Note about comparation PL/SQL packages and our schema/extensions

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От Pavel Stehule
Тема Note about comparation PL/SQL packages and our schema/extensions
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Msg-id CAFj8pRDAdUwJNANY9ZbK3Atp0NXt8hCKqo4=ybc+nutFer+bfA@mail.gmail.com
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Ответы Re: Note about comparation PL/SQL packages and our schema/extensions
Re: Note about comparation PL/SQL packages and our schema/extensions
Список pgsql-hackers
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Hi

I had talk about possibility to implement PL/SQL packages in Postgres.

The package concept is coming from ADA language and it is partially foreign/redundant element in SQL world. Oracle needs it for modularization, because schema plays different role there than in Postgres. My opinion about packages in Postgres is clean - the concept of schemas and extension is simple and just work. I don't see any big gap there. If we don't play Oracle compatibility game, then we don't need to implement class like Oracle package. But there are few features, that can help to PL/pgSQL developers - generally or with porting from Oracle.

1. The encapsulation and local scope - all objects in schema are accessible from other objects in schema  by default (can be rewritten by explicit granting). Local objects are visible only from objects in schema. This needs enhancing of our search_path mechanism.

2. The schema variables - a server side session (can be emulated now) and server side local schema session variables (doesn't exist) is pretty useful for storing some temp data or high frequent change data - and can significantly increase speed of some use cases. Now we emulate it via PLPerl shared array, but the encapsulation is missing.

3. The initialization routines - the routines called when any object from schema is used first time.

All three features we can emulate relative simply in C, and probably for all mentioned points we have some workaround (less/more ugly) for PL/pgSQL. Can be nice do it cleanly in PLpgSQL too.

I don't think we need ADA/ | PL/SQL Syntax - we can enhance our extension mechanism to support mentioned points.

Comments, notes?

Regards

Pavel

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