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From Vitaly Funstein <vfunst...@gmail.com>
Subject Re: Deferring merging of index segments
Date Mon, 04 Jun 2012 19:10:02 GMT
Thanks for the tip, Mike. After changing the three calls

IndexWriter.commit();

<revert merge policy to allow merging to happen>

IndexWriter.maybeMerge();
IndexWriter.waitForMerges();

to simply calling IndexWriter.close(true) the disk size and run time are
now very close to the case of parallel segment merges.

On Sat, Jun 2, 2012 at 6:43 AM, Michael McCandless <
lucene@mikemccandless.com> wrote:

> On Fri, Jun 1, 2012 at 8:09 PM, Vitaly Funstein <vfunstein@gmail.com>
> wrote:
> > Yes, I am only calling IndexWriter.addDocument()
>
> OK.
>
> > Interestingly, relative performance of either approach seems to greatly
> > depend on the number of documents per index. In both types of runs, I
> used
> > 10 writer threads, each writing documents with the same set of fields
> (but
> > random values), into its own index as fast as possible, on a 16 core box,
> > using a rotational disk for index storage (results from my original post
> > were obtained from a Fusion IO drive, and an even higher # of cores per
> > machine).
>
> Mmmmm Fusion IO drive :)
>
> > For smaller index sizes, the choice of whether to merge segments
> > in parallel makes much less of a difference, if at all.
> >
> > So the matrix looks like this:
> >
> > # docs/index     concurrent merges?      total time, sec    total disk
> size
> >
> ===========================================================================
> > 200K             Y                       56.8               1.5 G
> > 200K             N                       59.6               2.6 G
> > 1M               Y                       304                7.4 G
> > 1M               N                       493                14  G
> >
> > As you can see, the total size on disk is always much larger when merging
> > at the end; here are directory listings, for each case:
>
> OK so for a biggish index merging concurrently is faster; this is what
> I'd expect.
>
> > Concurrent merging:
> >
> > total 150M
> > -rw-r--r-- 1 bench perf    0 2012-06-01 16:33 write.lock
> > -rw-r--r-- 1 bench perf   87 2012-06-01 16:33 _a.fnm
> > -rw-r--r-- 1 bench perf  17M 2012-06-01 16:33 _a.tis
> > -rw-r--r-- 1 bench perf 186K 2012-06-01 16:33 _a.tii
> > -rw-r--r-- 1 bench perf 105K 2012-06-01 16:33 _a.prx
> > -rw-r--r-- 1 bench perf 4.8M 2012-06-01 16:33 _a.frq
> > -rw-r--r-- 1 bench perf   87 2012-06-01 16:33 _l.fnm
> > -rw-r--r-- 1 bench perf  17M 2012-06-01 16:33 _l.tis
> > -rw-r--r-- 1 bench perf 186K 2012-06-01 16:33 _l.tii
> > -rw-r--r-- 1 bench perf 105K 2012-06-01 16:33 _l.prx
> > -rw-r--r-- 1 bench perf 4.8M 2012-06-01 16:33 _l.frq
> > -rw-r--r-- 1 bench perf   87 2012-06-01 16:33 _w.fnm
> > -rw-r--r-- 1 bench perf  17M 2012-06-01 16:33 _w.tis
> > -rw-r--r-- 1 bench perf 186K 2012-06-01 16:33 _w.tii
> > -rw-r--r-- 1 bench perf 105K 2012-06-01 16:33 _w.prx
> > -rw-r--r-- 1 bench perf 4.8M 2012-06-01 16:33 _w.frq
> > -rw-r--r-- 1 bench perf   87 2012-06-01 16:33 _17.fnm
> > -rw-r--r-- 1 bench perf  17M 2012-06-01 16:33 _17.tis
> > -rw-r--r-- 1 bench perf 186K 2012-06-01 16:33 _17.tii
> > -rw-r--r-- 1 bench perf 105K 2012-06-01 16:33 _17.prx
> > -rw-r--r-- 1 bench perf 4.8M 2012-06-01 16:33 _17.frq
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:33 _1j.cfs
> > -rw-r--r-- 1 bench perf   87 2012-06-01 16:33 _1i.fnm
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:33 _1k.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:33 _1m.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:33 _1l.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:33 _1n.cfs
> > -rw-r--r-- 1 bench perf  17M 2012-06-01 16:33 _1i.tis
> > -rw-r--r-- 1 bench perf 186K 2012-06-01 16:33 _1i.tii
> > -rw-r--r-- 1 bench perf 105K 2012-06-01 16:33 _1i.prx
> > -rw-r--r-- 1 bench perf 4.8M 2012-06-01 16:33 _1i.frq
> > -rw-r--r-- 1 bench perf 148K 2012-06-01 16:33 _1p.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:33 _1o.cfs
> > -rw-r--r-- 1 bench perf  28M 2012-06-01 16:33 _0.cfx
> > -rw-r--r-- 1 bench perf 2.8K 2012-06-01 16:33 segments_2
> > -rw-r--r-- 1 bench perf   20 2012-06-01 16:33 segments.gen
> >
> > Deferred merging:
> >
> > total 261M
> > -rw-r--r-- 1 bench perf    0 2012-06-01 16:41 write.lock
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _0.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _1.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _3.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _2.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _4.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _6.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _5.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _7.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _9.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _8.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _a.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _c.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _b.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _d.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _f.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _e.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _g.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _i.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _h.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _j.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _l.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _k.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _m.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _n.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _p.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _o.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _q.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _s.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _r.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _t.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _v.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _u.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _w.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _x.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _z.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _y.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _11.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _10.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _13.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _12.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _16.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _15.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _14.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _18.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _17.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _1b.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _1a.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _19.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _1d.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _1c.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _1g.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _1f.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _1e.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _1j.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _1i.cfs
> > -rw-r--r-- 1 bench perf 2.3M 2012-06-01 16:41 _1h.cfs
> > -rw-r--r-- 1 bench perf  28M 2012-06-01 16:41 _0.cfx
> > -rw-r--r-- 1 bench perf 137K 2012-06-01 16:42 _1k.cfs
> > -rw-r--r-- 1 bench perf  12K 2012-06-01 16:42 segments_2
> > -rw-r--r-- 1 bench perf   20 2012-06-01 16:42 segments.gen
> > -rw-r--r-- 1 bench perf   87 2012-06-01 16:42 _1l.fnm
> > -rw-r--r-- 1 bench perf   87 2012-06-01 16:42 _1n.fnm
> > -rw-r--r-- 1 bench perf  17M 2012-06-01 16:42 _1l.tis
> > -rw-r--r-- 1 bench perf 186K 2012-06-01 16:42 _1l.tii
> > -rw-r--r-- 1 bench perf 105K 2012-06-01 16:42 _1l.prx
> > -rw-r--r-- 1 bench perf 4.8M 2012-06-01 16:42 _1l.frq
> > -rw-r--r-- 1 bench perf   87 2012-06-01 16:42 _1o.fnm
> > -rw-r--r-- 1 bench perf  17M 2012-06-01 16:42 _1n.tis
> > -rw-r--r-- 1 bench perf 186K 2012-06-01 16:42 _1n.tii
> > -rw-r--r-- 1 bench perf 105K 2012-06-01 16:42 _1n.prx
> > -rw-r--r-- 1 bench perf 4.8M 2012-06-01 16:42 _1n.frq
> > -rw-r--r-- 1 bench perf   87 2012-06-01 16:42 _1p.fnm
> > -rw-r--r-- 1 bench perf  17M 2012-06-01 16:42 _1o.tis
> > -rw-r--r-- 1 bench perf 186K 2012-06-01 16:42 _1o.tii
> > -rw-r--r-- 1 bench perf 105K 2012-06-01 16:42 _1o.prx
> > -rw-r--r-- 1 bench perf 4.8M 2012-06-01 16:42 _1o.frq
> > -rw-r--r-- 1 bench perf  17M 2012-06-01 16:42 _1p.tis
> > -rw-r--r-- 1 bench perf 186K 2012-06-01 16:42 _1p.tii
> > -rw-r--r-- 1 bench perf 105K 2012-06-01 16:42 _1p.prx
> > -rw-r--r-- 1 bench perf 4.8M 2012-06-01 16:42 _1p.frq
> > -rw-r--r-- 1 bench perf   87 2012-06-01 16:42 _1m.fnm
> > -rw-r--r-- 1 bench perf  17M 2012-06-01 16:42 _1m.tis
> > -rw-r--r-- 1 bench perf 186K 2012-06-01 16:42 _1m.tii
> > -rw-r--r-- 1 bench perf 105K 2012-06-01 16:42 _1m.prx
> > -rw-r--r-- 1 bench perf 4.8M 2012-06-01 16:42 _1m.frq
>
> Hmm: you should close the writer (or do a final commit) before testing
> the size of the index.  I suspect in the 2nd case because no final
> commit happened, the original segments are still around.
>
> Mike
>
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