[Monetdb-developers] are BAT ids are fixed

Stefan Manegold Stefan.Manegold at cwi.nl
Mon Mar 22 20:23:14 CET 2010

On Mon, Mar 22, 2010 at 11:45:21PM +0530, anshul gangwar wrote:
> hello,
>     I want to know whether BAT ids are fixed.

BAT ids are fixed for the life-time of a BAT, i.e., on creation, a BAT is
assigned an ID, which is keeps unchanged and exclusively until the BAT is
destroyed, again.

> If fixed then what does that
> BAT_select_(b=tmpr_2322): BATslice(v=tmp_2403, low=0, high=1)
> means?

This means that a range (or point) selection on a tail-sorted BAT is
executed by looking up the positions of the lower and higher bound of the
range (using binary search) and then getting the complete result as a
positional slice of the BAT between these two positions.

See MonetDB/src/gdk/gdk_batop.(mx|c) for details.


ps: Please note that the information you get about the runtime
    algorithm/implementaion choice (using --debug=$[2*1024*1204]) is mainly
    meant for core developers of MonetDB when analysing and debugging the
    system; hence, it is (a) not guaranteed to be complete and (b) makes
    only sense in case you know and understand the code in MonetDB/src/gdk/
    quite well ...
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| Dr. Stefan Manegold | mailto:Stefan.Manegold at cwi.nl |
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