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From 丁儒 <>
Subject Re:Re: memory cost in forceMerge(1)
Date Tue, 11 Aug 2015 10:51:43 GMT

The index will not change oftenly, so we call forceMerge in the end. Will forceMerge(1) cost
too much memory? And the final size of the index is 15GB. I just want to know why different
machine cost different time in forceMerge, them have the same cpu and disk, but different
size of memory. One has 24GB, the other has 48 GB. And i allocate -Xmx15GB for the application.

At 2015-08-11 12:30:38, "Erick Erickson" <> wrote:
>It is generally unnecessary to use forceMerge, that's a legacy from
>older versions of Lucene/Solr.
>Especially if the index is constantly changing, forceMerge generally
>is both expensive and not
>very useful.
>These indexes must be huge though if any of them are taking 8 hours.
>What's the background here?
>On Mon, Aug 10, 2015 at 6:28 PM, 丁儒 <> wrote:
>> GreetingsNow, i'm using lucene , the version is 4.10.3. For some reason, i called
forceMerge(1) in the end,and the final  space of the Index Library is 15 GB. . But i found
that forceMerge(1) cost a lot of time, and on different machines ,the time differs.  Is this
caused by the different size of memory of the macheines. One has 24GB memory, the other has
48GB memory. And the machine with 24 GB memory cost nearly 18 hours in forceMerge(1), and
the machine with 48 GB memory cost nearly 8 hours in forceMerge(1). I guess the forceMerge(1)
needs too much memory, so it costs more time in less memory machine. Am i right ?
>>     Also, can forceMerge(1)  speed up the search?
>> Thank you
>> All
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