joining Mnesia tables

Yariv Sadan <>
Tue Jun 6 20:41:30 CEST 2006


Hi,

I noticed the following comment in the QLC documentation
(http://erlang.org/doc/doc-5.5/lib/stdlib-1.14/doc/html/index.html) :

"Support for faster join of two tables will be added not later than in
R11. Depending on preferences and priorities some high level
optimizations may be added in the future."

I noticed this feature isn't in the latest release notes, so did some
digging and came across these old discussions:

http://www.erlang.org/ml-archive/erlang-questions/200511/msg00336.html
http://www.erlang.org/ml-archive/erlang-questions/200502/msg00278.html

I'm not a Mnesia expert, but if (according to the first thread) joins
can take 45 minutes on large tables, it  makes QLC (and maybe even
Mnesia) unusable for certain applications.

My questions are:
- Is QLC join optimization still a planned feature for OTP?
- In cases where joining 2 or more large tables is necessary, can such
joins be optimized manually? If so, what is the best procedure for
doing so?

Any insight is appreciated.

Thanks,
Yariv



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