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

java.lang.Object
  extended by org.apache.derby.impl.sql.compile.QueryTreeNode
      extended by org.apache.derby.impl.sql.compile.ValueNode
          extended by org.apache.derby.impl.sql.compile.VirtualColumnNode
All Implemented Interfaces:
Visitable

public class VirtualColumnNode
extends ValueNode

A VirtualColumnNode represents a virtual column reference to a column in a row returned by an underlying ResultSetNode. The underlying column could be in a base table, view (which could expand into a complex expression), subquery in the FROM clause, temp table, expression result, etc. By the time we get to code generation, all VirtualColumnNodes should stand only for references to columns in a base table within a FromBaseTable.


Field Summary
(package private)  int columnId
           
private  boolean correlated
           
private  ResultColumn sourceColumn
           
private  ResultSetNode sourceResultSet
           
 
Fields 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_INC_INDEX, AUTOINCREMENT_IS_AUTOINCREMENT_INDEX, AUTOINCREMENT_START_INDEX, isPrivilegeCollectionRequired
 
Constructor Summary
VirtualColumnNode()
           
 
Method Summary
 void generateExpression(ExpressionClassBuilder acb, MethodBuilder mb)
          ColumnNode's are against the current row in the system.
(package private)  boolean getCorrelated()
          Return whether or not this VCN is a correlated reference.
protected  int getOrderableVariantType()
          Return the variant type for the underlying expression.
 java.lang.String getSchemaName()
          Get the name of the schema the ResultColumn's table is in, if any.
 ResultColumn getSourceColumn()
          Return the ResultColumn that is the source of this VirtualColumnNode.
 ResultColumn getSourceResultColumn()
          Return the ResultColumn that is the source of this VirtualColumnNode.
 ResultSetNode getSourceResultSet()
          Return the ResultSetNode that is the source of this VirtualColumnNode.
 java.lang.String getTableName()
          Get the name of the table the ResultColumn is in, if any.
 DataTypeDescriptor getTypeServices()
          Get the DataTypeServices from this Node.
 void init(java.lang.Object sourceResultSet, java.lang.Object sourceColumn, java.lang.Object columnId)
          Initializer for a VirtualColumnNode.
 boolean isCloneable()
          Return whether or not this expression tree is cloneable.
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.
(package private)  void setCorrelated()
          Mark this VCN as a reference to a correlated column.
 void setType(DataTypeDescriptor dtd)
          Set the DataTypeServices for this ValueNode.
 boolean updatableByCursor()
          Return whether or not the ResultColumn is wirtable by a positioned update.
 
Methods inherited from class org.apache.derby.impl.sql.compile.ValueNode
bindExpression, bindExpression, categorize, changeToCNF, checkIsBoolean, checkTopPredicatesForEqualsConditions, constantExpression, copyFields, eliminateNots, evaluateConstantExpressions, genEqualsFalseTree, generate, generateFilter, genIsNullTree, genSQLJavaSQLTree, getClone, getColumnName, getConstantValueAsObject, getDataValueFactory, getTablesReferenced, getTransformed, getTypeCompiler, getTypeId, init, isBinaryEqualsOperatorNode, isBooleanFalse, isBooleanTrue, isConstantExpression, isInListProbeNode, isParameterNode, isRelationalOperator, isSameNodeType, optimizableEqualityNode, preprocess, putAndsOnTop, remapColumnReferencesToExpressions, requiresTypeFromContext, selectivity, setCollationInfo, setCollationInfo, setCollationUsingCompilationSchema, setCollationUsingCompilationSchema, setNullability, setTransformed, setType, setType, toString, verifyChangeToCNF, verifyEliminateNots, verifyPutAndsOnTop
 
Methods inherited from class org.apache.derby.impl.sql.compile.QueryTreeNode
accept, acceptChildren, bindOffsetFetch, bindRowMultiSet, bindUserType, checkReliability, checkReliability, convertDefaultNode, createTypeDependency, debugFlush, debugPrint, disablePrivilegeCollection, formatNodeString, foundString, generateAuthorizeCheck, getBeginOffset, getClassFactory, getCompilerContext, getContextManager, getCursorInfo, getDataDictionary, getDependencyManager, getEndOffset, getExecutionFactory, getGenericConstantActionFactory, getIntProperty, getLanguageConnectionContext, getNodeFactory, getNodeType, getNullNode, getParameterTypes, getRowEstimate, getSchemaDescriptor, getSchemaDescriptor, getStatementType, getTableDescriptor, getTypeCompiler, init, init, init, init, init, init, init, init, init, init, init, init, isAtomic, isInstanceOf, isPrivilegeCollectionRequired, isSessionSchema, isSessionSchema, makeConstantAction, makeTableName, makeTableName, nodeHeader, orReliability, parseStatement, printLabel, referencesSessionSchema, resolveTableToSynonym, setBeginOffset, setContextManager, setEndOffset, setNodeType, setRefActionInfo, stackPrint, treePrint, treePrint, verifyClassExist
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Field Detail

sourceResultSet

private ResultSetNode sourceResultSet

sourceColumn

private ResultColumn sourceColumn

columnId

int columnId

correlated

private boolean correlated
Constructor Detail

VirtualColumnNode

public VirtualColumnNode()
Method Detail

init

public void init(java.lang.Object sourceResultSet,
                 java.lang.Object sourceColumn,
                 java.lang.Object columnId)
          throws StandardException
Initializer for a VirtualColumnNode.

Overrides:
init in class QueryTreeNode
Parameters:
sourceResultSet - The ResultSetNode where the value is originating
sourceColumn - The ResultColumn where the value is originating
columnId - The columnId within the current Row
Throws:
StandardException - Thrown on error

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

getSourceResultSet

public ResultSetNode getSourceResultSet()
Return the ResultSetNode that is the source of this VirtualColumnNode.

Returns:
ResultSetNode

getSourceColumn

public ResultColumn getSourceColumn()
Return the ResultColumn that is the source of this VirtualColumnNode.

Returns:
ResultSetNode

getTableName

public java.lang.String getTableName()
Get the name of the table the ResultColumn is in, if any. This will be null if the user did not supply a name (for example, select a from t). The method will return B for this example, select b.a from t as b The method will return T for this example, select t.a from t

Overrides:
getTableName in class ValueNode
Returns:
A String containing the name of the table the Column is in. If the column is not in a table (i.e. is a derived column), it returns NULL.

getSchemaName

public java.lang.String getSchemaName()
                               throws StandardException
Get the name of the schema the ResultColumn's table is in, if any. The return value will be null if the user did not supply a schema name (for example, select t.a from t). Another example for null return value (for example, select b.a from t as b). But for following query select app.t.a from t, this will return APP

Overrides:
getSchemaName in class ValueNode
Returns:
A String containing the name of the schema for the Column's table. If the column is not in a schema (i.e. derived column), it returns NULL.
Throws:
StandardException

updatableByCursor

public boolean updatableByCursor()
Return whether or not the ResultColumn is wirtable by a positioned update.

Overrides:
updatableByCursor in class ValueNode
Returns:
TRUE, if the column is a base column of a table and is writable by a positioned update.

getSourceResultColumn

public ResultColumn getSourceResultColumn()
Return the ResultColumn that is the source of this VirtualColumnNode.

Overrides:
getSourceResultColumn in class ValueNode
Returns:
ResultSetNode

setCorrelated

void setCorrelated()
Mark this VCN as a reference to a correlated column. (It's source resultSet is an outer ResultSet.


getCorrelated

boolean getCorrelated()
Return whether or not this VCN is a correlated reference.

Returns:
Whether or not this VCN is a correlated reference.

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.

generateExpression

public void generateExpression(ExpressionClassBuilder acb,
                               MethodBuilder mb)
                        throws StandardException
ColumnNode's are against the current row in the system. This lets us generate a faster get that simply returns the column from the current row, rather than getting the value out and returning that, only to have the caller (in the situations needed) stuffing it back into a new column holder object. We will assume the general generate() path is for getting the value out, and use generateColumn() when we want to keep the column wrapped.

Overrides:
generateExpression in class ValueNode
Parameters:
acb - The ExpressionClassBuilder for the class being built
mb - The method the expression will go into
Throws:
StandardException - Thrown on error

getOrderableVariantType

protected int getOrderableVariantType()
                               throws StandardException
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 (constant expressions)

Overrides:
getOrderableVariantType in class ValueNode
Returns:
The variant type for the underlying expression.
Throws:
StandardException - thrown on error

getTypeServices

public DataTypeDescriptor getTypeServices()
Get the DataTypeServices from this Node.

Overrides:
getTypeServices in class ValueNode
Returns:
The DataTypeServices from this Node. This may be null if the node isn't bound yet.

setType

public void setType(DataTypeDescriptor dtd)
             throws StandardException
Description copied from class: ValueNode
Set the DataTypeServices for this ValueNode. This method is overridden in ParameterNode.

Overrides:
setType in class ValueNode
Parameters:
dtd - The DataTypeServices to set in this ValueNode
Throws:
StandardException

isEquivalent

protected boolean isEquivalent(ValueNode o)
                        throws StandardException
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:

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

Built on Thu 2010-12-23 20:49:13+0000, from revision ???

Apache Derby V10.6 Internals - Copyright © 2004,2007 The Apache Software Foundation. All Rights Reserved.