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java.lang.Objectorg.apache.derby.impl.sql.compile.QueryTreeNode
org.apache.derby.impl.sql.compile.ValueNode
org.apache.derby.impl.sql.compile.ConstantNode
abstract class ConstantNode
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 | |
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(package private) DataValueDescriptor |
value
|
Fields inherited from class org.apache.derby.impl.sql.compile.ValueNode |
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transformed |
Fields inherited from class org.apache.derby.impl.sql.compile.QueryTreeNode |
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AUTOINCREMENT_CREATE_MODIFY, AUTOINCREMENT_INC_INDEX, AUTOINCREMENT_IS_AUTOINCREMENT_INDEX, AUTOINCREMENT_START_INDEX, isPrivilegeCollectionRequired |
Constructor Summary | |
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ConstantNode()
Constructor for untyped nodes, which contain little information |
Method Summary | |
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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. |
protected boolean |
isEquivalent(ValueNode o)
Tests if this node is equivalent to the specified ValueNode. |
(package private) 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 java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait |
Field Detail |
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DataValueDescriptor value
Constructor Detail |
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ConstantNode()
Method Detail |
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public void init(java.lang.Object typeId, java.lang.Object nullable, java.lang.Object maximumWidth) throws StandardException
init
in class QueryTreeNode
typeId
- The Type ID of the datatypenullable
- True means the constant is nullablemaximumWidth
- The maximum number of bytes in the data value
StandardException
void setValue(DataValueDescriptor value)
public DataValueDescriptor getValue()
public java.lang.String toString()
toString
in class ValueNode
public boolean isCloneable()
isCloneable
in class ValueNode
public ValueNode getClone()
getClone
in class ValueNode
public ValueNode bindExpression(FromList fromList, SubqueryList subqueryList, java.util.Vector aggregateVector) throws StandardException
bindExpression
in class ValueNode
fromList
- The FROM list for the query this
expression is in, for binding columns.subqueryList
- The subquery list being built as we find SubqueryNodesaggregateVector
- The aggregate vector being built as we find AggregateNodes
StandardException
- Thrown on error. Although this class
doesn't throw this exception, it's subclasses do and hence this method
signature here needs to have throws StandardExceptionpublic boolean isConstantExpression()
isConstantExpression
in class ValueNode
public boolean constantExpression(PredicateList whereClause)
ValueNode
constantExpression
in class ValueNode
ValueNode.constantExpression(org.apache.derby.impl.sql.compile.PredicateList)
public void generateExpression(ExpressionClassBuilder acb, MethodBuilder mb) throws StandardException
generateExpression
in class ValueNode
acb
- The ExpressionClassBuilder for the class being builtmb
- The method the code to place the code
StandardException
- Thrown on errorabstract void generateConstant(ExpressionClassBuilder acb, MethodBuilder mb) throws StandardException
acb
- The ExpressionClassBuilder for the class being builtmb
- The method the code to place the code
StandardException
- Thrown on errorboolean isNull()
protected int getOrderableVariantType()
getOrderableVariantType
in class ValueNode
protected boolean isEquivalent(ValueNode o) throws StandardException
ValueNode
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:
isEquivalent
in class ValueNode
o
- the node to compare this ValueNode against.
true
if the two nodes are equivalent,
false
otherwise.
StandardException
|
Built on Thu 2012-03-29 21:53:33+0000, from revision ??? | ||||||||
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