Michael McCandless created LUCENE-4123:
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Summary: Add CachingRAMDirectory
Key: LUCENE-4123
URL: https://issues.apache.org/jira/browse/LUCENE-4123
Project: Lucene - Java
Issue Type: Bug
Components: core/store
Reporter: Michael McCandless
Assignee: Michael McCandless
The directory is very simple and useful if you have an index that you
know fully fits into available RAM. You could also use FileSwitchDir if
you want to leave some files (eg stored fields or term vectors) on disk.
It wraps any other Directory and delegates all writing (IndexOutput) to
it, but for reading (IndexInput), it allocates a single byte[] and fully
reads the file in and then serves requests off that single byte[]. It's
more GC friendly than RAMDir since it only allocates a single array per
file.
It has a few nocommits still, but all tests pass if I wrap the delegate
inside MockDirectoryWrapper using this.
I tested with 1M Wikipedia english index (would like to test w/ 10M docs
but I don't have enough RAM...); it seems to give a nice speedup:
{noformat}
Task QPS base StdDev base QPS cachedStdDev cached Pct
diff
Respell 197.00 7.27 203.19 8.17 -4% -
11%
PKLookup 121.12 2.80 125.46 3.20 -1% -
8%
Fuzzy2 66.62 2.62 69.91 2.85 -3% -
13%
Fuzzy1 206.20 6.47 222.21 6.52 1% -
14%
TermGroup100K 160.14 6.62 175.71 3.79 3% -
16%
Phrase 34.85 0.40 38.75 0.61 8% -
14%
TermBGroup100K 363.75 15.74 406.98 13.23 3% -
20%
SpanNear 53.08 1.11 59.53 2.94 4% -
20%
TermBGroup100K1P 222.53 9.78 252.86 5.96 6% -
21%
SloppyPhrase 70.36 2.05 79.95 4.48 4% -
23%
Wildcard 238.10 4.29 272.78 4.97 10% -
18%
OrHighMed 123.49 4.85 149.32 4.66 12% -
29%
Prefix3 288.46 8.10 350.40 5.38 16% -
26%
OrHighHigh 76.46 3.27 93.13 2.96 13% -
31%
IntNRQ 92.25 2.12 113.47 5.74 14% -
32%
Term 757.12 39.03 958.62 22.68 17% -
36%
AndHighHigh 103.03 4.48 133.89 3.76 21% -
39%
AndHighMed 376.36 16.58 493.99 10.00 23% -
40%
{noformat}
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