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

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.BaseColumnNode
All Implemented Interfaces:
Visitable

public 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
private  java.lang.String columnName
           
private  TableName tableName
           
 
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
BaseColumnNode()
           
 
Method Summary
 void generateExpression(ExpressionClassBuilder acb, MethodBuilder mb)
          Do the code generation for this node.
 java.lang.String getColumnName()
          Get the name of this column
protected  int getOrderableVariantType()
          Return the variant type for the underlying expression.
 java.lang.String getSchemaName()
          Get the user-supplied schema name for this column's table.
 java.lang.String getTableName()
          Get the user-supplied table name of this column.
 void init(java.lang.Object columnName, java.lang.Object tableName, java.lang.Object dts)
          Initializer for when you only have the column name.
protected  boolean isEquivalent(ValueNode o)
          Tests if this node is equivalent to the specified ValueNode.
 java.lang.String toString()
          Convert this object to a String.
 
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, getConstantValueAsObject, getDataValueFactory, getSourceResultColumn, getTablesReferenced, getTransformed, getTypeCompiler, getTypeId, getTypeServices, init, isBinaryEqualsOperatorNode, isBooleanFalse, isBooleanTrue, isCloneable, isConstantExpression, isInListProbeNode, isParameterNode, isRelationalOperator, isSameNodeType, 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, 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, printSubNodes, 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

columnName

private java.lang.String columnName

tableName

private TableName tableName
Constructor Detail

BaseColumnNode

public BaseColumnNode()
Method Detail

init

public void init(java.lang.Object columnName,
                 java.lang.Object tableName,
                 java.lang.Object dts)
          throws StandardException
Initializer for when you only have the column name.

Overrides:
init in class QueryTreeNode
Parameters:
columnName - The name of the column being referenced
tableName - The qualification for the column
dts - DataTypeServices for the column
Throws:
StandardException - Thrown on error

toString

public java.lang.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

public java.lang.String getColumnName()
Get the name of this column

Overrides:
getColumnName in class ValueNode
Returns:
The name of this column

getTableName

public java.lang.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

public java.lang.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

public 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

protected 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:

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.

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

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