複雑なクエリを最適化するレール

Question

ここでは、私はAPIメソッドを使用して正規化された名前のリストをサーバに送信し、それを指定されたPersonsオブジェクトの名前と照合します。それぞれの人には、私が戻したいものに関連する多くのPostオブジェクトがあります。私のデータベースクエリは次のようになります。

@articles = Article.joins(:artists).select("artists.*").where({:artists=>{:name=>keys}}).group("#{Article.col_list}").order("articles.publish_date DESC").limit(25) 

名のリストは、（100以上）が大きい場合、このクエリは、私の本番サーバー上の限り2秒を取ることができます。このクエリを高速に最適化するにはどうすればよいですか？

ここでは、クエリのEXPLAINを示します。

Limit (cost=9144.19..9144.20 rows=25 width=802) (actual time=4341.409..4341.431 rows=25 loops=1) 
    -> Sort (cost=9144.19..9150.74 rows=13096 width=802) (actual time=4341.408..4341.416 rows=25 loops=1) 
     Sort Key: articles.publish_date 
     Sort Method: top-N heapsort Memory: 47kB 
     -> HashAggregate (cost=9030.99..9070.28 rows=13096 width=802) (actual time=4255.854..4315.125 rows=3916 loops=1) 
       -> Nested Loop (cost=1581.27..8978.60 rows=13096 width=802) (actual time=7.443..3337.624 rows=39920 loops=1) 
        -> Hash Join (cost=1581.27..7650.04 rows=13096 width=4) (actual time=7.426..2627.426 rows=39920 loops=1) 
          Hash Cond: (articles_artists.artist_id = artists.id) 
          -> Seq Scan on articles_artists (cost=0.00..5476.38 rows=737461 width=8) (actual time=0.019..1310.806 rows=737515 loops=1) 
          -> Hash (cost=1579.83..1579.83 rows=413 width=4) (actual time=7.383..7.383 rows=300 loops=1) 
           Buckets: 1024 Batches: 1 Memory Usage: 8kB 
           -> Bitmap Heap Scan on artists (cost=477.60..1579.83 rows=413 width=4) (actual time=4.959..7.152 rows=300 loops=1) 
             Recheck Cond: ((name)::text = ANY ('{"A BOY NAMED EARTH","A ROCKET TO MOON","A SKYLIT DRIVE","A VISIBLE BOY","AARON GILLESPIE",AB,"ABBIE BARRETT",ABERFELDY,"ABRA NIIRE","ABSOLUTE ZERO",ACDC,"ADAM GREEN",ADELE,ADO,"ADRINA THORPE",ADVENTURE,AEROSMITH,"AESOP ROCK",AFI,AIR,"AIR TRAFFIC",AKON,"AL GREEN","ALANIS MORISSETTE",ALCENDOR,"ALEX CHILTON","ALEXI MURDOCH","ALIAS EHREN","ALICE RUSSELL","ALICIA KEYS","AMANDA PALMER","AMERICAN FOOTBALL","AMY MACDONALD","AMY WINEHOUSE","ANALOG REBELLION",ANBERLIN,"ANDREW BIRD","ANDREW HILL","ANGELS AIRWAVES",AQUEDUCT,"ARCADE FIRE","ARETHA FRANKLIN","ART BRUT","ART GARFUNKEL","ARTIC MONKEYS","ARTIC MONKEYS","AS TALL AS LIONS",ASHANTI,"ATLAS SOUND","ATTACK ATTACK!",AUTOLUX,"AVENUE D","AVRIL LAVIGNE","B JU",BACK2SQUARE1,"BAD ENGLISH",BALMORHEA,"BAND OF HORSES",BARCELONA,"BAXTER DURY","BEASTIE BOYS",BEATLES,BECK,"BELLE AND SEBASTIAN","BEN FOLDS FIVE","BEN MARTIN","BETTE MIDLER","BETTIE SERVEERT",BEYONCE,"BIFFY CLYRO","BILLY BRAGG","BILLY BRAGG AND BLOKES","BILLY JOEL","BILLY OCEAN",BIRDY,"BLACK EYED PEAS","BLACK KIDS",BLACKSTONE,"BLIND PILOT","BLINK 182","BLOC PARTY","BLOODHOUND GANG",BLUEBOY,BLUR,"BOB DYLAN","BOB MARLEY","BOB MARLEY WAILERS","BOMBAY BICYCLE CLUB","BON IVER","BONNIE TYLER",BONOBO,"BOX CAR RACER","BOYS LIKE GIRLS","BOYZ II MEN",BREAKBOT,"BRENDAN BENSON","BRETT ANDERSON",BRICOLAGE,"BRITNEY SPEARS",BRONCO,"BRUCE SPRINGSTEEN","BRUNO MARS",BUSH,"BUSTA RHYMES",BUSTED,CAESARS,"CAGE ELEPHANT",CAKE,CALLA,"CALVIN HARRIS",CAMRON,CAMRON,CAMP,CAMPING,"CANDIE PAYNE",CASHEW,"CASSANDRA WILSOM",CASSIDY,"CATE LE BON","CHARLIE FEATHERS","CHERRY GHOST",CHIC,CHICAGO,CHINGY,"CHRIS BROWN","CHRISTINA AGUILERA","CHRISTINA STURMER",CHUMBAWAMBA,CIRCLE,"CLARENCE CARTER",CLIPSE,"COBRA STARSHIP",COLDPLAY,COMMON,CONSPIRATORS,COOLIO,COPELAND,"COPY HAHO",CORNELIUS,CREED,CULTS,"CYNDI LAUPER","CYPRESS HILL","CAT EMPIRE",CURE,"DA LATA","DAFT PUNK",DALMINJO,DAMERO,"DARREN HANLON","DASHBOARD CONFESSIONAL",DATAROCK,"DAVID BOWIE","DAVID E SUGAR","DAVID GUETTA","DAVID KITT","DEATH CAB FOR CUTIE","DIANA KRALL",DIGITALISM,"DINOSAUR JR","DISCO INFERNO",DISCOVERY,"DIZZEE RASCAL",DMX,"DON BLACKMAN","DR DOG",DRAKE,DRUGSTORE,DIPLOMATS,DREAM,EAGLES,EDITORS,ELBOW,ELECTRELANE,"ELIZA DOOLITTLE","ELLE MILANO","ELLIE GOULDING","ELTON JOHN","ELVIS COSTELLO WITH BURT BACHARACH","ELVIS PRESLEY",EMBRACE,EMINEM,"EMMY GREAT","EMPIRE! EMPIRE!","ERIC CHURCH","ERIC CLAPTON","ERIN MCCARLEY",ERRORS,"EUGENE KELLY","EXPLOSIONS IN SKY",FABOLOUS,FAILURE,"FAITH EVANS","FAR EAST MOVEMENT",FAUNTS,FEIST,FELT,FIELDS,"FLEET FOXES","FLIGHT OF CONCHORDS","FLORENCE MACHINE",FOALS,"FOO FIGHTERS","FOSTER PEOPLE","FOUR TET","FRANK TURNER","FRANZ FEDINAND",FREE,"FLAMING LIPS",GORILLAZ,"GRATEFUL DEAD",IDLEWILD,"IMANI COPPOLA","IMOGEN HEAP",INCUBUS,INCUBUS,"IRON WINE","J DILLA","J COLE",JACK,"JACK JOHNSON",JACOBITES,"JAMES BLAKE","JAMES BLUNT","JAMES BONG","JAMES BROWN","JAMIE T","JAN DELAY","JANE CULLUM","JASON DERULO","JASON MORAN","JAY Z","JAY Z","JEFF WAYNE","JENNIFER LOPEZ","JENNY LEWIS",JEREMIH,"JIM JONES","JIMMY EAT WORLD","JOHN COLTRANE","JOHN LEGEND","JOHN MAYER","JOY DIVISION","JUELZ SANTANA","JUNIOR BOYS","JUSTIN TIMBERLAKE","KAISER CHEIFS",KANTE,"KANYE WEST",KARMA,"KATE NASH","KATE NASH","KATY PERRY",KESHA,KEANE,KEANE,"KELLY ROWLAND","KENNY G","KERI HILSON","KEVIN AYERS","KID CUDI","KID HARPOON","KID LOCO","KID ROCK","KINGS OF LEON",KILLERS,KOOKS,"LADY GAGA","LADY SOVEREIGN","LED ZEPPELIN","LEE DORSEY",LEMAR,LEMONGRASS,"LEROY HUTSON","LIL WAYNE","LILY ALLEN","LITTLE COMETS","LITTLE JOY","LL COOL J",LLOYD,"LLOYD BANKS","LONDON LOUNGE",LOST,LOVE,LUDACRIS,LUDIQUE,"LUPE FIASCO","LUTHER VANDROS","MACHINE HEAD","MACY GRAY",MADONNA,MAINO,"MANU CHAO","MAREN MONTAUK","MARIAH CAREY","MARK FRY","MARK MORRISON","MARK RONSON","MAROON 5","MARY J BLIGE","MASSIVE ATTACK","MAT KEARNEY","MATTHEW DEAR","MEAT LOAF",METALLICA,MGMT,"MICHAEL GIACCHINO","MICHAEL JACKSON","MILES DAVIS","MISSY ELLIOTT","MOBB DEEP","MODEST MOUSE","MODEST MOUSE",MONK,MOON,MORRISSEY,MOTZ,"MOVING HEARTS",MUSE,MUTEMATH,"MY WRITES","MORNING OF",NAS,"NE YO","NICKI MINAJ","NINE INCH NAILS","P DIDDY","PATRICK WATSON","PAUL MCCARTNEY","PEARL JAM","PEPE ALGILAR","PEPE WHITE","PETER GABRIEL",PHARRELL,"PHIL COLLINS",PHISH,PITBULL,PIXIES,POLICE,PRINCE,"R KELLY",RADIOHEAD,RAKIM,RANK,"RASCAL FLATTS","RAY CHARLES","RED HOT CHILI PEPPERS",REDNEX,REENO,"RELIENT K","RICK ROSS","RICKY NELSON",RIFT,RIHANNA,"ROBBIE WILLIAMS","ROD STEWART","RODNEY HUNTER",ROKOKO,"ROLLING STONES","ROSCOE DASH","ROY DAVIS JR","RYAN LESLIE","RYAN LESLIE",RZA,"SARAH MCLACHLAN","SARAH RUSSELL",SEAL,"SHANIA TWAIN",SHERWOOD,"SMASH MOUTH",SMITHS,"SNOOP DOGG","SOMETHING CORPORATE",SPOON,SPOON,"ST LUNATICS",STARS,"STAT QUO","STEELY DAN","STEVIE WONDER","STYLES P","SUNSET RUBDOWN",SUPERCHUNK,"SWIZZ BEATZ","SECRET HANDSHAKE",SMITHS,"T PAIN",TI,"TALIB KWELI","TAYLOR SWIFT","THROWING MUSES",TLC,"TOM JONES","TOM PETTY","TONY YAYO",TOOL,"TORI AMOS",TORTOISE,TRAIN,"TREY SONGZ","TRIBE CALLED QUEST",TUBBS,TYCHO,"WHITE STRIPES","WAKA FLOCKA FLAME",WALE,WILCO,"WILL SMITH",U2,USHER,"YEAH YEAH YEAHS","YEAR OF RABBIT","YOUNG BUCK","YOUNG JEEZY","ZAC BROWN BAND",2PAC,"50 CENT"}'::text[])) 
             -> Bitmap Index Scan on index_artists_on_name (cost=0.00..477.58 rows=413 width=0) (actual time=4.897..4.897 rows=311 loops=1) 
              Index Cond: ((name)::text = ANY ('{"A BOY NAMED EARTH","A ROCKET TO MOON","A SKYLIT DRIVE","A VISIBLE BOY","AARON GILLESPIE",AB,"ABBIE BARRETT",ABERFELDY,"ABRA NIIRE","ABSOLUTE ZERO",ACDC,"ADAM GREEN",ADELE,ADO,"ADRINA THORPE",ADVENTURE,AEROSMITH,"AESOP ROCK",AFI,AIR,"AIR TRAFFIC",AKON,"AL GREEN","ALANIS MORISSETTE",ALCENDOR,"ALEX CHILTON","ALEXI MURDOCH","ALIAS EHREN","ALICE RUSSELL","ALICIA KEYS","AMANDA PALMER","AMERICAN FOOTBALL","AMY MACDONALD","AMY WINEHOUSE","ANALOG REBELLION",ANBERLIN,"ANDREW BIRD","ANDREW HILL","ANGELS AIRWAVES",AQUEDUCT,"ARCADE FIRE","ARETHA FRANKLIN","ART BRUT","ART GARFUNKEL","ARTIC MONKEYS","ARTIC MONKEYS","AS TALL AS LIONS",ASHANTI,"ATLAS SOUND","ATTACK ATTACK!",AUTOLUX,"AVENUE D","AVRIL LAVIGNE","B JU",BACK2SQUARE1,"BAD ENGLISH",BALMORHEA,"BAND OF HORSES",BARCELONA,"BAXTER DURY","BEASTIE BOYS",BEATLES,BECK,"BELLE AND SEBASTIAN","BEN FOLDS FIVE","BEN MARTIN","BETTE MIDLER","BETTIE SERVEERT",BEYONCE,"BIFFY CLYRO","BILLY BRAGG","BILLY BRAGG AND BLOKES","BILLY JOEL","BILLY OCEAN",BIRDY,"BLACK EYED PEAS","BLACK KIDS",BLACKSTONE,"BLIND PILOT","BLINK 182","BLOC PARTY","BLOODHOUND GANG",BLUEBOY,BLUR,"BOB DYLAN","BOB MARLEY","BOB MARLEY WAILERS","BOMBAY BICYCLE CLUB","BON IVER","BONNIE TYLER",BONOBO,"BOX CAR RACER","BOYS LIKE GIRLS","BOYZ II MEN",BREAKBOT,"BRENDAN BENSON","BRETT ANDERSON",BRICOLAGE,"BRITNEY SPEARS",BRONCO,"BRUCE SPRINGSTEEN","BRUNO MARS",BUSH,"BUSTA RHYMES",BUSTED,CAESARS,"CAGE ELEPHANT",CAKE,CALLA,"CALVIN HARRIS",CAMRON,CAMRON,CAMP,CAMPING,"CANDIE PAYNE",CASHEW,"CASSANDRA WILSOM",CASSIDY,"CATE LE BON","CHARLIE FEATHERS","CHERRY GHOST",CHIC,CHICAGO,CHINGY,"CHRIS BROWN","CHRISTINA AGUILERA","CHRISTINA STURMER",CHUMBAWAMBA,CIRCLE,"CLARENCE CARTER",CLIPSE,"COBRA STARSHIP",COLDPLAY,COMMON,CONSPIRATORS,COOLIO,COPELAND,"COPY HAHO",CORNELIUS,CREED,CULTS,"CYNDI LAUPER","CYPRESS HILL","CAT EMPIRE",CURE,"DA LATA","DAFT PUNK",DALMINJO,DAMERO,"DARREN HANLON","DASHBOARD CONFESSIONAL",DATAROCK,"DAVID BOWIE","DAVID E SUGAR","DAVID GUETTA","DAVID KITT","DEATH CAB FOR CUTIE","DIANA KRALL",DIGITALISM,"DINOSAUR JR","DISCO INFERNO",DISCOVERY,"DIZZEE RASCAL",DMX,"DON BLACKMAN","DR DOG",DRAKE,DRUGSTORE,DIPLOMATS,DREAM,EAGLES,EDITORS,ELBOW,ELECTRELANE,"ELIZA DOOLITTLE","ELLE MILANO","ELLIE GOULDING","ELTON JOHN","ELVIS COSTELLO WITH BURT BACHARACH","ELVIS PRESLEY",EMBRACE,EMINEM,"EMMY GREAT","EMPIRE! EMPIRE!","ERIC CHURCH","ERIC CLAPTON","ERIN MCCARLEY",ERRORS,"EUGENE KELLY","EXPLOSIONS IN SKY",FABOLOUS,FAILURE,"FAITH EVANS","FAR EAST MOVEMENT",FAUNTS,FEIST,FELT,FIELDS,"FLEET FOXES","FLIGHT OF CONCHORDS","FLORENCE MACHINE",FOALS,"FOO FIGHTERS","FOSTER PEOPLE","FOUR TET","FRANK TURNER","FRANZ FEDINAND",FREE,"FLAMING LIPS",GORILLAZ,"GRATEFUL DEAD",IDLEWILD,"IMANI COPPOLA","IMOGEN HEAP",INCUBUS,INCUBUS,"IRON WINE","J DILLA","J COLE",JACK,"JACK JOHNSON",JACOBITES,"JAMES BLAKE","JAMES BLUNT","JAMES BONG","JAMES BROWN","JAMIE T","JAN DELAY","JANE CULLUM","JASON DERULO","JASON MORAN","JAY Z","JAY Z","JEFF WAYNE","JENNIFER LOPEZ","JENNY LEWIS",JEREMIH,"JIM JONES","JIMMY EAT WORLD","JOHN COLTRANE","JOHN LEGEND","JOHN MAYER","JOY DIVISION","JUELZ SANTANA","JUNIOR BOYS","JUSTIN TIMBERLAKE","KAISER CHEIFS",KANTE,"KANYE WEST",KARMA,"KATE NASH","KATE NASH","KATY PERRY",KESHA,KEANE,KEANE,"KELLY ROWLAND","KENNY G","KERI HILSON","KEVIN AYERS","KID CUDI","KID HARPOON","KID LOCO","KID ROCK","KINGS OF LEON",KILLERS,KOOKS,"LADY GAGA","LADY SOVEREIGN","LED ZEPPELIN","LEE DORSEY",LEMAR,LEMONGRASS,"LEROY HUTSON","LIL WAYNE","LILY ALLEN","LITTLE COMETS","LITTLE JOY","LL COOL J",LLOYD,"LLOYD BANKS","LONDON LOUNGE",LOST,LOVE,LUDACRIS,LUDIQUE,"LUPE FIASCO","LUTHER VANDROS","MACHINE HEAD","MACY GRAY",MADONNA,MAINO,"MANU CHAO","MAREN MONTAUK","MARIAH CAREY","MARK FRY","MARK MORRISON","MARK RONSON","MAROON 5","MARY J BLIGE","MASSIVE ATTACK","MAT KEARNEY","MATTHEW DEAR","MEAT LOAF",METALLICA,MGMT,"MICHAEL GIACCHINO","MICHAEL JACKSON","MILES DAVIS","MISSY ELLIOTT","MOBB DEEP","MODEST MOUSE","MODEST MOUSE",MONK,MOON,MORRISSEY,MOTZ,"MOVING HEARTS",MUSE,MUTEMATH,"MY WRITES","MORNING OF",NAS,"NE YO","NICKI MINAJ","NINE INCH NAILS","P DIDDY","PATRICK WATSON","PAUL MCCARTNEY","PEARL JAM","PEPE ALGILAR","PEPE WHITE","PETER GABRIEL",PHARRELL,"PHIL COLLINS",PHISH,PITBULL,PIXIES,POLICE,PRINCE,"R KELLY",RADIOHEAD,RAKIM,RANK,"RASCAL FLATTS","RAY CHARLES","RED HOT CHILI PEPPERS",REDNEX,REENO,"RELIENT K","RICK ROSS","RICKY NELSON",RIFT,RIHANNA,"ROBBIE WILLIAMS","ROD STEWART","RODNEY HUNTER",ROKOKO,"ROLLING STONES","ROSCOE DASH","ROY DAVIS JR","RYAN LESLIE","RYAN LESLIE",RZA,"SARAH MCLACHLAN","SARAH RUSSELL",SEAL,"SHANIA TWAIN",SHERWOOD,"SMASH MOUTH",SMITHS,"SNOOP DOGG","SOMETHING CORPORATE",SPOON,SPOON,"ST LUNATICS",STARS,"STAT QUO","STEELY DAN","STEVIE WONDER","STYLES P","SUNSET RUBDOWN",SUPERCHUNK,"SWIZZ BEATZ","SECRET HANDSHAKE",SMITHS,"T PAIN",TI,"TALIB KWELI","TAYLOR SWIFT","THROWING MUSES",TLC,"TOM JONES","TOM PETTY","TONY YAYO",TOOL,"TORI AMOS",TORTOISE,TRAIN,"TREY SONGZ","TRIBE CALLED QUEST",TUBBS,TYCHO,"WHITE STRIPES","WAKA FLOCKA FLAME",WALE,WILCO,"WILL SMITH",U2,USHER,"YEAH YEAH YEAHS","YEAR OF RABBIT","YOUNG BUCK","YOUNG JEEZY","ZAC BROWN BAND",2PAC,"50 CENT"}'::text[])) 
        -> Index Scan using articles_pkey on articles (cost=0.00..0.10 rows=1 width=802) (actual time=0.006..0.006 rows=1 loops=39920) 
          Index Cond: (articles.id = articles_artists.article_id) 
Total runtime: 4343.603 ms 
(18 rows) 

Answer 1

最新の25件の記事を無関係に取得しようとしているようです。だから私はそれらの最新の25の記事を選択し、アーティストテーブルとの結果を結合するサブクエリを使用します。

なぜこれは良いでしょうか？あなたの質問は結果を注文し、最新のものを取る前にすべてのアーティストとすべての記事を結合する一時的な結果を構築するので。

いいえ...間違っています。私は私の解決策が動かないことを意味する名前によってアーティストのどこの条件を見ます。

私は、私が助けることができるかどうか確認するために戻ってきました。アーティスト名「フィルタ」は、あなたが投稿した説明データのコストを見ると、最もコストがかかるものです。同様に、アーティスト名がすべて表示されていることにも注意してください.2回は、ネストされたループの内部で、この操作のために2回以上支払っていることを意味します。

できる場合は、フィルタを通過するアーティストテーブルである一時テーブルを作成します。その後、そのテーブルを使用して、前に説明した方法で記事ルックアップを実行すると、クエリがはるかに高速になります。

Answer 2

この1つが目立つ：

- > articles_artistsに配列スキャン（コスト= 0.00..5476.38行= 737461幅= 8）（実際の時間= 0.019..1310.806行= 737515のループ= 1）

を

クエリでEXPLAINを実行し、どこでも「Seq Scan」という用語を参照すると、すべての正しいインデックスがあることを確認する必要があるという印が表示されます。 articles_artistsを確認し、article_idとartist_idの両方にインデックスがあることを確認してください。

また、データベース上でVACUUM ANALYZEを実行して、処理が高速化するかどうかを確認してください。 PostgresqlのクエリオプティマイザはVACUUM ANALYZEによって生成された統計に依存するため、テーブルが実行されずに大幅に変更された場合、クエリのパフォーマンスが低下する可能性があります。

最後に、そのクエリを破棄し、データを収集するためにルビーを取得することを検討してください。場合によっては、複雑なクエリを適切に実行し、クライアントで手動で最適化するほどスマートになるようにデータベースを構築しようとしない方がよい場合もあります。

Answer 3

2つの問題があります。最初はミケーレが述べたseqスキャンです。 2番目はネストされたループ結合です。おそらく、その時点で多すぎるレコードが発生しているためです。

私はいくつかの項目をできるように選択されるように検索条件の面でクエリのさらに下にプッシュすることができるものを見てみます。

私の推測では、インデックスは、これらのインデックスを打つことができます場合は特に大きな違いはなく、追加の検索条件をすることはありませんということです。