comment on

It appears, from cursory examination, that commits on SQLite are implied to be slow.

From the DBD::SQLite documentation:

SQLite is fast, very fast. I recently processed my 72MB log file with it, inserting the data (400,000+ rows) by using transactions and only committing every 1000 rows (otherwise the insertion is quite slow), and then performing queries on the data. (Emphasis added)

From http://www.sqlite.org/cvstrac/wiki?p=PerformanceConsiderations, it says:

When doing lots of updates/inserts on a table it is a good idea to contain them within a transaction, . . . This will make SQLite write all the data to the disk in one go, vastly increasing performance. (Emphasis added)

Apparently, what's happening is there is a disk flush of the actual changes to the table upon commit. This apparently is to allow for preservation of committed data if the database crashes. Oracle and MySQL (using InnoDB) have REDO logs which capture the commands that made the change, then actually apply the changes when it's convenient or necessary. (MySQL, using MyISAM tables, doesn't have this guarantee. This is why you can have corruption of MyISAM tables, but not InnoDB tables.)

This constant flushing of the tables (and the attendant indices) looks to be why you have the performance issues.

Note: I don't have proof this is what's happening, but it seems like a reasonable guess.

Being right, does not endow the right to be rude; politeness costs nothing.
Being unknowing, is not the same as being stupid.
Expressing a contrary opinion, whether to the individual or the group, is more often a sign of deeper thought than of cantankerous belligerence.
Do not mistake your goals as the only goals; your opinion as the only opinion; your confidence as correctness. Saying you know better is not the same as explaining you know better.

In reply to Re: DBD::SQLite tuning by dragonchild
in thread DBD::SQLite tuning by perrin

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.


Just another Perl shrine
	PerlMonks