[FTS] up to 10x performance degradation when using large "query size" (limit) setting

Despite the actual amount of hits returned large "limit" impacts the throughput.

Some numbers:

Small dataset, low frequency terms, the search query returns only 1 hit.

size = 1, throughput = 21k

size = 10, throughput = 20k

size = 100, throughput = 9k

size = 1000, throughput = 2k