How to force a forcemerge?

[nisow95612]

@stephenb

So I assume you did this by closing the index and setting the codec and then re-opening the index... Correct?
And you did this when you already have a single segment?
And that segment was already BEST_SPEED?

Yes, you got it right.

• Technically I asked ILM to do it, but AFAIK ILM does exactly what you describe.
• Yes, I am having trouble switching coded on shards that already have only one segment.
• Yes. But I would say that segment was still BEST_SPEED.

@stephenb

It the answer to all those are yes... then I do not think forcemerge will work, as you experienced. I think if you will have to reindex.

Once you have one segment forvemerge is not going to do anything because it's about merging segments not the codec.. using the new codec It's just a side benefit when an actual merge is done

Yes, that is the reason why I opened this topic. I do not want to reindex again. Reindexing is what caused my problems, because I hit _source 50% bigger after reindex. Now I need to switch codecs to get that disk space back.

@stephenb

If you set the best_compression BEFORE you were merged to one segment then perhaps... I would need to test.

BTW I did test if you use forcemerge and it actually executes and merges because you have more than 1 segment it will "honor/use" the new codec.

Yes, any shards that had more segments switched to the new codec.
I was hoping one of you would suggest a trick to force the forcemerge to run.

E.g. I thought about creating new segments by adding a couple of dummy documents and then deleting them. But I am afraid that forcemerge will be too clever and just delete the new segments.