I have this upsert function that allows me to modify the fill_rate column of a row.
CREATE FUNCTION upsert_fillrate_alarming(integer, boolean) RETURNS VOID AS '
DECLARE
num ALIAS FOR $1;
dat ALIAS FOR $2;
BEGIN
LOOP
-- First try to update.
UPDATE alarming SET fill_rate = dat WHERE equipid = num;
IF FOUND THEN
RETURN;
END IF;
-- Since its not there we try to insert the key
-- Notice if we had a concurent key insertion we would error
BEGIN
INSERT INTO alarming (equipid, fill_rate) VALUES (num, dat);
RETURN;
EXCEPTION WHEN unique_violation THEN
-- Loop and try the update again
END;
END LOOP;
END;
' LANGUAGE 'plpgsql';
Is it possible to modify this function to take a column argument as well? Extra bonus points if there is a way to modify the function to take a column and a table.
As an alternative approach, you can do an upsert without a function by using an insert + update with where clauses to make them only succeed in the right case. E.g.
update mytable set col1='value1' where (col2 = 'myId');
insert into mytable select 'value1', 'myId' where not exists (select 1 from mytable where col2='myId');
Which would avoid having lots of custom postgres specific functions.
You want to read about dynamic commands in plsql.
Just build your query and invoke EXECUTE.
Maybe a simpler approach, just less line ;)
CREATE OR REPLACE FUNCTION upsert_tableName(arg1 type, arg2 type) RETURNS VOID AS $$
DECLARE
BEGIN
UPDATE tableName SET col1 = value WHERE colX = arg1 and colY = arg2;
IF NOT FOUND THEN
INSERT INTO tableName values (value, arg1, arg2);
END IF;
END;
$$ LANGUAGE 'plpgsql';
Related
Does anyone know if it possible to declare the COUNT value as a variable to call in queries/functions/triggers?
I would like to use the COUNT value to trigger data transfer from table1 to table2, triggering when the row count of table1 reaches 500.
FIX.....
Defining count function:
CREATE OR REPLACE FUNCTION count_function () RETURNS integer AS $$
BEGIN
RETURN (SELECT COUNT(*) FROM table1);
END $$ LANGUAGE plpgsql;
Calling the variable to trigger an event:
CREATE OR REPLACE FUNCTION save_table2()
RETURNS trigger AS
$$
BEGIN
IF count_function()>=500 THEN
INSERT INTO table2
values ('NEW.column1','NEW.column2');
END IF;
RETURN NEW;
END $$
LANGUAGE plpgsql;
CREATE TRIGGER copy_trigger
AFTER INSERT ON table1
FOR EACH ROW
EXECUTE PROCEDURE save_table2();
Have you tried this (should work on MySQL and SQL Server, maybe PostgreSQL, too)?
SELECT count_function();
On Oracle it would be
SELECT count_function() FROM DUAL;
To store the result in a variable you can do this:
DECLARE result int;
SET result = SELECT count_function();
In your case the trigger can be written as:
CREATE TRIGGER copy_trigger
AFTER INSERT ON table1
FOR EACH STATEMENT
WHEN count_function() >= 500
EXECUTE PROCEDURE save_table2 ();
Notice that >= means greater or equal. While => does not exist (or is not what it looks like).
If nothing else helps, you can do this:
CREATE OR REPLACE FUNCTION save_table2_on_500()
RETURNS VOID AS $$
DECLARE cnt INTEGER;
BEGIN
cnt := (SELECT COUNT(*) FROM table1);
IF cnt >= 500 THEN
EXECUTE PROCEDURE save_table2();
END IF;
END $$ LANGUAGE plpgsql;
CREATE TRIGGER copy_trigger_on_500
AFTER INSERT ON table1
FOR EACH STATEMENT
EXECUTE PROCEDURE save_table2_on_500();
EDIT: What was wrong with the code
I've used the keyword PROCEDURE because it is very common on various database systems (SQL Server, Oracle, MySQL). But it is not legit on PostgreSQL.
On PostgreSQL you must use FUNCTION and specify the return type VOID, which I think is kind of a contradiction, but I'm digressing on details here.
The full explanation of function vs procedure is here.
The difference is mainly that a function returns always a scalar value while a procedure may return nothing (VOID), a scalar value or a data table. It is more flexible but also has other caveats. Refer to the link above for more details.
You should call the function not the variable from the function:
SELECT count_function ()
Also in the function you do not need the variable and have this:
RETURN (SELECT COUNT(*) FROM table1);
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?
Is it possible to execute an update conditionally if a column exists?
For instance, I may have a column in a table and if that column exists I want that update executed, otherwise, just skip it (or catch its exception).
You can do it inside a function. If you don't want to use the function later you can just drop it afterwards.
To know if a column exists in a certain table, you can try to fetch it using a select(or a perform, if you're gonna discard the result) in information_schema.columns.
The query bellow creates a function that searches for a column bar in a table foo, and if it finds it, updates its value. Later the function is run, then droped.
create function conditional_update() returns void as
$$
begin
perform column_name from information_schema.columns where table_name= 'foo' and column_name = 'bar';
if found then
update foo set bar = 12345;
end if;
end;
$$ language plpgsql;
select conditional_update();
drop function conditional_update();
With the following table as example :
CREATE TABLE mytable (
idx INT
,idy INT
);
insert into mytable values (1,2),(3,4),(5,6);
you can create a custom function like below to update:
create or replace function fn_upd_if_col_exists(_col text,_tbl text,_val int) returns void as
$$
begin
If exists (select 1
from information_schema.columns
where table_schema='public' and table_name=''||_tbl||'' and column_name=''||_col||'' ) then
execute format('update mytable set '||_col||'='||_val||'');
raise notice 'updated';
else
raise notice 'column %s doesn''t exists on table %s',_col,_tbl;
end if;
end;
$$
language plpgsql
and you can call this function like:
select fn_upd_if_col_exists1('idz','mytable',111) -- won't update raise "NOTICE: column idz deosnt exists on table mytables"
select fn_upd_if_col_exists1('idx','mytable',111) --will upadate column idx with value 1111 "NOTICE: updated"
I am trying to have a dynamic variable that I can specify different column's with (depending on some if statements). Explained in code, I am trying to replace this:
IF (TG_TABLE_NAME='this') THEN INSERT INTO table1 (name_id) VALUES id.NEW END IF;
IF (TG_TABLE_NAME='that') THEN INSERT INTO table1 (lastname_id) VALUES id.NEW END IF;
IF (TG_TABLE_NAME='another') THEN INSERT INTO table1 (age_id) VALUES id.NEW END IF;
With this:
DECLARE
varName COLUMN;
BEGIN
IF (TG_TABLE_NAME='this') THEN varName = 'name_id';
ELSE IF (TG_TABLE_NAME='that') THEN varName = 'lastname_id';
ELSE (TG_TABLE_NAME='another') THEN varName = 'age_id';
END IF;
INSERT INTO table1 (varName) VALUES id.NEW;
END;
The INSERT string is just an example, it's actually something longer. I am a beginner at pgSQL. I've seen some examples but I'm only getting more confused. If you can provide an answer that is also more safe from SQL injection that would be awesome.
One way to do what you're looking for is to compose your INSERT statement dynamically based on the named table. The following function approximates the logic you laid out in the question:
CREATE OR REPLACE FUNCTION smart_insert(table_name TEXT) RETURNS VOID AS $$
DECLARE
target TEXT;
statement TEXT;
BEGIN
CASE table_name
WHEN 'this' THEN target := 'name_id';
WHEN 'that' THEN target := 'lastname_id';
WHEN 'another' THEN target := 'age_id';
END CASE;
statement :=
'INSERT INTO '||table_name||'('||target||') VALUES (nextval(''id''));';
EXECUTE statement;
END;
$$ LANGUAGE plpgsql;
Note that I'm using a sequence to populate these tables (the call to nextval). I'm not sure if that is your use case, but hopefully this example is extensible enough for you to modify it to fit your scenario. A contrived demo:
postgres=# SELECT smart_insert('this');
smart_insert
--------------
(1 row)
postgres=# SELECT smart_insert('that');
smart_insert
--------------
(1 row)
postgres=# SELECT name_id FROM this;
name_id
---------
101
(1 row)
postgres=# SELECT lastname_id FROM that;
lastname_id
-------------
102
(1 row)
Your example doesn't make a lot of sense. Probably over-simplified. Anyway, here is a trigger function for the requested functionality that inserts the new id in a selected column of a target table, depending on the triggering table:
CREATE OR REPLACE FUNCTION smart_insert(table_name TEXT)
RETURNS trigger AS
$func$
BEGIN
EXECUTE
'INSERT INTO table1 ('
|| CASE TG_TABLE_NAME
WHEN 'this' THEN 'name_id'
WHEN 'that' THEN 'lastname_id'
WHEN 'another' THEN 'age_id'
END CASE
||') VALUES ($1)'
USING NEW.id;
END
$func$ LANGUAGE plpgsql;
To refer to the id column of the new row, use NEW.id not id.NEW.
To pass a value to dynamic code, use the USING clause of EXECUTE. This is faster and more elegant, avoids casting to text and back and also makes SQL injection impossible.
Don't use many variables and assignments in plpgsql, where this is comparatively expensive.
If the listed columns of the target table don't have non-default column defaults, you don't even need dynamic SQL:
CREATE OR REPLACE FUNCTION smart_insert(table_name TEXT)
RETURNS trigger AS
$func$
BEGIN
INSERT INTO table1 (name_id, lastname_id, age_id)
SELECT CASE WHEN TG_TABLE_NAME = 'this' THEN NEW.id END
, CASE WHEN TG_TABLE_NAME = 'that' THEN NEW.id END
, CASE WHEN TG_TABLE_NAME = 'another' THEN NEW.id END;
END
$func$ LANGUAGE plpgsql;
A CASE expression without ELSE clause defaults to NULL, which is the default column default.
Both variants are safe against SQL injection.
I'm trying to create a function to get a field value from multiple tables in my database. I made script like this:
CREATE OR REPLACE FUNCTION get_all_changes() RETURNS SETOF RECORD AS
$$
DECLARE
tblname VARCHAR;
tblrow RECORD;
row RECORD;
BEGIN
FOR tblrow IN SELECT tablename FROM pg_catalog.pg_tables WHERE schemaname='public' LOOP /*FOREACH tblname IN ARRAY $1 LOOP*/
RAISE NOTICE 'r: %', tblrow.tablename;
FOR row IN SELECT MAX("lastUpdate") FROM tblrow.tablename LOOP
RETURN NEXT row;
END LOOP;
END LOOP;
END
$$
LANGUAGE 'plpgsql' ;
SELECT get_all_changes();
But it is not working, everytime it shows this error
tblrow.tablename" not defined in line "FOR row IN SELECT MAX("lastUpdate") FROM tblrow.tablename LOOP"
Your inner FOR loop must use the FOR...EXECUTE syntax as shown in the manual:
FOR target IN EXECUTE text_expression [ USING expression [, ... ] ] LOOP
statements
END LOOP [ label ];
In your case something along this line:
FOR row IN EXECUTE 'SELECT MAX("lastUpdate") FROM ' || quote_ident(tblrow.tablename) LOOP
RETURN NEXT row;
END LOOP
The reason for this is explained in the manual somewhere else:
Oftentimes you will want to generate dynamic commands inside your PL/pgSQL functions, that is, commands that will involve different tables or different data types each time they are executed. PL/pgSQL's normal attempts to cache plans for commands (as discussed in Section 39.10.2) will not work in such scenarios. To handle this sort of problem, the EXECUTE statement is provided[...]
Answer to your new question (mislabeled as answer):
This can be much simpler. You do not need to create a table just do define a record type.
If at all, you would better create a type with CREATE TYPE, but that's only efficient if you need the type in multiple places. For just a single function, you can use RETURNS TABLE instead :
CREATE OR REPLACE FUNCTION get_all_changes(text[])
RETURNS TABLE (tablename text
,"lastUpdate" timestamp with time zone
,nums integer) AS
$func$
DECLARE
tblname text;
BEGIN
FOREACH tblname IN ARRAY $1 LOOP
RETURN QUERY EXECUTE format(
$f$SELECT '%I', MAX("lastUpdate"), COUNT(*)::int FROM %1$I
$f$, tblname)
END LOOP;
END
$func$ LANGUAGE plpgsql;
A couple more points:
Use RETURN QUERY EXECUTE instead of the nested loop. Much simpler and faster.
Column aliases would only serve as documentation, those names are discarded in favor of the names declared in the RETURNS clause (directly or indirectly).
Use format() with %I to replace the concatenation with quote_ident() and %1$I to refer to the same parameter another time.
count() usually returns type bigint. Cast the integer, since you defined the column in the return type as such: count(*)::int.
Thanks,
I finally made my script like:
CREATE TABLE IF NOT EXISTS __rsdb_changes (tablename text,"lastUpdate" timestamp with time zone, nums bigint);
CREATE OR REPLACE FUNCTION get_all_changes(varchar[]) RETURNS SETOF __rsdb_changes AS /*TABLE (tablename varchar(40),"lastUpdate" timestamp with time zone, nums integer)*/
$$
DECLARE
tblname VARCHAR;
tblrow RECORD;
row RECORD;
BEGIN
FOREACH tblname IN ARRAY $1 LOOP
/*RAISE NOTICE 'r: %', tblrow.tablename;*/
FOR row IN EXECUTE 'SELECT CONCAT('''|| quote_ident(tblname) ||''') AS tablename, MAX("lastUpdate") AS "lastUpdate",COUNT(*) AS nums FROM ' || quote_ident(tblname) LOOP
/*RAISE NOTICE 'row.tablename: %',row.tablename;*/
/*RAISE NOTICE 'row.lastUpdate: %',row."lastUpdate";*/
/*RAISE NOTICE 'row.nums: %',row.nums;*/
RETURN NEXT row;
END LOOP;
END LOOP;
RETURN;
END
$$
LANGUAGE 'plpgsql' ;
Well, it works. But it seems I can only create a table to define the return structure instead of just RETURNS SETOF RECORD. Am I right?
Thanks again.