Обсуждение: pl/tcl trigger question
Hello everyone,
I'm working on a tiny trigger function that needs to ensure that all
values entered in a field are lowercase'd. I can't use pl/pgsql because
I have a dozen different columns (with different names) that need a
trigger that does this and pl'pgsql can't expand variable names to
fieldnames. Writing a dozen functions (one per columnname) is /way/ too
blunt so I tried pl/tcl (which I don't know):
----------------------------------------------------------------
-- first do:
-- createdb test
-- createlang pltcl test
drop function my_lowercase() cascade;
create function my_lowercase() returns trigger as '
set NEW($1) lower(NEW($1))
return [array get NEW]' language 'pltcl';
drop table mytab;
create table mytab (myfield varchar);
create trigger trig_mytab before insert or update on mytab
for each row execute procedure my_lowercase('myfield');
-- let's insert a string, hope it's lowercase'd
insert into mytab (myfield) values ('TEST');
select * from mytab;
-- wrong, myfield contains 'lower(NEW(myfield))'
----------------------------------------------------------------
Can someone please tell me what I'm doing wrong? It's probably
something very simple but I don't know TCL (and I'm planning to keep
the serverside programming on pl'pgsql as much as possible).
TIA!
On Tue, 2003-08-26 at 07:28, Jules Alberts wrote:
> Hello everyone,
>
> I'm working on a tiny trigger function that needs to ensure that all
> values entered in a field are lowercase'd. I can't use pl/pgsql because
> I have a dozen different columns (with different names) that need a
> trigger that does this and pl'pgsql can't expand variable names to
> fieldnames. Writing a dozen functions (one per columnname) is /way/ too
> blunt so I tried pl/tcl (which I don't know):
>
> ----------------------------------------------------------------
> -- first do:
> -- createdb test
> -- createlang pltcl test
>
> drop function my_lowercase() cascade;
> create function my_lowercase() returns trigger as '
> set NEW($1) lower(NEW($1))
> return [array get NEW]' language 'pltcl';
>
> drop table mytab;
> create table mytab (myfield varchar);
>
> create trigger trig_mytab before insert or update on mytab
> for each row execute procedure my_lowercase('myfield');
>
> -- let's insert a string, hope it's lowercase'd
> insert into mytab (myfield) values ('TEST');
> select * from mytab;
>
> -- wrong, myfield contains 'lower(NEW(myfield))'
> ----------------------------------------------------------------
>
> Can someone please tell me what I'm doing wrong? It's probably
> something very simple but I don't know TCL (and I'm planning to keep
> the serverside programming on pl'pgsql as much as possible).
>
You'll need a function a bit more complex than this, but to do what your
trying to do in the function above the function would be written as:
create or replace function my_lowercase() returns trigger as '
set NEW($1) [string tolower $NEW($1)]
return [array get NEW]' language 'pltcl';
Hope this helps, please post the final results when you get there.
Robert Treat
--
Build A Brighter Lamp :: Linux Apache {middleware} PostgreSQL
Ok the way you could do this is as follows:
create or replace function my_lowercase() returns trigger as '
foreach id [array names NEW] {
set NEW($id) [string tolower $NEW($id)]
}
return [array get NEW]
' language 'pltcl';
HTH
Darren
On 26 Aug 2003, Robert Treat wrote:
> On Tue, 2003-08-26 at 07:28, Jules Alberts wrote:
> > Hello everyone,
> >
> > I'm working on a tiny trigger function that needs to ensure that all
> > values entered in a field are lowercase'd. I can't use pl/pgsql because
> > I have a dozen different columns (with different names) that need a
> > trigger that does this and pl'pgsql can't expand variable names to
> > fieldnames. Writing a dozen functions (one per columnname) is /way/ too
> > blunt so I tried pl/tcl (which I don't know):
> >
> > ----------------------------------------------------------------
> > -- first do:
> > -- createdb test
> > -- createlang pltcl test
> >
> > drop function my_lowercase() cascade;
> > create function my_lowercase() returns trigger as '
> > set NEW($1) lower(NEW($1))
> > return [array get NEW]' language 'pltcl';
> >
> > drop table mytab;
> > create table mytab (myfield varchar);
> >
> > create trigger trig_mytab before insert or update on mytab
> > for each row execute procedure my_lowercase('myfield');
> >
> > -- let's insert a string, hope it's lowercase'd
> > insert into mytab (myfield) values ('TEST');
> > select * from mytab;
> >
> > -- wrong, myfield contains 'lower(NEW(myfield))'
> > ----------------------------------------------------------------
> >
> > Can someone please tell me what I'm doing wrong? It's probably
> > something very simple but I don't know TCL (and I'm planning to keep
> > the serverside programming on pl'pgsql as much as possible).
> >
>
> You'll need a function a bit more complex than this, but to do what your
> trying to do in the function above the function would be written as:
>
> create or replace function my_lowercase() returns trigger as '
> set NEW($1) [string tolower $NEW($1)]
> return [array get NEW]' language 'pltcl';
>
> Hope this helps, please post the final results when you get there.
>
> Robert Treat
>
--
Darren Ferguson
Op 26 Aug 2003 (12:38), schreef Robert Treat <xzilla@users.sourceforge.net>: > On Tue, 2003-08-26 at 07:28, Jules Alberts wrote: > > Hello everyone, > > > > I'm working on a tiny trigger function that needs to ensure that all > > values entered in a field are lowercase'd. I can't use pl/pgsql > > because I have a dozen different columns (with different names) that > > need a trigger that does this and pl'pgsql can't expand variable names > > to fieldnames. Writing a dozen functions (one per columnname) is /way/ > > too blunt so I tried pl/tcl (which I don't know): <bad attempt snipped> > You'll need a function a bit more complex than this, but to do what your > trying to do in the function above the function would be written as: > > create or replace function my_lowercase() returns trigger as ' > set NEW($1) [string tolower $NEW($1)] > return [array get NEW]' language 'pltcl'; > > Hope this helps, please post the final results when you get there. Hi Robert, It works great, thanks a lot! There is one little issue though: when I insert null values, the function fails. I think I can work around this by giving the columns a default value of '' in my table design, but I would like a more defensive approach, I.E. having my_lowercase() check for null values. Thanks again for any help, and sorry if I'm asking basic TCL questions, I don't know the language. Do you happen to know a good site where the language is explained? All I googled was about creating widgets, GUI stuff :-( > Robert Treat
Jules Alberts wrote: > Op 26 Aug 2003 (12:38), schreef Robert Treat <xzilla@users.sourceforge.net>: >> On Tue, 2003-08-26 at 07:28, Jules Alberts wrote: >> > Hello everyone, >> > >> > I'm working on a tiny trigger function that needs to ensure that all >> > values entered in a field are lowercase'd. I can't use pl/pgsql >> > because I have a dozen different columns (with different names) that >> > need a trigger that does this and pl'pgsql can't expand variable names >> > to fieldnames. Writing a dozen functions (one per columnname) is /way/ >> > too blunt so I tried pl/tcl (which I don't know): > > <bad attempt snipped> > >> You'll need a function a bit more complex than this, but to do what your >> trying to do in the function above the function would be written as: >> >> create or replace function my_lowercase() returns trigger as ' >> set NEW($1) [string tolower $NEW($1)] >> return [array get NEW]' language 'pltcl'; >> >> Hope this helps, please post the final results when you get there. > > Hi Robert, > > It works great, thanks a lot! There is one little issue though: when I > insert null values, the function fails. I think I can work around this > by giving the columns a default value of '' in my table design, but I > would like a more defensive approach, I.E. having my_lowercase() check > for null values. Have you tried the scriptics site http://www.scriptics.com/ under "web-resources->documentation"? There are some tutorials and howto's. create or replace function force_lower () returns trigger as ' foreach key $args { if {[info exists NEW($key)]} { set NEW($key) [string tolower $NEW($key)] } } return [array get NEW] ' language pltcl; create trigger force_lower before insert or update on mytable for each row execute procedure force_lower('field_1', 'field_n'); This works for a variable number of fields on every table and ignores NULL values. Jan -- #======================================================================# # It's easier to get forgiveness for being wrong than for being right. # # Let's break this rule - forgive me. # #================================================== JanWieck@Yahoo.com #