the-lost-art-of-plpgsql
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The document is a presentation by Robert Treat on PL/pgSQL, focusing on its usage for creating stored procedures and user-defined functions in PostgreSQL. It provides an overview of PL/pgSQL features, including examples of queries and functions, and discusses the differences between functions and stored procedures. The presentation emphasizes the utility of PL/pgSQL in server-side computation and its integration with PostgreSQL's features.
![Robert Treat (@robtreat2) the lost art of plpgsql
stored procedures, turned up to 11
postgres@pagila=# h create procedure
Command: CREATE PROCEDURE
Description: define a new procedure
Syntax:
CREATE [ OR REPLACE ] PROCEDURE
name ( [ [ argmode ] [ argname ] argtype [ { DEFAULT | = }
default_expr ] [, ...] ] )
{ LANGUAGE lang_name
| TRANSFORM { FOR TYPE type_name } [, ... ]
| [ EXTERNAL ] SECURITY INVOKER | [ EXTERNAL ] SECURITY DEFINER
| SET configuration_parameter { TO value | = value | FROM CURRENT }
| AS 'definition'
| AS 'obj_file', 'link_symbol'
} ...](https://image.slidesharecdn.com/lost-art-of-plpgsql-190606171950/85/the-lost-art-of-plpgsql-34-320.jpg)
![Robert Treat (@robtreat2) the lost art of plpgsql
stored procedures, turned up to 11
postgres@pagila=# h call
Command: CALL
Description: invoke a procedure
Syntax:
CALL name ( [ argument ] [, ...] )](https://image.slidesharecdn.com/lost-art-of-plpgsql-190606171950/85/the-lost-art-of-plpgsql-35-320.jpg)
the-lost-art-of-plpgsql
- 1. The Lost Art of PLPGSQL pgcon 2019 Robert Treat (@robtreat2) the lost art of plpgsql NOTE: There Will Be Code!
- 2. Robert Treat (@robtreat2) the lost art of plpgsql whoami? occasional dev | ops | dba currently lead u.s. operations at credativ open source services and support we build and run world class applications and infrastructure to empower our clients
- 3. Robert Treat (@robtreat2) the lost art of plpgsql whoami? @robtreat2 robert.treat@credativ.us https://www.linkedin.com/company/credativ-llc
- 4. Robert Treat (@robtreat2) the lost art of plpgsql a brief overview of postgres functions how many of you have used a postgres function?
- 5. Robert Treat (@robtreat2) the lost art of plpgsql why plpgsql server side / round trips stable api simplify portability*
- 6. Robert Treat (@robtreat2) the lost art of plpgsql a brief overview of postgres functions four types of postgres functions: • internal functions • query language functions (functions written in SQL) • procedural language functions (functions written in PL/pgSQL) • C-language functions they all work similarly and have overlapping bits, today we only care about procedural language functions specifically plpgsql ones
- 7. Robert Treat (@robtreat2) the lost art of plpgsql a brief overview of postgres functions https://www.postgresql.org/docs/current/sql-createfunction.html
- 8. Robert Treat (@robtreat2) the lost art of plpgsql a brief overview of plpgsql Chapter 42 “PL/pgSQL - SQL Procedural Language” note: you can write stored procedures in pure SQL, but this is not that
- 9. Robert Treat (@robtreat2) the lost art of plpgsql a very brief overview of plpgsql originally added in 6.4 (pl/tcl added in 6.3) installed by default in 9.0 minimal language for creating triggers and user defined functions add basic control structures to SQL “trusted” language for server side computation
- 10. Robert Treat (@robtreat2) the lost art of plpgsql a brief overview of plpgsql get diagnostics when doing dynamic query execution “get diagnostics” can be used for finding row count and call stack information additionally, /FOUND/ variable can be used to determine query outcomes 42.5.5 Obtaining the Result Status
- 11. Robert Treat (@robtreat2) the lost art of plpgsql an example plpgsql function CREATE OR REPLACE FUNCTION inventory_in_stock(p_inventory_id integer) RETURNS boolean LANGUAGE plpgsql AS $$ DECLARE v_rentals INTEGER; v_out INTEGER; BEGIN -- AN ITEM IS IN-STOCK IF THERE ARE EITHER NO ROWS IN THE rental TABLE -- FOR THE ITEM OR ALL ROWS HAVE return_date POPULATED SELECT count(*) INTO v_rentals FROM rental WHERE inventory_id = p_inventory_id; IF v_rentals = 0 THEN RETURN TRUE; END IF; SELECT COUNT(rental_id) INTO v_out FROM inventory LEFT JOIN rental USING(inventory_id) WHERE inventory.inventory_id = p_inventory_id AND rental.return_date IS NULL; IF v_out > 0 THEN RETURN FALSE; ELSE RETURN TRUE; END IF; END $$;
- 12. Robert Treat (@robtreat2) the lost art of plpgsql a brief overview of plpgsql CREATE OR REPLACE FUNCTION inventory_in_stock(p_inventory_id integer) RETURNS boolean LANGUAGE plpgsql AS $$ DECLARE v_rentals INTEGER; v_out INTEGER; BEGIN -- AN ITEM IS IN-STOCK IF THERE ARE EITHER NO ROWS IN THE rental TABLE -- FOR THE ITEM OR ALL ROWS HAVE return_date POPULATED SELECT count(*) INTO v_rentals FROM rental WHERE inventory_id = p_inventory_id; IF v_rentals = 0 THEN RETURN TRUE; END IF; SELECT COUNT(rental_id) INTO v_out FROM inventory LEFT JOIN rental USING(inventory_id) WHERE inventory.inventory_id = p_inventory_id AND rental.return_date IS NULL; IF v_out > 0 THEN RETURN FALSE; ELSE RETURN TRUE; END IF; END $$;
- 13. Robert Treat (@robtreat2) the lost art of plpgsql a brief overview of plpgsql CREATE OR REPLACE FUNCTION inventory_in_stock(p_inventory_id integer) RETURNS boolean LANGUAGE plpgsql AS $$ DECLARE v_rentals INTEGER; v_out INTEGER; BEGIN -- AN ITEM IS IN-STOCK IF THERE ARE EITHER NO ROWS IN THE rental TABLE -- FOR THE ITEM OR ALL ROWS HAVE return_date POPULATED SELECT count(*) INTO v_rentals FROM rental WHERE inventory_id = p_inventory_id; IF v_rentals = 0 THEN RETURN TRUE; END IF; SELECT COUNT(rental_id) INTO v_out FROM inventory LEFT JOIN rental USING(inventory_id) WHERE inventory.inventory_id = p_inventory_id AND rental.return_date IS NULL; IF v_out > 0 THEN RETURN FALSE; ELSE RETURN TRUE; END IF; END $$;
- 14. Robert Treat (@robtreat2) the lost art of plpgsql a brief overview of plpgsql CREATE OR REPLACE FUNCTION inventory_in_stock(p_inventory_id integer) RETURNS boolean LANGUAGE plpgsql AS $$ DECLARE v_rentals INTEGER; v_out INTEGER; BEGIN -- AN ITEM IS IN-STOCK IF THERE ARE EITHER NO ROWS IN THE rental TABLE -- FOR THE ITEM OR ALL ROWS HAVE return_date POPULATED SELECT count(*) INTO v_rentals FROM rental WHERE inventory_id = p_inventory_id; IF v_rentals = 0 THEN RETURN TRUE; END IF; SELECT COUNT(rental_id) INTO v_out FROM inventory LEFT JOIN rental USING(inventory_id) WHERE inventory.inventory_id = p_inventory_id AND rental.return_date IS NULL; IF v_out > 0 THEN RETURN FALSE; ELSE RETURN TRUE; END IF; END $$;
- 15. Robert Treat (@robtreat2) the lost art of plpgsql an example plpgsql function CREATE OR REPLACE FUNCTION inventory_in_stock(p_inventory_id integer) RETURNS boolean LANGUAGE plpgsql AS $$ DECLARE v_rentals INTEGER; v_out INTEGER; BEGIN -- AN ITEM IS IN-STOCK IF THERE ARE EITHER NO ROWS IN THE rental TABLE -- FOR THE ITEM OR ALL ROWS HAVE return_date POPULATED SELECT count(*) INTO v_rentals FROM rental WHERE inventory_id = p_inventory_id; IF v_rentals = 0 THEN RETURN TRUE; END IF; SELECT COUNT(rental_id) INTO v_out FROM inventory LEFT JOIN rental USING(inventory_id) WHERE inventory.inventory_id = p_inventory_id AND rental.return_date IS NULL; IF v_out > 0 THEN RETURN FALSE; ELSE RETURN TRUE; END IF; END $$;
- 16. Robert Treat (@robtreat2) the lost art of plpgsql an example plpgsql function CREATE OR REPLACE FUNCTION inventory_in_stock(p_inventory_id integer) RETURNS boolean LANGUAGE plpgsql AS $$ DECLARE v_rentals INTEGER; v_out INTEGER; BEGIN -- AN ITEM IS IN-STOCK IF THERE ARE EITHER NO ROWS IN THE rental TABLE -- FOR THE ITEM OR ALL ROWS HAVE return_date POPULATED SELECT count(*) INTO v_rentals FROM rental WHERE inventory_id = p_inventory_id; IF v_rentals = 0 THEN RETURN TRUE; END IF; SELECT COUNT(rental_id) INTO v_out FROM inventory LEFT JOIN rental USING(inventory_id) WHERE inventory.inventory_id = p_inventory_id AND rental.return_date IS NULL; IF v_out > 0 THEN RETURN FALSE; ELSE RETURN TRUE; END IF; END $$;
- 17. Robert Treat (@robtreat2) the lost art of plpgsql an example plpgsql function CREATE OR REPLACE FUNCTION inventory_in_stock(p_inventory_id integer) RETURNS boolean LANGUAGE plpgsql AS $$ DECLARE v_rentals INTEGER; v_out INTEGER; BEGIN -- AN ITEM IS IN-STOCK IF THERE ARE EITHER NO ROWS IN THE rental TABLE -- FOR THE ITEM OR ALL ROWS HAVE return_date POPULATED SELECT count(*) INTO v_rentals FROM rental WHERE inventory_id = p_inventory_id; IF v_rentals = 0 THEN RETURN TRUE; END IF; SELECT COUNT(rental_id) INTO v_out FROM inventory LEFT JOIN rental USING(inventory_id) WHERE inventory.inventory_id = p_inventory_id AND rental.return_date IS NULL; IF v_out > 0 THEN RETURN FALSE; ELSE RETURN TRUE; END IF; END $$;
- 18. Robert Treat (@robtreat2) the lost art of plpgsql an example plpgsql function CREATE OR REPLACE FUNCTION inventory_in_stock(p_inventory_id integer) RETURNS boolean LANGUAGE plpgsql AS $$ DECLARE v_rentals INTEGER; v_out INTEGER; BEGIN -- AN ITEM IS IN-STOCK IF THERE ARE EITHER NO ROWS IN THE rental TABLE -- FOR THE ITEM OR ALL ROWS HAVE return_date POPULATED SELECT count(*) INTO v_rentals FROM rental WHERE inventory_id = p_inventory_id; IF v_rentals = 0 THEN RETURN TRUE; END IF; SELECT COUNT(rental_id) INTO v_out FROM inventory LEFT JOIN rental USING(inventory_id) WHERE inventory.inventory_id = p_inventory_id AND rental.return_date IS NULL; IF v_out > 0 THEN RETURN FALSE; ELSE RETURN TRUE; END IF; END $$;
- 19. Robert Treat (@robtreat2) the lost art of plpgsql an example plpgsql function CREATE OR REPLACE FUNCTION inventory_in_stock(p_inventory_id integer) RETURNS boolean LANGUAGE plpgsql AS $$ DECLARE v_rentals INTEGER; v_out INTEGER; BEGIN -- AN ITEM IS IN-STOCK IF THERE ARE EITHER NO ROWS IN THE rental TABLE -- FOR THE ITEM OR ALL ROWS HAVE return_date POPULATED SELECT count(*) INTO v_rentals FROM rental WHERE inventory_id = p_inventory_id; IF v_rentals = 0 THEN RETURN TRUE; END IF; SELECT COUNT(rental_id) INTO v_out FROM inventory LEFT JOIN rental USING(inventory_id) WHERE inventory.inventory_id = p_inventory_id AND rental.return_date IS NULL; IF v_out > 0 THEN RETURN FALSE; ELSE RETURN TRUE; END IF; END $$;
- 20. Robert Treat (@robtreat2) the lost art of plpgsql an example plpgsql function CREATE OR REPLACE FUNCTION inventory_in_stock(p_inventory_id integer) RETURNS boolean LANGUAGE plpgsql AS $$ DECLARE v_rentals INTEGER; v_out INTEGER; BEGIN -- AN ITEM IS IN-STOCK IF THERE ARE EITHER NO ROWS IN THE rental TABLE -- FOR THE ITEM OR ALL ROWS HAVE return_date POPULATED SELECT count(*) INTO v_rentals FROM rental WHERE inventory_id = p_inventory_id; IF v_rentals = 0 THEN RETURN TRUE; END IF; SELECT COUNT(rental_id) INTO v_out FROM inventory LEFT JOIN rental USING(inventory_id) WHERE inventory.inventory_id = p_inventory_id AND rental.return_date IS NULL; IF v_out > 0 THEN RETURN FALSE; ELSE RETURN TRUE; END IF; END $$;
- 21. Robert Treat (@robtreat2) the lost art of plpgsql an example plpgsql function CREATE OR REPLACE FUNCTION inventory_in_stock(p_inventory_id integer) RETURNS boolean LANGUAGE plpgsql AS $$ DECLARE v_rentals INTEGER; v_out INTEGER; BEGIN -- AN ITEM IS IN-STOCK IF THERE ARE EITHER NO ROWS IN THE rental TABLE -- FOR THE ITEM OR ALL ROWS HAVE return_date POPULATED SELECT count(*) INTO v_rentals FROM rental WHERE inventory_id = p_inventory_id; IF v_rentals = 0 THEN RETURN TRUE; END IF; SELECT COUNT(rental_id) INTO v_out FROM inventory LEFT JOIN rental USING(inventory_id) WHERE inventory.inventory_id = p_inventory_id AND rental.return_date IS NULL; IF v_out > 0 THEN RETURN FALSE; ELSE RETURN TRUE; END IF; END $$;
- 22. Robert Treat (@robtreat2) the lost art of plpgsql an example plpgsql function CREATE OR REPLACE FUNCTION inventory_in_stock(p_inventory_id integer) RETURNS boolean LANGUAGE plpgsql AS $$ DECLARE v_rentals INTEGER; v_out INTEGER; BEGIN -- AN ITEM IS IN-STOCK IF THERE ARE EITHER NO ROWS IN THE rental TABLE -- FOR THE ITEM OR ALL ROWS HAVE return_date POPULATED SELECT count(*) INTO v_rentals FROM rental WHERE inventory_id = p_inventory_id; IF v_rentals = 0 THEN RETURN TRUE; END IF; SELECT COUNT(rental_id) INTO v_out FROM inventory LEFT JOIN rental USING(inventory_id) WHERE inventory.inventory_id = p_inventory_id AND rental.return_date IS NULL; IF v_out > 0 THEN RETURN FALSE; ELSE RETURN TRUE; END IF; END $$;
- 23. Robert Treat (@robtreat2) the lost art of plpgsql an example plpgsql function CREATE OR REPLACE FUNCTION inventory_in_stock(p_inventory_id integer) RETURNS boolean LANGUAGE plpgsql AS $$ DECLARE v_rentals INTEGER; v_out INTEGER; BEGIN -- AN ITEM IS IN-STOCK IF THERE ARE EITHER NO ROWS IN THE rental TABLE -- FOR THE ITEM OR ALL ROWS HAVE return_date POPULATED SELECT count(*) INTO v_rentals FROM rental WHERE inventory_id = p_inventory_id; IF v_rentals = 0 THEN RETURN TRUE; END IF; SELECT COUNT(rental_id) INTO v_out FROM inventory LEFT JOIN rental USING(inventory_id) WHERE inventory.inventory_id = p_inventory_id AND rental.return_date IS NULL; IF v_out > 0 THEN RETURN FALSE; ELSE RETURN TRUE; END IF; END $$;
- 24. Robert Treat (@robtreat2) the lost art of plpgsql an example plpgsql procedure postgres@pagila=# select inventory_in_stock(42); inventory_in_stock -------------------- t (1 row)
- 25. Robert Treat (@robtreat2) the lost art of plpgsql how to plpgsql user defined functions do scripts stored procedures
- 26. postgres@pagila=# DO $$ DECLARE v_row record; BEGIN FOR v_row IN SELECT film_id, title, rating FROM film WHERE film_id < 10 LOOP IF v_row.rating ='G'::mpaa_rating THEN RAISE NOTICE '% is safe for tv',v_row.title; END IF; END LOOP; END$$ ; NOTICE: ACE GOLDFINGER is safe for tv NOTICE: AFFAIR PREJUDICE is safe for tv NOTICE: AFRICAN EGG is safe for tv DO Robert Treat (@robtreat2) the lost art of plpgsql at least one slide on DO scripts https://www.postgresql.org/docs/current/sql-do.html
- 27. postgres@pagila=# DO$$ BEGIN vacuum actor; vacuum film; END $$; ERROR: VACUUM cannot be executed from a function CONTEXT: SQL statement "vacuum actor" PL/pgSQL function inline_code_block line 1 at SQL statement Robert Treat (@robtreat2) the lost art of plpgsql at least one slide on DO scripts
- 28. Robert Treat (@robtreat2) the lost art of plpgsql what even is a procedure? enter stored procedures
- 29. Robert Treat (@robtreat2) the lost art of plpgsql what even is a procedure? but first a history
- 30. Robert Treat (@robtreat2) the lost art of plpgsql what even is a procedure? “other databases say” functions: user defined code that executes some set of commands and returns a result stored procedures: user defined code that executes some set of commands returning no result
- 31. Robert Treat (@robtreat2) the lost art of plpgsql what even is a procedure? create function smored_promedure() returns void as $$ begin return; end $$ language plpgsql; postgres@pagila=# select smored_promedure(); smored_promedure ------------------ (1 row)
- 32. Robert Treat (@robtreat2) the lost art of plpgsql what even is a procedure? “in postgres, functions are equivalent to stored procedures, and can be used interchangeably”
- 33. Robert Treat (@robtreat2) the lost art of plpgsql stored procedures, turned up to 11 sql standard based allow transaction control
- 34. Robert Treat (@robtreat2) the lost art of plpgsql stored procedures, turned up to 11 postgres@pagila=# h create procedure Command: CREATE PROCEDURE Description: define a new procedure Syntax: CREATE [ OR REPLACE ] PROCEDURE name ( [ [ argmode ] [ argname ] argtype [ { DEFAULT | = } default_expr ] [, ...] ] ) { LANGUAGE lang_name | TRANSFORM { FOR TYPE type_name } [, ... ] | [ EXTERNAL ] SECURITY INVOKER | [ EXTERNAL ] SECURITY DEFINER | SET configuration_parameter { TO value | = value | FROM CURRENT } | AS 'definition' | AS 'obj_file', 'link_symbol' } ...
- 35. Robert Treat (@robtreat2) the lost art of plpgsql stored procedures, turned up to 11 postgres@pagila=# h call Command: CALL Description: invoke a procedure Syntax: CALL name ( [ argument ] [, ...] )
- 36. Robert Treat (@robtreat2) the lost art of plpgsql an example plpgsql procedure CREATE OR REPLACE PROCEDURE inventory_in_sproc(p_inventory_id integer) LANGUAGE plpgsql AS $$ DECLARE v_rentals INTEGER; v_out INTEGER; BEGIN -- AN ITEM IS IN-STOCK IF THERE ARE EITHER NO ROWS IN THE rental TABLE -- FOR THE ITEM OR ALL ROWS HAVE return_date POPULATED SELECT count(*) INTO v_rentals FROM rental WHERE inventory_id = p_inventory_id; IF v_rentals = 0 THEN RAISE NOTICE ‘TRUE’; END IF; SELECT COUNT(rental_id) INTO v_out FROM inventory LEFT JOIN rental USING(inventory_id) WHERE inventory.inventory_id = p_inventory_id AND rental.return_date IS NULL; IF v_out > 0 THEN RAISE NOTICE ‘FALSE’; ELSE RAISE NOTICE ‘TRUE’; END IF; END $$;
- 37. Robert Treat (@robtreat2) the lost art of plpgsql an example plpgsql procedure CREATE OR REPLACE PROCEDURE inventory_in_sproc(p_inventory_id integer) LANGUAGE plpgsql AS $$ DECLARE v_rentals INTEGER; v_out INTEGER; BEGIN -- AN ITEM IS IN-STOCK IF THERE ARE EITHER NO ROWS IN THE rental TABLE -- FOR THE ITEM OR ALL ROWS HAVE return_date POPULATED SELECT count(*) INTO v_rentals FROM rental WHERE inventory_id = p_inventory_id; IF v_rentals = 0 THEN RAISE NOTICE ‘TRUE’; END IF; SELECT COUNT(rental_id) INTO v_out FROM inventory LEFT JOIN rental USING(inventory_id) WHERE inventory.inventory_id = p_inventory_id AND rental.return_date IS NULL; IF v_out > 0 THEN RAISE NOTICE ‘FALSE’; ELSE RAISE NOTICE ‘TRUE’; END IF; END $$;
- 38. Robert Treat (@robtreat2) the lost art of plpgsql an example plpgsql procedure postgres@pagila=# call inventory_in_sproc(42); NOTICE: TRUE CALL postgres@pagila=# select inventory_in_stock(42); inventory_in_stock -------------------- t (1 row)
- 39. Robert Treat (@robtreat2) the lost art of plpgsql an example plpgsql procedure CREATE OR REPLACE PROCEDURE inventory_in_shock( IN p_inventory_id integer, INOUT p_instock boolean DEFAULT false ) LANGUAGE plpgsql AS $$ DECLARE v_rentals INTEGER; v_out INTEGER; BEGIN -- AN ITEM IS IN-STOCK IF THERE ARE EITHER NO ROWS IN THE rental TABLE -- FOR THE ITEM OR ALL ROWS HAVE return_date POPULATED SELECT count(*) INTO v_rentals FROM rental WHERE inventory_id = p_inventory_id; IF v_rentals = 0 THEN p_instock := TRUE; END IF; SELECT COUNT(rental_id) INTO v_out FROM inventory LEFT JOIN rental USING(inventory_id) WHERE inventory.inventory_id = p_inventory_id AND rental.return_date IS NULL; IF v_out > 0 THEN p_instock := FALSE; ELSE p_instock := TRUE; END IF; END $$;
- 40. Robert Treat (@robtreat2) the lost art of plpgsql an example plpgsql procedure postgres@pagila=# call inventory_in_sproc(42); NOTICE: TRUE CALL postgres@pagila=# select inventory_in_stock(42); inventory_in_stock -------------------- t (1 row) postgres@pagila=# call inventory_in_shock(42); p_instock ----------- t (1 row)
- 41. Robert Treat (@robtreat2) the lost art of plpgsql plpgsql procedure transaction control postgres@pagila=# create table xx (xx int); CREATE TABLE postgres@pagila=# create or replace procedure xx() as $$ begin insert into xx select 1; rollback; insert into xx select 2; commit; insert into xx select 3; rollback; end $$ language plpgsql; CREATE PROCEDURE postgres@pagila=# call xx(); CALL postgres@pagila=# select * from xx; xx ---- 2 (1 row)
- 42. Robert Treat (@robtreat2) the lost art of plpgsql plpgsql procedure transaction control postgres@pagila=# create or replace procedure merry_maids() as $$ begin vacuum actor; end $$ language plpgsql; CREATE PROCEDURE postgres@pagila=# call merry_maids(); ERROR: VACUUM cannot be executed from a function CONTEXT: SQL statement "vacuum actor” * fyi, you can do this with analyze
- 43. Robert Treat (@robtreat2) the lost art of plpgsql more to do! certain ddl - create index concurrently vacuum support multiple result-sets
- 44. #thankyou Robert Treat (@robtreat2) the lost art of plpgsql