Debugging Your PL/pgSQL Code

Who Am I?
● Jim Mlodgenski
– jimm@openscg.com
– @jim_mlodgenski
● Director
– United States PostgreSQL (www.postgresql.us)
● Co-organizer of
– Philly PUG (www.phlpug.org)
– NYC PUG (www.nycpug.org)
● CTO, OpenSCG
– www.openscg.com

Fantasy Football
● Fantasy football is a
statistical game in
which players compete
against each other by
managing groups of
real players or position
units selected from
American football
teams.

Business Rules
● Passing
– Touchdown (4 points)
– Every 25 yards (1 point)
– Interception (-1 point)
● Rushing
● Receiving

Procedures
CREATE OR REPLACE FUNCTION rushing_score(p_player_key VARCHAR,
p_year int,
p_week int)
RETURNS INT AS
$$
DECLARE
score INT;
BEGIN
-- 1 point for every 10 yards rushing
SELECT r.yards/10
INTO score
FROM rushing r, games g
WHERE r.game_id = g.game_id
AND g.year = p_year
AND g.week = p_week
AND r.player_key = p_player_key;
IF score IS NULL THEN
RETURN 0;
END IF;
RETURN score;
END;
$$ LANGUAGE plpgsql;

Procedures
CREATE OR REPLACE FUNCTION player_game_score(p_player_key VARCHAR, p_year int, p_week int)
...
BEGIN
score := 0;
-- Get the position of the player
SELECT position
INTO l_position
FROM player
WHERE player_key = p_player_key;
IF l_position = 'qb' THEN
score := score + passing_score(p_player_key, p_year, p_week);
score := score + rushing_score(p_player_key, p_year, p_week);
score := score + td_score(p_player_key, p_year, p_week);
ELSIF l_position = 'rb' THEN
score := score + rushing_score(p_player_key, p_year, p_week);
ELSIF l_position = 'wr' THEN
score := score + receiving_score(p_player_key, p_year, p_week);
ELSIF l_position = 'te' THEN
score := score + receiving_score(p_player_key, p_year, p_week);
ELSE
return 0;
END IF;
return score;
END;

Procedures
CREATE OR REPLACE FUNCTION avg_yearly_score(p_player_key
VARCHAR,
p_year int)
RETURNS REAL AS
$$
DECLARE
score INT;
i INT;
BEGIN
score := 0;
FOR i IN 1..17 LOOP
score := score + player_game_score(p_player_key,
p_year, i);
END LOOP;
RETURN score/16.0;
END;

Debugging: RAISE
CREATE OR REPLACE FUNCTION passing_score(p_player_key VARCHAR, p_year int, p_week
int)
RETURNS INT AS
$$
...
BEGIN
score := 0;
-- 1 point for every 25 yards passing
SELECT p.pass_yards/25
INTO yardage_score
FROM passing p, games g
WHERE p.game_id = g.game_id
AND g.year = p_year
AND g.week = p_week
AND p.player_key = p_player_key;
IF yardage_score IS NULL THEN
yardage_score := 0;
END IF;
RAISE NOTICE 'Passing Yards Score: %', yardage_score;

Debugging: RAISE
nfl=# select passing_score('BreeDr00',
2005, 5);
NOTICE: Passing Yards Score: 8
NOTICE: Passing TD Score: 4
NOTICE: Interception Score: -2
passing_score
---------------
10
(1 row)

Debugger
git://git.postgresql.org/git/pldebugger.git
make USE_PGXS=1
make install USE_PGXS=1
- OR -
http://community.openscg.com/se/postgresql/packages.jsp
shared_preload_libraries =
'$libdir/plugin_debugger'
CREATE EXTENSION pldbgapi;

Debugging: RAISE
nfl=# SELECT p.first_name, p.last_name,
p.position,
avg_yearly_score(p.player_key, 2006) AS score
FROM player p
WHERE p.player_key IN (SELECT *
FROM yearly_player(2005))
AND avg_yearly_score(p.player_key, 2006) > 10
ORDER BY 4 DESC;

Debugging: RAISE
CONTEXT: PL/pgSQL function player_game_score(character varying,integer,integer) line 15 at assignment
PL/pgSQL function avg_yearly_score(character varying,integer) line 9 at assignment
NOTICE: Interception Score: 0
...

Track Functions
set track_functions = 'PL';
nfl=# SELECT * FROM pg_stat_user_functions;
funcid | schemaname | funcname | calls | total_time | self_time
--------+------------+-------------------+-------+------------+-----------
20564 | public | avg_yearly_score | 547 | 7011.25 | 13.33
20565 | public | passing_score | 1666 | 1551.862 | 1551.862
20566 | public | player_game_score | 9299 | 6997.92 | 188.718
20567 | public | receiving_score | 4811 | 2465.982 | 2465.982
20568 | public | rushing_score | 4488 | 2303.934 | 2303.934
20569 | public | td_score | 9299 | 487.424 | 487.424
20570 | public | yearly_player | 1 | 14.139 | 14.139
(7 rows)

Profiler
https://bitbucket.org/openscg/plprofiler.git
make USE_PGXS=1
make install USE_PGXS=1
- OR -
http://community.openscg.com/se/postgresql/packages.jsp
shared_preload_libraries =
'$libdir/plprofiler.so'
CREATE EXTENSION plprofiler;

Profiler
nfl=# SELECT * FROM pl_profiler;
ERROR: plprofiler must be loaded and enabled
STATEMENT: SELECT * FROM pl_profiler;
nfl=# SELECT pl_profiler_enable(true);
pl_profiler_enable
--------------------
t
(1 row)

Profiler
nfl=# SELECT * FROM pl_profiler;
func_oid | line_number | line | exec_count | total_time | longest_time
----------+-------------+----------------------------------------------------------------------+------------+------------+--------------
99155 | 1 | | 0 | 0 | 0
99155 | 2 | DECLARE | 0 | 0 | 0
99155 | 3 | l_position VARCHAR; | 0 | 0 | 0
99155 | 4 | score INT; | 0 | 0 | 0
99155 | 5 | BEGIN | 0 | 0 | 0
99155 | 6 | score := 0; | 9299 | 5519 | 18
99155 | 7 | | 0 | 0 | 0
99155 | 8 | -- Get the position of the player | 0 | 0 | 0
99155 | 9 | SELECT position | 9299 | 114556 | 136
99155 | 10 | INTO l_position | 0 | 0 | 0
99155 | 11 | FROM player | 0 | 0 | 0
99155 | 12 | WHERE player_key = p_player_key; | 0 | 0 | 0
99155 | 13 | | 0 | 0 | 0
99155 | 14 | IF l_position = 'qb' THEN | 9299 | 7011451 | 2854
99155 | 15 | score := score + passing_score(p_player_key, p_year, p_week); | 1666 | 1591910 | 2101
99155 | 16 | score := score + rushing_score(p_player_key, p_year, p_week); | 1666 | 873194 | 744
99155 | 17 | score := score + td_score(p_player_key, p_year, p_week); | 1666 | 138214 | 320
99155 | 18 | ELSIF l_position = 'rb' THEN | 0 | 0 | 0
99155 | 19 | score := score + rushing_score(p_player_key, p_year, p_week); | 2822 | 1470068 | 961
99155 | 21 | ELSIF l_position = 'wr' THEN | 0 | 0 | 0
99155 | 22 | score := score + receiving_score(p_player_key, p_year, p_week); | 3111 | 1649303 | 1028
99155 | 24 | ELSIF l_position = 'te' THEN | 0 | 0 | 0
99155 | 25 | score := score + receiving_score(p_player_key, p_year, p_week); | 1700 | 902277 | 870
99155 | 27 | ELSE | 0 | 0 | 0
99155 | 28 | return 0; | 0 | 0 | 0
99155 | 29 | END IF; | 0 | 0 | 0

Profiler
nfl=# SELECT func_oid::regprocedure, line_number, substr(line, 0, 30),
nfl-# (total_time::numeric)/(exec_count::numeric), exec_count
nfl-# FROM pl_profiler
nfl-# WHERE exec_count > 0
nfl-# ORDER BY 4 DESC;
func_oid | line_number | substr | ?column? | exec_count
------------------------------------------------------+-------------+-------------------------------+------------------------+------------
yearly_player(integer) | 3 | RETURN QUERY SELECT DISTINC | 27455.000000000000 | 1
avg_yearly_score(character varying,integer) | 8 | FOR i IN 1..17 LOOP | 12840.711151736746 | 547
player_game_score(character varying,integer,integer) | 15 | score := score + passing | 926.8511404561824730 | 1666
avg_yearly_score(character varying,integer) | 9 | score := score + player_g | 755.1645338208409506 | 9299
player_game_score(character varying,integer,integer) | 14 | IF l_position = 'qb' THEN | 735.3543391762555113 | 9299
player_game_score(character varying,integer,integer) | 25 | score := score + receivi | 518.6929411764705882 | 1700
player_game_score(character varying,integer,integer) | 22 | score := score + receivi | 512.6878817100610736 | 3111
receiving_score(character varying,integer,integer) | 6 | SELECT r.yards/10 | 507.6599459571814592 | 4811
player_game_score(character varying,integer,integer) | 19 | score := score + rushing | 503.4840538625088590 | 2822
player_game_score(character varying,integer,integer) | 16 | score := score + rushing | 503.2094837935174070 | 1666
rushing_score(character varying,integer,integer) | 6 | SELECT r.yards/10 | 495.7384135472370766 | 4488
passing_score(character varying,integer,integer) | 11 | SELECT p.pass_yards/25 | 417.8895558223289316 | 1666
passing_score(character varying,integer,integer) | 37 | SELECT p.interceptions * -2 | 409.1992797118847539 | 1666
player_game_score(character varying,integer,integer) | 17 | score := score + td_scor | 83.6602641056422569 | 1666
passing_score(character varying,integer,integer) | 24 | SELECT p.passing * 4 | 83.1236494597839136 | 1666
td_score(character varying,integer,integer) | 6 | SELECT t.other * 6 | 50.4611248521346381 | 9299
player_game_score(character varying,integer,integer) | 9 | SELECT position | 13.0637702978814926 | 9299
passing_score(character varying,integer,integer) | 19 | IF yardage_score IS NULL TH | 2.2893157262905162 | 1666
passing_score(character varying,integer,integer) | 45 | IF int_score IS NULL THEN | 2.1248499399759904 | 1666
rushing_score(character varying,integer,integer) | 14 | IF score IS NULL THEN | 2.1033868092691622 | 4488
receiving_score(character varying,integer,integer) | 14 | IF score IS NULL THEN | 2.0700478071087092 | 4811
td_score(character varying,integer,integer) | 14 | IF score IS NULL THEN | 1.9494569308527799 | 9299

Summary
● Be careful running these tools on
production systems
– They do have some performance impact
● Building the extensions are simple, but still
require a development environment
● The debugger and the profiler use the
same hooks so at the moment they can not
be used at the same time

Questions?
jimm@openscg.com
@jim_mlodgenski

Debugging Your PL/pgSQL Code

More Related Content

Viewers also liked (20)

More from Jim Mlodgenski (6)

Recently uploaded (20)

Debugging Your PL/pgSQL Code