Hi,
shortest answer is: yes.
Longer answer is: In case the BATs that enter the actual join operator are (still) sorted and the kernels know that they are sorted (i.e., the respective property is set), then the join operator will use a merge-join algorithm.
Whether these prerequisites hold depends on a number of factors, among others whether the base BATs are indeed know to be sorted, and which operators they go through before hitting the join, i.e., the generated MAL plan, which is generated without knowing that the base BATs are sorted.
Stefan
On Mon, Dec 19, 2011 at 09:56:54AM +0100, Viktor Rosenfeld wrote:
Hi,
I know that when a table is sorted on a column, value look-ups on that column will use a binary search instead of a linear search. Is there a similar benefit for joins? E.g. if I have 2 tables that contain a sorted column C and I do an equality join on this column (or a self-join using 2 aliases of the same table), I would expect a traditional DBMS to do a merge-join.
Cheers, Viktor
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