Re: SQL/PSM implemenation for PostgreSQL (roadmap)

>Am Montag, 4. Dezember 2006 13:09 schrieb Pavel Stehule:
> > I am work on implementation of SQL/PSM language for PostgreSQL.
>
>Do you have an analysis of the differences between PL/pgSQL and SQL/PSM?
>It
>seems they might be variants of the same language rather than separate
>implementations, but no one knows for sure.

Some changes are cosmetic, and some not. You can see on current sql/psm
runtime rewriting gram.y and minimal changes in other files. But this
languages are really different. The mayor difference is in exception
handling. The idea is total different.

Individual chapter is sql/psm procedures and unbounded select. SQL/PSM
propably don't need it, but current implementations support it. This has
deeper reasons, one is different concept of return output sets in Oracle and
Sybase based databases. I like this concept (unbounded selects) but it isn't
part of sql/psm and it isn't current topic.

What I had to solve. In sql/psm is sqlstate more important and designates
level of error. In Postgresql sqlstate and error level are independent.
Next, I can solve exception and warnings in sql/psm 3 diffirent ways.
PostgreSQL and (PL/SQL) can handle only exception in one way. I belive so
some procedures, can be shared, but current runtime use global variables
which break sharing.

Other are similar (semantic), but s syntax is total different. Please, see
syntax for declare variables. I don't know history about SQL/PSM (know it
anybody?) and I don't know why is sql/psm different from pl/sql. Older
version of sql/psm was similar to oracle's language.

Every RDBMS supports only subset of SQL/PSM (some parts are unspecified).
Its main goal for me for now - create referential implementation. Next steps
are far. You can belive, I can spent long time in searching of any sources
for sql/psm. One is only and it is ISO/IEC 9075-4.

Best regards

Pavel Stehule

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