… key solution for random selection only work when the IDs for movies are distributed uniformly over the range 1..MAX(id)? Yes, there… there’s a gap of id‘s between 47000 and 50000 with no movies, but your random number generator picks values in that… “gap” will be picked more frequently. Nearly every solution for randomly choosing rows involves some compromise, either of performance, or of…
Comment: ORDER BY ... LIMIT Performance Optimization
September 2, 2006 By 100 Comments
… row_ids or there are few holes and you do not care about a bit skewed distribution – use this approach – select random(id) in the range and find row close to it. If you need multiple rows or there is no sequential integer ids…. For example generate 1.000.000 of random rows at once. Now have as simple counter of how much of random rows you…
Post: New distribution of random generator for sysbench - Zipf
May 9, 2012 By 3 Comments
Sysbench has three distribution for random numbers: uniform, special and gaussian. I mostly use uniform and … incoming benchmarks with this distribution. Follow @VadimTk !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src=”//platform.twitter.com/widgets.js…
Post: Missing Data - rows used to generate result set
July 20, 2008 By 15 Comments
…table scan row accesses may be much faster than random index lookups row accesses in the same table) … is the number of rows which MySQL used to generate result set. Comparing this number with number of rows…use Full Text Search indexes. If you have WHERE ID%100=0 you can have extra column divisible_…
Comment: ORDER BY ... LIMIT Performance Optimization
September 15, 2007 By 100 Comments
…. i.id (smaller-equal) a.id and the i.id (greater) a.id This brings trouble as well because the random number is generated inside the query resulting with two different random numbers. This can be overcome by making a pre-query to generate…
Comment: ORDER BY ... LIMIT Performance Optimization
September 15, 2007 By 100 Comments
…-rand a.id This brings trouble as well because the random number is generated inside the query resulting with two different random numbers. This can be overcome by making a pre-query to generate…
Comment: ORDER BY ... LIMIT Performance Optimization
September 27, 2006 By 100 Comments
… sequence of random row ID something like: id rnd 1 456 2 123 3 905 So you have sequential row number and random values. Now when you need N random you can do select rnd from tbl where id> LIMIT N; If N is random… all random data is used – for some application looping is enough for others you need to make sure you generate enough random data…
Post: Testing Fusion-io ioDrive2 Duo
May 10, 2012 By 21 Comments
… show the results for both single card and raid (Duo). Random writes, async: We see stable and predictable write performance, with… MiB/s for Duo. Now with separation per thread for random read synchronous IO: There is also excellent response time characteristics… to previous generation ioDrive. Follow @VadimTk !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d…
Post: To UUID or not to UUID ?
March 13, 2007 By 28 Comments
… your application needs. It may be (user_id,msg_id) in some cases but in many auto_increment …be stored in optimized sort order to minimize how random they are – there is timestamp based part in …increment and which could be used to have values generated at same point in time physically local in …
Post: Replaying database load with Percona Playback
October 25, 2012 By 9 Comments
… workload, data set or queries. Those tools just run random queries against random generated data. The best way to run a benchmark is… DISTINCT ol_i_id FROM order_line WHERE ol_w_id = 1 AND ol_d_id = 10 AND ol_o_id < 3415 AND ol_o_id >= (3415 – 20); Why there…
