[Exherbo-dev] PostgreSQL packge split and slotting

Thomas Berger loki at lokis-chaos.de
Mon Aug 20 08:50:17 UTC 2018

Hi all, 

i have proposed a MR[1] for the PostgreSQL package.

The main reason for this MR is they way PostgreSQL handles upgrades.

The best practice is to use the `pg_upgrade` utility. But this tool needs both 
( meaning "old" and "new" ) major versions installed. currently, the user will 
have to dump and import the complete database, to do an upgrade.

Another reason for this is, that as a PostgreSQL DBA and developer, i need to 
test certain things against different versions of the database. Other people 
may have the same needs.

During the development process for the slotting of dev-db/postgresql, there 
was some discussion how to handle the PostgreSQL client binaries.

Best practice for PostgreSQL is, to use always the latest binaries. This could 
be done with alternatives, but there are some caveats with this:

- handling alternatives is a pain in the ass.
- removing the highest slot of the package (because it is unused, does not 
work with the used software, ...) may break things. 
-- Depending on the "best version" may be a solution, but it adds unneeded 
dependencies. libpq is downwards compatible, meaning that nevers versions of 
the library will work with programs linked against an older version. So, there 
is not always a need to rebuild, just because the "best slot during 
installation" was removed.

- the biggest issue is `pg_config`. As pg_config is used to find the correct 
library paths it would always point to the slotted install directory, making 
the dependencies for clients even worse. And the same tool is used for server-
side extensions, which require to always be build against the correct server 
version. Fiddling with pg_config would be nasty and could break some things 
very hard. 

So, i decided to split the package in client ( unslotted ) and a slotted 
server package.

I used the instruction from the PostgreSQL Docs[2] for the client only 
installation as a base for potsgresql-client. 

[1] https://gitlab.exherbo.org/exherbo/arbor/merge_requests/143
[2] https://www.postgresql.org/docs/10/static/install-procedure.html

So long, 

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