One of my projects just ran into an issue where tests would fail one devs machine and not on another’s! Turns out the issue was that the developers were running different versions of postgres. Postgres made a change between 9.3 and 9.4 where 9.4 queries of not true returned all records with false or null, and, in 9.3., the same queries only returned records with false (null did not count as not true).
Startup code to check the DB version
Let’s alert the team that the version of postgres is not the desired version…
One of my projects is using this bit of code to make sure we’re all on the same version of Postgres. Note, the code does not error out if the version does not match. This is because the wrong version of the DB is often functional, so let’s not stop team members in their tracks!
Upgrading Postgres, with help from zsh
So you might need to update postgres. Here’s a few tips.
I’m using “postgresapp” even though I use brew for most other dependencies on my Mac.
- Download postgresapp: http://postgresapp.com/
- Instructions for upgrading existing DBs: http://postgresapp.com/documentation/install.html
I’ve got a bunch of dbs, so I want to script this
ZSH Script to dump your dbs
dbs=(db_name db_name2 db_etc)
for db in $dbs; do
db_dump="${db}.sql"
echo "RUNNING: pg_dump $db > $db_dump"
pg_dump $db > $db_dump
done
We can do better than using echo to print the line we’re running:
exe() { echo "\$ $@" ; "$@" ; }
dbs=(db_name db_name2 db_etc)
for db in $dbs; do
db_dump="${db}.sql"
exe psql --command="create database $db"
exe psql -d $db -f $db_dump
done
Couple notes:
- Once you’ve defined a variable, like
dbs, you don’t need to run that again in the same shell. - zsh (and all shell scripting) is VERY whitespace sensitive.
- Play around with shell scripting. It’s super useful. Experiment with “echo” to print out what you might execute.
- Very useful to echo important command that you run. That exe function works well:
exe() { echo “$ $@” ; “$@” ; }
## Variations on the for loop
These are all the same.
```zsh
dbs=(d1 d2 d3)
for db in $dbs; do echo $db; done
for db (d1 d2 d3); do echo $db; done
for db in d1 d2 d3; do echo $db; done