public abstract class ConstantNode extends ValueNode
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
AUTOINCREMENT_CREATE_MODIFY, AUTOINCREMENT_INC_INDEX, AUTOINCREMENT_IS_AUTOINCREMENT_INDEX, AUTOINCREMENT_START_INDEX
Constructor and Description |
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ConstantNode() |
Modifier and Type | Method and Description |
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void |
copyFrom(QueryTreeNode node)
Fill this node with a deep copy of the given node.
|
java.lang.Object |
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 |
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 |
setValue(java.lang.Object value)
Set the value in this ConstantNode.
|
java.lang.String |
toString()
Convert this object to a String.
|
getColumnName, getSchemaName, getSourceResultColumn, getTableName, getType, getTypeId, init, isBinaryEqualsOperatorNode, isBooleanFalse, isBooleanTrue, isInListProbeNode, isParameterNode, isRelationalOperator, isSameNodeType, setNullability, setType
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, init, isInstanceOf, makeTableName, makeTableName, nodeHeader, printLabel, printSubNodes, setBeginOffset, setDebugOutput, setEndOffset, setNodeType, setParserContext, setUserData, stackPrint, treePrint, treePrint, treePrint
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 valueStandardException
public void copyFrom(QueryTreeNode node) throws StandardException
copyFrom
in class ValueNode
StandardException
public java.lang.Object getValue()
public void setValue(java.lang.Object value)
public java.lang.String toString()
public boolean isConstantExpression()
isConstantExpression
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
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