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Update TODO list.
This commit is contained in:
Bruce Momjian
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@ -528,3 +528,89 @@ Jan
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From owner-pgsql-hackers@hub.org Thu Sep 23 11:01:06 1999
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Thu, 23 Sep 1999 10:18:02 -0400 (EDT)
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To: wieck@debis.com (Jan Wieck)
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cc: pgsql-hackers@postgreSQL.org
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Subject: Re: [HACKERS] Progress report: buffer refcount bugs and SQL functions
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In-reply-to: Your message of Thu, 23 Sep 1999 03:19:39 +0200 (MET DST)
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<m11TxXw-0003kLC@orion.SAPserv.Hamburg.dsh.de>
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Date: Thu, 23 Sep 1999 10:18:01 -0400
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Message-ID: <13251.938096281@sss.pgh.pa.us>
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From: Tom Lane <tgl@sss.pgh.pa.us>
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Sender: owner-pgsql-hackers@postgreSQL.org
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Precedence: bulk
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Status: RO
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wieck@debis.com (Jan Wieck) writes:
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> Tom Lane wrote:
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>> What I am wondering, though, is whether this addition is actually
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>> necessary, or is it a bug that the functions aren't run to completion
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>> in the first place?
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> I've said some time (maybe too long) ago, that SQL functions
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> returning tuple sets are broken in general.
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Indeed they are. Try this on for size (using the regression database):
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SELECT p.name, p.hobbies.equipment.name FROM person p;
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SELECT p.hobbies.equipment.name, p.name FROM person p;
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You get different result sets!?
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The problem in this example is that ExecTargetList returns the isDone
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flag from the last targetlist entry, regardless of whether there are
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incomplete iterations in previous entries. More generally, the buffer
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leak problem that I started with only occurs if some Iter nodes are not
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run to completion --- but execQual.c has no mechanism to make sure that
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they have all reached completion simultaneously.
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What we really need to make functions-returning-sets work properly is
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an implementation somewhat like aggregate functions. We need to make
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a list of all the Iter nodes present in a targetlist and cycle through
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the values returned by each in a methodical fashion (run the rightmost
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through its full cycle, then advance the next-to-rightmost one value,
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run the rightmost through its cycle again, etc etc). Also there needs
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to be an understanding of the hierarchy when an Iter appears in the
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arguments of another Iter's function. (You cycle the upper one for
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*each* set of arguments created by cycling its sub-Iters.)
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I am not particularly interested in working on this feature right now,
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since AFAIK it's a Berkeleyism not found in SQL92. What I've done
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is to hack ExecTargetList so that it behaves semi-sanely when there's
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more than one Iter at the top level of the target list --- it still
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doesn't really give the right answer, but at least it will keep
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generating tuples until all the Iters are done at the same time.
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It happens that that's enough to give correct answers for the examples
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shown in the misc regress test. Even when it fails to generate all
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the possible combinations, there will be no buffer leaks.
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So, I'm going to declare victory and go home ;-). We ought to add a
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TODO item along the lines of
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* Functions returning sets don't really work right
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in hopes that someone will feel like tackling this someday.
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regards, tom lane
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************
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@ -1,86 +0,0 @@
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From owner-pgsql-hackers@hub.org Thu Sep 23 11:01:06 1999
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Thu, 23 Sep 1999 10:18:02 -0400 (EDT)
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To: wieck@debis.com (Jan Wieck)
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||||
cc: pgsql-hackers@postgreSQL.org
|
||||
Subject: Re: [HACKERS] Progress report: buffer refcount bugs and SQL functions
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In-reply-to: Your message of Thu, 23 Sep 1999 03:19:39 +0200 (MET DST)
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<m11TxXw-0003kLC@orion.SAPserv.Hamburg.dsh.de>
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Date: Thu, 23 Sep 1999 10:18:01 -0400
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Message-ID: <13251.938096281@sss.pgh.pa.us>
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From: Tom Lane <tgl@sss.pgh.pa.us>
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Sender: owner-pgsql-hackers@postgreSQL.org
|
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Precedence: bulk
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Status: RO
|
||||
|
||||
wieck@debis.com (Jan Wieck) writes:
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> Tom Lane wrote:
|
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>> What I am wondering, though, is whether this addition is actually
|
||||
>> necessary, or is it a bug that the functions aren't run to completion
|
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>> in the first place?
|
||||
|
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> I've said some time (maybe too long) ago, that SQL functions
|
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> returning tuple sets are broken in general.
|
||||
|
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Indeed they are. Try this on for size (using the regression database):
|
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|
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SELECT p.name, p.hobbies.equipment.name FROM person p;
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SELECT p.hobbies.equipment.name, p.name FROM person p;
|
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|
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You get different result sets!?
|
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|
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The problem in this example is that ExecTargetList returns the isDone
|
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flag from the last targetlist entry, regardless of whether there are
|
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incomplete iterations in previous entries. More generally, the buffer
|
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leak problem that I started with only occurs if some Iter nodes are not
|
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run to completion --- but execQual.c has no mechanism to make sure that
|
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they have all reached completion simultaneously.
|
||||
|
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What we really need to make functions-returning-sets work properly is
|
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an implementation somewhat like aggregate functions. We need to make
|
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a list of all the Iter nodes present in a targetlist and cycle through
|
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the values returned by each in a methodical fashion (run the rightmost
|
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through its full cycle, then advance the next-to-rightmost one value,
|
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run the rightmost through its cycle again, etc etc). Also there needs
|
||||
to be an understanding of the hierarchy when an Iter appears in the
|
||||
arguments of another Iter's function. (You cycle the upper one for
|
||||
*each* set of arguments created by cycling its sub-Iters.)
|
||||
|
||||
I am not particularly interested in working on this feature right now,
|
||||
since AFAIK it's a Berkeleyism not found in SQL92. What I've done
|
||||
is to hack ExecTargetList so that it behaves semi-sanely when there's
|
||||
more than one Iter at the top level of the target list --- it still
|
||||
doesn't really give the right answer, but at least it will keep
|
||||
generating tuples until all the Iters are done at the same time.
|
||||
It happens that that's enough to give correct answers for the examples
|
||||
shown in the misc regress test. Even when it fails to generate all
|
||||
the possible combinations, there will be no buffer leaks.
|
||||
|
||||
So, I'm going to declare victory and go home ;-). We ought to add a
|
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TODO item along the lines of
|
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* Functions returning sets don't really work right
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in hopes that someone will feel like tackling this someday.
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regards, tom lane
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************
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119
doc/TODO.detail/null
Normal file
119
doc/TODO.detail/null
Normal file
@ -0,0 +1,119 @@
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From owner-pgsql-general@hub.org Fri Oct 9 18:22:09 1998
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To: pgsql-general@postgreSQL.org
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Subject: Re: [GENERAL] Making NULLs visible.
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Message-ID: <Pine.GSO.3.96.981009181716.545B-100000@gecko>
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MIME-Version: 1.0
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On Fri, 9 Oct 1998, Bruce Momjian wrote:
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> [Charset iso-8859-1 unsupported, filtering to ASCII...]
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> > > Yes, \ always outputs as \\, excepts someone changed it last week, and I
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> > > am requesting a reversal. Do you like the \N if it is unique?
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> >
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> > Well, it's certainly clear, but could be confused with \n (newline). Can we
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> > have \0 instead?
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>
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> Yes, but it is uppercase. \0 looks like an octal number to me, and I
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> think we even output octals sometimes, don't we?
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>
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my first suggestion may have been hare-brained, but why not just make the
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specifics of the output user-configurable. So if the user chooses \0, so
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be it, if the user chooses \N so be it, if the user likes NULL so be it.
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but the option would only have one value per database at any given point
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in time. so database x could use \N on tuesday and NULL on wednesday, but
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database x could never have two references to the characters(s) used to
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represent a null value.
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steve
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From owner-pgsql-general@hub.org Sun Oct 11 17:31:08 1998
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Date: Sun, 11 Oct 1998 16:28:41 -0400 (EDT)
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From: Thomas Good <tomg@admin.nrnet.org>
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To: pgsql-general@postgreSQL.org
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Subject: Re: [GENERAL] Making NULLs visible.
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In-Reply-To: <Pine.GSO.3.96.981009181716.545B-100000@gecko>
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Watching all this go by...as a guy who has to move alot of data
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from legacy dbs to postgres, I've gotten used to \N being a null.
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My vote, if I were allowed to cast one, would be to have one null
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and that would be the COPY command null. I have no difficulty
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distinguishing a null from a newline...
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At the pgsql command prompt I would find seeing \N rather reassuring.
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I've seen alot of these little guys.
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---------- Sisters of Charity Medical Center ----------
|
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Department of Psychiatry
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----
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Thomas Good <tomg@q8.nrnet.org>
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Coordinator, North Richmond C.M.H.C. Information Systems
|
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75 Vanderbilt Ave, Quarters 8 Phone: 718-354-5528
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Staten Island, NY 10304 Fax: 718-354-5056
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