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:
- 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
- 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
-
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 How to display code and escape characters
are good places to start.
|