I have a table with about 3 dozen VARCHAR columns that all need the same cleanup before the record is inserted into the database (convert empty string to NULL). There are multiple apps accessing the DB, so I'd like to do this in a trigger. I could write code to check and set each column, but I'd like to loop through the columns instead. The function I wrote does not produce an error, but it also does not set empty columns to NULL.
CREATE OR REPLACE FUNCTION public.validate_flds() RETURNS trigger AS
$BODY$
DECLARE
coldata VARCHAR;
collist VARCHAR[];
BEGIN
collist := ARRAY[NEW.fld01,NEW.fld02,NEW.fld03];
FOREACH coldata IN ARRAY collist LOOP
IF coldata = '' THEN coldata := NULL; END IF;
END LOOP;
RETURN NEW;
END;
$BODY$
LANGUAGE plpgsql;
What am I missing?
In
IF coldata = '' THEN coldata := NULL; END IF;
you alter the value of the variable while the NEW record remains unchanged. There is no easy way to do what you want in a loop. I would suggest using NULLIF().
begin
new.fld01:= nullif(new.fld01, '');
new.fld02:= nullif(new.fld02, '');
new.fld03:= nullif(new.fld03, '');
return new;
end;
Related
i am trying to check if a element is present in an array using plpgsql.
and i am receiving "array subscript must have integer" error while executing the function.
select test('IND') should return true and select test('ING') should return false
Below is the code
create or replace function test(country varchar)
returns varchar
language plpgsql
AS $function$
declare
results varchar;
countryarr varchar[3];
i varchar[];
begin
countryarr := array['IND','USA','MEX'];
foreach i slice 1 in array countryarr
loop
if countryarr[i]=country
then results := 'TRUE';
else
results := 'FALSE';
end if;
end loop;
return results;
end;
$function$
;
Your i is defined as a varchar[] in your code. It cannot be used as an integer.
You want something like this:
create or replace function test(country varchar)
returns varchar
language plpgsql
AS $function$
declare
countryarr varchar[3];
i text;
begin
countryarr := array['IND','USA','MEX'];
foreach i in array countryarr
loop
if i = country
then return 'TRUE';
end if;
end loop;
return 'FALSE';
end;
$function$
;
A better solution for what you are trying to achieve is:
create or replace function test(country varchar)
returns varchar
language sql
AS $function$
select case
when country = any(array['IND', 'USA', 'MEX']) then 'TRUE'
else 'FALSE'
end;
$function$;
Let your function return a boolean. Then it reduces to a single SQL statement.
create or replace function is_valid_country(country_in varchar)
returns boolean
language sql
immutable strict
AS $$
select country_in = any(array['IND', 'USA', 'MEX']) ;
$$;
with test(country) as
( values ('IND'), ('USA'), ('MEX'), ('CAN'),('UK') )
select country, is_valid_country(country) is_valid
from test;
This can be used in any subsequent sql statement. And the optimizer can in-line it.
I'm a beginner in plpgsql and working on a project which requires me to write a function that returns two variables in the form of 2 columns (res,Result). I've done a quite a bit of searching but didn't find answer for the same. The reference to my code is below
CREATE OR REPLACE FUNCTION propID(character varying)
RETURNS SETOF RECORD AS $val$
DECLARE
t_row record;
res BOOLEAN;
result character varying;
value record;
BEGIN
FOR t_row IN SELECT property_id FROM property_table WHERE ward_id::TEXT = $1 LOOP
RAISE NOTICE 'Analyzing %', t_row;
res := false; -- here i'm going to replace this value with a function whos return type is boolean in future
result := t_row.property_id;
return next result; --here i want to return 2 variables (res,result) in the form of two columns (id,value)
END LOOP;
END;
$val$
language plpgsql;
Any help on the above query would be very much appreciated.
Assuming that property_id and ward_id are integers you can achieve your goal in a simple query like this:
select some_function_returning_boolean(property_id), property_id
from property_table
where ward_id = 1; -- input parameter
If you absolutely need a function, it can be an SQL function like
create or replace function prop_id(integer)
returns table (res boolean, id int) language sql
as $$
select some_function_returning_boolean(property_id), property_id
from property_table
where ward_id = $1
$$;
In a plpgsql function you should use return query:
create or replace function prop_id(integer)
returns table (res boolean, id int) language plpgsql
as $$
begin
return query
select some_function_returning_boolean(property_id), property_id
from property_table
where ward_id = $1;
end
$$;
I am creating trigger in PostgresSQL. On update I would like to compare all of the values in a Hstore column and update changes in my mirror table. I managed to get names of my columns in variable k but I am not able to get values using it from NEW and OLD.
CREATE OR REPLACE FUNCTION function_replication() RETURNS TRIGGER AS
$BODY$
DECLARE
k text;
BEGIN
FOR k IN SELECT key FROM EACH(hstore(NEW)) LOOP
IF NEW.k != OLD.k THEN
EXECUTE 'UPDATE ' || TG_TABLE_NAME || '_2' || 'SET ' || k || '=' || new.k || ' WHERE ID=$1.ID;' USING OLD;
END IF;
END LOOP;
RETURN NEW;
END;
$BODY$
language plpgsql;
You should operate on hstore representations of the records new and old. Also, use the format() function for better control and readibility.
create or replace function function_replication()
returns trigger as
$body$
declare
newh hstore = hstore(new);
oldh hstore = hstore(old);
key text;
begin
foreach key in array akeys(newh) loop
if newh->key != oldh->key then
execute format(
'update %s_2 set %s = %L where id = %s',
tg_table_name, key, newh->key, oldh->'id');
end if;
end loop;
return new;
end;
$body$
language plpgsql;
Another version - with minimalistic numbers of updates - in partially functional design (where it is possible).
This trigger should be AFTER trigger, to be ensured correct behave.
CREATE OR REPLACE FUNCTION function_replication()
RETURNS trigger AS $$
DECLARE
newh hstore;
oldh hstore;
update_vec text[];
pair text[];
BEGIN
IF new IS DISTINCT FROM old THEN
IF new.id <> old.id THEN
RAISE EXCEPTION 'id should be immutable';
END IF;
newh := hstore(new); oldh := hstore(old); update_vec := '{}';
FOREACH pair SLICE 1 IN ARRAY hstore_to_matrix(newh - oldh)
LOOP
update_vec := update_vec || format('%I = %L', pair[1], pair[2]);
END LOOP;
EXECUTE
format('UPDATE %I SET %s WHERE id = $1',
tg_table_name || '_2',
array_to_string(update_vec, ', '))
USING old.id;
END IF;
RETURN NEW; -- the value is not important in AFTER trg
END;
$$ LANGUAGE plpgsql;
CREATE TABLE foo(id int PRIMARY KEY, a int, b int);
CREATE TABLE foo_2(LIKE foo INCLUDING ALL);
CREATE TRIGGER xxx AFTER UPDATE ON foo
FOR EACH ROW EXECUTE PROCEDURE function_replication();
INSERT INTO foo VALUES(1, NULL, NULL);
INSERT INTO foo VALUES(2, 1,1);
INSERT INTO foo_2 VALUES(1, NULL, NULL);
INSERT INTO foo_2 VALUES(2, 1,1);
UPDATE foo SET a = 20, b = 30 WHERE id = 1;
UPDATE foo SET a = NULL WHERE id = 1;
This code is little bit more complex, but all what should be escaped is escaped and reduce number of executed UPDATE commands. UPDATE is full SQL command and the overhead of full SQL commands should be significantly higher than code that reduce number of full SQL commands.
I have a simple mission is inserting huge MD5 values into tables (partitioned table), and have created a trigger and also a trigger function to instead of INSERT operation. And in function I checked the first two characters of NEW.md5 to determine which table should be inserted.
DECLARE
tb text;
BEGIN
IF TG_OP = 'INSERT' THEN
tb = 'samples_' || left(NEW.md5, 2);
EXECUTE(format('INSERT INTO %s VALUES (%s);', tb, NEW.*)); <- WRONG
END IF;
RETURN NULL;
END;
The question is how to concat the NEW.* into the SQL statement?
Best with the USING clause of EXECUTE:
CREATE FUNCTION foo ()
RETURNS trigger AS
$func$
BEGIN
IF TG_OP = 'INSERT' THEN
EXECUTE format('INSERT INTO %s SELECT $1.*'
, 'samples_' || left(NEW.md5, 2);
USING NEW;
END IF;
RETURN NULL;
END
$func$ LANGUAGE plpgsql;
And EXECUTE does not require parentheses.
And you are aware that identifiers are folded to lower case unless quoted where necessary (%I instead of %s in format()).
More details:
INSERT with dynamic table name in trigger function
How to dynamically use TG_TABLE_NAME in PostgreSQL 8.2?
How can I get all column names and their values in trigger function because i need to validate all column values before inserting into the table.I have tried below code.If we know that column name means we can get the value easily by using NEW object in trigger function as NEW.myColumnName.But here I need to get the column name dynamically...
CREATE FUNCTION insert_update_validate() RETURNS TRIGGER AS $$
DECLARE
BEGIN
FOR i IN 0..(TG_ARGV-1) LOOP
IF TG_ARGV[i] IS NULL THEN
RAISE EXCEPTION 'cannot have null VALUE', NEW.TG_ARGV[i];
END LOOP;
RETURN NEW;
END;
$$ LANGUAGE plpgsql;
Since hstore is part of PostgreSQL, casting a row to hstore is the primary method to iterate on its columns, at least in a plpgsql context. Otherwise as a language it doesn't provide any construct to extract column names from rows.
Basically it's about iterating over each(store(NEW)). Here's a skeleton you may use:
CREATE FUNCTION insert_update_validate() RETURNS TRIGGER AS $$
DECLARE
k text;
v text;
BEGIN
FOR k,v IN select key,value from each(hstore(NEW)) LOOP
if v is null then
raise exception 'value is null for column %', k;
end if;
END LOOP;
RETURN NEW;
END;
$$ LANGUAGE plpgsql;