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PORails Optimizing Complicated Query
 

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  1. PORails Optimizing Complicated Query
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    <p>Here's the background, I have an API method thats sending a normalized list of names to my server which then matches up the names to given Persons objects. Each person has many Post objects related to them that I want to return. My database query looks like this:</p> <pre><code> @articles = Article.joins(:artists).select("artists.*").where({:artists=&gt;{:name=&gt;keys}}).group("#{Article.col_list}").order("articles.publish_date DESC").limit(25) </code></pre> <p>This query can take as long as 2 seconds on my production server when the list of names is large (over 100). How can I optimize this query so its fast?</p> <p>Here is the EXPLAIN for the query.</p> <pre><code> Limit (cost=9144.19..9144.20 rows=25 width=802) (actual time=4341.409..4341.431 rows=25 loops=1) -&gt; 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 -&gt; HashAggregate (cost=9030.99..9070.28 rows=13096 width=802) (actual time=4255.854..4315.125 rows=3916 loops=1) -&gt; Nested Loop (cost=1581.27..8978.60 rows=13096 width=802) (actual time=7.443..3337.624 rows=39920 loops=1) -&gt; 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) -&gt; Seq Scan on articles_artists (cost=0.00..5476.38 rows=737461 width=8) (actual time=0.019..1310.806 rows=737515 loops=1) -&gt; 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 -&gt; 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[])) -&gt; 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[])) -&gt; 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) </code></pre>
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    1. COThis is really a DB optimization question. Take a look at your log file to find the actual SQL query, and run it through `EXPLAIN`. If that doesn't point you in the right direction, add that info to the question. There might be an index missing for the join.
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    2. COPlease post the actual SQL emitted by AR for this query. Do you have an index on articles_artists(artist_id)?
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