how to fix postgres after updating/upgrading brew

Question

I upgraded to mavericks and had some trouble installing/compiling new gems so I reinstalled xcode and did a brew update and upgrade. Gems work now, and even postgres continued to work for a while until a recent reboot. Now postgres seems to be having issues.

postgres:

postgres does not know where to find the server configuration file.
You must specify the --config-file or -D invocation option or set the PGDATA environment variable.


brew info postgres:

postgresql: stable 9.3.2 (bottled)
http://www.postgresql.org/
Conflicts with: postgres-xc
/usr/local/Cellar/postgresql/9.2.4 (2842 files, 39M)
  Built from source
/usr/local/Cellar/postgresql/9.3.2 (2924 files, 39M) *
  Poured from bottle

postgres -D /usr/local/var/postgres:

FATAL:  database files are incompatible with server
DETAIL:  The data directory was initialized by PostgreSQL version 9.2, which is not compatible with this version 9.3.2.

What should I do now to get my database working again?

Answer 1

For 9.2 to 9.5, on El Capitan, I ran into a couple problems which might help others.

It seems now the name of the package used in the switch statement has changed to include the version number (postgresql92 vs postgresql). So, I needed to have the added step of unlinking the current version of postgres:

brew unlink postgresql
brew link postgresql92
brew switch postgresql92 9.2.13 # match version

In order to perform the dump I needed to start the postgres server,

pg_ctl -D /usr/local/var/postgres -l /usr/local/var/postgres/server.log start

But then I ran into the dreaded:

psql: could not connect to server: No such file or directory
    Is the server running locally and accepting
    connections on Unix domain socket "/tmp/.s.PGSQL.5432"?

I check out the logs and found this:

could not open directory "pg_tblspc": No such file or directory

According to this answer by Donovan, Yosemite and El Capitan remove some needed directories. So I also needed to add those directories back in using this awesome command by Nate

mkdir /usr/local/var/postgres/{pg_tblspc,pg_twophase,pg_stat,pg_stat_tmp,pg_replslot,pg_snapshots}/

So the full updated version is:

brew tap homebrew/versions
brew install postgresql92
brew unlink postgresql
brew switch postgresql92 9.2.13 # might need to check this one, could be newer by the time you read this
mkdir /usr/local/var/postgres/{pg_tblspc,pg_twophase,pg_stat,pg_stat_tmp,pg_replslot,pg_snapshots}/
pg_ctl -D /usr/local/var/postgres -l /usr/local/var/postgres/server.log start
pg_dumpall > ninedottwo-dump
pg_ctl -D /usr/local/var/postgres stop
brew unlink postgresql92
brew uninstall postgresql92
brew switch postgresql 9.5.2 # again, check version
pg_ctl -D /usr/local/var/postgres -l /usr/local/var/postgres/server.log start
createdb # i got an error about my database not existing, so i had to run this
psql < ninedottwo-dump
bundle install # need to make sure you have pg gem for 9.5
bundle exec rails s

All credit goes to sentinel, Nate, and Donovan. Thanks so much!

Answer 2

You need to get a copy of PostgreSQL 9.2 installed somehow, to be able to access the existing data directory.

Options for installing 9.2 via Homebrew include:

• Get a checkout of Homebrew from before the postgresql formula was upgraded to 9.3.
• Install postgresql92 from homebrew/versions tap.
• Install postgresql-9.2 from petere/postgresql tap (disclosure: that's my project).
• Install from source.

Then you ought to upgrade that to 9.3 using either pg_dump or pg_upgrade.

pg_upgrade comes for this very purpose, and using it is straightforward. Just make sure you're specifying the right paths for the old data and binaries ( -d and -b ) and the right paths to the new data and binaries (-D and -B):

pg_upgrade \
-d /usr/local/var/postgres/9.2/ -D /usr/local/var/postgres/9.3/ \
-b /usr/local/Cellar/postgresql/9.2.4/bin/ -B /usr/local/Cellar/postgresql/9.3.2/bin/

If everything goes fine, you can then cleanup old versions with brew cleanup postgresql, and since a new version of PostgreSQL means new versions of the native libraries that are used by the Ruby pg gem, you may want to recompile it:

gem uninstall pg
ARCHFLAGS="-arch x86_64" gem install pg

Answer 3

$ brew tap homebrew/versions
$ brew install postgresql92
$ brew switch postgresql 9.2.8 # might need to check this one, could be newer by the time you read this
$ pg_dumpall > ninedottwo-dump
$ brew uninstall postgresql92
$ brew switch postgresql 9.3.4 # again, check version
$ pg_ctl -D /usr/local/var/postgres -l /usr/local/var/postgres/server.log start
$ createdb # i got an error about my database not existing, so i had to run this
$ psql < ninedottwo-dump
$ bundle exec rails s

Thanks to Peter for getting me started in the right direction.

edit: this'll teach me to upgrade everything all at once...