Re: [HACKERS] DEFAULT of domain ignored in plpgsql (8.4.1)
On 21 Nov 2009, at 02:56, Josh Berkus wrote: Would a patch that changes that have any chance of being accepted? Or is the gain (not having to repeat the DEFAULT clause, and being able to maintain it at one place instead of many) considered too small compared to the risk of breaking existing code? I don't think there's a lot of risk of code breakage; few people use domains, fewer use them with defaults, and you might be the only one using them as variable types. And there are going to be more substantial backwards compat issues with the lexer changes anyway. As long as we remember to flag the compatibility issue in the release notes, I don't see it as a problem. we use domains with defaults, a lot. That's one of the purposes of domains, to have certain type, constraint, and default. -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] DEFAULT of domain ignored in plpgsql (8.4.1)
Josh Berkus j...@agliodbs.com writes: (2) this change, while very useful, does change what had been a simple rule (All variables are NULL unless specifically set otherwise) into a conditional one (All variables are NULL unless set otherwise OR unless they are declared as domain types with defaults). Do people feel that the new behavior would be sufficiently intuitive to avoid user confusion? I'm inclined to leave it alone. It complicates the mental model, and frankly attaching defaults to domains was not one of the SQL committee's better ideas anyway. It's *fundamentally* non-orthogonal. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] DEFAULT of domain ignored in plpgsql (8.4.1)
On Sat, Nov 21, 2009 at 7:26 AM, Josh Berkus j...@agliodbs.com wrote:
Would a patch that changes that have any chance of being accepted? Or is
the gain (not having to repeat the DEFAULT clause, and being able to
maintain it at one place instead of many) considered too small compared
to the risk of breaking existing code?
I don't think there's a lot of risk of code breakage; few people use
domains, fewer use them with defaults, and you might be the only one
using them as variable types. And there are going to be more
substantial backwards compat issues with the lexer changes anyway. As
long as we remember to flag the compatibility issue in the release
notes, I don't see it as a problem.
However, there are some other issues to be resolved:
(1) what should be the interaction of DEFAULT parameters and domains
with defaults?
The function's DEFAULT parameter should take precedence over the default of
the domain.
(2) this change, while very useful, does change what had been a simple
rule (All variables are NULL unless specifically set otherwise) into a
conditional one (All variables are NULL unless set otherwise OR unless
they are declared as domain types with defaults). Do people feel that
the new behavior would be sufficiently intuitive to avoid user confusion?
I see this as a straight-forward extension to what we've had till now; and I
bet some users would've definitely expected them to work this way in the
past..
(3) Last I checked, there were still several places in which domains did
not behave consistently in stored procedures. I think that Elein had
some unfinished patches in this regard -- you'll want to search the
archives and the TODO list.
One thing to remember is that, that this behavior should be supported in all
PLs that support domain types as variables.
Best regards,
--
Lets call it Postgres
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Re: [HACKERS] DEFAULT of domain ignored in plpgsql (8.4.1)
Tom Lane wrote: Josh Berkus j...@agliodbs.com writes: (2) this change, while very useful, does change what had been a simple rule (All variables are NULL unless specifically set otherwise) into a conditional one (All variables are NULL unless set otherwise OR unless they are declared as domain types with defaults). Do people feel that the new behavior would be sufficiently intuitive to avoid user confusion? I'm inclined to leave it alone. It complicates the mental model, and frankly attaching defaults to domains was not one of the SQL committee's better ideas anyway. It's *fundamentally* non-orthogonal. I've always though of domains as being a kind of subtype of it's base type. In this picture, DEFAULTs for domains correspond to overriding the default constructor of the type (thinking C++ now), and seem like a natural thing to have. But maybe that's more a C++ programmers than a database designers point of view... I've just checked how rowtypes behave, and while the set to null unless specifically set otherwise rule kind of holds for them, their NULL value seems to be special-cased enough to blur the line quite a bit create or replace function myt() returns t as $body$ declare r t; begin raise notice 'r: %, r is null: %', r, (r is null); return r; end; $body$ language plpgsql immutable; select myt(),myt() is null; gives: NOTICE: r: (,), r is null: t NOTICE: r: (,), r is null: t myt | ?column? -+-- (,) | f Strange I think... And at least half of an exception to the simple always null unless specifically set otherwise rule It also seems that while domain DEFAULTs are ignored, the resulting (null-initialized) variable is still checked against the domain's constraints, including a potential NOT NULL constraint create domain myint as int not null; create or replace function myint() returns myint as $body$ declare i myint; begin return i; end; $body$ language plpgsql immutable; raises ERROR: domain myint does not allow null values CONTEXT: PL/pgSQL function myint line 3 during statement block local variable initialization This has the potential to cause some headache I think if you use domains to prohibit NULL values because they make no semantic sense for your application, and depend on DEFAULT to fill in some other value (like an empty string or an empty array). best regards, Florian Pflug smime.p7s Description: S/MIME Cryptographic Signature
Re: [HACKERS] DEFAULT of domain ignored in plpgsql (8.4.1)
Gurjeet Singh wrote: On Sat, Nov 21, 2009 at 7:26 AM, Josh Berkus j...@agliodbs.com mailto:j...@agliodbs.com wrote: However, there are some other issues to be resolved: (1) what should be the interaction of DEFAULT parameters and domains with defaults? The function's DEFAULT parameter should take precedence over the default of the domain. I think Josh was pondering whether create domain myint as int default 0; create function f(i myint) ...; should behave like create function f(i myint default 0) ...; and hence call f(0) if you do select f();, or instead raise an error because no f with zero parameters is defined (as it does now). I'd say no, because no default should be treated the same as default null, so for consistency we'd then have to also support create function g(i int) ...; select g(); And of course throw an error if there was another function defined as create function g() ...; This way leads to madness... If one really wanted to do that, there'd have to be an OPTIONAL clause for function parameters that works like DEFAULT, but doesn't take a default value and instead uses the type's default (NULL except for domains with DEFAULT clause). But I wouldn't got that far, personally... best regards, Florian Pflug smime.p7s Description: S/MIME Cryptographic Signature
Re: [HACKERS] DEFAULT of domain ignored in plpgsql (8.4.1)
On lör, 2009-11-21 at 22:20 +0100, Florian G. Pflug wrote: I'm inclined to leave it alone. It complicates the mental model, and frankly attaching defaults to domains was not one of the SQL committee's better ideas anyway. It's *fundamentally* non-orthogonal. I've always though of domains as being a kind of subtype of it's base type. In this picture, DEFAULTs for domains correspond to overriding the default constructor of the type (thinking C++ now), and seem like a natural thing to have. But maybe that's more a C++ programmers than a database designers point of view... There are other things in the SQL standard to do that, like types with inheritance and types with constructors. We have already overextended domains enough beyond what the SQL standards says, mostly because these other things that are the correct solution are not implemented yet. -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] DEFAULT of domain ignored in plpgsql (8.4.1)
On Thu, Nov 19, 2009 at 9:06 PM, Florian G. Pflug f...@phlo.org wrote: Hi It seems that pl/pgsql ignores the DEFAULT value of domains for local variables. With the following definitions in place create domain myint as int default 0; create or replace function myint() returns myint as $body$ declare v_result myint; begin return v_result; end; $body$ language plpgsql immutable; issuing select myint(); returns NULL, not 0 on postgres 8.4.1 If the line v_result myint; is changes to v_result myint default 0; than 0 is returned as expected. I've tried to create a patch, but didn't see how I'd convert the result from get_typedefault() (A Node*, presumeably the parsetree corresponding to the default expression?) into a plan that I could store in a PLpgSQL_expr. I guess I'd need something like SPI_prepare_plan that takes a parse tree instead of a query string. Or am I on a completely wrong track there? While trying to cook up a patch I've also stumbled over what I perceive as a bug relating to DOMAINS and column DEFAULTs. I'll write that up in a second E-Mail to avoid confusion. I suggest adding this to the open CommitFest (2010-01) at https://commitfest.postgresql.org/action/commitfest_view/open ...Robert -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] DEFAULT of domain ignored in plpgsql (8.4.1)
Robert Haas wrote: On Thu, Nov 19, 2009 at 9:06 PM, Florian G. Pflug f...@phlo.org wrote: I've tried to create a patch, but didn't see how I'd convert the result from get_typedefault() (A Node*, presumeably the parsetree corresponding to the default expression?) into a plan that I could store in a PLpgSQL_expr. I guess I'd need something like SPI_prepare_plan that takes a parse tree instead of a query string. Or am I on a completely wrong track there? While trying to cook up a patch I've also stumbled over what I perceive as a bug relating to DOMAINS and column DEFAULTs. I'll write that up in a second E-Mail to avoid confusion. I suggest adding this to the open CommitFest (2010-01) at https://commitfest.postgresql.org/action/commitfest_view/open Hm, but I don't (yet) have a patch to add... best regards, Florian Pflug smime.p7s Description: S/MIME Cryptographic Signature
Re: [HACKERS] DEFAULT of domain ignored in plpgsql (8.4.1)
On Fri, Nov 20, 2009 at 12:51 PM, Florian G. Pflug f...@phlo.org wrote: Robert Haas wrote: On Thu, Nov 19, 2009 at 9:06 PM, Florian G. Pflug f...@phlo.org wrote: I've tried to create a patch, but didn't see how I'd convert the result from get_typedefault() (A Node*, presumeably the parsetree corresponding to the default expression?) into a plan that I could store in a PLpgSQL_expr. I guess I'd need something like SPI_prepare_plan that takes a parse tree instead of a query string. Or am I on a completely wrong track there? While trying to cook up a patch I've also stumbled over what I perceive as a bug relating to DOMAINS and column DEFAULTs. I'll write that up in a second E-Mail to avoid confusion. I suggest adding this to the open CommitFest (2010-01) at https://commitfest.postgresql.org/action/commitfest_view/open Hm, but I don't (yet) have a patch to add... Woops, I saw an attachment and thought there was a patch, but it was just smime.p7s... sorry for the noise. ...Robert -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] DEFAULT of domain ignored in plpgsql (8.4.1)
Florian G. Pflug f...@phlo.org writes: It seems that pl/pgsql ignores the DEFAULT value of domains for local variables. The plpgsql documentation seems entirely clear on this: The DEFAULT clause, if given, specifies the initial value assigned to the variable when the block is entered. If the DEFAULT clause is not given then the variable is initialized to the SQL null value. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] DEFAULT of domain ignored in plpgsql (8.4.1)
Tom Lane wrote: Florian G. Pflug f...@phlo.org writes: It seems that pl/pgsql ignores the DEFAULT value of domains for local variables. The plpgsql documentation seems entirely clear on this: The DEFAULT clause, if given, specifies the initial value assigned to the variable when the block is entered. If the DEFAULT clause is not given then the variable is initialized to the SQL null value. Hm, must have missed that paragraph :-(. Sorry for that. Would a patch that changes that have any chance of being accepted? Or is the gain (not having to repeat the DEFAULT clause, and being able to maintain it at one place instead of many) considered too small compared to the risk of breaking existing code? best regards, Florian Pflug smime.p7s Description: S/MIME Cryptographic Signature
Re: [HACKERS] DEFAULT of domain ignored in plpgsql (8.4.1)
Would a patch that changes that have any chance of being accepted? Or is the gain (not having to repeat the DEFAULT clause, and being able to maintain it at one place instead of many) considered too small compared to the risk of breaking existing code? I don't think there's a lot of risk of code breakage; few people use domains, fewer use them with defaults, and you might be the only one using them as variable types. And there are going to be more substantial backwards compat issues with the lexer changes anyway. As long as we remember to flag the compatibility issue in the release notes, I don't see it as a problem. However, there are some other issues to be resolved: (1) what should be the interaction of DEFAULT parameters and domains with defaults? (2) this change, while very useful, does change what had been a simple rule (All variables are NULL unless specifically set otherwise) into a conditional one (All variables are NULL unless set otherwise OR unless they are declared as domain types with defaults). Do people feel that the new behavior would be sufficiently intuitive to avoid user confusion? (3) Last I checked, there were still several places in which domains did not behave consistently in stored procedures. I think that Elein had some unfinished patches in this regard -- you'll want to search the archives and the TODO list. --Josh Berkus -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
