Hi! I have some questions as to how MonetDB/XQuery should be compared fairly to other systems. If I re-run a query multiple times in a single call to `mclient`, is any calculation re-used? How about if I run multiple similar queries in a single call? Example: $ cat www.xq count(doc("dblp")//www) $ cat www_s10.xq (count(doc("dblp")//www), count(doc("dblp")//www), count(doc("dblp")//www), count(doc("dblp")//www), count(doc("dblp")//www), count(doc("dblp")//www), count(doc("dblp")//www), count(doc("dblp")//www), count(doc("dblp")//www), count(doc("dblp")//www)) $ cat www_s100.xq (count(doc("dblp")//www), ... count(doc("dblp")//www)) $ mclient --language=xquery --time < www.xq 11760 Timer 22.552 msec (Assert we are running hot.) $ mclient --language=xquery --time < www.xq 11760 Timer 21.661 msec $ mclient --language=xquery --time < www_s10.xq 11760, [snip] 11760 Timer 33.063 msec $ mclient --language=xquery --time < www_s100.xq 11760, [snip] 11760 Timer 252.414 msec So the average execution times are 22, 3.3 and 2.5 milliseconds. Is the extra cost for the first query just starting up the client program, or is some calculation re-used? If we now look at more expensive queries: $ cat dblp_authors.xq count(doc("dblp")/dblp//author[text()="Grzegorz Rozenberg"]) Just repeating the same: $ cat dblp_authors_s10.xq (count(doc("dblp")/dblp//author[text()="Grzegorz Rozenberg"]), count(doc("dblp")/dblp//author[text()="Grzegorz Rozenberg"]), count(doc("dblp")/dblp//author[text()="Grzegorz Rozenberg"]), count(doc("dblp")/dblp//author[text()="Grzegorz Rozenberg"]), count(doc("dblp")/dblp//author[text()="Grzegorz Rozenberg"]), count(doc("dblp")/dblp//author[text()="Grzegorz Rozenberg"]), count(doc("dblp")/dblp//author[text()="Grzegorz Rozenberg"]), count(doc("dblp")/dblp//author[text()="Grzegorz Rozenberg"]), count(doc("dblp")/dblp//author[text()="Grzegorz Rozenberg"]), count(doc("dblp")/dblp//author[text()="Grzegorz Rozenberg"]), count(doc("dblp")/dblp//author[text()="Grzegorz Rozenberg"])) Different but related queries: $ cat dblp_authors_x10.xq (count(doc("dblp")/dblp//author[text()="Grzegorz Rozenberg"]), count(doc("dblp")/dblp//author[text()="Wen Gao"]), count(doc("dblp")/dblp//author[text()="Irith Pomeranz"]), count(doc("dblp")/dblp//author[text()="Hector Garcia-Molina"]), count(doc("dblp")/dblp//author[text()="Moshe Y. Vardi"]), count(doc("dblp")/dblp//author[text()="Joseph Y. Halpern"]), count(doc("dblp")/dblp//author[text()="Noga Alon"]), count(doc("dblp")/dblp//author[text()="Wei Li"]), count(doc("dblp")/dblp//author[text()="Ming Li"]), count(doc("dblp")/dblp//author[text()="Donald F. Towsley"]) ) $ mclient --language=xquery --time < dblp_authors.xq 351 Timer 1238.436 msec $ mclient --language=xquery --time < dblp_authors.xq 351 Timer 1253.927 msec $ mclient --language=xquery --time < dblp_authors_s10.xq 351, ... 351 Timer 1284.191 msec $ mclient --language=xquery --time < dblp_authors_x10.xq 351, 347, 346, 341, 334, 334, 330, 320, 320, 317 Timer 2610.589 msec Here the average times are 1238, 128 and 261 milliseconds. Here the difference is clearly not just startup of the client. If this was not a client-server architecture, I would guess the difference came from opening files, getting stuff into cache, etc.. Are there similar reasons here? What parts of the calculations are actually done inside the client, if any? If the answer is none, why is this behavior seen? In conclusion: When running multiple queries, what would be the most fair way to compare MonetDB/XQuery to other client/server architectures in your view? Concatenating the queries in a single call to `mclient`, or multiple calls? When timing a single query, can it be repeated multiple times in a single call, and the average taken, without being unfair? If I use for example MS SQL Server 2008, there is no gain from a single invocation of the client, whether I have multiple SQL statements SELECT x.query('$q) FROM t; ..., SELECT x.query('$q) FROM t; Or a single SQL statement with a list of XPath queries SELECT x.query('($q, ..., $q)') FROM t; Klem fra Nils -- http://www.idi.ntnu.no/~nilsgri/ Why is this thus? What is the reason of this thusness? - Artemus Ward