VirtualColumnNode (Apache Derby V10.14 Internals)

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

All Implemented Interfaces:

Visitable
```
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

Fields
Modifier and Type Field Description

(package private) int columnId

private boolean correlated

private ResultColumn sourceColumn

private ResultSetNode sourceResultSet
- 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
- Fields inherited from class org.apache.derby.impl.sql.compile.ValueNode
  transformed

Fields
Modifier and Type	Field	Description
`(package private) int`	`columnId`
`private boolean`	`correlated`
`private ResultColumn`	`sourceColumn`
`private ResultSetNode`	`sourceResultSet`

Constructor Summary

Constructors
Constructor	Description
`VirtualColumnNode(ResultSetNode sourceResultSet, ResultColumn sourceColumn, int columnId, ContextManager cm)`	Constructor for a VirtualColumnNode.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`(package private) 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.
`(package private) java.lang.String`	`getSchemaName()`	Get the name of the schema the ResultColumn's table is in, if any.
`(package private) ResultColumn`	`getSourceColumn()`	Return the ResultColumn that is the source of this VirtualColumnNode.
`(package private) ResultColumn`	`getSourceResultColumn()`	Return the ResultColumn that is the source of this VirtualColumnNode.
`(package private) ResultSetNode`	`getSourceResultSet()`	Return the ResultSetNode that is the source of this VirtualColumnNode.
`(package private) java.lang.String`	`getTableName()`	Get the name of the table the ResultColumn is in, if any.
`DataTypeDescriptor`	`getTypeServices()`	Get the DataTypeServices from this Node.
`(package private) boolean`	`isCloneable()`	Return whether or not this expression tree is cloneable.
`(package private) boolean`	`isEquivalent(ValueNode o)`	Tests if this node is equivalent to the specified ValueNode.
`(package private) 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 java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

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, referencesSessionSchema, resolveTableToSynonym, setBeginOffset, setEndOffset, setRefActionInfo, stackPrint, taggedWith, treePrint, treePrint, verifyClassExist

Methods inherited from class org.apache.derby.impl.sql.compile.ValueNode
bindExpression, bindExpression, categorize, changeToCNF, checkIsBoolean, checkTopPredicatesForEqualsConditions, constantExpression, copyFields, eliminateNots, evaluateConstantExpressions, genEqualsFalseTree, generate, genIsNullTree, genSQLJavaSQLTree, getClone, getColumnName, getConstantValueAsObject, getDataValueFactory, getTablesReferenced, getTransformed, getTypeCompiler, getTypeId, isBinaryEqualsOperatorNode, isBooleanFalse, isBooleanTrue, isConstantExpression, isInListProbeNode, isParameterNode, isRelationalOperator, isSameNodeKind, optimizableEqualityNode, preprocess, putAndsOnTop, remapColumnReferencesToExpressions, requiresTypeFromContext, selectivity, setCollationInfo, setCollationInfo, setCollationUsingCompilationSchema, setCollationUsingCompilationSchema, setNullability, setTransformed, setType, setType, toString, verifyChangeToCNF, verifyEliminateNots, verifyPutAndsOnTop

- Field Detail
  - sourceResultSet
```
private ResultSetNode sourceResultSet
```
  - sourceColumn
```
private ResultColumn sourceColumn
```
  - columnId
```
int columnId
```
  - correlated
```
private boolean correlated
```
- Constructor Detail
  - VirtualColumnNode
```
VirtualColumnNode(ResultSetNode sourceResultSet,
                  ResultColumn sourceColumn,
                  int columnId,
                  ContextManager cm)
           throws StandardException
```
    Constructor for a VirtualColumnNode.
    
    Parameters:
    
    sourceResultSet - The ResultSetNode where the value is originating
    
    sourceColumn - The ResultColumn where the value is originating
    
    columnId - The columnId within the current Row
    
    cm - The context manager
    
    Throws:
    
    StandardException
- Method Detail
  - printSubNodes
```
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
```
ResultSetNode getSourceResultSet()
```
    Return the ResultSetNode that is the source of this VirtualColumnNode.
    
    Returns:
    
    ResultSetNode
  - getSourceColumn
```
ResultColumn getSourceColumn()
```
    Return the ResultColumn that is the source of this VirtualColumnNode.
    
    Returns:
    
    ResultSetNode
  - getTableName
```
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
```
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
```
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
```
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
```
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 final 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 final 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
```
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:
    - 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 class ValueNode
    
    Parameters:
    
    o - the node to compare this ValueNode against.
    
    Returns:
    
    true if the two nodes are equivalent, false otherwise.
    
    Throws:
    
    StandardException

Class VirtualColumnNode

Field Summary

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

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

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

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

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

Field Detail

sourceResultSet

sourceColumn

columnId

correlated

Constructor Detail

VirtualColumnNode

Method Detail

printSubNodes

getSourceResultSet

getSourceColumn

getTableName

getSchemaName

updatableByCursor

getSourceResultColumn

setCorrelated

getCorrelated

isCloneable

generateExpression

getOrderableVariantType

getTypeServices

setType

isEquivalent