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advice on extensions needed

From: Brook Milligan <brook(at)biology(dot)nmsu(dot)edu>
To: pgsql-hackers(at)postgresql(dot)org
Subject: advice on extensions needed
Date: 2000-08-25 14:08:50
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Lists: pgsql-hackers
I'm in the process of extending PostgreSQL and need a bit of advice
that I don't seem to get from the manuals.

- When dynamically linking functions must there be at most one
  function per shared object module or can there be multiple external
  entry points within a single shared object?

- If the latter, will multiple copies of the file be loaded (e.g., one
  per function invoked) or will the same copy be used to resolve all
  the multiple external entry points?

- I am writing some functions to handle some new types.  These
  functions logically should share code.  How should the shared object
  modules be structured in order to allow code sharing among
  functions?  (This question is obviously related to the previous

- Is it possible to write functions to automatically convert one
  extended type into another?  If so, how should this be done?

- Some of my types will be complex and so it makes sense to have
  functions extract components of the types (an analogy is what
  datepart() does).  Should such functions return character strings or
  some other type?  If they return an appropriate built-in (or
  extended?) type will the needed conversion be provided
  automatically depending on context?

By the way, the new web pages seem to be missing some links.  For
example, the "users-lounge/documentation" link just goes to a
directory; shouldn't there be an actual page with links to the various
components of the documentation?

Also, in the docs for Chapter 5. Extending SQL: Types there is a code
example with the following:

	elog(WARN, ...);

elog.h does not define WARN.  Should this be changed to NOTICE in the

Thanks for your help.



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