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Thread: pl/tcl trigger question

pl/tcl trigger question

From
"Jules Alberts"
Date:
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!

Re: pl/tcl trigger question

From
Robert Treat
Date:
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

Re: pl/tcl trigger question

From
darren@crystalballinc.com
Date:
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

Re: pl/tcl trigger question

From
"Jules Alberts"
Date:
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

Re: pl/tcl trigger question

From
Jan Wieck
Date:

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

--
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