/**
* Returns the first non-static cell in the ColumnFamily. This is necessary to avoid recording a
* static column as the "last" cell seen in a reversed query. Because we will always query static
* columns alongside the normal data for a page, they are not a good indicator of where paging
* should resume. When we begin the next page, we need to start from the last non-static cell.
*/
protected Column firstNonStaticColumn(ColumnFamily cf) {
for (Column column : cf) {
ColumnDefinition def = cfm.getColumnDefinitionFromColumnName(column.name());
if (def == null || def.type != ColumnDefinition.Type.STATIC) return column;
}
return null;
}
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);
}