getTablesReferenced, getTransformed, getTypeCompiler, getTypeId, getTypeServices, init, isBinaryEqualsOperatorNode, isBooleanFalse, isBooleanTrue, isParameterNode, isRelationalOperator, optimizableEqualityNode, preprocess, putAndsOnTop, remapColumnReferencesToExpressions, selectivity, setClause, setDescriptor, setTransformed, setType, updatableByCursor, verifyChangeToCNF, verifyEliminateNots, verifyPutAndsOnTop

Methods inherited from class org.apache.derby.impl.sql.compile.QueryTreeNode

accept, bind, convertDefaultNode, debugFlush, debugPrint, executeSchemaName, executeStatementName, formatNodeString, foundString, generate, generateAuthorizeCheck, getBeginOffset, getClassFactory, getCompilerContext, getContextManager, getCursorInfo, getDataDictionary, getDependencyManager, getEndOffset, getExecutionFactory, getGenericConstantActionFactory, getIntProperty, getLanguageConnectionContext, getNodeFactory, getNodeType, getNullNode, getParameterTypes, getRowEstimate, getSchemaDescriptor, getSchemaDescriptor, getSPSName, getStatementType, getTableDescriptor, getTypeCompiler, init, init, init, init, init, init, init, init, init, init, init, init, isAtomic, isInstanceOf, isSessionSchema, isSessionSchema, makeConstantAction, makeResultDescription, makeTableName, needsSavepoint, nodeHeader, optimize, parseQueryText, printLabel, printSubNodes, referencesSessionSchema, resolveTableToSynonym, setBeginOffset, setContextManager, setEndOffset, setNodeType, setRefActionInfo, treePrint, treePrint, verifyClassExist

Methods inherited from class java.lang.Object

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

Field Detail

value

protected DataValueDescriptor value

Constructor Detail

ConstantNode

ConstantNode()

Constructor for untyped nodes, which contain little information

Method Detail

init

public void init(java.lang.Object typeId,
                 java.lang.Object nullable,
                 java.lang.Object maximumWidth)
          throws StandardException

Initializer for non-numeric types

Overrides:

init in class QueryTreeNode

Parameters:

typeId - The Type ID of the datatype

nullable - True means the constant is nullable

maximumWidth - The maximum number of bytes in the data value

Throws:

StandardException

setValue

void setValue(DataValueDescriptor value)

Set the value in this ConstantNode.

getValue

public DataValueDescriptor getValue()

Get the value in this ConstantNode

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

isCloneable

public boolean isCloneable()

Return whether or not this expression tree is cloneable.

Overrides:

isCloneable in class ValueNode

Returns:

boolean Whether or not this expression tree is cloneable.

getClone

public ValueNode getClone()

Return a clone of this node.

Overrides:

getClone in class ValueNode

Returns:

ValueNode A clone of this node.

bindExpression

public ValueNode bindExpression(FromList fromList,
                                SubqueryList subqueryList,
                                java.util.Vector aggregateVector)

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

aggregateVector - The aggregate vector being built as we find AggregateNodes

Returns:

The new top of the expression 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.

constantExpression

public 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:

ValueNode.constantExpression(org.apache.derby.impl.sql.compile.PredicateList)

generateExpression

public void generateExpression(ExpressionClassBuilder acb,
                               MethodBuilder mb)
                        throws StandardException

For a ConstantNode, we generate the equivalent literal value. A null is generated as a Null value cast to the type of the constant node. The subtypes of ConstantNode generate literal expressions for non-null values.

Overrides:

generateExpression in class ValueNode

Parameters:

acb - The ExpressionClassBuilder for the class being built

mb - The method the code to place the code

Returns:

The compiled Expression, if the constant is a null value, null if the constant is not a null value (confusing, huh?)

Throws:

StandardException - Thrown on error

generateConstant

abstract void generateConstant(ExpressionClassBuilder acb,
                               MethodBuilder mb)
                        throws StandardException

This generates the proper constant. It is implemented by every specific constant node (e.g. IntConstantNode).

Parameters:

acb - The ExpressionClassBuilder for the class being built

mb - The method the code to place the code

Returns:

The compiled Expression,

Throws:

StandardException - Thrown on error

isNull

public boolean isNull()

Return whether or not this node represents a typed null constant.

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 VARIANT - immutable

Overrides:

getOrderableVariantType in class ValueNode

Returns:

The variant type for the underlying expression.