Beefy Boxes and Bandwidth Generously Provided by pair Networks
We don't bite newbies here... much
 
PerlMonks  

comment on

( #3333=superdoc: print w/replies, xml ) Need Help??
My expectation is that most databases would use a well-known datastructure (such as a BTree) to store this kind of data. Which avoids a million directory entries, and also allows for variable length data. I admit that an RDBMS might do this wrong. But I'd expect most of them to get it right first try. Certainly BerkeleyDB will.

Using DB_File:

  1. 512,000,000 numbers appended randomly to one of 1,000,000 records indexed by pack 'N', $fileno

    Actual data stored (1000000 * 512 * 4) : 1.90 GB

    Total filesize on disk : 4.70 GB

    Total runtime (projected based on 1%) : 47 hours

  2. 512,000,000 numbers written one per record, indexed by pack 'NN', $fileno, $position (0..999,999 / 0 .. 512 (ave)).

    Actual data stored (1000000 * 512 * 4) : 1.90 GB

    Total filesize on disk : 17.00 GB (Estimate)

    Total runtime (projected based on 1%) : 80 hours* (default settings)

    Total runtime (projected based on 1%) : 36 hours* ( cachesize => 100_000_000 )

    (*) Projections based on 1% probably grossly under-estimate total runtime as it was observed that even at these low levels of fill, each new .1% required longer than the previous.

    Further, I left the latter test running while I slept. It had reached 29.1% prior to leaving it. 5 hours later it had reached 31.7%. I suspect that it might never complete.

Essentially, this bears out exactly what I predicted at Re: Combining Ultra-Dynamic Files to Avoid Clustering (Ideas?)( A DB won't help).


Examine what is said, not who speaks.
"Efficiency is intelligent laziness." -David Dunham
"Think for yourself!" - Abigail
"Memory, processor, disk in that order on the hardware side. Algorithm, algoritm, algorithm on the code side." - tachyon

In reply to Re^3: Combining Ultra-Dynamic Files to Avoid Clustering (Ideas?)( A DB won't help) by BrowserUk
in thread Combining Ultra-Dynamic Files to Avoid Clustering (Ideas?) by rjahrman

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 musing on the Monastery: (2)
As of 2021-10-27 23:52 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?
    My first memorable Perl project was:







    Results (95 votes). Check out past polls.

    Notices?