Re: Caching of TermDocs
The caching by TermScorer of the next 32 Docs is a way to speed up the serial (in order) reading of docs from the TermDocs object (probably coming direct from disk). I would like to hold a significant amount of the index in memory but use the disk index as a spill over. Obviously the best situation is to hold in memory only the information that is likely to be used again soon. It seems that caching TermDocs would allow popular search terms to be searched more efficiently while the less common terms would need to be read from disk. Has anyone else done this? Know of a better approach? - Original Message - From: Paul Elschot [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Tuesday, July 27, 2004 3:07 AM Subject: Re: Caching of TermDocs On Monday 26 July 2004 21:41, John Patterson wrote: Is there any way to cache TermDocs? Is this a good idea? Lucene does this internally by buffering up to 32 document numbers in advance for a query Term. You can view the details here in case you're interested: http://cvs.apache.org/viewcvs.cgi/jakarta-lucene/src/java/org/apache/lucene/search/TermScorer.java It uses the TermDocs.read() method to fill a buffer of document numbers. Is this what you had in mind? Regards, Paul - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: Caching of TermDocs
John Patterson wrote: I would like to hold a significant amount of the index in memory but use the disk index as a spill over. Obviously the best situation is to hold in memory only the information that is likely to be used again soon. It seems that caching TermDocs would allow popular search terms to be searched more efficiently while the less common terms would need to be read from disk. The operating system already caches recent disk i/o. So what you'd save primarily would be the overhead of parsing the data. However the parsed form, a sequence of docNo and freq ints, is nearly eight times as large as its compressed size in the index. So your cache would consume a lot of memory. Whether it this provide much overall speedup depends on the distribution of common terms in your query traffic. If you have a few terms that are searched very frequently then it might pay off. In my experience with general-purpose search engines this is not usually the case: folks seem to use rarer words in queries than they do in ordinary text. But in some search applications perhaps the traffic is more skewed. Only some experiments would tell for sure. Doug - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: Caching of TermDocs
Cool. I'll give it a try. Looks like extending FilterIndexReader is the way to go. Or possibly I could cache the compressed form at a lower level getting the best of both worlds. I'll look into both ways, profile the app, and post my results. - Original Message - From: Doug Cutting [EMAIL PROTECTED] To: Lucene Users List [EMAIL PROTECTED] Sent: Tuesday, July 27, 2004 8:33 PM Subject: Re: Caching of TermDocs John Patterson wrote: I would like to hold a significant amount of the index in memory but use the disk index as a spill over. Obviously the best situation is to hold in memory only the information that is likely to be used again soon. It seems that caching TermDocs would allow popular search terms to be searched more efficiently while the less common terms would need to be read from disk. The operating system already caches recent disk i/o. So what you'd save primarily would be the overhead of parsing the data. However the parsed form, a sequence of docNo and freq ints, is nearly eight times as large as its compressed size in the index. So your cache would consume a lot of memory. Whether it this provide much overall speedup depends on the distribution of common terms in your query traffic. If you have a few terms that are searched very frequently then it might pay off. In my experience with general-purpose search engines this is not usually the case: folks seem to use rarer words in queries than they do in ordinary text. But in some search applications perhaps the traffic is more skewed. Only some experiments would tell for sure. Doug - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Caching of TermDocs
Is there any way to cache TermDocs? Is this a good idea? - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: Caching of TermDocs
On Monday 26 July 2004 21:41, John Patterson wrote: Is there any way to cache TermDocs? Is this a good idea? Lucene does this internally by buffering up to 32 document numbers in advance for a query Term. You can view the details here in case you're interested: http://cvs.apache.org/viewcvs.cgi/jakarta-lucene/src/java/org/apache/lucene/search/TermScorer.java It uses the TermDocs.read() method to fill a buffer of document numbers. Is this what you had in mind? Regards, Paul - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
