com.akiban.sql.parser
Class VirtualColumnNode

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

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

AUTOINCREMENT_CREATE_MODIFY, AUTOINCREMENT_INC_INDEX, AUTOINCREMENT_IS_AUTOINCREMENT_INDEX, AUTOINCREMENT_START_INDEX

Constructor Summary

VirtualColumnNode()

Method Summary

void	copyFrom(QueryTreeNode node) Fill this node with a deep copy of the given node.
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.
ResultSetNode	getSourceResultSet() Return the ResultSetNode that is the source of this VirtualColumnNode.
String	getTableName() Get the name of the table the ResultColumn is in, if any.
DataTypeDescriptor	getType() Get the DataTypeDesciptor from this Node.
void	init(Object sourceResultSet, Object sourceColumn, Object columnId) Initializer for a VirtualColumnNode.
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	setType(DataTypeDescriptor dtd) Set the DataTypeDescriptor for this ValueNode.

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

getColumnName, getSourceResultColumn, getTypeId, init, isBinaryEqualsOperatorNode, isBooleanFalse, isBooleanTrue, isConstantExpression, isInListProbeNode, isParameterNode, isRelationalOperator, isSameNodeType, setNullability, toString

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, 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

VirtualColumnNode

public VirtualColumnNode()

Method Detail

init

public void init(Object sourceResultSet,
                 Object sourceColumn,
                 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

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

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:

ResultColumn

getTableName

public 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 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

getType

public DataTypeDescriptor getType()

Get the DataTypeDesciptor from this Node.

Overrides:

getType in class ValueNode

Returns:

The DataTypeDescriptor 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 DataTypeDescriptor for this ValueNode. This method is overridden in ParameterNode.

Overrides:

setType in class ValueNode

Parameters:

dtd - The DataTypeDescriptor 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:

• 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