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(dot)stehule(at)gmail(dot)com
> <mailto:pavel(dot)stehule(at)gmail(dot)com>> wrote:
>
>
>
> 2015-04-13 10:43 GMT+02:00 Albe Laurenz <laurenz(dot)albe(at)wien(dot)gv(dot)at
> <mailto:laurenz(dot)albe(at)wien(dot)gv(dot)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