Hi Stefan, Thank you very much for your suggestions. They are very helpful. I am also trying to understand the hashjoin() implementation in gdk/gdk_join.c. I am aware of the classical *multi-pass partitioned hash join* as described in the literature: [1] Main memory hash joins on multi-core CPUs: tuning to the underlying hardware. Cagri Balkesen et al. ICDE13 [2] Optimizing main-memory join on modern hardware. Stefan Manegold et al. TKDE (2002) I was trying to follow the idea in these papers to understand the implementation of hash join in MonetDB but failed. Do you have any suggestions? Are there any other papers/documents I can refer to? Thanks. Best regards, XU Wenjian

Hi Wenjian,

you might want to consider studying the logical (relational) >and physical (MAL) plans, or debug your SQL queries; for >details see https://www.monetdb.org/Documentation/Manuals/SQLreference/Runtime

You might also want to consider using the MAL debugger >directly; cf., https://www.monetdb.org/Documentation/Manuals/MonetDB/debugger

Also, a combination of mserver5's --trace and ->gdk_debug=2097152 ("ALGOMASK") might be useful.

Best, Stefan

...

* Hi, *>> >>* My objective is to investigate that, given an SPJ query, how are BATs *>>* *physically* processed (changed) among relational algebra operators (e.g., *>>* select, join). I do not care about how query is translated into execution plan *>>* in MAL, what I care is the interaction of operators in the kernel (aka., gdk) . *>> >>* My current plan is to add some debug information in those operators (e.g., *>>* functions in src/gdk_join.c, src/gdk_select.c) and re-compile the system. Then, *>>* I will pose an SPJ query (through console) and check the system log to see how *>>* those operators are invoked in sequence. *>> >>* But this method seems inefficient and I would like to ask if

----- On Jul 8, 2015, at 11:42 AM, Xu,Wenjian zeroxwj at gmail.com https://www.monetdb.org/mailman/listinfo/developers-list wrote: there are any *>>* alternatives, for example, is it possible to debug the system *step-by-step* *>>* given an input query (or its logical query plan). *>> >>* Thank you very much for any kind help. *>> >>* Best regards, *>>* Wenjian *>> >> >*>*