Re: schema or database

On 4/13/15 6:21 AM, Anil Menon wrote:
> In addition to all these comments
>
> - If you use multiple databases, if you want to keep some "common"
> tables (example counties_Table, My_company_details), its going to be a pain
> - if you want to access tables across databases - you might need to
> start using FDWs (which is going to be a administrative pain - syncing
> passwords and stuff)
> - you could set up security easier with multiple schemas - example userA
> can only use schema A and no access to other schemas

Please don't top-post.

> On Mon, Apr 13, 2015 at 4:48 PM, Pavel Stehule <pavel.stehule@gmail.com
> <mailto:pavel.stehule@gmail.com>> wrote:
>
>
>
>     2015-04-13 10:43 GMT+02:00 Albe Laurenz <laurenz.albe@wien.gv.at
>     <mailto:laurenz.albe@wien.gv.at>>:
>
>         Michael Cheung wrote:
>         > I have many similar database to store data for every customer.
>         > Structure of database is almost the same.
>         > As I use same application to control all these data, so I can only use
>         > one database user to connect to these database.
>         > And I have no needs to query table for different customer together.
>         >
>         > I wonder which I should use, different shema or different database to store data?
>         >
>         > I 'd like to know the advantage and disadvantage for using schema or database.
>
>         In addition to what others have said:
>
>         If you use multiple schemas within one database, the danger is
>         greater that
>         data are written to or read from the wrong schema if your
>         application has a bug
>         ans does not make sure to always set search_path or qualify
>         every access with a
>         schema name.
>
>         With multiple databases you are guaranteed not to access data
>         from a different
>         database.
>
>         The main downside that I see to multiple databases is the
>         overhead: each of
>         the databases will have its own pg_catalog tables.
>
>
>     It can be advantage - if your schema is pretty complex - thousands
>     procedures, tables, then separate pg_catalog can be better - there
>     are issues with pg_dump, pg_restore.
>
>     So it depends on catalog size and complexity.

Two things no one has mentioned. First, you could also use row-level
security. If you plan on each customer having a fairly small amount of
data, this is by far your most efficient option. Anything else will
result in either huge catalogs or a lot of wasted catalog space.

Second, if you do per-database, that makes it trivial to scale across
multiple servers.

Regarding backups; you can easily do partial either way with pg_dump;
there's really no difference. You can't do partial with PITR, but that's
true for both schema and database.
--
Jim Nasby, Data Architect, Blue Treble Consulting
Data in Trouble? Get it in Treble! http://BlueTreble.com