Beefy Boxes and Bandwidth Generously Provided by pair Networks
There's more than one way to do things
 
PerlMonks  

comment on

( #3333=superdoc: print w/replies, xml ) Need Help??
A straight SQL join statement is running horribly slow on my DB and our DBA can offer no suggestions for tuning.

Five million rows isn't that large, if the system is properly sized for it, and the database is tuned correctly. (which may be big 'if's).

I know nothing about your data, or what database you're using, so it's really hard to give specific help. (for instance, you can override Oracle's join behavior by giving hints). Even in other languages, exactly how you write your SQL can result in you doing a sort-merge join vs. a correlated join... In some situations, indexes can hurt you, and you'll want to make sure the tables are properly analyzed by the database so it knows when those times are. EXPLAIN PLAN in Oracle, and EXPLAIN in mySQL are your friends.

(I'm not going to say that your DBA hasn't already done this ... but I've worked with a few DBAs who weren't much more than an operator on a mainframe. Your database might not be tuned for this sort of operation, but that's no reason that you shouldn't be able to perform this in SQL, with a little prep work.)


In reply to Re: Space Efficiency of Hashes by jhourcle
in thread Space Efficiency of Hashes by Anonymous Monk

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post; it's "PerlMonks-approved HTML":



  • Are you posting in the right place? Check out Where do I post X? to know for sure.
  • Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:
    <code> <a> <b> <big> <blockquote> <br /> <dd> <dl> <dt> <em> <font> <h1> <h2> <h3> <h4> <h5> <h6> <hr /> <i> <li> <nbsp> <ol> <p> <small> <strike> <strong> <sub> <sup> <table> <td> <th> <tr> <tt> <u> <ul>
  • Snippets of code should be wrapped in <code> tags not <pre> tags. In fact, <pre> tags should generally be avoided. If they must be used, extreme care should be taken to ensure that their contents do not have long lines (<70 chars), in order to prevent horizontal scrolling (and possible janitor intervention).
  • Want more info? How to link or or How to display code and escape characters are good places to start.
Log In?
Username:
Password:

What's my password?
Create A New User
Domain Nodelet?
Chatterbox?
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others pondering the Monastery: (6)
As of 2022-09-27 10:46 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?
    I prefer my indexes to start at:




    Results (119 votes). Check out past polls.

    Notices?