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SQLiteで高速全文検索〜日本語編〜
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shoby
August 20, 2014
Technology
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SQLiteで高速全文検索〜日本語編〜
【第8回】potatotips (iOS/Android開発Tips共有会)
shoby
August 20, 2014
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Transcript
42-JUFͰ ߴશจݕࡧ ʙຊޠฤʙ @shobyshoby
ࣗݾհ pixivͰΞϓϦͭͬͯ͘·͢
ຊ
iOSΞϓϦͰ SQLiteΛͬͯ ຊޠΛ ߴʹશจݕࡧ͍ͨ͠
֓ཁ
42-JUFͷશจݕࡧ֦ு ຊޠͷτʔΫϯׂ ݕࡧॱҐ σϞ
42-JUFͷ શจݕࡧ֦ு
SQLite FTS3 and FTS4 Extensions http://www.sqlite.org/fts3.html
iOS 6 SDK͔Β σϑΥϧτͰ͑Δ
جຊతͳ͍ํ
CREATE VIRTUAL TABLE article USING fts4 (title, body); FTS4 ςʔϒϧ
INSERT INSERT INTO article(title, body) VALUES ('Apple', 'I have iPhone4
and iPhone5s');
جຊతͳQuery SELECT * FROM article WHERE body MATCH 'iPhone5s'; term
match SELECT * FROM article WHERE body MATCH 'iPhone*'; term-prefix match
phrase match SELECT * FROM article WHERE body MATCH 'have
iPhone*'; ◦I have iPhone5s ×I have Android and iPhone5s
ಛघͳQuery SELECT * FROM article WHERE article MATCH 'iPhone*'; all
columns SELECT * FROM article WHERE article MATCH 'title:Apple iPhone*'; specified column
؆୯ʂ
※ͨͩ͠ӳޠʹݶΔ
ຊޠͷ߹ɺ FTSͷTokenizer͕ ͏·͘tokenʹ͚ΒΕͳ͍
FTSͷTokenizer͕ ͏·͘ѻ͑Δܗࣜʹ Ճͯ͠σʔλΛೖΕΑ͏ʂ
ຊޠͷ τʔΫϯׂ
FTSͷςʔϒϧʹ ֯εϖʔεͰ ׂͨ͠σʔλΛೖΕΔ
CREATE TABLE article (id, title, body); CREATE VIRTUAL TABLE articleTokens
USING fts4 (articleId, titleTokens, bodyTokens); ݩσʔλΛೖΕΔςʔϒϧ FTSςʔϒϧ
INSERT͍ͨ͠σʔλ INSERT INTO article(id, title, body) VALUES (1, 'Ξοϓϧ', 'ࢲΞΠϑΥʔϯ4ͱΞΠϑΥʔϯ5sΛ͍࣋ͬͯ·
͢'); ! INSERT INTO articleTokens(articleId, titleTokens, bodyTokens) VALUES (1, 'Ξοϓϧ', 'ࢲ ΞΠϑΥʔϯ4 ͱ ΞΠϑΥʔϯ5s Λ ࣋ͬ ͍ͯ·͢');
͍͛ͨSELECT SELECT * FROM article JOIN ( SELECT articleId FROM
articleTokens WHERE bodyTokens MATCH 'ΞΠϑΥʔϯ*' LIMIT 100; ) AS result ON article.id = result.articleId ORDER BY article.id;
τʔΫϯׂ͢Δ
CFStringTokenizer
෦ͰMeCabΛͬͯ ܗଶૉղੳͯ͠ΔΒ͍͠ http://stackoverflow.com/questions/8280824/how-to-use- cfstringtokenizer-with-chinese-and-japanese
- (NSArray *)tokenArrayWithString:(NSString *)string { NSLocale *locale = [[NSLocale alloc]
initWithLocaleIdentifier:@"ja"]; CFRange range = CFRangeMake(0, CFStringGetLength((CFStringRef)string)); CFStringTokenizerRef tokenizer = CFStringTokenizerCreate(kCFAllocatorDefault, (CFStringRef)string, range, kCFStringTokenizerUnitWordBoundary, (CFLocaleRef)locale); NSMutableArray *tokenArray = [NSMutableArray array]; while(CFStringTokenizerAdvanceToNextToken(tokenizer) != kCFStringTokenizerTokenNone) { CFRange tokenRange = CFStringTokenizerGetCurrentTokenRange(tokenizer); if(range.location != kCFNotFound) { NSString *token = [string substringWithRange:NSMakeRange(tokenRange.location, tokenRange.length)]; [tokenArray addObject:token]; } } CFRelease(tokenizer); return tokenArray; }
INSERT
tokenArrayΛ ֯εϖʔεͰ࿈݁ͯ͠ INSERT͢Δ [tokenArray componentsJoinedByString:@" "];
ݕࡧ
֤Tokenʹ * ΛՃ͠ ֯εϖʔεͰ࿈݁ͯ͠ QueryΛΈཱͯΔ NSMutableArray *searchTokens = [NSMutableArray arrayWithCapacity:tokenArray.count];
for (NSString *token in tokenArray) { [searchTokens addObject:[token stringByAppendingString:@"*"]]; } [searchTokens componentsJoinedByString:@" "];
ݕࡧॱҐ
Ϛον͕ߴ͍ॱʹ ݁ՌΛฦ͍ͨ͠
SQLite ಠࣗͷSQLؔΛ ఆٛͰ͖Δ
rank()ͱ͍͏ SQL͕ؔ ͋ͬͨͱ͢Δͱ…
͍͛ͨSELECT SELECT * FROM article JOIN ( SELECT articleId, rank(matchinfo(articleTokens,
'pcnalx')) AS rank FROM articleTokens WHERE bodyTokens MATCH 'ΞΠϑΥʔϯ*' LIMIT 100; ) AS result ON article.id = result.articleId ORDER BY rank DESC;
match_info() ! ϚονใΛฦ͢ FTSͷؔ http://www.sqlite.org/fts3.html#matchinfo
match_info()͔Β ϚονείΞΛฦ͢ SQLؔΛ࡞Ζ͏ʂ
CݴޠͰ…
ϚονείΞͷ ΞϧΰϦζϜ
Okapi BM25 http://en.wikipedia.org/wiki/Okapi_BM25
sqlite-okapi-bm25 https://github.com/rads/sqlite-okapi-bm25
ंྠͷ࠶ൃ໌ ආ͚ΒΕͨ ※ҙ ୯Ұͷcolumnʹ͔͠ରԠ͍ͯ͠ͳ͍ͷͰ ඞཁͳΒFork͢Δ
σϞ
·ͱΊ
42-JUFͷ'54Λ͏ͱɺߴʹ શจݕࡧͰ͖Δ ຊޠࣄલʹ5PLFOׂ͕ඞཁ ݕࡧॱҐಠࣗ42-ؔΛ࡞ͬͯ ରԠ͢Δ
͓͠·͍