# This is a method I use when working with slow ruby scripts that<\/span><\/div># operate on huge datasets.<\/span><\/div>#<\/span><\/div># It caches the return value of a block of extremely slow code<\/span><\/div># in a file so that subsequent runs are fast.<\/span><\/div>#<\/span><\/div># It's indispensable to me when doing edit-debug-edit-debug-edit<\/span><\/div># cycles on giant datasets.<\/span><\/div> <\/div>
# loads ruby object from a cache file or (if cache file doesn't exist) runs<\/span><\/div># provided block and writes result to cache file<\/span><\/div>def<\/span> cache<\/span>(<\/span>file<\/span>)<\/span><\/div> if<\/span> File<\/span>.<\/span>exists?<\/span>(<\/span>file<\/span>)<\/span><\/div> STDERR<\/span>.<\/span>puts<\/span> "(used cache)"<\/span><\/div> Marshal<\/span>.<\/span>load<\/span>(<\/span>File<\/span>.<\/span>read<\/span>(<\/span>file<\/span>))<\/span><\/div> else<\/span><\/div> object<\/span> =<\/span> yield<\/span><\/div> File<\/span>.<\/span>open<\/span>(<\/span>file<\/span>,<\/span> 'w'<\/span>)<\/span> {<\/span> |<\/span>f<\/span>|<\/span> f<\/span>.<\/span>print<\/span> Marshal<\/span>.<\/span>dump<\/span>(<\/span>object<\/span>)<\/span> }<\/span><\/div> object<\/span><\/div> end<\/span><\/div>end<\/span><\/div> <\/div>
# usage example (loading 8,000 marc-xml files)<\/span><\/div> <\/div>
STDERR<\/span>.<\/span>puts<\/span> "loading marc files"<\/span><\/div>marc_records<\/span> =<\/span> cache<\/span>(<\/span>'marc_records.cache'<\/span>)<\/span> do<\/span><\/div> marc_records<\/span> =<\/span> {}<\/span><\/div> marc_files<\/span>.<\/span>each<\/span> do<\/span> |<\/span>f<\/span>|<\/span><\/div> doc<\/span> =<\/span> Document<\/span>.<\/span>new<\/span>(<\/span>File<\/span>.<\/span>read<\/span>(<\/span>f<\/span>))<\/span><\/div> title<\/span> =<\/span> doc<\/span>.<\/span>elements<\/span>[<\/span>'//datafield[@tag="245"]/subfield[@code="a"]'<\/span>]<\/span><\/div> marc_records<\/span>[<\/span>f<\/span>]<\/span> =<\/span> title<\/span>.<\/span>text<\/span><\/div> end<\/span><\/div> marc_records<\/span><\/div>end<\/span><\/div> <\/div><\/pre><\/div>\n \n <\/div>\n\n