Merge Document increasing some doc count why?

Elastic Stack Elasticsearch
1

Before merge my index status is

green open client 4m5zLWWweSzzWsYoJ4MewpeQ 5 1 344914 79523 1.1gb 654.6mb

when i did merge operation by curl -XPOST 192.168.1.101:9200/client/_forcemerge?max_num_segments=1

I found some increment in documents

green open client 4m5zLWWweSzzWsYoJ4MewpeQ 5 1 345135 0 819.8mb 409.9mb

Why this document count increase 344914 to 345135 happened, is any chance to get include deleted documents? what actually merge did?

2

Did you recently insert some documents into this index? It is possible that the 344914 document count didn't include documents added since the last refresh, but that a refresh occurred at around the same time as the force merge.

3

no there is no any insertion, is there any chance to no of doc will increase after forcemerge? there was 3 million small doc [among 4 billion doc] forcemerge taken 30 min.. can i reduce this time?

4

Not as far as I know.

Force-merging is an intensive operation that involves re-writing the whole index, so I'd expect it to take some time. Why do you want it to be faster?