StackOverflow2013

Note that there are some explanatory texts on larger screens.

plurals

PODoing an "ORDER BY ... LIMIT ..." style query on a hash in KRL
text
Body
copied!<p>Say I have a hash with a list of delivery drivers (for the classic <a href="http://www.ep-ts.com/content/view/80/111/" rel="nofollow">flower shop scenario</a>). Each driver has a rating and an event signal URL (ESL). I want to raise an event only to the top three drivers in that list, sorted by ranking.</p> <p>With a relational database, I'd run a query like this:</p> <pre><code>SELECT esl FROM driver ORDER BY ranking LIMIT 3; </code></pre> <p>Is there a way to do this in KRL? There are two requirements:</p> <ol> <li>A way to sort the hash</li> <li>A way to limit the number of times a <code>foreach</code> iterates</li> </ol> <p>The second could be solved like this:</p> <pre><code>rule reset_counter { select when rfq delivery_ready noop(); always { clear ent:loop_counter; raise explicit event loop_drivers; } } rule loop_on_drivers { select when explicit loop_drivers foreach app:drivers setting (driver) pre { esl = driver.pick("$.esl"); } if (ent:loop_counter < 3) then { // Signal the driver's ESL } always { ent:loop_counter += 1 from 0; } } </code></pre> <p>But that's kind of kludgy. Is there a more KRL-ish way to do it? And how should I solve the ordering problem?</p> <p>EDIT: Here's the format of the <code>app:drivers</code> array, to make the question easier to answer:</p> <pre><code>[ { "id": "1", "rating": "5", "esl": "http://example.com/esl" }, { "id": "2", "rating": "3", "esl": "http://example.com/esl2" } ] </code></pre>

Querying!

Guidance

An individual column

Larger individual text columns get their own page to allow for proper reading.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload