Re: [HACKERS] proposal: PLpgSQL parallel assignemnt
2017-06-02 19:05 GMT+02:00 Pavel Stehule : > > > 2017-06-02 10:15 GMT+02:00 Pavel Stehule : > >> >> >> 2017-06-02 10:06 GMT+02:00 Craig Ringer : >> >>> On 2 June 2017 at 15:51, Pavel Stehule wrote: >>> >>> > a, b := fx(); >>> > >>> > Comments, notes, ideas? >>> >>> I'd be pretty happy to have >>> >>> (a, b) = (x, y); >>> (a, b) = f(x); >>> >>> which is SQL-esque. >>> >> >> This is not too far to my proposal - and it is fully adequate >> alternative. >> > > The ANSI form is related to SET or UPDATE commands - so in this case I see > classic languages style https://en.wikipedia.org/wiki/ > Assignment_(computer_science) better. The assign statement in PLpgSQL is > not related to embedded SQL. If we introduce SQL syntax and SET commands > for schema variables then ( ) syntax is perfect, but for := PLpgSQL I am > not sure > > It is maybe strange, but > > SET (a,b) = (SELECT a,b FROM foo) > > a, b := fx() > > are sentences from two independent worlds and different syntax can be > correct (depends how much we would to integrate procedural and SQL worlds > .. 100% T-SQL, 80% SQL/PSM, ..20% PLpgSQL or 5%PL/SQL) > More thoughts: 1. syntax (a,b) := f() ... can mean - assign record to temporary composite (a,b) 2. syntax a,b := f() ... can mean - unpack result composite and assign to a, b fields so both syntaxes has sense although we don't introduce relation to SQL - on this way a,b := 10, 20 -- ok .. attach a=c1, b=c2 a,b := (10,20) -- ok .. attach a = r.c1, b = r.c2 (a,b) := (10,20) -- ok attach ct = rt (a,b) := 10,20 -- ok attach ct = row(c1, c2) @1 syntax says "create composite target", @2 syntax says "unpack result". Both should to work. Personally I prefer @1 .. due less parenthesis Regards Pavel > Regards > > Pavel > > >> >> >>> >>> But what, if anything, does Ada do? >>> >> >> What I know, no, Ada has not this statement - but the design of OUT >> parameters in Ada absolutely different than PostgreSQL - so in this case we >> cannot to use Ada language as our base :( >> >> Regards >> >> Pavel >> >> >>> >>> -- >>> Craig Ringer http://www.2ndQuadrant.com/ >>> PostgreSQL Development, 24x7 Support, Training & Services >>> >> >> >
Re: [HACKERS] proposal: PLpgSQL parallel assignemnt
2017-06-02 10:15 GMT+02:00 Pavel Stehule : > > > 2017-06-02 10:06 GMT+02:00 Craig Ringer : > >> On 2 June 2017 at 15:51, Pavel Stehule wrote: >> >> > a, b := fx(); >> > >> > Comments, notes, ideas? >> >> I'd be pretty happy to have >> >> (a, b) = (x, y); >> (a, b) = f(x); >> >> which is SQL-esque. >> > > This is not too far to my proposal - and it is fully adequate alternative. > The ANSI form is related to SET or UPDATE commands - so in this case I see classic languages style https://en.wikipedia.org/wiki/Assignment_(computer_science) better. The assign statement in PLpgSQL is not related to embedded SQL. If we introduce SQL syntax and SET commands for schema variables then ( ) syntax is perfect, but for := PLpgSQL I am not sure It is maybe strange, but SET (a,b) = (SELECT a,b FROM foo) a, b := fx() are sentences from two independent worlds and different syntax can be correct (depends how much we would to integrate procedural and SQL worlds .. 100% T-SQL, 80% SQL/PSM, ..20% PLpgSQL or 5%PL/SQL) Regards Pavel > > >> >> But what, if anything, does Ada do? >> > > What I know, no, Ada has not this statement - but the design of OUT > parameters in Ada absolutely different than PostgreSQL - so in this case we > cannot to use Ada language as our base :( > > Regards > > Pavel > > >> >> -- >> Craig Ringer http://www.2ndQuadrant.com/ >> PostgreSQL Development, 24x7 Support, Training & Services >> > >
Re: [HACKERS] proposal: PLpgSQL parallel assignemnt
2017-06-02 10:06 GMT+02:00 Craig Ringer : > On 2 June 2017 at 15:51, Pavel Stehule wrote: > > > a, b := fx(); > > > > Comments, notes, ideas? > > I'd be pretty happy to have > > (a, b) = (x, y); > (a, b) = f(x); > > which is SQL-esque. > This is not too far to my proposal - and it is fully adequate alternative. > > But what, if anything, does Ada do? > What I know, no, Ada has not this statement - but the design of OUT parameters in Ada absolutely different than PostgreSQL - so in this case we cannot to use Ada language as our base :( Regards Pavel > > -- > Craig Ringer http://www.2ndQuadrant.com/ > PostgreSQL Development, 24x7 Support, Training & Services >
Re: [HACKERS] proposal: PLpgSQL parallel assignemnt
On 2 June 2017 at 15:51, Pavel Stehule wrote: > a, b := fx(); > > Comments, notes, ideas? I'd be pretty happy to have (a, b) = (x, y); (a, b) = f(x); which is SQL-esque. But what, if anything, does Ada do? -- Craig Ringer http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
[HACKERS] proposal: PLpgSQL parallel assignemnt
Hi Some modern or old languages (GO, Lua, CLU) has similarly designed function OUT parameters like PLpgSQL. In these languages is usually supported parallel assignment. It is not supported by PLpgSQL - there is workaround - using SELECT FROM, but it is workaround. The implementation of PA is trivial. Current state: == CREATE OR REPLACE FUNCTION fx(OUT a int, OUT b int) AS $$ ... possibilities of CALL and assignment recvar := fx(); rowvar := fx(); SELECT * FROM fx() INTO a, b; Lua, Golang like proposal: a, b := fx(); Comments, notes, ideas? Regards Pavel
