Who uses time series or column-oriented databases and why?

Like any database technology platform, time series databases have found specialized applications in several industries, including telecommunications, utility, finance, and military.

For example, cell carriers use time series databases to monitor peak mobile phone usage. Similarly, utilities use them to study optimal tariff structure to shape on-peak or off-peak electricity usage.

See wikipedia for more on time series and column-oriented databases.

‘exit’ fails to terminate kdb console. How do I gracefully exit a kdb process?

exit 0 or \\ or simply control+d from a console.

Inside a function, the double backslash requires escaping. Use value “\\\\” or system “\\\\”

Note: kdb process exits can be trapped via .z.exit.

How do i interpret the output of function .Q.w[]?

An example explains it best:

$ rlwrap q
KDB+ 2.7 2011.02.16 Copyright © 1993-2011 Kx Systems
q).Q.w[] used| 108432   / bytes malloced
heap| 67108864 / heap bytes available
peak| 67108864 / heap high-watermark in bytes
wmax| 0        / workspace limit from -w param
mmap| 0        / amount of memory mapped
syms| 537      / number of symbols interned
symw| 15616    / bytes used by 537 symbols

Note how .Q.w is simply a pretty print output of \w and the workspace memory footprint from \w 0

k){`used`heap`peak`wmax`mmap`syms`symw!(.”\\w”),.”\\w 0″}
108304 67108864 67108864 0 0j

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