Beefy Boxes and Bandwidth Generously Provided by pair Networks
Do you know where your variables are?
 
PerlMonks  

Comment on

( #3333=superdoc: print w/ replies, xml ) Need Help??

Tie::File builds the index every time you tie the file, and doesn't store the index. That means every time a script starts up, Tie::File has to skim through the entire 'big file' to find all line endings or record separators. Building this index consumes O(n) time, every time the index is built. The entire point of File::Index is to avoid rebuilding the index file unless you specifically tell it to do so.

File::Index is helpful for 'big files' that don't change frequently. File::Index builds an index and stores it for future use. That way, the next time the script is run, the index alread exists, and item lookups will occur in O(1) time. Building the index still consumes O(n) time, but the index is only built once, or at worst, when you tell it to be rebuilt.

I also used packed longs for the index so that the index file is as compact as is practical. And finding the Nth entry in the index file doesn't require reading through the entire file, it just involves seeking to LONG_SIZE * entry-number into the index file... an O(1) operation.


Dave


In reply to Re^2: Proof of concept: File::Index by davido
in thread Proof of concept: File::Index by davido

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



  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • Outside of code tags, you may need to use entities for some characters:
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.
  • Log In?
    Username:
    Password:

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

    How do I use this? | Other CB clients
    Other Users?
    Others lurking in the Monastery: (12)
    As of 2014-10-21 14:34 GMT
    Sections?
    Information?
    Find Nodes?
    Leftovers?
      Voting Booth?

      For retirement, I am banking on:










      Results (105 votes), past polls