Class BaseColumnNode

java.lang.Object

org.apache.derby.impl.sql.compile.QueryTreeNode

org.apache.derby.impl.sql.compile.ValueNode

org.apache.derby.impl.sql.compile.BaseColumnNode

All Implemented Interfaces:

Visitable

class BaseColumnNode
extends ValueNode

A BaseColumnNode represents a column in a base table. The parser generates a BaseColumnNode for each column reference. A column refercence could be a column in a base table, a column in a view (which could expand into a complex expression), or a column in a subquery in the FROM clause. By the time we get to code generation, all BaseColumnNodes should stand only for columns in base tables.

Field Summary

Fields

Modifier and Type	Field	Description
private String	columnName
private TableName	tableName

Fields inherited from class ValueNode

transformed

Fields inherited from class QueryTreeNode

AUTOINCREMENT_CREATE_MODIFY, AUTOINCREMENT_CYCLE, AUTOINCREMENT_INC_INDEX, AUTOINCREMENT_IS_AUTOINCREMENT_INDEX, AUTOINCREMENT_START_INDEX

Constructor Summary

Constructors

Constructor	Description
BaseColumnNode(String columnName, TableName tableName, DataTypeDescriptor dtd, ContextManager cm)	Constructor for a referenced column name

Method Summary

Modifier and Type	Method	Description
(package private) void	acceptChildren(Visitor v)	Accept a visitor on all child nodes.
(package private) void	generateExpression(ExpressionClassBuilder acb, MethodBuilder mb)	Do the code generation for this node.
(package private) String	getColumnName()	Get the name of this column
protected int	getOrderableVariantType()	Return the variant type for the underlying expression.
(package private) String	getSchemaName()	Get the user-supplied schema name for this column's table.
(package private) String	getTableName()	Get the user-supplied table name of this column.
(package private) boolean	isEquivalent(ValueNode o)	Tests if this node is equivalent to the specified ValueNode.
String	toString()	Convert this object to a String.

Methods inherited from class ValueNode

bindExpression, bindExpression, categorize, changeToCNF, checkIsBoolean, checkTopPredicatesForEqualsConditions, constantExpression, copyFields, eliminateNots, evaluateConstantExpressions, genEqualsFalseTree, generate, genIsNullTree, genSQLJavaSQLTree, getClone, getConstantValueAsObject, getDataValueFactory, getSourceResultColumn, getTablesReferenced, getTransformed, getTypeCompiler, getTypeId, getTypeServices, isBinaryEqualsOperatorNode, isBooleanFalse, isBooleanTrue, isCloneable, isConstantExpression, 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 QueryTreeNode

accept, 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

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Details

columnName

private String columnName

tableName

private TableName tableName

Constructor Details

BaseColumnNode

BaseColumnNode(String columnName,
 TableName tableName,
 DataTypeDescriptor dtd,
 ContextManager cm)
        throws StandardException

Constructor for a referenced column name

Parameters:

columnName - The name of the column being referenced

tableName - The qualification for the column

dtd - Data type descriptor for the column

cm - Context manager

Throws:

StandardException

Method Details

toString

public String toString()

Convert this object to a String. See comments in QueryTreeNode.java for how this should be done for tree printing.

Overrides:

toString in class ValueNode

Returns:

This object as a String

getColumnName

String getColumnName()

Get the name of this column

Overrides:

getColumnName in class ValueNode

Returns:

The name of this column

getTableName

String getTableName()

Get the user-supplied table name of this column. 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:

The user-supplied name of this column. Null if no user- supplied name.

getSchemaName

String getSchemaName()
              throws StandardException

Get the user-supplied schema name for this column's table. This will be null if the user did not supply a 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:

The schema name for this column's table

Throws:

StandardException

generateExpression

void generateExpression(ExpressionClassBuilder acb,
 MethodBuilder mb)
                 throws StandardException

Do the code generation for this node. Should never be called.

Overrides:

generateExpression in class ValueNode

Parameters:

acb - The ExpressionClassBuilder for the class being built

mb - The method the code to place the code

Throws:

StandardException - Thrown on error

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 (constant expressions)

Overrides:

getOrderableVariantType in class ValueNode

Returns:

The variant type for the underlying expression.

isEquivalent

boolean isEquivalent(ValueNode o)

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.

acceptChildren

void acceptChildren(Visitor v)
             throws StandardException

Description copied from class: QueryTreeNode

Accept a visitor on all child nodes. All sub-classes that add fields that should be visited, should override this method and call accept(v) on all visitable fields, as well as super.acceptChildren(v) to make sure all visitable fields defined by the super-class are accepted too.

Overrides:

acceptChildren in class QueryTreeNode

Parameters:

v - the visitor

Throws:

StandardException - on errors raised by the visitor