Class ConstantNode
- All Implemented Interfaces:
Visitable
- Direct Known Subclasses:
BitConstantNode
,BooleanConstantNode
,CharConstantNode
,NumericConstantNode
,UntypedNullConstantNode
,UserTypeConstantNode
,XMLConstantNode
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
FieldsFields inherited from class org.apache.derby.impl.sql.compile.ValueNode
transformed
Fields inherited from class org.apache.derby.impl.sql.compile.QueryTreeNode
AUTOINCREMENT_CREATE_MODIFY, AUTOINCREMENT_CYCLE, AUTOINCREMENT_INC_INDEX, AUTOINCREMENT_IS_AUTOINCREMENT_INDEX, AUTOINCREMENT_START_INDEX
-
Constructor Summary
ConstructorsConstructorDescriptionConstantNode
(TypeId typeId, boolean nullable, int maximumWidth, ContextManager cm) -
Method Summary
Modifier and TypeMethodDescription(package private) ValueNode
bindExpression
(FromList fromList, SubqueryList subqueryList, List<AggregateNode> aggregates) Bind this expression.(package private) boolean
constantExpression
(PredicateList whereClause) Return whether or not this expression tree represents a constant value.(package private) abstract void
This generates the proper constant.(package private) void
For a ConstantNode, we generate the equivalent literal value.(package private) ValueNode
getClone()
Return a clone of this node.protected int
Return the variant type for the underlying expression.(package private) DataValueDescriptor
getValue()
Get the value in this ConstantNode(package private) boolean
Return whether or not this expression tree is cloneable.(package private) boolean
Return whether or not this expression tree represents a constant expression.(package private) boolean
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.toString()
Convert this object to a String.Methods inherited from class org.apache.derby.impl.sql.compile.ValueNode
bindExpression, categorize, changeToCNF, checkIsBoolean, checkTopPredicatesForEqualsConditions, copyFields, eliminateNots, evaluateConstantExpressions, genEqualsFalseTree, generate, genIsNullTree, genSQLJavaSQLTree, getColumnName, getConstantValueAsObject, getDataValueFactory, getSchemaName, getSourceResultColumn, getTableName, getTablesReferenced, getTransformed, getTypeCompiler, getTypeId, getTypeServices, isBinaryEqualsOperatorNode, isBooleanFalse, isBooleanTrue, isInListProbeNode, isParameterNode, isRelationalOperator, isSameNodeKind, optimizableEqualityNode, preprocess, putAndsOnTop, remapColumnReferencesToExpressions, requiresTypeFromContext, selectivity, setCollationInfo, setCollationInfo, setCollationUsingCompilationSchema, setCollationUsingCompilationSchema, setNullability, setTransformed, setType, setType, setType, updatableByCursor, verifyChangeToCNF, verifyEliminateNots, verifyPutAndsOnTop
Methods inherited from class org.apache.derby.impl.sql.compile.QueryTreeNode
accept, acceptChildren, addTag, addUDTUsagePriv, addUDTUsagePriv, bindOffsetFetch, bindRowMultiSet, bindUserCatalogType, bindUserType, checkReliability, checkReliability, convertDefaultNode, copyTagsFrom, createTypeDependency, debugFlush, debugPrint, disablePrivilegeCollection, formatNodeString, generateAuthorizeCheck, getBeginOffset, getClassFactory, getCompilerContext, getContext, getContextManager, getDataDictionary, getDependencyManager, getEndOffset, getExecutionFactory, getGenericConstantActionFactory, getIntProperty, getLanguageConnectionContext, getLongProperty, getNullNode, getOffsetOrderedNodes, getOptimizerFactory, getOptimizerTracer, getParameterTypes, getSchemaDescriptor, getSchemaDescriptor, getStatementType, getTableDescriptor, getTypeCompiler, getUDTDesc, isAtomic, isPrivilegeCollectionRequired, isSessionSchema, isSessionSchema, makeConstantAction, makeTableName, makeTableName, nodeHeader, optimizerTracingIsOn, orReliability, parseSearchCondition, parseStatement, printLabel, printSubNodes, referencesSessionSchema, resolveTableToSynonym, setBeginOffset, setEndOffset, setRefActionInfo, stackPrint, taggedWith, treePrint, treePrint, verifyClassExist
-
Field Details
-
value
DataValueDescriptor value
-
-
Constructor Details
-
ConstantNode
ConstantNode(TypeId typeId, boolean nullable, int maximumWidth, ContextManager cm) throws StandardException - Throws:
StandardException
-
ConstantNode
ConstantNode(ContextManager cm)
-
-
Method Details
-
setValue
Set the value in this ConstantNode. -
getValue
DataValueDescriptor getValue()Get the value in this ConstantNode -
toString
Convert this object to a String. See comments in QueryTreeNode.java for how this should be done for tree printing. -
isCloneable
boolean isCloneable()Return whether or not this expression tree is cloneable.- Overrides:
isCloneable
in classValueNode
- Returns:
- boolean Whether or not this expression tree is cloneable.
-
getClone
ValueNode getClone()Return a clone of this node. -
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. In this case, there are no sub-expressions, and the return type is already known, so this is just a stub.- Overrides:
bindExpression
in classValueNode
- Parameters:
fromList
- The FROM list for the query this expression is in, for binding columns.subqueryList
- The subquery list being built as we find SubqueryNodesaggregates
- The aggregate list being built as we find AggregateNodes- Returns:
- The new top of the expression tree.
- Throws:
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 StandardException
-
isConstantExpression
boolean isConstantExpression()Return whether or not this expression tree represents a constant expression.- Overrides:
isConstantExpression
in classValueNode
- Returns:
- Whether or not this expression tree represents a constant expression.
-
constantExpression
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 classValueNode
- Returns:
- True means this expression tree represents a constant value.
- See Also:
-
generateExpression
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 classValueNode
- Parameters:
acb
- The ExpressionClassBuilder for the class being builtmb
- The method the code to place the code- 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 builtmb
- The method the code to place the code- Throws:
StandardException
- Thrown on error
-
isNull
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 classValueNode
- Returns:
- The variant type for the underlying expression.
-
isEquivalent
Description copied from class:ValueNode
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 classValueNode
- Parameters:
o
- the node to compare this ValueNode against.- Returns:
true
if the two nodes are equivalent,false
otherwise.- Throws:
StandardException
-