/**
* Insert rows while we keep getting duplicates from the merge run whose scan is in the open scan
* array entry indexed by scanindex.
*/
void mergeARow(int scanindex) throws StandardException {
if (SanityManager.DEBUG) {
// Unless there's a bug, the scan index will refer
// to an open scan. That's because we never put
// a scan index for a closed scan into the sort
// buffer (via setNextAux).
SanityManager.ASSERT(openScans[scanindex] != null);
}
DataValueDescriptor[] row;
// Read rows from the merge run and stuff them into the
// sort buffer for as long as we encounter duplicates.
do {
row = sortObserver.getArrayClone();
// Fetch the row from the merge run.
if (!openScans[scanindex].fetchNext(row)) {
// If we're out of rows in the merge run, close the scan.
openScans[scanindex].close();
openScans[scanindex] = null;
return;
}
// Save the index of this merge run with
// the row we're putting in the sort buffer.
sortBuffer.setNextAux(scanindex);
} while (sortBuffer.insert(row) == SortBuffer.INSERT_DUPLICATE);
}
/** Initialize the scan, returning false if there was some error. */
public boolean init(TransactionManager tran) throws StandardException {
if (SanityManager.DEBUG) {
// We really expect to have at least one
// merge run.
SanityManager.ASSERT(mergeRuns != null);
SanityManager.ASSERT(mergeRuns.size() > 0);
// This sort scan also expects that the
// caller has ensured that the sort buffer
// capacity will hold a row from all the
// merge runs.
SanityManager.ASSERT(sortBuffer.capacity() >= mergeRuns.size());
}
// Clear the sort buffer.
sortBuffer.reset();
// Create an array to hold a scan controller
// for each merge run.
openScans = new StreamContainerHandle[mergeRuns.size()];
if (openScans == null) return false;
// Open a scan on each merge run.
int scanindex = 0;
Enumeration e = mergeRuns.elements();
while (e.hasMoreElements()) {
// get the container id
long id = ((Long) e.nextElement()).longValue();
Transaction rawTran = tran.getRawStoreXact(); // get raw transaction
int segmentId = StreamContainerHandle.TEMPORARY_SEGMENT;
openScans[scanindex++] = rawTran.openStreamContainer(segmentId, id, hold);
}
// Load the initial rows.
for (scanindex = 0; scanindex < openScans.length; scanindex++) mergeARow(scanindex);
// Success!
return true;
}
/**
* Move to the next position in the scan.
*
* @see org.apache.derby.iapi.store.access.ScanController#next
*/
public boolean next() throws StandardException {
current = sortBuffer.removeFirst();
if (current != null) mergeARow(sortBuffer.getLastAux());
return (current != null);
}
