A PostgreSQL's plpgsql interpreter uses a two step checking. First step is syntax checking when function is validated - it is done on function's creation time or when function is executed first time in a session. Second step - a deeper checks of embedded SQL and expressions are done in runtime when SQL or expression is evaluated first time in a session. This step is slower and this technique eliminates checking of SQL or expressions that are never evaluated (but some errors can be found too late).
plpgsql_lint ensures a deep validation of all embedded SQL and expressions (not only evaluated) every time when function is started.
- copy the source code to PostgreSQL's source code tree (8.4.x, 9.0.x, 9.1.x, [9.2.x], 9.3.x) - to contrib directory
- compile it there and install it - make; make install
postgres=# load 'plpgsql'; LOAD postgres=# load 'plpgsql_lint'; LOAD postgres=# CREATE TABLE t1(a int, b int); CREATE TABLE postgres=# CREATE OR REPLACE FUNCTION public.f1() RETURNS void LANGUAGE plpgsql AS $function$ DECLARE r record; BEGIN FOR r IN SELECT * FROM t1 LOOP RAISE NOTICE '%', r.c; -- there is bug - table t1 missing "c" column END LOOP; END; $function$; CREATE FUNCTION postgres=# select f1(); ERROR: record "r" has no field "c" CONTEXT: SQL statement "SELECT r.c" PL/pgSQL function "f1" line 5 at RAISE
The function f1() can be executed successfully without active plpgsql_lint, because table t1 is empty and RAISE statement will never be executed. When plpgsql_lint is active, then this badly written expression is identified.
This module can be deactivated by setting
SET plpgsql.enable_lint TO false;
plpgsql_lint should find almost all errors on really static code. When developer uses some PLpgSQL's dynamic features like dynamic SQL or record data type, then false positives are possible. These should be rare - in well written code - and then the affected function should be redesigned or plpgsql_lint should be disabled for this function.
CREATE OR REPLACE FUNCTION f1() RETURNS void AS $$ DECLARE r record; BEGIN FOR r IN EXECUTE 'SELECT * FROM t1' LOOP RAISE NOTICE '%', r.c; END LOOP; END; $$ LANGUAGE plpgsql SET plpgsql.enable_lint TO false;
A usage of plpgsql_lint adds a small overhead and you should use it only in develop or preprod environments.
This module doesn't check queries that are assembled in runtime. It is not possible to identify result of dynamic queries - so plpgsql_lint cannot to set correct type to record variables and cannot to check a dependent SQLs and expressions. Don't use record variable as target for dynamic queries or disable plpgsql_lint for functions that use a dynamic queries.
plpgsql_lint cannot to verify queries over temporary tables that are created in plpgsql's function runtime. For this use case is necessary to create a fake temp table or disable plpgsql_lint for this function.
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