I have a trigger function that is called by several tables when COLUMN A is updated, so that COLUMN B can be updated based on value from a different function. (More complicated to explain than it really is). The trigger function takes in col_a and col_b since they are different for the different tables.
IF needs_updated THEN
sql = format('($1).%2$s = dbo.foo(($1).%1$s); ', col_a, col_b);
EXECUTE sql USING NEW;
END IF;
When I try to run the above, the format produces this sql:
($1).NameText = dbo.foo(($1).Name);
When I execute the SQL with the USING I am expecting something like this to happen (which works when executed straight up without dynamic sql):
NEW.NameText = dbo.foo(NEW.Name);
Instead I get:
[42601] ERROR: syntax error at or near "$1"
How can I dynamically update the column on the record/composite type NEW?
This isn't going to work because NEW.NameText = dbo.foo(NEW.Name); isn't a correct sql query. And I cannot think of the way you could dynamically update variable attribute of NEW. My suggestion is to explicitly define behaviour for each of your tables:
IF TG_TABLE_SCHEMA = 'my_schema' THEN
IF TG_TABLE_NAME = 'my_table_1' THEN
NEW.a1 = foo(NEW.b1);
ELSE IF TG_TABLE_NAME = 'my_table_2' THEN
NEW.a2 = foo(NEW.b2);
... etc ...
END IF;
END IF;
First: This is a giant pain in plpgsql. So my best recommendation is to do this in some other PL, such as plpythonu or plperl. Doing this in either of those would be trivial. Even if you don't want to do the whole trigger in another PL, you could still do something like:
v_new RECORD;
BEGIN
v_new := plperl_function(NEW, column_a...)
The key to doing this in plpgsql is creating a CTE that has what you need in it:
c_new_old CONSTANT text := format(
'WITH
NEW AS (SELECT (r).* FROM (SELECT ($1)::%1$s r) s)
, OLD AS (SELECT (r).* FROM (SELECT ($2)::%1$s r) s
'
, TG_RELID::regclass
);
You will also need to define a v_new that is a plain record. You could then do something like:
-- Replace 2nd field in NEW with a new value
sql := c_new_old || $$SELECT row(NEW.a, $3, NEW.c) FROM NEW$$
EXECUTE sql INTO v_new USING NEW, OLD, new_value;
Related
I have a function that uses RECORD to temporarily store the data. I can use it - it's fine. My problem is that I can't hardcode columns I need to get from the RECORD. I must do it dynamically. Something line:
DECLARE
r1 RECORD;
r2 RECORD;
BEGIN
for r1 in Select column_name
from columns_to_process
where process_now = True
loop
for r2 in Select *
from my_data_table
where whatever
loop
-----------------------------
here I must call column by its name that is unknown at design time
-----------------------------
... do something with
r2.(r1.column_name)
end loop;
end loop;
END;
Does anyone know how to do it?
best regards
M
There is no need to select the all the qualifying rows and compute the total in a loop. Actually when working with SQL try to drop the word loop for your vocabulary; instead just use sum(column_name) in the select. The issue here is that you do not know what column to sum when the query is written, and all structural components(table names, columns names, operators, etc) must be known before submitting. You cannot use a variable for a structural component - in this case a column name. To do that you must use dynamic sql - i.e. SQL statement built by the process. The following accomplishes that: See example here.
create or replace function sum_something(
the_something text -- column name
, for_id my_table.id%type -- my_table.id
)
returns numeric
language plpgsql
as $$
declare
k_query_base constant text :=
$STMT$ Select sum(%I) from my_table where id = %s; $STMT$;
l_query text;
l_sum numeric;
begin
l_query = format(k_query_base, the_something, for_id);
raise notice E'Rumming Statememt:\n %',l_query; -- for prod raise Log
execute l_query into l_sum;
return l_sum;
end;
$$;
Well, after some time I figured out that I could use temporary table instead of RECORD. Doing so gives me all advantages of using dynamic queries so I can call any column by its name.
DECLARE
_my_var bigint;
BEGIN
create temporary table _my_temp_table as
Select _any, _column, _you, _need
from _my_table
where whatever = something;
execute 'Select ' || _any || ' from _my_temp_table' into _my_var;
... do whatever
END;
However I still believe that there should be a way to call records field by it's name.
I have a long and complex plpgsql function that creates a bunch of temporary tables nested within a while statement to get the optimal result. When the condition has been met I insert the result into an existing table, the function is far to long to post here but this is an example:
CREATE OR REPLACE FUNCTION public.test_function(id_input integer, val_input numeric)
RETURNS VOID AS
$BODY$
DECLARE
id_input numeric = $1;
val_input numeric = $2;
BEGIN
WHILE test_val < 0
LOOP
CREATE TEMP TABLE temp_table AS
SELECT a.existing_val - val_input AS new_val
FROM existing_table a
WHERE a.id = id_input;
test_val := (SELECT new_val FROM temp_table);
val_input := val_input + 1;
END LOOP;
INSERT INTO output_table (id, new_val)
SELECT a.id, a.new_val
FROM temp_table a;
END;
$BODY$
LANGUAGE plpgsql;
The function works if I call it like this SELECT test_function(1, 1000) However I would like run this function on a table with 60,000+ rows, like this:
SELECT test_function(a.id, a.val_input)
FROM data_table a;
It works when I use a subset of the data_table, say 1000 rows. However when I run it on the full table (60,000+ rows) I get the following error "AbortTransaction while in COMMIT state". After some reading I found out COMMITS, so in my case the inserts do not occur until the function has finished running which takes about 4 hours. So does anyone know what is going on?
As a workaround I tried nesting the function in a DO statement so the inserts are committed straight away:
DO
$do$
DECLARE
r data_table%rowtype;
BEGIN
FOR r IN
SELECT * FROM data_table
LOOP
SELECT public.test_function(r.id, r.val_input);
END LOOP;
END
$do$;
However then I get the following error "ERROR: query has no destination for result data", which I guess means I need to rewrite the function to use PERFORM instead of SELECT. However I have not had any luck with this as yet.
Any ideas?
Since you are not interested in the function result, you should use
PERFORM public.test_function(r.id, r.val_input);
instead of
SELECT public.test_function(r.id, r.val_input);
The latter syntax would only work if you add INTO some_variable as a destination for the query result.
Thank you all for your suggestions. I ended up using Jim Jones's suggestion and converting the function to a procedure which allowed me to use COMMIT after I did the INSERT. I also followed Jeremy's suggestion and moved from temp tables to CTE's. This solved the problem for me.
I am very new to DB2 even though have experience in Oracle. I am not able to resolve this issue.I have a requirement where I need to find missing child records in the parent table .The parent table , child table and the join_key are all passed as input parameter.
I have tried this in a procedure was able to achieve this, but the admin wants it in a function so that they can just use it in a select statment and get the result in a table format. Since the parent table , child table and the join_key are comming as input parement, I am not able to run them as dynamic sql.
create or replace function missing_child_rec(PARENT_TBL VARCHAR(255),JOIN_KEY VARCHAR(255),CHILD_TBL VARCHAR(255))
RETURNS TABLE(Key VARCHAR(255))
LANGUAGE SQL
BEGIN
DECLARE V_SQL VARCHAR(500);
DECLARE C_SQL CURSOR WITH RETURN FOR S_SQL;
SET V_PARENT_TAB = PARENT_TBL;
SET V_KEY = JOIN_KEY;
SET V_CHILD_TAB = CHILD_TBL;
SET V_SQL = 'SELECT DISTINCT '|| JOIN_KEY || ' FROM ' || V_CHILD_TAB || ' A WHERE NOT EXISTS
(SELECT ' ||V_KEY || ' FROM ' || V_PARENT_TAB || ' B WHERE A.'||JOIN_KEY || '= B.'||JOIN_KEY ||' )' ;
PREPARE S_SQL FROM V_SQL;
OPEN C_SQL;
CLOSE C_SQL;
RETURN
END
When I try to compile it , it says prepare is invalid , I have tried even execute immediate but that also gave error.Can you please help me with how to use dynamic sql in UDF or an alternative logic for this problem
There is more than one way to solve this, here's one way.
If you already have a working stored-procedure that returns the correct result-set then you can call that stored-procedure from a pipelined table function. The idea is that a pipelined table function can consume the result-set and pipe it to the caller.
This will work on Db2-LUW v10.1 or higher, as long as the database is not partitioned over multiple nodes.
It may work on Db2-for-i v7.1 or higher.
It will not work with Db2 for Z/os at current versions.
Suppose your stored procedure is sp_missing_child_rec and it takes the same input parameters as the function you show in your question, and suppose the data type of the join column is varchar(100).
The pipelined wrapper table function would look something like this:
--#SET TERMINATOR #
create or replace function missing_child_rec(PARENT_TBL VARCHAR(255),JOIN_KEY VARCHAR(255),CHILD_TBL VARCHAR(255))
returns table ( join_column_value varchar(100))
begin
declare v_rs result_set_locator varying;
declare v_row varchar(100); -- to match the join_column_datatype, adjust as necessary
declare sqlstate char(5) default '00000';
CALL sp_missing_child_rec( parent_tbl, join_key, child_tbl);
associate result set locator (v_rs) with procedure sp_missing_child_rec ;
allocate v_rscur cursor for result set v_rs;
fetch from v_rscur into v_row;
while ( sqlstate = '00000') do
pipe(v_row);
fetch from v_rscur into v_row;
end while;
return;
end#
select * from table(missing_child_rec( 'parent_table' , 'join_column', 'child_table'))
#
I'm working with PostgreSQL 9.5.
I'm creating a trigger in PL/pgSQL, that adds a record to a table (synthese_poly) when an INSERT is performed on a second table (operation_poly), with other tables data.
The trigger works well, except for some variables, that are not filled (especially the ones I try to fill with an array_to_string() function).
This is the code:
-- Function: bdtravaux.totablesynth_fn()
-- DROP FUNCTION bdtravaux.totablesynth_fn();
CREATE OR REPLACE FUNCTION bdtravaux.totablesynth_fn()
RETURNS trigger AS
$BODY$
DECLARE
varoperateur varchar;
varchantvol boolean;
BEGIN
IF (TG_OP = 'INSERT') THEN
varsortie_id := NEW.sortie;
varopeid := NEW.operation_id;
--The following « SELECT » queries take data in third-party tables and fill variables, which will be used in the final insertion query.
SELECT array_to_string(array_agg(DISTINCT oper.operateurs),'; ')
INTO varoperateur
FROM bdtravaux.join_operateurs oper INNER JOIN bdtravaux.operation_poly o ON (oper.id_joinop=o.id_oper)
WHERE o.operation_id = varopeid;
SELECT CASE WHEN o.ope_chvol = 0 THEN 'f' ELSE 't' END as opechvol INTO varchantvol
FROM bdtravaux.operation_poly o WHERE o.operation_id = varopeid;
-- «INSERT» query
INSERT INTO bdtravaux.synthese_poly (soperateur, schantvol) SELECT varoperateur, varchantvol;
RAISE NOTICE 'varoperateur value : (%)', varoperateur;
RAISE NOTICE 'varchantvol value : (%)', varchantvol;
END IF;
RETURN NEW;
END;
$BODY$
LANGUAGE plpgsql VOLATILE
COST 100;
ALTER FUNCTION bdtravaux.totablesynth_fn()
OWNER TO postgres;
And this is the trigger :
-- Trigger: totablesynth on bdtravaux.operation_poly
-- DROP TRIGGER totablesynth ON bdtravaux.operation_poly;
CREATE TRIGGER totablesynth
AFTER INSERT
ON bdtravaux.operation_poly
FOR EACH ROW
WHEN ((new.chantfini = true))
EXECUTE PROCEDURE bdtravaux.totablesynth_fn();
The varchantvol variable is correctly filled, but varoperateur stays desperately empty (NULL value) (and so on for the corresponding field in the synthese_poly table).
Note:
The SELECT array_to_string(…) ... query itself (launched with pgAdmin, without INTO varoperateur and replacing varopeid with a value) works well, and returns a string.
I tried to change array_to_string() function and variables' data types (using ::varchar or ::text …), nothing works.
Do you see what can happen?
using array_agg
You can replace array_to_string(array_agg(DISTINCT oper.operateurs),'; ') with
string_agg(DISTINCT oper.operateurs,'; ')
And you can use order by to sort the text in the agregate
string_agg(DISTINCT oper.operateurs,'; ' ORDER BY oper.operateurs)
My educated guess: you have a trigger with BEFORE INSERT ON bdtravaux.operation_poly. And operation_id is its serial PK column.
In this case, the query with WHERE o.operation_id = varopeid
(where varopeid has been filled with NEW.operation_id) can never find any rows because the row is not in the table, yet.
array_agg() has no role in this.
Would work with a trigger AFTER INSERT ON bdtravaux.operation_poly. But if id_oper is from the same inserted row, you can just simplify to:
SELECT array_to_string(array_agg(DISTINCT oper.operateurs),'; ')
INTO varoperateur
FROM bdtravaux.join_operateurs oper
WHERE oper.id_joinop = NEW.id_oper;
And keep the BEFORE trigger.
The whole function might be simpler, can probably done with a single query.
I want to loop through a query, but also retain the actual record for the next loop, so I can compare two adjacent rows.
CREATE OR REPLACE FUNCTION public.test ()
RETURNS void AS
$body$
DECLARE
previous RECORD;
actual RECORD;
query TEXT;
isdistinct BOOLEAN;
tablename VARCHAR;
columnname VARCHAR;
firstrow BOOLEAN DEFAULT TRUE;
BEGIN
tablename = 'naplo.esemeny';
columnname = 'esemeny_id';
query = 'SELECT * FROM ' || tablename || ' LIMIT 2';
FOR actual IN EXECUTE query LOOP
--do stuff
--save previous record
IF NOT firstrow THEN
EXECUTE 'SELECT ($1).' || columnname || ' IS DISTINCT FROM ($2).' || columnname
INTO isdistinct USING previous, actual;
RAISE NOTICE 'previous: %', previous.esemeny_id;
RAISE NOTICE 'actual: %', actual.esemeny_id;
RAISE NOTICE 'isdistinct: %', isdistinct;
ELSE
firstrow = false;
END IF;
previous = actual;
END LOOP;
RETURN;
END;
$body$
LANGUAGE 'plpgsql'
VOLATILE
CALLED ON NULL INPUT
SECURITY INVOKER
COST 100;
The table:
CREATE TABLE naplo.esemeny (
esemeny_id SERIAL,
felhasznalo_id VARCHAR DEFAULT "current_user"() NOT NULL,
kotesszam VARCHAR(10),
idegen_azonosito INTEGER,
esemenytipus_id VARCHAR(10),
letrehozva TIMESTAMP WITHOUT TIME ZONE DEFAULT now() NOT NULL,
szoveg VARCHAR,
munkalap_id VARCHAR(13),
ajanlat_id INTEGER,
CONSTRAINT esemeny_pkey PRIMARY KEY(esemeny_id),
CONSTRAINT esemeny_fk_esemenytipus FOREIGN KEY (esemenytipus_id)
REFERENCES naplo.esemenytipus(esemenytipus_id)
ON DELETE RESTRICT
ON UPDATE RESTRICT
NOT DEFERRABLE
)
WITH (oids = true);
The code above doesn't work, the following error message is thrown:
ERROR: could not identify column "esemeny_id" in record data type
LINE 1: SELECT ($1).esemeny_id IS DISTINCT FROM ($2).esemeny_id
^
QUERY: SELECT ($1).esemeny_id IS DISTINCT FROM ($2).esemeny_id
CONTEXT: PL/pgSQL function "test" line 18 at EXECUTE statement
LOG: duration: 0.000 ms statement: SET DateStyle TO 'ISO'
What am I missing?
Disclaimer: I know the code doesn't make too much sense, I only created so I can demonstrate the problem.
This does not directly answer your question, and may be of no use at all, since you did not really describe your end goal.
If the end goal is to be able to compare the value of a column in the current row with the value of the same column in the previous row, then you might be much better off using a windowing query:
SELECT actual, previous
FROM (
SELECT mycolumn AS actual,
lag(mycolumn) OVER () AS previous
FROM mytable
ORDER BY somecriteria
) as q
WHERE previous IS NOT NULL
AND actual IS DISTINCT FROM previous
This example prints the rows where the current row is different from the previous row.
Note that I added an ORDER BY clause - it does not make sense to talk about "the previous row" without specifying ordering, otherwise you would get random results.
This is plain SQL, not PlPgSQL, but if you can wrap it in a function if you want to dynamically generate the query.
I am pretty sure, there is a better solution for your actual problem. But to answer the question asked, here is a solution with polymorphic types:
The main problem is that you need well known composite types to work with. the structure of anonymous records is undefined until assigned.
CREATE OR REPLACE FUNCTION public.test (actual anyelement, _col text
, OUT previous anyelement) AS
$func$
DECLARE
isdistinct bool;
BEGIN
FOR actual IN
EXECUTE format('SELECT * FROM %s LIMIT 3', pg_typeof(actual))
LOOP
EXECUTE format('SELECT ($1).%1$I IS DISTINCT FROM ($2).%1$I', _col)
INTO isdistinct
USING previous, actual;
RAISE NOTICE 'previous: %; actual: %; isdistinct: %'
, previous, actual, isdistinct;
previous := actual;
END LOOP;
previous := NULL; -- reset dummy output (optional)
END
$func$ LANGUAGE plpgsql;
Call:
SELECT public.test(NULL::naplo.esemeny, 'esemeny_id')
I am abusing an OUT parameter, since it's not possible to declare additional variables with a polymorphic composite type (at least I have failed repeatedly).
If your column name is stable you can replace the second EXECUTE with a simple expression.
I am running out of time, explanation in these related answers:
Declare variable of composite type in PostgreSQL using %TYPE
Refactor a PL/pgSQL function to return the output of various SELECT queries
Asides:
Don't quote the language name, it's an identifier, not a string.
Do you really need WITH (oids = true) in your table? This is still allowed, but largely deprecated in modern Postgres.