/**
* Extract out and return the subquery, with a PRN on top. (See FromSubquery.preprocess() for more
* details.)
*
* @param numTables The number of tables in the DML Statement
* @return ResultSetNode at top of extracted tree.
* @exception StandardException Thrown on error
*/
public ResultSetNode extractSubquery(int numTables) throws StandardException {
JBitSet newJBS;
ResultSetNode newPRN;
newPRN =
(ResultSetNode)
getNodeFactory()
.getNode(
C_NodeTypes.PROJECT_RESTRICT_NODE,
subquery, /* Child ResultSet */
resultColumns, /* Projection */
null, /* Restriction */
null, /* Restriction as PredicateList */
null, /* Subquerys in Projection */
null, /* Subquerys in Restriction */
tableProperties,
getContextManager());
/* Set up the PRN's referencedTableMap */
newJBS = new JBitSet(numTables);
newJBS.set(tableNumber);
newPRN.setReferencedTableMap(newJBS);
((FromTable) newPRN).setTableNumber(tableNumber);
return newPRN;
}
/**
* This overload variant of optimizeStatement is used by subclass CursorNode (as well as a minion
* for the no-arg variant).
*
* @param offset Any OFFSET row count, or null
* @param fetchFirst Any FETCH FIRST row count or null
* @exception StandardException Thrown on error
* @see DMLStatementNode#optimizeStatement()
*/
protected void optimizeStatement(ValueNode offset, ValueNode fetchFirst)
throws StandardException {
resultSet = resultSet.preprocess(getCompilerContext().getNumTables(), null, (FromList) null);
resultSet = resultSet.optimize(getDataDictionary(), null, 1.0d);
resultSet = resultSet.modifyAccessPaths();
// Any OFFSET/FETCH FIRST narrowing must be done *after* any rewrite of
// the query tree (if not, underlying GROUP BY fails), but *before* the
// final scroll insensitive result node set is added - that one needs
// to sit on top - so now is the time.
//
// This example statement fails if we wrap *before* the optimization
// above:
// select max(a) from t1 group by b fetch first row only
//
// A java.sql.ResultSet#previous on a scrollable result set will fail
// if we don't wrap *after* the ScrollInsensitiveResultSetNode below.
//
// We need only wrap the RowCountNode set if at least one of the
// clauses is present.
if (offset != null || fetchFirst != null) {
resultSet = wrapRowCountNode(resultSet, offset, fetchFirst);
}
/* If this is a cursor, then we
* need to generate a new ResultSetNode to enable the scrolling
* on top of the tree before modifying the access paths.
*/
if (this instanceof CursorNode) {
ResultColumnList siRCList;
ResultColumnList childRCList;
ResultSetNode siChild = resultSet;
/* We get a shallow copy of the ResultColumnList and its
* ResultColumns. (Copy maintains ResultColumn.expression for now.)
*/
siRCList = resultSet.getResultColumns();
childRCList = siRCList.copyListAndObjects();
resultSet.setResultColumns(childRCList);
/* Replace ResultColumn.expression with new VirtualColumnNodes
* in the ScrollInsensitiveResultSetNode's ResultColumnList. (VirtualColumnNodes include
* pointers to source ResultSetNode, this, and source ResultColumn.)
*/
siRCList.genVirtualColumnNodes(resultSet, childRCList);
/* Finally, we create the new ScrollInsensitiveResultSetNode */
resultSet =
(ResultSetNode)
getNodeFactory()
.getNode(
C_NodeTypes.SCROLL_INSENSITIVE_RESULT_SET_NODE,
resultSet,
siRCList,
null,
getContextManager());
// Propagate the referenced table map if it's already been created
if (siChild.getReferencedTableMap() != null) {
resultSet.setReferencedTableMap((JBitSet) siChild.getReferencedTableMap().clone());
}
}
}
