Hello all!
Our company has some headaches in our application development
and deployment process. The chief problem is, "creating stages",
which to this audience is, cloning a database efficiently,
making and testing a few changes, perhaps recording the
differences between databases, and then dropping the database.
I'm eternally grateful for someone who pointed out that we
should be using "CREATE DATABASE ... WITH TEMPLATE". However,
this has two big disadvantages. First, it only works if you
can kick the users off the clone. Secondly, it still takes
time, uses disk space, etc. We have some big databases.
I was also thinking about using ZFS with PostgreSQL to do
some sort of copy-on-write. However, this would require me
to spawn a whole *new* PostgreSQL instance. In both of these
cases, you lose your cache...
So, I was wondering... could PostgreSQL grow the ability to
"CLONE" a database by re-using existing file system blocks,
sharing them across databases? This would perhaps be fast,
keep the shared memory cache relevant for both the old copy
and the clone, and remove WAL overhead. Then, if the block
has to be edited, it'd be cloned in memory, and the clone
would be flushed.
I'm just imagining a world where "deploying" a new version
of our software that makes very small catalog changes and
tweaks a few rows would be... quick. Quick to try, check,
test, and even deploy on live servers.
Best,
Clark
