On Sun, Dec 11, 2011 at 10:47 AM, Platonides <[email protected]> wrote: > You seem to think that piping the output from bzip2 will hold the xml > dump uncompressed in memory until your script processes it. That's wrong. > bzip2 will begin uncompressing and writing to the pipe, when the pipe > fills, it will get blocked. As your perl script reads from there, > there's space freed and the unbzipping can progress.
This is correct, but the overall memory usage depends on the XML library and programming technique being used. For XML that is too large to comfortably fit in memory, there are techniques to allow for the script to process the data before the entire XML file is parsed (google "SAX" or "stream-oriented parsing"). But this requires more advanced programming techniques, such as callbacks, compared to the more naive method of parsing all the XML into a data structure and then returning the data structure. That naive technique can result in large memory use if, say, the program tries to create a memory array of every page revision on enwiki. Of course if the perl script is doing the parsing itself, by just matching regular expressions, this is not hard to do in a stream-oriented way. - Carl _______________________________________________ Toolserver-l mailing list ([email protected]) https://lists.wikimedia.org/mailman/listinfo/toolserver-l Posting guidelines for this list: https://wiki.toolserver.org/view/Mailing_list_etiquette
