4 ms·

I disagree, it's quite elegant if you think in terms of relational algebra operators: * Projection (Π): awk and cut for simple cases * Selection (σ): grep for

by nextos 7y ago

I disagree, it's quite elegant if you think in terms of relational algebra operators: * Projection (Π): awk and cut for simple cases * Selection (σ): grep for simple cases, otherwise sed & awk * Rename (ρ): sed * Set operators: join, comm...

agumonkey 7y ago
ntfsql dreams
chongli 7y ago
Bravo! This is one of the most insightful comments I've read in a long time! I have been using some of these tools for years but I never thought of describing them this way. Now I can think of writing a complex query in relational algebra and translating it into these commands in a very natural way.
- _TwoFinger 7y ago
  Here's an interesting article that links shell scripting and relational algebra - http://matt.might.net/articles/sql-in-the-shell/ http://matt.might.net/articles/sql-in-the-shell/
graphpapa 7y ago
I’m pretty mathsy but I don’t get this
- rz2k 7y ago
  It is from relational algebra used in database theory. There is an excerpt from one of the first MOOCS offered here on Lagunitas now.[1] It is pretty intuitive once you get the hang of it. [1] https://lagunita.stanford.edu/courses/DB/RA/SelfPaced/course/ https://lagunita.stanford.edu/courses/DB/RA/SelfPaced/course...
  - graphpapa 7y ago
    Thank you for this context
bloopernova 7y ago
Thank you, and thank you (really, not sarcasm) for the new stuff I have to learn about relational algebra. I'm a huge fan of wide/shallow knowledge that allows me to dive into a subject quickly.
thomas2718 7y ago
Indeed, and with a bit of tuning (e.g., using mawk for most things), one can get quite good performance. [1] The project also provides a translator from Datalog to bash scripts [2]. Disclaimer: I was one of the authors [1] https://www.thomasrebele.org/publications/2018_report_bashlog.pdf https://www.thomasrebele.org/publications/2018_report_bashlo... [2] https://www.thomasrebele.org/projects/bashlog/datalog https://www.thomasrebele.org/projects/bashlog/datalog

by nextos 7y ago

agumonkey 7y ago

ntfsql dreams

chongli 7y ago

Bravo! This is one of the most insightful comments I've read in a long time! I have been using some of these tools for years but I never thought of describing them this way. Now I can think of writing a complex query in relational algebra and translating it into these commands in a very natural way.

_TwoFinger 7y ago
Here's an interesting article that links shell scripting and relational algebra - http://matt.might.net/articles/sql-in-the-shell/ http://matt.might.net/articles/sql-in-the-shell/

graphpapa 7y ago

I’m pretty mathsy but I don’t get this

rz2k 7y ago
It is from relational algebra used in database theory. There is an excerpt from one of the first MOOCS offered here on Lagunitas now.[1] It is pretty intuitive once you get the hang of it. [1] https://lagunita.stanford.edu/courses/DB/RA/SelfPaced/course/ https://lagunita.stanford.edu/courses/DB/RA/SelfPaced/course...
- graphpapa 7y ago
  Thank you for this context

bloopernova 7y ago

Thank you, and thank you (really, not sarcasm) for the new stuff I have to learn about relational algebra. I'm a huge fan of wide/shallow knowledge that allows me to dive into a subject quickly.

thomas2718 7y ago

Indeed, and with a bit of tuning (e.g., using mawk for most things), one can get quite good performance. [1] The project also provides a translator from Datalog to bash scripts [2]. Disclaimer: I was one of the authors [1] https://www.thomasrebele.org/publications/2018_report_bashlog.pdf https://www.thomasrebele.org/publications/2018_report_bashlo... [2] https://www.thomasrebele.org/projects/bashlog/datalog https://www.thomasrebele.org/projects/bashlog/datalog