Hi On Sat, 2017-06-10 at 09:17 -0700, Steven Grimm wrote: > On Sat, Jun 10, 2017 at 1:46 AM, Alban Hertroys <haramrae@xxxxxxxxx> > wrote: > > I notice that you're declaring your ResultSet variable inside the > loop, which means that you create and destroy it frequently. I've > been told that this is a pattern that the GC has trouble keeping up > with (although that was around the Java 5 era), so you might be > seeing the effects of memory churn in your client instead of in the > database. > > Sadly, no, it doesn't help. I'd be pretty surprised if that was it, > though, given that it consistently happens with the bind variable and > never happens without; surely the result set's GC behavior would be > the same in either case? > > For grins, I tried running with the -verbosegc option to log GC > activity: > > Two bind variables 48 16 13 8 6 5 6 7 5 115 110 > 109 132 108 110 113 109 113 108 108 > Equality bind variable 5 6 6 5 6 6 6 6 7 6 8 > 8 5 6 4 5 5 5 5 5 > [GC (Allocation Failure) 65536K->2293K(251392K), 0.0035075 secs] > LIKE bind variable 5 5 6 5 6 5 5 6 6 110 107 > 112 116 118 107 112 115 105 104 104 > No bind variables 5 5 4 5 5 4 5 5 4 6 5 > 6 5 8 4 4 4 4 5 4 > > So there's only one GC run and it takes about 3 milliseconds. That > result is the same whether the ResultSet is declared inside or > outside the loop. > > -Steve I ran your test and here are my results:- :~/softdev/java_apps$ java BindTest Two bind variables 402 15 13 14 13 13 15 14 9 39 46 45 41 39 41 38 39 38 40 38 Equality bind variable 9 15 9 10 12 13 10 13 10 9 9 9 7 8 7 8 8 10 8 7 LIKE bind variable 9 9 9 8 10 8 8 8 8 40 40 41 37 38 3 9 39 39 42 38 38 No bind variables 13 9 9 9 9 11 10 8 9 8 9 10 8 9 9 8 9 9 8 12 :~/softdev/java_apps$ java BindTest Two bind variables 57 17 17 15 15 14 13 14 13 38 47 42 40 39 39 41 37 39 38 37 Equality bind variable 8 9 9 10 14 15 10 13 10 10 10 8 8 9 13 8 9 8 9 8 LIKE bind variable 10 9 11 10 9 8 9 8 8 39 38 43 43 39 3 9 37 38 38 43 39 No bind variables 9 9 11 9 9 9 8 9 9 8 9 10 9 15 10 9 9 9 9 13 Using Java version 1.8.0_131 postgresql-9.4.1212.jar PostgreSQL 9.6.3 on x86_64-pc-linux-gnu, compiled by gcc (Debian 6.3.0- 18) 6.3.0 20170516, 64-bit You'll notice that the first time it ran the database was "cold" and it took 402, whereas the second time it dropped to 57. If I have time today I might alter it to used named variables and see if that makes a difference. Cheers, Rob -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
