com.akiban.sql.parser
Class ColumnReference

java.lang.Object
  com.akiban.sql.parser.QueryTreeNode
      com.akiban.sql.parser.ValueNode
          com.akiban.sql.parser.ColumnReference

All Implemented Interfaces:

Visitable

public class ColumnReference
extends ValueNode

A ColumnReference represents a column in the query tree. The parser generates a ColumnReference 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.

Field Summary

Fields inherited from class com.akiban.sql.parser.QueryTreeNode

AUTOINCREMENT_CREATE_MODIFY, AUTOINCREMENT_INC_INDEX, AUTOINCREMENT_IS_AUTOINCREMENT_INDEX, AUTOINCREMENT_START_INDEX

Constructor Summary

ColumnReference()

Method Summary

void	copyFrom(QueryTreeNode node) Fill this node with a deep copy of the given node.
String	getColumnName() Get the name of this column
String	getSchemaName() Get the user-supplied schema name of this column.
String	getSQLColumnName() Get the column name for purposes of error messages or debugging.
String	getTableName() Get the user-supplied table name of this column.
TableName	getTableNameNode() Return the table name as the node it is.
void	init(Object columnName, Object tableName) Initializer.
void	init(Object columnName, Object tableName, Object tokBeginOffset, Object tokEndOffset) Initializer.
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.
void	setTableNameNode(TableName tableName)
String	toString() Convert this object to a String.

Methods inherited from class com.akiban.sql.parser.ValueNode

getSourceResultColumn, getType, getTypeId, init, isBinaryEqualsOperatorNode, isBooleanFalse, isBooleanTrue, isConstantExpression, isInListProbeNode, isParameterNode, isRelationalOperator, isSameNodeType, setNullability, setType

Methods inherited from class com.akiban.sql.parser.QueryTreeNode

accept, convertDefaultNode, debugFlush, debugPrint, formatNodeString, getBeginOffset, getDebugOutput, getEndOffset, getNodeFactory, getNodeType, getNullNode, getParserContext, getStatementType, getUserData, init, init, init, init, init, init, init, init, init, init, init, isInstanceOf, makeTableName, makeTableName, nodeHeader, printLabel, setBeginOffset, setDebugOutput, setEndOffset, setNodeType, setParserContext, setUserData, stackPrint, treePrint, treePrint, treePrint

Methods inherited from class java.lang.Object

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

Constructor Detail

ColumnReference

public ColumnReference()

Method Detail

init

public void init(Object columnName,
                 Object tableName,
                 Object tokBeginOffset,
                 Object tokEndOffset)

Initializer. This one is called by the parser where we could be dealing with delimited identifiers.

Overrides:

init in class QueryTreeNode

Parameters:

columnName - The name of the column being referenced

tableName - The qualification for the column

tokBeginOffset - begin position of token for the column name identifier from parser.

tokEndOffsetend - position of token for the column name identifier from parser.

init

public void init(Object columnName,
                 Object tableName)

Initializer.

Overrides:

init in class QueryTreeNode

Parameters:

columnName - The name of the column being referenced

tableName - The qualification for the column

copyFrom

public void copyFrom(QueryTreeNode node)
              throws StandardException

Fill this node with a deep copy of the given node.

Overrides:

copyFrom in class ValueNode

Throws:

StandardException

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

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

getSQLColumnName

public String getSQLColumnName()

Get the column name for purposes of error messages or debugging. This returns the column name as used in the SQL statement. Thus if it was qualified with a table, alias name that will be included.

Returns:

The column name in the form [[schema.]table.]column

getColumnName

public String getColumnName()

Get the name of this column

Overrides:

getColumnName in class ValueNode

Returns:

The name of this column

getTableName

public 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.

getTableNameNode

public TableName getTableNameNode()

Return the table name as the node it is.

Returns:

the column's table name.

setTableNameNode

public void setTableNameNode(TableName tableName)

getSchemaName

public String getSchemaName()

Get the user-supplied schema name of this column. 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 Code generation of aggregate functions relies on this method

Overrides:

getSchemaName in class ValueNode

Returns:

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

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:

• 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