Re: How to create c language in postgresql database. Thanks.

On 06/13/2012 03:35 AM, leaf_yxj wrote:
> Hi John,
> Thanks for your useful info. I really apprecaite it. I got this
> problem when the SAS application try to install the scoring model. So
> I am very confused.
> > 1) What's the info in .dll/.so ?
>
> thats the binary code compiled and linked from C, windows calls this
> DLL (Dynamic Link Library), while unix usually calls it SO (Shared
> Object). Mac OSX has yet another name (dylib or something).
> ---- Grace comments : this need the superuser privileges on the server
> to copy those .so ( we are on the linux server) to the postgresql
> server ?
> correct ????
And to dynamically link them into the PostgreSQL executable to run them.

Most importantly, you have to COMPLTELY AND UTTERLY TRUST YOUR DEV TEAM.
If you let them install a C library they've written, you've given them
total power over your database, so they can just use their C function to
give themselves superuser privs if they want it. This isn't a bad thing;
C functions are extremely fast and powerful tools in a database, you
just have to trust the person or people who wrote them.

A C library also has much greater opportunity to muck up your database.
In particular it can crash database backends very easily. You need to
know the people who wrote it are competent and tested it well in a
non-production environment.

You need to read about "dlopen" or "LoadLibrary", about dynamic linking,
about compilation and shared libraries in C, etc. Right now you don't
have the background in how this works to make appropriate decisions; you
have to either trust your dev team to do the right thing, or tell them
to do what they need to without using a C library and accept that may
mean you're stopping them from doing their jobs properly.

> > 2) .sql scrap is the binary installation file?
>
> the .sql is the CREATE FUNCTION statement mostly.
> --- Grace comments : we already grant create privileges on the saslib
> schema. So it means they can this scrap by themselves ???

No, you have to be a superuser to install C functions, because they have
*total* access to all of PostgreSQL and can bypass all security and
authentication completely.

--
Craig Ringer