Log Server Window Counts

A log server stores entries [timestamp, severity, message], where timestamp is an integer and severity is a string such as "ERROR". The logs are not necessarily in timestamp order.

Each query is [start, end, severity] with start <= end. Its answer is the number of log entries whose severity equals severity exactly (case-sensitive) and whose timestamp satisfies start <= timestamp <= end.

Return one row [severity, count] per query, in the same order as queries. A severity that never appears simply has count 0.

There can be many logs and many queries, so avoid scanning every log for every query.