Links #62

• Public Work Public Work is a search engine for public domain content. Explore 100,000+ copyright-free images from The MET, New York Public Library, and other sources
• My Org Roam Notes Workflow by Hugo Cisneros
• How I publish my digital garden to the web with org-publish

How I use :dbconnection in org files

In the post "Followup on secrets in my work notes" Magnus Therning mentions a feature in Org Babel I contributed to (in ob-sql.el, to be more precise).

You can see my old post for details about that feature, but basically, the patch allows one to use a :dbconnection header argument in a source block to reference a connection defined in sql-connection-alist.

The question in Magnus' post is a signal somebody is actually using this feature, so I am pleased. Perhaps I should also follow up, describing how I use this feature in my workflow. This will constitute another example of how to manage secrets.

I use Org, among other things, to keep work "lab notes" that usually contain SQL queries on different databases.

At work, pretty much all databases are Postgresql or Redshift, and I keep connection details in ~/.pgpass, following this format:

In other words, every DB definition is made of two lines: the first is a comment, with the name of the database (with no spaces); the second contains the actual connection details.

In my Emacs configuration, then, I have this function:

(defun get-connection-alist (filename)
  "Gets PG connections details from ~/.pgpass file (FILENAME)."
  (with-current-buffer (find-file-noselect filename)
        (let ((lines (split-string (buffer-string) "\n" t)))
          (when lines
            (cl-loop for (k v) in (seq-partition lines 2)
                  collect (cl-destructuring-bind (host port db user password)
                              (split-string v ":" nil)
                            `(,(replace-regexp-in-string "^#\s+" "" k)
                              (sql-product 'postgres)
                              (sql-port ,(string-to-number port))
                              (sql-server ,host)
                              (sql-user ,user)
                              (sql-database ,db)
                              (sql-password ,password))))))))

and

(setq sql-connection-alist (get-connection-alist "~/.pgpass"))

I use Emacs in daemon mode and it's not unusual Emacs to stay up for weeks, so I also have an automatic way to incorporate .pgpass changes, using filenotify.

(file-notify-add-watch
 "~/.pgpass" '(change)
 (lambda (evt)
   (setq sql-connection-alist
         (get-connection-alist "~/.pgpass"))))

Links #61

• Calculating Empires — A Genealogy of Technology and Power Since 1500
• Game UI Database
• Galois Theory

The Hygieia Fountain in Hamburg

I recently spent a weekend in Hamburg to visit friends. While exploring the city my attention was caught, for some reason, by the fountain situated in the courtyard of the city hall, and the sculptures that surround it. It's called Hygieia Fountain.

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Hygieia as the goddess of health and hygiene in Greek mythology and its surrounding figures represents the power and pureness of the water. It was built in remembrance of the cholera epidemic in 1892, the former technical purpose was air cooling in the city hall

Links #60

• Stations and transfers

  For the last 10 years I have been able to draw around 1,753 stations from different European cities, motivated by the curiosity of understanding how engineers were able to fit underground stations comprising 4 or 5 lines under Place de la République in Paris or the Puerta del Sol in Madrid.

• Votes on the First Draft Common Lisp Manual with discussions about early Common Lisp
• Metacircular Semantics for Common Lisp Special Forms
• Data Manipulation in Clojure Compared to R and Python