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Date: 29 Aug 1995 03:41:00 +0100
From: dirk@luedi.tng.oche.de (Dirk Lütjens)
To: postgres@postgres.Berkeley.EDU
Message-ID: <5smCBOGPJAB@luedi.tng.oche.de>
Subject: different questions
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Resent-Date: Mon, 28 Aug 95 19:03:54 -0700
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Hello,

my Name is Dirk, and I'm new in working with postgres 4.2. Therefor there
are a lot of questions for me. I've already read the manual, the manpages, 
the tutorial and other papers related to postgres, but didn't fond the
answers to my questions. 
I'm working with Linux 1.2.6 on a i486.

1.) I like to create a new datatype e.g. with

	define function circle_in 
		(language ="c", returntype =circle) 
		arg is (any)
		as "/usr/local/postgres/src/examples/circle.o" \g
	define function circle_out 
		(language ="c", returntype =any) 
		arg is (any)
		as "/usr/local/postgres/src/examples/circle.o" \g
	define type circle
		(internallength = 24,
		 input = circle_in, output = circle_out)  \g

	and correct C-Functions.
    There is no problem with the datatype. But what to do if the input data
    to circle_in has not the correct form. e.g. I would like to make a range
    check in the circle_in c-function. How can I tell postgres, not to append
    the new tuple with this bad data. Returning a NULL don't work.

2.) Isn't there another possibility to create complexe user types
    except converting the abstract data to a string, sending it as a String 
    to postgres, converting it to abstract data, and vice versa. 

3.) How to handle portals?
 a.)Let's think I created a class with
	create Name (Familiename=string, Name = string, ...)\g
    and filled it with usefull data
	append Name (Familiename="Bollo", Name = "Hain", ...)\g
	append Name (Familiename="Tull", Name ="Jethro", ....)\g
    
    I started a query with
	begin\g
	retrieve portal test (Name.all)\g
	fetch 1 in test\g
    I got
	---------------------------------------------------
	| Familiename | Name        | ...
	---------------------------------------------------
	| Bollo       | Hain        | ...
	---------------------------------------------------
    again
	fetch 1 in test\g
	---------------------------------------------------
	| Familiename | Name        | ...
	---------------------------------------------------
	| Tull        | Jethro      | ...
	---------------------------------------------------
     The next fetch will produce only the header
	fetch 1 in test\g
	---------------------------------------------------
	| Familiename | Name        | ...
	---------------------------------------------------
     and a fetch backward don't work correct
	fetch backward 1 in test\g
	---------------------------------------------------
	| Familiename | Name        | ...
	---------------------------------------------------
     Closing the portal will produce
	close test\g
	NOTICE:Aug 29 02:51:35:PortalHeapMemoryFree: 0x1d6f90 not in alloc set!
	NOTICE:Aug 29 02:51:35:PortalHeapMemoryFree: 0x1d6f50 not in alloc set!

     WHY, and how to get around this?

 b.) In the postgres related paper "The Design of Postgres" is written:
	" ...
		replace EMP(salary=NewSalary)
		where EMP.name="Smith"
		fetch 20 into P
	The Replace command modifies Smith's tuple in the EMP relation and 
	the Fetch command synchronizes the buffer ... "
     But not in my version. When I replace a tuple in the database and
     try to get the updated tuple out of the database with
	fetch backward 1 in P\g
	fetch 1 in P\g
     I'll get the old version. After
	close P\g
	end\g
	begin\g
	retrieve ...
	fetch 20 into P\g
     the updated tuple is ok. How to get around first ending the transaction?

4.) Is there anybody out there?
	I'am subscribed to the postgres newsgroup since one month. But
	I got only one mail with a question. I would like to read the
        answers too, if there are any, or are the answers privat ?-)

Huh, that was a long one. I hope somebody out there can help me. 

Hope to hear something

Dirk


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