sql - mysql count performance -

- 

 select count(*) mytable; select count(table_id) mytable; //table_id primary_key

both query running slow on table 10 million rows. wondering why since wouldn't easy mysql keep counter gets updated on insert,update , delete?
, there way improve query? used explain didn't much.

as cherouvim pointed out in comments, depends on storage engine.

myisam keep count of table rows, , can keep accurate since locks myisam supports table lock.

innodb supports transactions, , needs table scan count rows.

http://www.mysqlperformanceblog.com/2006/12/01/count-for-innodb-tables/


Comments

Post a Comment

Popular posts from this blog

html - How can i make an element from a bottom stacking context stays in front of another higher stacking context? -

-
Image
this question has answer here: override css z-index stacking context 1 answer how can make element contained in stacking context @ bottom of stacking order appears in front of element in different stacking context higher in stacking order ? e.g: html: <div class="parent-1"></div> <div class="parent-2"> <div class="pepe"></div> <div class="pepin"></div> </div> css: .parent-1{ position: absolute; z-index: 10; background-color: green; } .parent-2 { position: absolute; z-index: 5; background-color: red; } .pepe, .pepin{ background-color: blue; } .pepin{ position: fixed; z-index: 100; } this have (this it's suppose happen): this want: bare in mind can't change elemnts order in html neither remove z-index ...
Read more

python - TypeError: start must be a integer -

-
i trying draw 5 turtles, getting typeerror on line 25. here code: import turtle wn = turtle.screen() redrose = turtle.turtle() color = input("what background color be?") fillcolor_f = input("what color of rose be?") redrose.hideturtle() redrose.speed(30) redrose.penup() redrose.left(180) redrose.forward(175) redrose.right(90) redrose.forward(30) redrose.right(90) redrose.pendown() def drawrose(red): redrose.color("pink") redrose.fillcolor(fillcolor_f) redrose.fill(true) in range(red): redrose.forward(i) redrose.right(49) in range(5): drawrose(redrose) redrose.penup() redrose.forward(350) redrose.right(144) redrose.pendown() redrose.fill(false) drawrose(50) wn.bgcolor(color) i trying draw 5 roses, produces errors. doing in interactivepython.org. you recursively calling drawrose wrong parameter. on line 23 ( for in range(red): ) expect red integer...
Read more

html - href attribute breaking an element -

-
here html <a class="button special" href="http://secure.hostgator.com/~affiliat/cgi-bin/affiliates/clickthru.cgi?id=vpspricing&page=http://www.hostgator.com/vps-hosting">select</a> some css--i don't think important including anyway. background-color: #449403; box-shadow: none !important; color: #fff !important; margin-left: 2px; i've pinned down being value in href since http://www.google.com work , various other urls. element shows in inspect element not show in gui , have no idea why. there character in there should escaping? embarrassing adblocker blocking link...
Read more