On Mon, Mar 24, 2008 at 5:05 PM, Michael Schmidt
I have two tables of the form
R1(x INTEGER, y INTEGER) R2(x INTEGER, y INTEGER)
where x and y both are NOT NULL and may both contain duplicate values (however, the combination (a,b) is unique). My questions are the following:
a.) Is there a possibility to create a /clustered/ index on the x-column (or a clustered combined x-y index?). I could also create a PRIMARY KEY on (x,y). Would this result in a clustered index? Is there any command to find out which indices are clustered?
MonetDB does not support user defined clustered indeces. To have the same effect you will have to sort your data on x-y be explicitly stating it on your insert command, like: INSERT INTO table_name (...) ORDER BY X,Y MonetDb then will know that your data is sorted and result in optimized plans. As far as I know there is no command to see the indices since there are no user indices.
b.) Does MonetDB support MergeJoins? I.e., assume I have a clustered index on columns R1.a and R2.a and perform a join on these columns, will this join be realized by an efficient merge join?
If your data is sorted, MonetDB will choose a fast merge join. Which version of MonetDB are you using? Stable release or from the cvs? I hope I could help, lefteris
Best regards, Michael
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