Hi Lee,
Actually, the exists() in your code might be the slowest part of your code. The collection call is likely backed by an index, so quick. The exists works on a sequence however. It could be that it is optimized under the hood to use xdmp:estimate in this case, but not sure. Could try to rewrite that. But actually, I would test at all. A collection-delete of an empty collection won’t take time I’d say. So wouldn’t worry about that too much. What remains is the initial collection, which returns a sequence. If you are not collecting the results, MarkLogic doesn’t need to keep it in memory. Could very well be that it is streamed in the outer for loop. Otherwise try chunking it in batches of 10k. Remember that deletes in ML are fast! It’s just a flag on each fragment.. Kind regards, Geert *Van:* [email protected] [mailto: [email protected]] *Namens *Lee, David *Verzonden:* donderdag 17 november 2011 20:41 *Aan:* General Mark Logic Developer Discussion ( [email protected]) *Onderwerp:* [MarkLogic Dev General] "Joins" in search:search or cts:search I suspect the answer is "no" ... but just plugging the brains out there .. For good or bad I use this architype. I have many "summary" documents say "/logs/1.xml" , "/logs/2.xml" which belongs to the collection "/summaries" There can be many (100k+) Each summary document lists a refernce to external URL's (in this case Amazon S3) from which data could be loaded. If I load the data I put each group into a collection named by the URL of the summary. So say I have 10,000 XML documents referenced by doc("/logs/1.xml") If I choose to load them, they will end up in collection "/logs/1.xml". These summaries are in the collection say "/summaries" The reason for this is for the ability to easily bulk delete blocks of documents based on their summaries. I can list the summaries and by a simple exists( collection( $url) ) cant tell if any actual log documents have been loaded. NOW: I want to be able to delete all records by summary but only if the documents have been loaded. Suppose I had 100k summary URL's I could do for $url in collection("/summaries") if( exists( collection( $url) ) then xdmp:collection-delete($url) else () This works and all ... but suppose I want something more efficiient. Overall there may be only say 1% of the summary documents actually loaded. Furthermore if there were LOTS of ones loaded the above would timeout. So I spawn a thread to delete say [1 to 10] of every summary collection ... but say I have 100k collections most of the threads do nothing. So I have to revert to the above to first check if the collection has anything before spawning a thread. Quesiton: Is there a cts:search option which can do a collection query based on the results of the search itself ? that is (pseudo code) in one cts:search for $c in collection("x")/document-uri(.) if( exists( collection( $c) ) return $c doing this in FLOWR is very slow ... but its what I'm resorting to .... ---------------------------------------- David A. Lee Senior Principal Software Engineer Epocrates, Inc. [email protected] 812-482-5224
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