Re: psql backward compatibility

On 11/18/20 8:05 AM, Stephen Haddock wrote:
> Hello,
> 
> When upgrading an older version of postgres, version 8.4 for example, to 
> a newer version such as 9.6, does the data have to be migrated immediately?
> 
> It looks like the recommended method is to dump the data, upgrade, 
> initialize a new cluster, and then restore the dumped data into the 
> newer version. My question is whether the data dump and restore must be 
> done immediately. It appears that 9.6 is able to run against the older 
> cluster (DB service starts, queries work, etc), and the data could be 
> migrated days or weeks later. I don't know if that is asking for issues 
> down the line though such as 9.6 corrupting the data due to 
> incompatibilities between the two versions.

https://www.postgresql.org/docs/9.6/app-pgdump.html

"Because pg_dump is used to transfer data to newer versions of 
PostgreSQL, the output of pg_dump can be expected to load into 
PostgreSQL server versions newer than pg_dump's version. pg_dump can 
also dump from PostgreSQL servers older than its own version. 
(Currently, servers back to version 7.0 are supported.) "


The above is for Postgres 9.6 version of pg_dump. Newer versions(10+) go 
back to Postgres 8.0.  You can dump the old server at anytime. The 
important thing to remember is to dump the old server using the new 
servers version of pg_dump. So in your case pg_dump(9.6) against 
server(8.4).

> 
> Thanks!


-- 
Adrian Klaver
adrian.klaver@aklaver.com