{"id":4574,"date":"2014-12-04T10:00:00","date_gmt":"2014-12-04T01:00:00","guid":{"rendered":"http:\/\/www.techscore.com\/blog\/?p=4574"},"modified":"2018-11-14T16:33:50","modified_gmt":"2018-11-14T07:33:50","slug":"postgresql%e3%81%a7%e3%82%a4%e3%83%b3%e3%83%87%e3%83%83%e3%82%af%e3%82%b9%e3%82%92%e5%8a%b9%e7%8e%87%e9%ab%98%e3%81%8f%e5%88%a9%e7%94%a8%e3%81%97%e3%82%88%e3%81%86","status":"publish","type":"post","link":"https:\/\/www.techscore.com\/blog\/2014\/12\/04\/postgresql%e3%81%a7%e3%82%a4%e3%83%b3%e3%83%87%e3%83%83%e3%82%af%e3%82%b9%e3%82%92%e5%8a%b9%e7%8e%87%e9%ab%98%e3%81%8f%e5%88%a9%e7%94%a8%e3%81%97%e3%82%88%e3%81%86\/","title":{"rendered":"PostgreSQL\u3067\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u3092\u52b9\u7387\u826f\u304f\u5229\u7528\u3057\u3088\u3046"},"content":{"rendered":"<p>\u3069\u3046\u3082\u3001Beno\u00eet\u3067\u3059\u3002<\/p>\n<p><a title=\"TECHSCORE Advent Calendar 2014\" href=\"http:\/\/www.techscore.com\/blog\/2014\/11\/27\/techscore-advent-calendar-2014\/\">TECHSCORE Advent Calendar 2014<\/a> \u306e 4 \u65e5\u76ee\u306e\u6295\u7a3f\u3067\u3059\u3002<\/p>\n<p>PostgreSQL\u3067\u306f\u3044\u308d\u3044\u308d\u306a\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u7a2e\u985e\u304c\u5b58\u5728\u3059\u308b\u3002\u4f7f\u3044\u65b9\u3082\u69d8\u3005\u3067\u3042\u308b\u3002\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u7a2e\u985e\u306e\u6982\u8981\u306e\u3042\u3068\u306b\u4e00\u756a\u4f7f\u308f\u308c\u308bB-tree\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u306e\u4f7f\u3044\u9053\u3084\u4fdd\u5b88\u306e\u8a71\u3057\u3092\u6df1\u3081\u3066\u3044\u304f\u3002<\/p>\n<p>\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u3068\u306f\u7279\u5b9a\u306e\u9805\u76ee\u3092\u7d20\u65e9\u304f\u53c2\u7167\u3067\u304d\u308b\u3088\u3046\u306b\u3059\u308b\u305f\u3081\u306e\u3082\u306e\u3002B-tree\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u306b\u95a2\u3057\u3066\u306f\u30bd\u30fc\u30c8\u306b\u4f7f\u3046\u3053\u3068\u3082\u3067\u304d\u308b\u3002<\/p>\n<h2>\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u306e\u7a2e\u985e<\/h2>\n<p>PostgreSQL\u306f\u3044\u308d\u3044\u308d\u306a\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u306b\u5bfe\u5fdc\u3057\u3066\u3044\u308b\u3002<\/p>\n<ul>\n<li><strong>B-tree\u30a4\u30f3\u30c7\u30c3\u30af\u30b9<\/strong>\u3001CREATE INDEX \u3092\u5229\u7528\u3059\u308b\u3068\u30c7\u30d5\u30a9\u30eb\u30c8\u3067\u9078\u629e\u3055\u308c\u308b\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u3067\u3042\u308b\u3002B\u306e\u5b57\u306f\u30d0\u30e9\u30f3\u30b9\u306e\u610f\u5473\u3067\u3001\u30a4\u30e1\u30fc\u30b8\u3068\u3057\u3066\u306ftree\uff08\u6728\u69cb\u9020\uff09\u306eroot\uff08\u6839\uff09\u304b\u3089leaf\uff08\u6700\u4e0b\u5c64\u306e\u30ce\u30fc\u30c9\uff09\u307e\u3067\u306e\u968e\u5c64\u6570\u304c\u306a\u308b\u3079\u304f\u63c3\u3046\u3088\u3046\u306b\u30d0\u30e9\u30f3\u30b9\u3092\u53d6\u308b\u3002B-tree\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u306f\u3069\u306e\u30c7\u30fc\u30bf\u578b\u3082\u5bfe\u5fdc\u3057\u3066\u3044\u308b\u4e8b\u3001NULL\u5024\u3082\u6271\u3046\u3053\u3068\u304c\u3067\u304d\u308b\u4e8b\u3001\u7b49\u4fa1\u6027\u3060\u3051\u3067\u306a\u304f\u7bc4\u56f2\u3084\u6bd4\u8f03\u691c\u7d22\u306b\u4f7f\u3046\u3053\u3068\u304c\u3067\u304d\u308b\u70b9\u304c\u7279\u5fb4\u3067\u3042\u308b\u3002\u5c1a\u3001\u30ad\u30e3\u30c3\u30b7\u30f3\u30b0\u3068\u306e\u76f8\u6027\u306f\u3059\u3054\u304f\u3044\u3044\u3002<\/li>\n<li><strong>Hash\u30a4\u30f3\u30c7\u30c3\u30af\u30b9<\/strong>\u306f\u5358\u7d14\u306a\u7b49\u4fa1\u6027\u6bd4\u8f03\u306e\u307f\u3092\u6271\u3046\u3053\u3068\u304c\u3067\u304d\u308b\u3002\u3057\u304b\u3057\u306a\u304c\u3089\u3001\u904b\u7528\u3067\u306e\u30c7\u30e1\u30ea\u30c3\u30c8\u304c\u3042\u308b\u3053\u3068\u304b\u3089\u304a\u52e7\u3081\u306f\u3057\u306a\u3044\u3002Hash\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u306e\u64cd\u4f5c\u306fWAL\u306b\u8a18\u9332\u3055\u308c\u306a\u3044\u3001\u30c7\u30fc\u30bf\u30d9\u30fc\u30b9\u304c\u30af\u30e9\u30c3\u30b7\u30e5\u3057\u305f\u5f8c\u306bREINDEX\u3067\u518d\u69cb\u7bc9\u3057\u306a\u3051\u308c\u3070\u306a\u3089\u306a\u3044\u53ef\u80fd\u6027\u304c\u3042\u308b\u3002\u307e\u305f\u3001\u6700\u521d\u306e\u30d0\u30c3\u30af\u30a2\u30c3\u30d7\u3092\u53d6\u5f97\u3057\u3066\u4ee5\u964d\u3001\u30b9\u30c8\u30ea\u30fc\u30df\u30f3\u30b0\u30ec\u30d7\u30ea\u30b1\u30fc\u30b7\u30e7\u30f3\u3084\u30d5\u30a1\u30a4\u30eb\u30d9\u30fc\u30b9\u306e\u30ec\u30d7\u30ea\u30b1\u30fc\u30b7\u30e7\u30f3\u3067\u306f\u5909\u66f4\u304c\u53cd\u6620\u3055\u308c\u306a\u3044\u305f\u3081\u3001\u305d\u306e\u5f8c\u30cf\u30c3\u30b7\u30e5\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u3092\u4f7f\u3046\u30af\u30a8\u30ea\u306f\u8aa4\u3063\u305f\u7d50\u679c\u3092\u8fd4\u3059\u306e\u3060\u3002<\/li>\n<li><strong>Generalized Inverted Indexes\uff08GIN\u3001\u6c4e\u7528\u8ee2\u7f6e\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\uff09<\/strong>\u306f\u4e00\u3064\u884c\u3078\u8907\u6570\u306e\u5024\u3092\u30de\u30c3\u30d4\u30f3\u30b0\u3059\u308b\u6642\u306b\u5229\u7528\u3059\u308b\u3002\u6587\u66f8\u3084\u914d\u5217\u306a\u3069\u8907\u6570\u306e\u30ad\u30fc\u3092\u6301\u3064\u5024\u3092\u6271\u3046\u3053\u3068\u304c\u3067\u304d\u308b\u3002<\/li>\n<li><strong>Generalized Search Tree\uff08GiST\u3001\u6c4e\u7528\u691c\u7d22\u30c4\u30ea\u30fc\uff09<\/strong>\u306f\u5358\u4e00\u7a2e\u985e\u306e\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u3067\u306f\u306a\u304f\u3001\u591a\u304f\u306e\u7570\u306a\u308b\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u6226\u7565\u3092\u5b9f\u88c5\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u308b\u57fa\u76e4\u3067\u3042\u308b\u3002B-tree\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u3068\u540c\u3058\u3088\u3046\u306b\u30d0\u30e9\u30f3\u30b9\u3055\u308c\u305f\u6728\u69cb\u9020\u304c\u4f5c\u3089\u308c\u305f\u4e0a\u3067\u3001\u7b49\u4fa1\u6027\u3068\u7bc4\u56f2\u4ee5\u5916\u306e\u30af\u30a8\u30ea\u306b\u3082\u5bfe\u5fdc\u3067\u304d\u308b\u3002\u5e7e\u4f55\u30c7\u30fc\u30bf\u578b\u3084\u5168\u6587\u691c\u7d22\u306b\u4f7f\u3046\u3002<\/li>\n<\/ul>\n<p>\u3053\u3053\u304b\u3089\u306fB-tree\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u306e\u6539\u5584\u3092\u5c3d\u304f\u3059\u8a71\u3057\u306b\u96c6\u4e2d\u3057\u3088\u3046\u3002<\/p>\n<h2>\u4f55\u6545\u30af\u30a8\u30ea\u306f\u79c1\u304c\u4f5c\u3063\u305f\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u3092\u5229\u7528\u3057\u306a\u3044\u306e\u304b<\/h2>\n<p>PostgreSQL\u306e\u30d7\u30e9\u30f3\u30ca\u304c\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u3092\u5229\u7528\u3057\u306a\u3044\u7406\u7531\u306f\u3044\u308d\u3044\u308d\u8003\u3048\u3089\u308c\u308b\u3002\u7406\u7531\u304c\u5c11\u3057\u4e0d\u660e\u306b\u307f\u3048\u3066\u3082\u30d7\u30e9\u30f3\u30ca\u306f\u57fa\u672c\u6b63\u3057\u304f\u6c7a\u3081\u3066\u3044\u308b\u3002\u540c\u3058\u30af\u30a8\u30ea\u3067\u3082\u6761\u4ef6\u306b\u3088\u3063\u3066\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u3092\u5229\u7528\u3057\u305f\u308a\u3057\u306a\u304b\u3063\u305f\u308a\u3059\u308b\u3002\u4f8b\u3048\u3070\u3001<span class=\"lang:default decode:true  crayon-inline \">select * from foo where bar = 1<\/span>\u306e\u5834\u5408\u306f\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u3092\u5229\u7528\u3057\u3066\u3082\u3001<span class=\"lang:default decode:true  crayon-inline \">select * from foo where bar = 2<\/span>\u306e\u5834\u5408\u306f\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u3092\u5229\u7528\u3057\u306a\u3044\u3068\u3044\u3046\u3053\u3068\u3082\u3042\u308a\u5f97\u308b\u30022\u3067\u3042\u308b<code>bar<\/code>\u304c\u3059\u3054\u304f\u591a\u3044\u5834\u5408\u306f <code>index scan<\/code> \u3088\u308a <code>sequential scan<\/code> \u306e\u65b9\u304c\u901f\u3044\u3002\u3053\u306e\u5834\u5408\u3001\u30d7\u30e9\u30f3\u30ca\u306f\u8ca0\u8377\u306e\u4f4e\u3044\u65b9\u6cd5\u3092\u9078\u3076\u3002<\/p>\n<h2>\u90e8\u5206\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\uff08Partial\uff09<\/h2>\n<p>\u90e8\u5206\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u306f\u30c6\u30fc\u30d6\u30eb\u306e\u4e00\u90e8\u306e\u30ec\u30b3\u30fc\u30c9\u3060\u3051\u306b\u9069\u7528\u3059\u308b\u3002WHERE\u53e5\u3067\u6307\u5b9a\u3057\u305f\u6761\u4ef6\u3092\u6e80\u305f\u3059\u30ec\u30b3\u30fc\u30c9\u306b\u5bfe\u3057\u3066\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u306f\u4f5c\u6210\u3055\u308c\u308b\u3002\u5bfe\u8c61\u306e\u30ec\u30b3\u30fc\u30c9\u3092\u6e1b\u3089\u3059\u3053\u3068\u3067\u3001\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u306e\u30b9\u30c8\u30ec\u30fc\u30b8\u304c\u5c0f\u3055\u304f\u3001\u4fdd\u5b88\u304c\u3057\u3084\u3059\u304f\u3001\u901f\u5ea6\u304c\u901f\u304f\u306a\u308b\u3068\u3053\u308d\u304c\u9577\u6240\u3067\u3042\u308b\u3002<br \/>\n\u4f8b\u3048\u3070\u3001gmail\u4e0a\u3067 <code>starred<\/code> \u3068\u3044\u3046\u30b9\u30bf\u30fc\u4ed8\u304d\u3068\u306a\u308b\u30e1\u30fc\u30eb\u306b\u5bfe\u3057\u3066\u51e6\u7406\u3092\u3059\u308b\u5834\u5408\u306f\u3001\u3053\u3046\u3044\u3046\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u304c\u4f5c\u308c\u308b\u3002<\/p>\n<pre class=\"lang:pgsql decode:true \">CREATE INDEX email_starred_created_at_index ON emails(created_at) WHERE starred IS TRUE;<\/pre>\n<h2>\u5f0f\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\uff08Expression\uff09<\/h2>\n<p>\u5f0f\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u306f\u3068\u3042\u308b\u65b9\u6cd5\u3001\u95a2\u6570\u306a\u3069\u3067\u5909\u63db\u3055\u308c\u305f\u30c7\u30fc\u30bf\u3092\u691c\u7d22\u3059\u308b\u6642\u306b\u4f7f\u3046\u3002PostgreSQL\u3067\u306f\u5909\u63db\u3055\u308c\u305f\u5024\u306b\u5bfe\u3057\u3066\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u3092\u4f5c\u6210\u3067\u304d\u308b\u306e\u3067\u3001\u4ed6\u306e\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u3068\u540c\u3058\u304f\u3089\u3044\u306e\u30d1\u30d5\u30a9\u30fc\u30de\u30f3\u30b9\u3092\u767a\u63ee\u3059\u308b\u3002\u4f8b\u3048\u3070\u3001\u5927\u6587\u5b57\u30fb\u5c0f\u6587\u5b57\u304c\u6df7\u5728\u3059\u308b\u30e1\u30fc\u30eb\u30a2\u30c9\u30ec\u30b9\u306b\u5bfe\u3057\u3066\u3001\u5927\u6587\u5b57\u30fb\u5c0f\u6587\u5b57\u3092\u533a\u5225\u305b\u305a\u691c\u7d22\u3057\u305f\u3044\u5834\u5408\u3001\u8981\u3059\u308b\u306b <span class=\"lang:pgsql decode:true  crayon-inline \">WHERE lower(email) = 'email@domain'<\/span> \u3068\u3044\u3046\u6761\u4ef6\u3092\u5229\u7528\u3057\u305f\u3044\u5834\u5408\u3001\u3053\u3046\u3044\u3046\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u3092\u4f5c\u308c\u3070\u3044\u3044\u3002<\/p>\n<pre class=\"lang:pgsql decode:true \">CREATE INDEX users_lower_email ON users(lower(email));<\/pre>\n<p>\u3082\u3046\u4e00\u3064\u4f8b\u3048\u3070\u3001TIMESTAMP\u578b\u3067\u4fdd\u5b58\u3055\u308c\u3066\u3044\u308b\u65e5\u4ed8\u306b\u5bfe\u3057\u3066DATE\u578b\u3068\u3057\u3066\u691c\u7d22\u3057\u305f\u3044\u5834\u5408\u306f <span class=\"lang:pgsql decode:true  crayon-inline \">CREATE INDEX articles_day ON articles ( date(published_at) )<\/span> \u3000\u3092\u4f5c\u3063\u3066\u3001 <span class=\"lang:pgsql decode:true  crayon-inline \">WHERE date(articles.created_at) = date('2011-11-11')<\/span> \u3067\u691c\u7d22\u3067\u304d\u308b\u3002<\/p>\n<h2>\u30e6\u30cb\u30fc\u30af\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\uff08Unique\uff09<\/h2>\n<p>\u30e6\u30cb\u30fc\u30af\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u306f\u91cd\u8907\u3057\u305f\u5024\u3092\u8a31\u53ef\u3057\u306a\u3044\u3082\u306e\u3067\u3042\u308b\u3002\u30e6\u30cb\u30fc\u30af\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u306e\u9577\u6240\u306f2\u3064\u8003\u3048\u308c\u3066\u3001\u30c7\u30fc\u30bf\u306e\u6574\u5408\u6027\u3068\u30d1\u30d5\u30a9\u30fc\u30de\u30f3\u30b9\u3002\u30e6\u30cb\u30fc\u30af\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u3067\u306e\u691c\u7d22\u306f\u57fa\u672c\u901f\u3044\u3002<br \/>\n\u30a2\u30d7\u30ea\u30b1\u30fc\u30b7\u30e7\u30f3\u5074\u3067\u5024\u304c\u91cd\u8907\u3057\u306a\u3044\u3088\u3046\u306b\u5236\u9650\u3092\u304b\u3051\u3066\u3082\u540c\u6642\u30a2\u30af\u30bb\u30b9\u306e\u5834\u5408\u306b\u91cd\u8907\u3057\u305f\u5024\u304c\u30c7\u30fc\u30bf\u30d9\u30fc\u30b9\u306b\u4fdd\u5b58\u3055\u308c\u3066\u3057\u307e\u3046\u3053\u3068\u304c\u3042\u308b\u3002\u91cd\u8907\u3057\u305f\u5024\u3092\u8a31\u3055\u306a\u3044\u5834\u5408\u306f\u5fc5\u305a\u3001\u30c7\u30fc\u30bf\u30d9\u30fc\u30b9\u30ec\u30d9\u30eb\u3067\u30e6\u30cb\u30fc\u30af\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u304b\u4e00\u610f\u5236\u7d04\u3092\u304b\u3051\u308b\u3079\u304d\u3002<\/p>\n<h2>\u8907\u6570\u5217\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\uff08Multi-column\uff09<\/h2>\n<p>PostgreSQL\u3067\u306f\u8907\u6570\u5217\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u3092\u6271\u3048\u308b\u304c\u3001\u305d\u308c\u304c\u3044\u3064\u5229\u7528\u3055\u308c\u308b\u304b\u7406\u89e3\u3059\u308b\u3053\u3068\u306f\u5927\u4e8b\u3002\u8907\u6570\u5217\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u304c\u306a\u304f\u3066\u3082PostgreSQL\u306e\u30d7\u30e9\u30f3\u30ca\u306f\u5185\u90e8\u7684\u306b\u30d3\u30c3\u30c8\u30de\u30c3\u30d7\u3092\u4f5c\u6210\u3057\u3066\u8907\u6570\u306e\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u3092\u7d44\u307f\u5408\u308f\u305b\u3066\u5229\u7528\u3067\u304d\u308b\u3002\u3069\u306e\u5217\u3067\u3082\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u306e\u767a\u884c\u304c\u53ef\u80fd\u3060\u3057\u3001\u30d7\u30e9\u30f3\u30ca\u306f\u305d\u306e\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u3092\u4f7f\u3063\u3066\u304f\u308c\u308b\u304b\u3089\u3001\u30d9\u30f3\u30c1\u30de\u30fc\u30af\u3092\u884c\u3063\u3066\u8907\u6570\u5217\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u304c\u5fc5\u8981\u3060\u3063\u305f\u3068\u3044\u3046\u8a3c\u660e\u3092\u3057\u3066\u304b\u3089\u5229\u7528\u3057\u3088\u3046\u3002<br \/>\n\u8907\u6570\u5217\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u306f\u30af\u30a8\u30ea\u3092\u6700\u9069\u5316\u3067\u304d\u308b\u6761\u4ef6\u304c\u3042\u308b\u3002\u30af\u30a8\u30ea\u306e\u4e2d\u3001\u53c2\u7167\u3055\u308c\u3066\u3044\u308b\u5217\u306f\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u306e\u4e2d\u306b\u3042\u308b\u5217\u3068\u540c\u3058\u9806\u756a\u3067\u306a\u3051\u308c\u3070\u306a\u3089\u306a\u3044\u4e8b\u3002\u305d\u308c\u3068\u9055\u3063\u3066\u3001\u8907\u6570\u306e\u5358\u4e00\u5217\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u306f\u305d\u306e\u6761\u4ef6\u306b\u5236\u5fa1\u3055\u308c\u3066\u3044\u306a\u3044\u3002<br \/>\n\u4f8b\u3048\u3070\u3001\u30a2\u30d7\u30ea\u30b1\u30fc\u30b7\u30e7\u30f3\u306b <span class=\"lang:pgsql decode:true  crayon-inline \">WHERE a = x AND b = y<\/span> \u53c8\u306f <span class=\"lang:pgsql decode:true  crayon-inline \">WHERE a = x<\/span> \u306e\u6761\u4ef6\u304c\u3088\u304f\u4f7f\u308f\u308c\u308b\u306a\u3089 <code>(a, b)<\/code> \u5217\u306b\u8907\u6570\u5217\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u3092\u767a\u884c\u3059\u308b\u4fa1\u5024\u304c\u3042\u308b\u304b\u3082\u3057\u308c\u306a\u3044\u3002\u4f46\u3057\u3001 <span class=\"lang:pgsql decode:true  crayon-inline \">WHERE b = y<\/span> \u306e\u5834\u5408\u306f\u901a\u7528\u3057\u306a\u3044\u3002\u203b\u8907\u6570\u5217\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u3092\u767a\u884c\u3057\u305f\u4e0a\u3067 a \u5217\u3060\u3051\u306b\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u3092\u8cbc\u308b\u4e8b\u306f\u5197\u9577\u306b\u306a\u308b\u306e\u3067\u4e0d\u8981\u3002<\/p>\n<h2>B-tree\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u306e\u30bd\u30fc\u30c8<\/h2>\n<p>\u30c7\u30d5\u30a9\u30eb\u30c8\u3067\u3001B-tree\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u306f\u6607\u9806\u3067\u30bd\u30fc\u30c8\u3055\u308c\u308b\u3002\u964d\u9806\u3067\u30bd\u30fc\u30c8\u3059\u308b\u3088\u3046\u306b\u5b9a\u7fa9\u3059\u308b\u3053\u3068\u3082\u3067\u304d\u308b\u3002\u30d6\u30ed\u30b0\u3068\u304b\u3060\u3068\u3001\u6295\u7a3f\u306f\u6700\u65b0\u9806\u3067\u8868\u793a\u3059\u308b\u4e8b\u304c\u3088\u304f\u3042\u308b\u3002\u6295\u7a3f\u65e5\u6642\u306f <code>published_at<\/code> \u3068\u3057\u3066\u3001\u516c\u958b\u3055\u308c\u3066\u3044\u306a\u3044\u6295\u7a3f\u306f <code>published_at<\/code> \u304c NULL \u3068\u3059\u308b\u3002<br \/>\n\u3053\u306e\u5834\u5408\u306f\u3001\u3053\u3046\u3044\u3046\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u304c\u4f5c\u308c\u308b\u3002<\/p>\n<pre class=\"lang:pgsql decode:true \">CREATE INDEX articles_published_at_index ON articles(published_at DESC NULLS LAST);<\/pre>\n<p>\u30a2\u30d7\u30ea\u30b1\u30fc\u30b7\u30e7\u30f3\u4e0a\u3067\u6295\u7a3f\u304c\u8868\u793a\u3055\u308c\u308b\u9806\u4f4d\u306b\u5408\u308f\u305b\u305f\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u3092\u4f5c\u308b\u4e8b\u3067\u30d1\u30d5\u30a9\u30fc\u30de\u30f3\u30b9\u304c\u4e0a\u304c\u308b\u3002\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u306b\u30bd\u30fc\u30c8\u6761\u4ef6\u304c\u542b\u307e\u308c\u3066\u3044\u306a\u3051\u308c\u3070\u3001PostgreSQL\u306fsequential scan\u3092\u884c\u3063\u3066\u304b\u3089\u30bd\u30fc\u30c8\u3092\u5b9f\u65bd\u3059\u308b\u306e\u3067\u3057\u3087\u3046\u3002<br \/>\n\u4eca\u56de\u306f\u7a7a\u5024\uff08NULL\uff09\u3092\u6700\u5f8c\u306b\u56de\u3057\u305f\u3044\u304b\u3089\u3053\u306e\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u3092\u5229\u7528\u3059\u308b\u610f\u5473\u304c\u3042\u3063\u305f\u3002\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u306f\u3069\u306e\u9806\u4f4d\u304b\u3089\u3082\u691c\u7d22\u3067\u304d\u308b\u306e\u3067\u6607\u9806\u306e\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u304c\u5b58\u5728\u3059\u308c\u3070\u964d\u9806\u306e\u691c\u7d22\u3067\u3082\u540c\u3058\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u306e\u5229\u7528\u304c\u3067\u304d\u308b\u3002\u8907\u6570\u5217\u306b\u30d0\u30e9\u30d0\u30e9\u306a\u9806\u4f4d\u3067\u3001\u4f8b\u3048\u3070 <span class=\"lang:pgsql decode:true  crayon-inline \">ORDER BY a ASC, b DESC<\/span> \u3001\u8907\u6570\u5217\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u306b\u3082\u5229\u7528\u3055\u308c\u308b\u3002<\/p>\n<h2>\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u306e\u4fdd\u5b88<\/h2>\n<p>PostgreSQL\u3067\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u306f\u5168\u3066\u306e\u60c5\u5831\u3092\u6301\u3061\u306f\u3057\u306a\u3044\u3002\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u304c\u5229\u7528\u3055\u308c\u3066\u4e00\u81f4\u3059\u308b\u884c\u304c\u898b\u3064\u304b\u3063\u3066\u3082PostgreSQL\u306f\u30c7\u30a3\u30b9\u30af\u306b\u60c5\u5831\u3092\u53d6\u5f97\u3059\u308b\u306e\u3060\u3002\u66f4\u306b\u3001\u60c5\u5831\u306e\u53ef\u8996\u6027\u3082\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u306b\u306a\u304f\u3066\u3001PostgreSQL\u306f\u30c7\u30a3\u30b9\u30af\u306b\u60c5\u5831\u3092\u53d6\u5f97\u3059\u308b\u5fc5\u8981\u304c\u3067\u308b\u3002<\/p>\n<blockquote><p>\u203b PostgreSQL 9.2 \u304b\u3089 <a title=\"Index Only Scan\" href=\"http:\/\/www.techscore.com\/blog\/category\/%E8%A8%98%E4%BA%8B\/%E9%80%A3%E8%BC%89\/postgresql-index-only-scan-%E5%A5%AE%E9%97%98%E8%A8%98\/\" target=\"_blank\">Index Only Scan<\/a> \u304c\u5897\u3048\u3066\u30c6\u30fc\u30d6\u30eb\u306b\u30a2\u30af\u30bb\u30b9\u3057\u306a\u304f\u3066\u826f\u3044\u5834\u5408\u3082\u3067\u304d\u305f\u3002<\/p><\/blockquote>\n<p>\u305d\u308c\u3092\u610f\u8b58\u3057\u3066\u3001\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u3092\u5229\u7528\u3059\u308b\u610f\u5473\u304c\u306a\u3044\u5834\u5408\u3082\u601d\u3044\u3064\u304f\u3002\u30c7\u30a3\u30b9\u30af\u3078\u306e\u30a2\u30af\u30bb\u30b9\u3092\u5341\u5206\u6e1b\u3089\u3059\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u3067\u306a\u3051\u308c\u3070\u306a\u3089\u306a\u3044\u3002\u4f8b\u3048\u3070\u3001\u884c\u6570\u306e\u591a\u3044\u30c6\u30fc\u30d6\u30eb\u306b\u5bfe\u3057\u3066\u4e3b\u30ad\u30fc\u3092\u691c\u7d22\u3059\u308b\u5834\u5408\u306f\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u306e\u4fa1\u5024\u304c\u3042\u308b\u3002sequential scan\u3092\u884c\u3046\u3088\u308a\u3082\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u306e\u4e2d\u306b\u8a72\u5f53\u306e\u884c\u3092\u53d6\u308a\u51fa\u3057\u3066\u304b\u3089\u30c7\u30a3\u30b9\u30af\u306b\u30a2\u30af\u30bb\u30b9\u3057\u3066\u60c5\u5831\u3092\u53d6\u5f97\u3059\u308b\u3002\u9006\u306b\u884c\u6570\u306e\u5c11\u306a\u3044\u30c6\u30fc\u30d6\u30eb\u3067\u4f4f\u6240\u306e\u9805\u76ee\u3092\u691c\u7d22\u3059\u308b\u5834\u5408\u3001\u30d7\u30e9\u30f3\u30ca\u306f\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u3092\u53c2\u7167\u305b\u305a\u306bsequential scan \u3092\u884c\u3046\u3002\u305d\u306e\u5217\u306b\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u304c\u5b58\u5728\u3057\u3066\u3082\u5229\u7528\u3055\u308c\u306a\u3044\u306e\u3067\u306f\u3001\u30b9\u30c8\u30ec\u30fc\u30b8\u3084\u7ba1\u7406\u30b3\u30b9\u30c8\u3057\u304b\u6b8b\u3089\u306a\u3044\u306e\u3067\u640d\u306b\u306a\u308b\u3002<\/p>\n<p>\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u3092\u4f5c\u6210\u3059\u3079\u304d\u304b\u5224\u65ad\u3059\u308b\u5834\u5408\u306f\u3001\u958b\u767a\u74b0\u5883\u306a\u3069\u30c7\u30fc\u30bf\u6570\u304c\u5c11\u306a\u3044\u74b0\u5883\u3067\u884c\u308f\u306a\u3044\u307b\u3046\u304c\u826f\u3044\u3002\u30c7\u30fc\u30bf\u304c\u5c11\u306a\u3044\u74b0\u5883\u3060\u3068\u3001\u30d7\u30e9\u30f3\u30ca\u306f\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u3092\u5229\u7528\u3057\u306a\u3044\u65b9\u304c\u52b9\u7387\u304c\u826f\u3044\u3068\u5224\u65ad\u3059\u308b\u305f\u3081\u3001\u672c\u756a\u74b0\u5883\u306b\u8fd1\u3044\u74b0\u5883\u3067\u78ba\u304b\u3081\u308b\u3079\u304d\u3002<\/p>\n<p>\u672c\u756a\u74b0\u5883\u306b\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u3092\u767a\u884c\u3059\u308b\u969b\u3001\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u304c\u8a72\u5f53\u30c6\u30fc\u30d6\u30eb\u306b\u30ed\u30c3\u30af\u3092\u304b\u3051\u308b\u4e8b\u3092\u5fd8\u308c\u3066\u306f\u3044\u3051\u306a\u3044\u3002\u3088\u308a\u9045\u3044\u65b9\u6cd5\u3060\u304cWrite\u30d6\u30ed\u30c3\u30af\u3092\u304b\u3051\u306a\u3044 <span class=\"lang:pgsql decode:true  crayon-inline \">CREATE INDEX CONCURRENTLY<\/span> \u3092\u5229\u7528\u3059\u308b\u3053\u3068\u3082\u3067\u304d\u308b\u3002\u203b <span class=\"lang:pgsql decode:true  crayon-inline \">CREATE INDEX<\/span> \u3060\u3051\u306a\u3089Read\u30d6\u30ed\u30c3\u30af\u306f\u304b\u304b\u3089\u306a\u3044\u304cWrite\u30d6\u30ed\u30c3\u30af\u304c\u304b\u304b\u308b\u3002<\/p>\n<p>\u6700\u5f8c\u306b\u3001\u66f4\u65b0\u30fb\u524a\u9664\u304c\u7e70\u308a\u8fd4\u3055\u308c\u308b\u3068\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u306f\u5f90\u3005\u306b\u52a3\u5316\u3059\u308b\u3002 <span class=\"lang:pgsql decode:true  crayon-inline \">REINDEX<\/span> \u3067\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u3092\u518d\u69cb\u7bc9\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u308b\u3002<span class=\"lang:pgsql decode:true  crayon-inline \">REINDEX<\/span> \u306f\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u306b\u5bfe\u3059\u308b\u30ed\u30c3\u30af\u304c\u304b\u304b\u308b\u306e\u3067\u5229\u7528\u6642\u306f\u6ce8\u610f\u3057\u3088\u3046\u3002<span class=\"lang:pgsql decode:true  crayon-inline \">CREATE INDEX<\/span> \u3068\u5c11\u3057\u9055\u3063\u3066\u3001Read\u30d6\u30ed\u30c3\u30af\u306f\u304b\u304b\u308b\u4e8b\u3082\u3042\u308b\u3001\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u3092\u4f7f\u7528\u3057\u306a\u3044 <span class=\"lang:pgsql decode:true  crayon-inline \">SELECT<\/span> \u306f\u30d6\u30ed\u30c3\u30af\u3057\u306a\u3044\u304c\u3001\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u3092\u4f7f\u7528\u3059\u308b <span class=\"lang:pgsql decode:true  crayon-inline \">SELECT<\/span> \u306f\u30d6\u30ed\u30c3\u30af\u3059\u308b\u306e\u3060\u3002\u5bfe\u7b56\u3068\u3057\u3066\u306f\u5225\u540d\u3067 <span class=\"lang:pgsql decode:true  crayon-inline \">CONCURRENTLY<\/span> \u306b\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u3092\u767a\u884c\u3057\u3066\u3001\u53e4\u3044\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u3092 <span class=\"lang:pgsql decode:true  crayon-inline \">DROP<\/span> \u3057\u3066\u3001\u65b0\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u3092\u524d\u306e\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u540d\u306b\u5909\u3048\u305f\u3089\u3044\u3044\u3002\u624b\u9593\u306b\u898b\u3048\u308b\u3057\u3001\u4e00\u6642\u7684\u306b\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u304c2\u3064\u5b58\u5728\u3059\u308b\u306e\u3067\u3001\u305d\u306e\u9593\u306f\u30d1\u30d5\u30a9\u30fc\u30de\u30f3\u30b9\u304c\u52a3\u5316\u3059\u308b\u3051\u308c\u3069\u3001\u30ed\u30c3\u30af\u306f\u304b\u304b\u3089\u306a\u3044\u3002<\/p>\n<p>\u4ee5\u4e0a\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u3069\u3046\u3082\u3001Beno\u00eet\u3067\u3059\u3002<\/p>\n<p>TECHSCORE Advent Calendar 2014 \u306e 4 \u65e5\u76ee\u306e\u6295\u7a3f\u3067\u3059\u3002<\/p>\n<p>PostgreSQL\u3067\u306f\u3044\u308d\u3044\u308d\u306a\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u7a2e\u985e\u304c\u5b58\u5728\u3059\u308b\u3002\u4f7f\u3044\u65b9\u3082\u69d8\u3005\u3067\u3042\u308b\u3002<br \/><a href=\"https:\/\/www.techscore.com\/blog\/2014\/12\/04\/postgresql%e3%81%a7%e3%82%a4%e3%83%b3%e3%83%87%e3%83%83%e3%82%af%e3%82%b9%e3%82%92%e5%8a%b9%e7%8e%87%e9%ab%98%e3%81%8f%e5%88%a9%e7%94%a8%e3%81%97%e3%82%88%e3%81%86\/\">\u7d9a\u304d\u3092\u8aad\u3080...<\/a><\/p>\n","protected":false},"author":18,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[18],"tags":[141,206],"_links":{"self":[{"href":"https:\/\/www.techscore.com\/blog\/wp-json\/wp\/v2\/posts\/4574"}],"collection":[{"href":"https:\/\/www.techscore.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.techscore.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.techscore.com\/blog\/wp-json\/wp\/v2\/users\/18"}],"replies":[{"embeddable":true,"href":"https:\/\/www.techscore.com\/blog\/wp-json\/wp\/v2\/comments?post=4574"}],"version-history":[{"count":17,"href":"https:\/\/www.techscore.com\/blog\/wp-json\/wp\/v2\/posts\/4574\/revisions"}],"predecessor-version":[{"id":4832,"href":"https:\/\/www.techscore.com\/blog\/wp-json\/wp\/v2\/posts\/4574\/revisions\/4832"}],"wp:attachment":[{"href":"https:\/\/www.techscore.com\/blog\/wp-json\/wp\/v2\/media?parent=4574"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.techscore.com\/blog\/wp-json\/wp\/v2\/categories?post=4574"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.techscore.com\/blog\/wp-json\/wp\/v2\/tags?post=4574"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}