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From Mark Miller <>
Subject Re: Difference between softCommit and hardCommit?
Date Thu, 15 Nov 2012 14:43:54 GMT
Hard commit is about persistence - you should usually use it with
openSearcher=false now. It flushes deletes, calls fsync, ensures data
is on stable storage. It also flushes the update log.

Soft commit is about visibility. It does not flush deletes or call
fsync. It opens a new Searcher from the Writer and is much faster.
Soft commit is what allows for NRT (Near Realtime indexing). You can
do it once a second or even faster if you really need to (though it
will thrash your caches, so you only want to go as low as you need).

We wanted to rename soft commit before 4, but we never got to it.

- Mark

On Thu, Nov 15, 2012 at 2:26 AM, Per Steffensen <> wrote:
> Hi
> Will anyone please explain the difference between softCommit and hardCommit
> (maybe just called commit)? Not only seen from the users perspective, but
> also a few technical details, please.
> Regards, Per Steffensen
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- Mark

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