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From Michael McCandless <>
Subject Re: FST performance difference b/w build() & load()
Date Wed, 03 Jul 2013 19:37:50 GMT
Which Lucene version?

A "just built" FST stores its bytes in smallish (64 KB I think) pages,
while a loaded-from-disk FST uses much larger pages (1 GB I think).

But I would expect the loaded FST to be faster, not the other way around.

How much of a speed difference are you seeing?  And are you restarting
the JVM in between the two runs?  (Ie fresh JVM for the "just built"
case, and a fresh JVM for the "loaded from disk" case).

Mike McCandless

On Wed, Jul 3, 2013 at 3:31 PM, Michael Garski <> wrote:
> Hello -
> I've observed a noticeable performance difference in looking up completions in a WFSTCompletionLookup
when it is created using the build() method with a TermFreqIterator versus one that is created
by loading a previously saved instance, with the instance created from the build method being
faster. The saved lookup is ~275MB on disk. I have not dug in to determine why this is, but
is this to be expected?
> Thanks,
> Michael
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