Archive for August, 2016

31 August, 2016

My Picks for PgOpen 2016

by gorthx

We’re back in Dallas for our 6th year of PostgresOpen!  This year, we’re out at the Westin Galleria, which I’m told has an ice rink. (Is it too late for someone bring the Slonik costume?)

In addition to choosing the talks for the program, part of my conference committee duties involve being a room host. I won’t get to see everything I want, but here’s five that are at the top of my “wish list”:

  • Denish Patel’s Advanced Postgres monitoring – always looking for ways to do this better
  • *Of course* I will be in Grant McAlister’s RDS talk
  • Shaun Thomas clearly and simply explains even advanced topics, and I usually come out of the room thinking “BOY am I glad I don’t have to deal with THAT situation”. This year is Elephant Herd as a Service
  • Sounds like there are some “interesting” stories behind Ilya Kosmodemiansky’s PostgreSQL Worst Practices
  • And we are really excited to have Alexander Korotkov and Oleg Bartunov join our conference to talk about RUM indexes!

A couple of other sessions I recommend:

Check out Dimitri Fontaine’s You’d Better Have Tested Backups ; it’s pretty hair-raising.

Want to contribute back to Postgres, but don’t know where to start? Review some patches! David Steele will give you some pointers.

We will be having Lightning Talks, as usual. If you want to get the jump on everyone else, you can sign up here.

What’s new this year: instead of an auction, we’re having a golf tournament.  I’ve never golfed before and am looking forward to giving it a try. Come join us, it’ll be a hoot. (There is a dress code so pack accordingly if you think you might want to play.)

See you in Dallas in a few weeks! Stop by the reg desk and say hello.

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22 August, 2016

Easy clock dimension table

by gorthx

We’re currently redesigning our data warehouse, and we’re experimenting with a clock (or time, or time-of-day) dimension to represent the time of day, separate from the date dimension we already use. This table should contain a record for each minute of a day, allowing us to easily determine business hours in various timezones, etc etc.

I’m not entirely sure it’s going to work for us just yet; we have a lot of timestamp data, and seems like it’s more trouble than it’s worth1. But it never hurts to proof-of-concept something, right? (Except for all those times the proof-of-concept ends up being the production system…)

Anyway, somebody commented that “you could have the analyst whip up the dataset in just a few hours” … :sideeye: or, I could do it myself in Postgres in just a few minutes:

CREATE TABLE clock_dimension (
 id serial primary key
 , full_timestamp time
 , hour_of_day_24 integer
 , hour_of_day_12 integer
 , am_pm text
 , minute_of_hour integer
 , business_hours_weekday boolean
 , business_hours_weekend boolean
 );

-- fill it with values
INSERT INTO clock_dimension (full_timestamp) VALUES (
generate_series('2016-08-05 00:00'::timestamp, '2016-08-05 23:59'::timestamp, '1 minute')::time
);
UPDATE clock_dimension SET
hour_of_day_24 = date_part('hour', full_timestamp)
, hour_of_day_12 = CASE
WHEN date_part('hour', full_timestamp) > 12
THEN date_part('hour', full_timestamp) - 12
WHEN date_part('hour', full_timestamp) = 0
THEN 12
ELSE date_part('hour', full_timestamp)
END
, am_pm = CASE
WHEN date_part('hour', full_timestamp) >=12
THEN 'pm'
ELSE 'am'
END
, minute_of_hour = date_part('minute', full_timestamp)
, business_hours_weekday = CASE
WHEN full_timestamp BETWEEN '08:00' AND '21:00'
THEN 't'::boolean
ELSE 'f'::boolean
END
, business_hours_weekend = 'f'
;

Sample data:

 id  | full_timestamp | hour_of_day_24 | hour_of_day_12 | am_pm | minute_of_hour | business_hours_weekday | business_hours_weekend 
-----+----------------+----------------+----------------+-------+----------------+------------------------+------------------------
 901 | 15:00:00       |             15 |              3 | pm    |              0 | t                      | f
 902 | 15:01:00       |             15 |              3 | pm    |              1 | t                      | f
 903 | 15:02:00       |             15 |              3 | pm    |              2 | t                      | f
 904 | 15:03:00       |             15 |              3 | pm    |              3 | t                      | f
 905 | 15:04:00       |             15 |              3 | pm    |              4 | t                      | f
 906 | 15:05:00       |             15 |              3 | pm    |              5 | t                      | f
 907 | 15:06:00       |             15 |              3 | pm    |              6 | t                      | f
 908 | 15:07:00       |             15 |              3 | pm    |              7 | t                      | f
 909 | 15:08:00       |             15 |              3 | pm    |              8 | t                      | f
 910 | 15:09:00       |             15 |              3 | pm    |              9 | t                      | f
 911 | 15:10:00       |             15 |              3 | pm    |             10 | t                      | f
 912 | 15:11:00       |             15 |              3 | pm    |             11 | t                      | f
 913 | 15:12:00       |             15 |              3 | pm    |             12 | t                      | f
 914 | 15:13:00       |             15 |              3 | pm    |             13 | t                      | f
 915 | 15:14:00       |             15 |              3 | pm    |             14 | t                      | f
 916 | 15:15:00       |             15 |              3 | pm    |             15 | t                      | f



1 – see also http://www.kimballgroup.com/2004/02/design-tip-51-latest-thinking-on-time-dimension-tables/

1 August, 2016

Upgrade Ubuntu 15.04 to 16.04

by gorthx

I use Ubuntu on my home machines, and tend to rely on the GUI Software Updater for upgrades & such.  Life happens and I left one of them on 15.04 past EOL, and the Software Updater didn’t provide an upgrade path directly to 16.04.  I had to upgrade to 15.10 first, which is also EOL.

Here’s what I pieced together from various forums around the net.  (I took this after-the-fact from my command-line history;  I’ll take better notes next time.)

apt-get update
apt-get upgrade # make sure system is as up-to-date as possible
apt-get autoremove # clean up some leftover crap

apt-get dist-upgrade # recommended next step on one of the forums,
                     # but didn't actually do anything
                     # and I probably could have skipped this

do-release-upgrade -d # supposely this should have worked without the -d
                      # but it didn't
                      # -d means "latest development release"

And booyah, I’m on 15.10 and could continue on to 16.04.