I am no technical expert on MonetDB. But, we have been using MonetDB for more than a year now. So, I can give you couple of suggestions (or workarounds) that might help based on our experience. We are using a third-party application that generates queries and sends them to MonetDB which has a transaction table with more than 1.6billion records and growing (timeseries data like yours..) linked to dimensional tables. The kinds of queries that are being generated are almost exact type that you are showing, some sort of an aggregation query using group by and filtered with where clause.

 

One thing that we noticed with queries with joins is that inner join seems to be significantly faster than left/right joins even if the results are no different between the 3 types of joins. I know that might not be an option for you. But, it works for our use case.

 

Another thing that we noticed is if you add constraints, ie primary and foreign keys, you will get better performance. I think you might already have them in your tables though....

 

We are in the process of testing Oct-2010SP1 release so we can upgrade our Nov-2009SP2 environment. We are seeing significant performance improvement in most of our typical queries and much smaller memory footprint with the Oct-2010SP1 release. But, we see some performance degradation with queries based on views instead of tables. You might want to try the Nov-2009 optimizer and see if that helps. You can do this by specifyng the Nov-2009 optimizer in the monetdb5.conf file.

On Wed, Feb 23, 2011 at 4:24 AM, Rob Berentsen <rhberentsen@gmail.com> wrote:

Hello,

 

I'm new to monetdb and installed it two weeks ago to do some tests. I was very much impressed with the speed on large tables, but in some of my latest tests regarding subparts of these tables based on a unix timestamp the time was the same as querying the whole table. Does anyone know what I can do to get higher speeds on queries in monetdb that only use part of the table, like partition pruning, explicit foreign keys or unique statements, indexes or some other way?

 

I have the following two tables and number of records:

 

CREATE TABLE table1 (T1vid INT NOT NULL, T1Field1 VARCHAR(20) NOT NULL, T1Field2 TINYINT NOT NULL);
This table has about 400.000 records. The records are non time bounded, it's just a list. The T1vid is an increased ID, but not generated in momentdb at the moment, but in mysql

 

CREATE TABLE table2 (T2mid INT NOT NULL, T2vid INT NOT NULL, T2timestamp INT NOT NULL, T2Field1 INT NOT NULL, T2Field2 INT NOT NULL);

This table has about 1.000.000 records and a unix_timestamp field. It get a few new records every second and records older then 24 hours are deleted. The T2mid-field refers to some other table that's not in momentdb's database, so just an integer. The T2vid-field however refers to the T1vid-field in table1 (a foreign key, but i didn't define it that way).

 

The following query takes about 3,5 seconds, it doesnt't have the timestamp included in the WHERE-clause:

SELECT SUM(t2.T2Field2), t1.T1Field1, t1.T1Field2, (t2.T2timestamp / 3600) as interval
            FROM table2 AS t2

            LEFT JOIN table 1 AS t1 ON t1.T1vid=t2.T2vid

            WHERE t2.T2Field1=8 AND t2.T2vid IN (list of 15 unique v.T1vid ID's)
            GROUP BY interval, t1.T1Field1, t1.T1Field2 ORDER BY interval DESC;

Resulting is a list of the 15 v.T1vid ID's times the number of interval's. t2.T2timestamp is now devided by 3600 and grouped on this result, so each set of 15 v.T1vid ID's would reflect 1 hour, returning max 24x15 rows.

 

The following query also takes about 3,5 seconds, but it does have the timestamp included in the WHERE-clause. It only needs to access 1 hour of data instead of the whole 24 hours, and groups it into intervals of 5 minutes (300 sec):

SELECT SUM(t2.T2Field2), t1.T1Field1, t1.T1Field2, (t2.T2timestamp / 300) as interval
            FROM table2 AS t2

            LEFT JOIN table 1 AS t1 ON t1.T1vid=t2.T2vid

            WHERE t2.T2timestamp BETWEEN 1298360000 AND 1298363600

            AND t2.T2Field1=8 AND t2.T2vid IN (list of 15 unique v.T1vid ID's)
            GROUP BY interval, t1.T1Field1, t1.T1Field2 ORDER BY interval DESC;

 

t2.T2timestamp is now devided by 300, so each set of 15 v.T1vid ID's would reflect 5 minuntes, returning max 12x15 rows.

 

I would very much appreciate any help or hints; please let me know any question you might have.

 

 

Kind regards,

Rob Berentsen

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