Remove view TODO.detail.

doc/TODO.detail/view

-From pgsql-general-owner+M10387@postgresql.org Mon Jun  4 22:02:55 2001
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-To: Rasmus Resen Amossen <spunk@rhk.dk>
-cc: pgsql-general@postgresql.org
-Subject: Re: [GENERAL] Re: Updating views 
-In-Reply-To: <3B1C16EC.8D9FB57B@rhk.dk> 
-References: <20010605001048.A2133@lorien.net> <3B1C16EC.8D9FB57B@rhk.dk>
-Comments: In-reply-to Rasmus Resen Amossen <spunk@rhk.dk>
-	message dated "Tue, 05 Jun 2001 01:17:00 +0200"
-Date: Mon, 04 Jun 2001 21:42:57 -0400
-Message-ID: <9925.991705377@sss.pgh.pa.us>
-From: Tom Lane <tgl@sss.pgh.pa.us>
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-Rasmus Resen Amossen <spunk@rhk.dk> writes:
-> OK, but I can't see how to make a single rule that allows me to update
-> an arbitray set of attributes from an arbitray where-clause.
-
-The reason the system doesn't do that for you is that it's *hard* to
-figure out what to do for an arbitrary where-clause.  An automatic rule
-has no chance of doing the right thing, because the right thing depends
-on what you intend.  For example, if your view has
-	select ... where a>5;
-what do you think ought to happen if someone tries to insert a row
-with a<5?  Is that an error?  A no-op?  Does the row go in anyway,
-you just can't see it in the view?  Does the row go into some other
-table instead?  Is it OK to change the A column at all?  It all depends
-on the semantics of your database design.  So you have to figure out
-what you want and write rules that do it.
-
-The mechanics of the rule are not that painful once you've decided what
-the reverse mapping from inserted/updated data to underlying tables
-ought to be.  One thing that may help is to realize that you don't need
-a separate rule for each combination of set of attributes that might be
-updated.  "new.*" is defined for all columns including the ones that
-didn't change, so you can just do something like
-
-	update ... set f1 = new.f1, f2 = new.f2, ...
-
-without worrying about just which columns the user tried to update.
-Likewise, the where clause in the user's query is not yours to worry
-about; that condition gets added onto the stuff in your rule.
-
-> In other words: I want to make the update of 'exview' transparent to
-> 'extable'.
-
-If it's really transparent, one wonders why you bothered with a view
-at all.  Useful views tend to be nontrivial mappings of the underlying
-data, which is why it's nontrivial to figure out what the reverse
-mapping ought to be.
-
-			regards, tom lane
-
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