RE: b and g must be aligned

Hi Miguel, I didn't do that much testing in terms of performance as the aggregation we were creating was non-iterative - what I was trying to do was ensure that when we used my custom aggregation in the same query as other iterative aggregations e.g. count() or sum() - we could still use mitosis (and therefore parallel computation) of the group aggregates for those that supported it. I can provide you with the sources if you wish - there are only a couple of changes to opt_mergetable and opt_prelude to detect the new modules I've defined and to either run it iteratively (like the existing aggr module entries or to call mat.pack() on the inputs to the aggregation function to ensure you get a materialised Bat of the complete data when you want to use the non-iterative approach. This was just experimental work so it's not been committed or approved in any way by the MonetDB team, nor can I make any claims as to the real efficacy of this approach :-) Regards, Scott -----Original Message----- From: users-list [mailto:users-list-bounces+scott.mathieson=pb.com@monetdb.org] On Behalf Of Miguel Ping Sent: 14 August 2013 17:32 To: users-list@monetdb.org Subject: Re: b and g must be aligned I renamed the module definition in udf.mal: module batudf; TO module aggr; reinstalled, and it did the trick. I still don't understand how it works with a fresh table. I'm guessing there's some history feeding the mal planner (queryhistory or callhistory steps?). Scott, did you do any tests to check the difference beween iterative and non-iterative versions? And finally, can you share the patch you mention? I'm interested in applying the patch if it's much faster than the "regular" version. Thanks -- Miguel On 08/14/2013 03:55 PM, Niels Nes wrote:

Miguel

As pointed out by scott, the easiest fix is to put your aggregation function (as we expect) into the aggr mal namespace.

Then mitosis won't trigger for queries with your aggregation, but other queries still get mitosis/mergetable.

The complex solution is to add your case (2 step aggregation) into the mergetable code (and fix mitosis that it doesn't bail out on your aggregation).

Niels

On Wed, Aug 14, 2013 at 03:20:06PM +0100, Miguel Ping wrote:

...

Here:

*without* mitosis +------------------------------------------------------------------------------------------------+ | mal | +==================================================================== +============================+ | function user.s13_1{autoCommit=true}(A0:lng,A1:lng):void; | | X_27 := nil:bat[:oid,:lng]; | | X_39:bat[:oid,:str] := nil:bat[:oid,:str]; | barrier X_68 := | language.dataflow(); | | X_4 := sql.mvc(); | | X_8 := sql.bind(X_4,"wa_sapo_pt_audience","kpi_2013_07","ts",0); | | X_5:bat[:oid,:oid] := sql.tid(X_4,"wa_sapo_pt_audience","kpi_2013_07"); | | X_65 := algebra.subselect(X_8,X_5,A0,A1,true,true,false); | | (X_11,r1_11) := sql.bind(X_4,"wa_sapo_pt_audience","kpi_2013_07","ts",2); | | X_66 := algebra.subselect(r1_11,A0,A1,true,true,false); | | X_14 := sql.bind(X_4,"wa_sapo_pt_audience","kpi_2013_07","ts",1); | | X_67 := algebra.subselect(X_14,X_5,A0,A1,true,true,false); | | X_16 := sql.subdelta(X_65,X_5,X_11,X_66,X_67); | | X_18 := sql.bind(X_4,"wa_sapo_pt_audience","kpi_2013_07","ts_day",0); | | (X_20,r1_26) := sql.bind(X_4,"wa_sapo_pt_audience","kpi_2013_07","ts_day",2); | | X_22 := sql.bind(X_4,"wa_sapo_pt_audience","kpi_2013_07","ts_day",1); | | X_23 := sql.projectdelta(X_16,X_18,X_20,r1_26,X_22); | | (X_24,r1_34,r2_34) := group.subgroupdone(X_23); | | X_27 := algebra.leftfetchjoin(r1_34,X_23); | | X_29 := | sql.bind(X_4,"wa_sapo_pt_audience","kpi_2013_07","h_visitors_regist | er",0); | | (X_33,r1_49) := | sql.bind(X_4,"wa_sapo_pt_audience","kpi_2013_07","h_visitors_regist | er",2); | | X_36 := | sql.bind(X_4,"wa_sapo_pt_audience","kpi_2013_07","h_visitors_regist | er",1); | | X_38 := sql.projectdelta(X_16,X_29,X_33,r1_49,X_36); | | X_39:bat[:oid,:str] := batudf.subhllagg(X_38,X_24,r1_34,true); | | language.pass(X_5); | language.pass(X_23); | language.pass(X_16); | | language.pass(r1_34); | exit X_68; | | X_42 := sql.resultSet(2,1,X_27); | | sql.rsColumn(X_42,"wa_sapo_pt_audience.kpi_2013_07","ts_day","bigin | t",64,0,X_27); | | sql.rsColumn(X_42,"wa_sapo_pt_audience.kpi_2013_07","L1","clob",188 | 1,0,X_39); | | X_51 := io.stdout(); | | sql.exportResult(X_51,X_42); | | end s13_1; | +------------------------------------------------------------------------------------------------+

*with mitosis* +-------------------------------------------------------------------------------------------------------------------------------------+ | mal | +==================================================================== +=================================================================+ | function user.s14_1{autoCommit=true}(A0:lng,A1:lng):void; | | X_18 := nil:bat[:oid,:lng]; | | X_27:bat[:oid,:str] := nil:bat[:oid,:str]; | barrier X_157 := | language.dataflow(); | | X_4 := sql.mvc(); | | X_63:bat[:oid,:lng] := sql.bind(X_4,"wa_sapo_pt_audience","kpi_2013_07","ts",0,0,4); | | X_56:bat[:oid,:oid] := sql.tid(X_4,"wa_sapo_pt_audience","kpi_2013_07",0,4); | | X_104 := algebra.subselect(X_63,X_56,A0,A1,true,true,false); | | (X_67:bat[:oid,:oid] ,X_68:bat[:oid,:lng] ) := sql.bind(X_4,"wa_sapo_pt_audience","kpi_2013_07","ts",2,0,4); | | X_108 := algebra.subselect(X_68,A0,A1,true,true,false); | | X_112 := sql.subdelta(X_104,X_56,X_67,X_108); | | X_75:bat[:oid,:lng] := sql.bind(X_4,"wa_sapo_pt_audience","kpi_2013_07","ts_day",0,0,4); | | (X_79:bat[:oid,:oid] ,X_80:bat[:oid,:lng] ) := sql.bind(X_4,"wa_sapo_pt_audience","kpi_2013_07","ts_day",2,0,4); | | X_120 := sql.projectdelta(X_112,X_75,X_79,X_80); | | (X_124,X_125,X_126) := group.subgroupdone(X_120); | | X_127 := algebra.leftfetchjoin(X_125,X_120); | | X_64:bat[:oid,:lng] := sql.bind(X_4,"wa_sapo_pt_audience","kpi_2013_07","ts",0,1,4); | | X_58:bat[:oid,:oid] := sql.tid(X_4,"wa_sapo_pt_audience","kpi_2013_07",1,4); | | X_105 := algebra.subselect(X_64,X_58,A0,A1,true,true,false); | | (X_69:bat[:oid,:oid] ,X_70:bat[:oid,:lng] ) := sql.bind(X_4,"wa_sapo_pt_audience","kpi_2013_07","ts",2,1,4); | | X_109 := algebra.subselect(X_70,A0,A1,true,true,false); | | X_113 := sql.subdelta(X_105,X_58,X_69,X_109); | | X_76:bat[:oid,:lng] := sql.bind(X_4,"wa_sapo_pt_audience","kpi_2013_07","ts_day",0,1,4); | | (X_81:bat[:oid,:oid] ,X_82:bat[:oid,:lng] ) := sql.bind(X_4,"wa_sapo_pt_audience","kpi_2013_07","ts_day",2,1,4); | | X_121 := sql.projectdelta(X_113,X_76,X_81,X_82); | | (X_128,X_129,X_130) := group.subgroupdone(X_121); | | X_131 := algebra.leftfetchjoin(X_129,X_121); | | X_65:bat[:oid,:lng] := sql.bind(X_4,"wa_sapo_pt_audience","kpi_2013_07","ts",0,2,4); | | X_60:bat[:oid,:oid] := sql.tid(X_4,"wa_sapo_pt_audience","kpi_2013_07",2,4); | | X_106 := algebra.subselect(X_65,X_60,A0,A1,true,true,false); | | (X_71:bat[:oid,:oid] ,X_72:bat[:oid,:lng] ) := sql.bind(X_4,"wa_sapo_pt_audience","kpi_2013_07","ts",2,2,4); | | X_110 := algebra.subselect(X_72,A0,A1,true,true,false); | | X_114 := sql.subdelta(X_106,X_60,X_71,X_110); | | X_77:bat[:oid,:lng] := sql.bind(X_4,"wa_sapo_pt_audience","kpi_2013_07","ts_day",0,2,4); | | (X_83:bat[:oid,:oid] ,X_84:bat[:oid,:lng] ) := sql.bind(X_4,"wa_sapo_pt_audience","kpi_2013_07","ts_day",2,2,4); | | X_122 := sql.projectdelta(X_114,X_77,X_83,X_84); | | (X_132,X_133,X_134) := group.subgroupdone(X_122); | | X_135 := algebra.leftfetchjoin(X_133,X_122); | | X_66:bat[:oid,:lng] := sql.bind(X_4,"wa_sapo_pt_audience","kpi_2013_07","ts",0,3,4); | | X_62:bat[:oid,:oid] := sql.tid(X_4,"wa_sapo_pt_audience","kpi_2013_07",3,4); | | X_107 := algebra.subselect(X_66,X_62,A0,A1,true,true,false); | | (X_73:bat[:oid,:oid] ,X_74:bat[:oid,:lng] ) := sql.bind(X_4,"wa_sapo_pt_audience","kpi_2013_07","ts",2,3,4); | | X_111 := algebra.subselect(X_74,A0,A1,true,true,false); | | X_10 := sql.bind(X_4,"wa_sapo_pt_audience","kpi_2013_07","ts",1); | | X_53 := algebra.subselect(X_10,X_62,A0,A1,true,true,false); | | X_115 := sql.subdelta(X_107,X_62,X_73,X_111,X_53); | | X_78:bat[:oid,:lng] := sql.bind(X_4,"wa_sapo_pt_audience","kpi_2013_07","ts_day",0,3,4); | | (X_85:bat[:oid,:oid] ,X_86:bat[:oid,:lng] ) := sql.bind(X_4,"wa_sapo_pt_audience","kpi_2013_07","ts_day",2,3,4); | | X_14 := sql.bind(X_4,"wa_sapo_pt_audience","kpi_2013_07","ts_day",1); | | X_123 := sql.projectdelta(X_115,X_78,X_85,X_86,X_14); | | (X_136,X_137,X_138) := group.subgroupdone(X_123); | | X_139 := algebra.leftfetchjoin(X_137,X_123); | | X_149 := mat.packIncrement(X_127,4); | | X_150 := mat.packIncrement(X_149,X_131); | | X_151 := mat.packIncrement(X_150,X_135); | | X_15 := mat.packIncrement(X_151,X_139); | | (X_16,r1_34,X_140) := group.subgroupdone(X_15); | | X_18 := algebra.leftfetchjoin(r1_34,X_15); | | X_89:bat[:oid,:str] := | sql.bind(X_4,"wa_sapo_pt_audience","kpi_2013_07","h_visitors_regist | er",0,0,4); | | (X_96:bat[:oid,:oid] ,X_97:bat[:oid,:str] ) := | sql.bind(X_4,"wa_sapo_pt_audience","kpi_2013_07","h_visitors_regist | er",2,0,4); | | X_145 := sql.projectdelta(X_112,X_89,X_96,X_97); | | X_91:bat[:oid,:str] := | sql.bind(X_4,"wa_sapo_pt_audience","kpi_2013_07","h_visitors_regist | er",0,1,4); | | (X_98:bat[:oid,:oid] ,X_99:bat[:oid,:str] ) := | sql.bind(X_4,"wa_sapo_pt_audience","kpi_2013_07","h_visitors_regist | er",2,1,4); | | X_146 := sql.projectdelta(X_113,X_91,X_98,X_99); | | X_93:bat[:oid,:str] := | sql.bind(X_4,"wa_sapo_pt_audience","kpi_2013_07","h_visitors_regist | er",0,2,4); | | (X_100:bat[:oid,:oid] ,X_101:bat[:oid,:str] ) := | sql.bind(X_4,"wa_sapo_pt_audience","kpi_2013_07","h_visitors_regist | er",2,2,4); | | X_147 := sql.projectdelta(X_114,X_93,X_100,X_101); | | X_95:bat[:oid,:str] := | sql.bind(X_4,"wa_sapo_pt_audience","kpi_2013_07","h_visitors_regist | er",0,3,4); | | (X_102:bat[:oid,:oid] ,X_103:bat[:oid,:str] ) := | sql.bind(X_4,"wa_sapo_pt_audience","kpi_2013_07","h_visitors_regist | er",2,3,4); | | X_24 := | sql.bind(X_4,"wa_sapo_pt_audience","kpi_2013_07","h_visitors_regist | er",1); | | X_148 := sql.projectdelta(X_115,X_95,X_102,X_103,X_24); | | X_153 := mat.packIncrement(X_145,4); | | X_154 := mat.packIncrement(X_153,X_146); | | X_155 := mat.packIncrement(X_154,X_147); | | X_26 := mat.packIncrement(X_155,X_148); | | X_27:bat[:oid,:str] := batudf.subhllagg(X_26,X_16,r1_34,true); | | language.pass(X_56); | language.pass(X_120); | | language.pass(X_58); | language.pass(X_121); | language.pass(X_60); | | language.pass(X_122); | language.pass(X_62); | | language.pass(X_123); | language.pass(X_15); | | language.pass(X_112); | language.pass(X_113); | | language.pass(X_114); | language.pass(X_115); | | language.pass(r1_34); | exit X_157; | | X_152:bat[:oid,:lng] := nil:bat[:oid,:lng]; | | X_156:bat[:oid,:str] := nil:bat[:oid,:str]; | | X_30 := sql.resultSet(2,1,X_18); | | sql.rsColumn(X_30,"wa_sapo_pt_audience.kpi_2013_07","ts_day","bigin | t",64,0,X_18); | | sql.rsColumn(X_30,"wa_sapo_pt_audience.kpi_2013_07","L1","clob",188 | 1,0,X_27); | | X_39 := io.stdout(); | | sql.exportResult(X_39,X_30); | | end s14_1; | +-------------------------------------------------------------------------------------------------------------------------------------+

On 08/14/2013 02:10 PM, Niels Nes wrote:

...

On Wed, Aug 14, 2013 at 02:04:27PM +0100, Miguel Ping wrote:

...

I've been tinkering a little more, if I use either the minimal_pipe, no_mitosis_pipe or the sequential_pipe optimizers the error no longer occurs. I've specified the set of optimizers to use, and it seems that the optimizer step that's problematic is the *mitosis* step.

Where can I learn more about this optimizer? Can someone shed some light? Could you send us the explain outputs of both with and without mitosis/mergetable. This may give us a hint of what goes wrong.

My guess, is that the subhllagg should probably be added (recognized).

Niels

...

Thanks! -- Miguel

On 08/13/2013 03:59 PM, Miguel Ping wrote:

...

I'm trying to come up with a small sample, but it is hard.

- I currently have a small dataset (~600 rows) which gives me the error. - BUT if I export that data onto a *new* table, the error doesn't happen. This makes it hard to provide a proper sample.

Running explain on the same query for these two tables, the plan is different: the error plan seems to use the new subgroup feature for aggregates which was released in a recent MonetDB version (11.15.x?) .

* Does monetdb keep some sort of internal table statistics that feed the MAL planner? * Can I force the query to use the 'old' aggregate function? * Can you guys point me to the part where the group BAT is calculated? my guess is that the group ids are not being calculated correctly, hence the difference between g->U->count and b->U->count. I'm guessing the culprit is around here:

... | (X_16,r1_34,X_140) := group.subgroupdone(X_15); | X_18 := algebra.leftfetchjoin(r1_34,X_15); ... | X_27:bat[:oid,:str] := | batudf.subhllagg(X_26,X_16,r1_34,true); #r1_r4 should be the bat* gid

I have tried the same dataset with MonetDB 11.13.7 (which had the 'old' aggregate definition) and the query works as expected. I don't want to do a downgrade since I don't even know if the data files are compatible.

Thanks, Miguel

On 08/13/2013 11:35 AM, Martin Kersten wrote:

...

If it is hitting before your code, then please provide the smallest (SQL) test case to reproduce it locally.

Thanks, Martin

On 8/13/13 11:27 AM, Miguel Ping wrote: > The query calls a custom aggregate function, but the error > occurs before hitting my code; the code path just starts to prepare things (it's just the boilerplate to run a custom aggr function), and it hits the error while calling BATgroupaggrinit. In fact, BATgroupaggrinit is the very first thing that the BAThllaggr function calls; Also according to Sjoerd, it's a bug: > > "If this happens when running a SQL query, it's a bug. I don't > think NULLs have anything to do with it. NULL values are stored in-line. You might want to look at b->U->count, g->U->count, b->H->seq, g->H->seq, b->H->dense, g->H->dense when the misalignment happens (either in the debugger or by using printf--but realize that count and seq are not int, so %d is not going to work). Also things like the MAL plan (prepend SQL query with EXPLAIN) and the stack trace might be useful." > > Thanks. > > > On 08/13/2013 08:51 AM, Stefan Manegold wrote: >> Dear Miguel, >> >> I am not aware of any "hllaggr()" function in the MonetDB >> release, so I assume the error occurs in your code. Not know >> your code at all, I'm afraid we cannot be of much help. >> >> Best, >> Stefan >> >> On Mon, Aug 12, 2013 at 06:59:33PM +0100, Miguel Ping wrote: >>> Some more info: >>>> SELECT count(*) FROM wa_sapo_pt_audience.kpi_2013_07 WHERE >>> ts>=1373410800000 AND ts<=1374706799000; >>> ==> 764314 >>> >>>> SELECT count(distinct(ts_day)) FROM >>> wa_sapo_pt_audience.kpi_2013_07 WHERE ts>=1373410800000 AND >>> ts<=1374706799000; ==> 15 >>> >>> it seems that b.count is the row count, while g.count is >>> something like the distinct count, with 2 more values? >>> >>> On 08/12/2013 05:50 PM, Miguel Ping wrote: >>>> Hi, I'm resurrecting this since I've been out of town and >>>> only today I got a chance to investigate further. I've >>>> recompiled with >>>> -O0 to prevent optimizations from "hiding" the values, and in >>>> the debugger I got this: >>>> >>>> b->U->count BUN 764314 >>>> g->U->count BUN 17 >>>> b->H->seq oid 0 >>>> g->H->seq oid 0 >>>> b->H->dense unsigned int 1 >>>> g->H->dense unsigned int 1 >>>> >>>> >>>> The stack call is as follows: >>>> >>>> BAThllaggr() at udf.c >>>> AGGRsubhllaggcand() at udf.c >>>> AGGRsubhllagg() at udf.c >>>> malCommandCall() at mal_interpreter.c >>>> runMALsequence() at mal_interpreter.c >>>> DFLOWworker() at mal_dataflow.c >>>> start_thread() at pthread_create.c >>>> clone() at clone.S >>>> 0x0 >>>> >>>> -------- Original Message -------- >>>> Subject: Re: b and g must be aligned >>>> Date: Fri, 26 Jul 2013 11:34:53 +0100 >>>> From: Sjoerd Mullender >>>> Reply-To: Communication channel for MonetDB users >>>> >>>> To: Communication channel for MonetDB users >>>> >>>> >>>> >>>> -----BEGIN PGP SIGNED MESSAGE----- >>>> Hash: SHA1 >>>> >>>> On 2013-07-26 12:23, Miguel Ping wrote: >>>>> On 07/25/2013 01:51 PM, Sjoerd Mullender wrote: On >>>>> 2013-07-25 14:04, Miguel Ping wrote: >>>>>>>> Hi all, >>>>>>>> >>>>>>>> We're hitting this error "b and g must be aligned". I >>>>>>>> tracked the src to a commit about some alignment code >>>>>>>> thing in >>>>>>>> gdk_calc: >>>>>>>> http://www.mail-archive.com/checkin-list@monetdb.org/msg0 >>>>>>>> 9731.html >>>>>>>> >>>>>>>> >>>> (Fix alignment conversion in compatibility code for grouped >>>>>>>> aggregates.) >>>>>>>> >>>>>>>> Can you guys please explain what's the reason behind this >>>>>>>> error? I can't understand by just looking to the src of >>>>>>>> gdk_calc.c >>>>>>>> >>>>>>>> Thanks! >>>>> When using grouped aggregates, the grouping bat must be >>>>> aligned with the value bat. The value bat is b and contains >>>>> the values you want to aggregate. The group bat is g and >>>>> contains for each value in b the group (an oid) it belongs >>>>> to. Equal group ids means the same group. These bats must >>>>> be aligned, because we need to know for each value in b to >>>>> which group it belongs. Aligned means: same length, and same >>>>> head column values. The head columns must be dense (a >>>>> sequence of numbers starting at some value, and each next >>>>> value exactly one larger than the previous). Dense >>>>> sequences are usually not stored explicitly in MonetDB. We >>>>> only store the first value in the hseqbase field. So the >>>>> hseqbase fields of b and g must be equal. The one exception >>>>> to this is when the bats are both empty. This last exception is the change to gdk_calc.c in that changeset. >>>>> >>>>> -- Sjoerd Mullender >>>>>> _______________________________________________ users-list >>>>>> mailinglistusers-list@monetdb.org >>>>>> http://mail.monetdb.org/mailman/listinfo/users-list >>>>>> >>>>>> >>>>> Thanks for your explanation. I still don't understand how >>>>> can there be a misalignment. I would expect MonetDB to feed >>>>> my hll aggregate functions with the correct values. Can it >>>>> be that I may have some NULL values and the validation is >>>>> failing because of that? >>>> If this happens when running a SQL query, it's a bug. >>>> I don't think NULLs have anything to do with it. NULL values >>>> are stored in-line. >>>> You might want to look at b->U->count, g->U->count, >>>> b->H->seq, >>>> g->H->seq, b->H->dense, g->H->dense when the misalignment >>>> g->H->happens >>>> (either in the debugger or by using printf--but realize that >>>> count and seq are not int, so %d is not going to work). >>>> Also things like the MAL plan (prepend SQL query with >>>> EXPLAIN) and the stack trace might be useful. >>>> >>>> - -- Sjoerd Mullender >>>> -----BEGIN PGP SIGNATURE----- >>>> Version: GnuPG v1.4.13 (GNU/Linux) >>>> Comment: Using GnuPG with Thunderbird >>>> -http://www.enigmail.net/ >>>> >>>> iQCVAwUBUfJQyT7g04AjvIQpAQK/JAP9HCp/aFaYWv0jodfPUnSRVgFSsdjTn >>>> /VL >>>> ttSsmAF+yomGMDIne2311f/D51F3/nte7Utx+01lgvArapWErhjGN1hzPSr5L >>>> ttSsmAF+Qbs >>>> PZ6dUfNcH8Rt2AtT3uSxfkFZy9VRDCNNXPei43IgMS2HxVZ48pnAVkNcpBbW3 >>>> Gms >>>> GwdvU7bSZtM= >>>> =2zSg >>>> -----END PGP SIGNATURE----- >>>> _______________________________________________ >>>> users-list mailing list >>>> users-list@monetdb.org >>>> http://mail.monetdb.org/mailman/listinfo/users-list >>>> >>>> >>>> >>>> >>>> >>>> >>> _______________________________________________ >>> users-list mailing list >>> users-list@monetdb.org >>> http://mail.monetdb.org/mailman/listinfo/users-list > _______________________________________________ > users-list mailing list > users-list@monetdb.org > http://mail.monetdb.org/mailman/listinfo/users-list _______________________________________________ users-list mailing list users-list@monetdb.org http://mail.monetdb.org/mailman/listinfo/users-list

_______________________________________________ users-list mailing list users-list@monetdb.org http://mail.monetdb.org/mailman/listinfo/users-list

_______________________________________________ users-list mailing list users-list@monetdb.org http://mail.monetdb.org/mailman/listinfo/users-list -- Niels Nes, Centrum Wiskunde & Informatica (CWI) Science Park 123, 1098 XG Amsterdam, The Netherlands room L3.14, phone ++31 20 592-4098sip:4098@sip.cwi.nl url:http://www.cwi.nl/~niels e-mail:Niels.Nes@cwi.nl

---

users-list mailing list users-list@monetdb.org http://mail.monetdb.org/mailman/listinfo/users-list -- Niels Nes, Centrum Wiskunde & Informatica (CWI) Science Park 123, 1098 XG Amsterdam, The Netherlands room L3.14, phone ++31 20 592-4098sip:4098@sip.cwi.nl url:http://www.cwi.nl/~niels e-mail:Niels.Nes@cwi.nl

_______________________________________________ users-list mailing list users-list@monetdb.org http://mail.monetdb.org/mailman/listinfo/users-list ________________________________