private int discardHead(
ColumnFamily cf,
int toDiscard,
ColumnFamily copy,
Iterator<Column> iter,
DeletionInfo.InOrderTester tester) {
ColumnCounter counter = columnCounter();
List<Column> staticColumns = new ArrayList<>(cfm.staticColumns().size());
// Discard the first 'toDiscard' live, non-static columns
while (iter.hasNext()) {
Column c = iter.next();
// if it's a static column, don't count it and save it to add to the trimmed results
ColumnDefinition columnDef = cfm.getColumnDefinitionFromColumnName(c.name());
if (columnDef != null && columnDef.type == ColumnDefinition.Type.STATIC) {
staticColumns.add(c);
continue;
}
counter.count(c, tester);
// once we've discarded the required amount, add the rest
if (counter.live() > toDiscard) {
for (Column staticColumn : staticColumns) copy.addColumn(staticColumn);
copy.addColumn(c);
while (iter.hasNext()) copy.addColumn(iter.next());
}
}
return Math.min(counter.live(), toDiscard);
}
private int discardTail(
ColumnFamily cf,
int toDiscard,
ColumnFamily copy,
Iterator<Column> iter,
DeletionInfo.InOrderTester tester) {
// Redoing the counting like that is not extremely efficient.
// This is called only for reversed slices or in the case of a race between
// paging and a deletion (pretty unlikely), so this is probably acceptable.
int liveCount = columnCounter().countAll(cf).live();
ColumnCounter counter = columnCounter();
// Discard the last 'toDiscard' live (so stop adding as sound as we're past 'liveCount -
// toDiscard')
while (iter.hasNext()) {
Column c = iter.next();
counter.count(c, tester);
if (counter.live() > liveCount - toDiscard) break;
copy.addColumn(c);
}
return Math.min(liveCount, toDiscard);
}