Postgres Pro Enterprise : Documentation: 15: H.5. plpgsql_check — static code analysis for PL/pgSQL : Postgres Professional

H.5. plpgsql_check — static code analysis for PL/pgSQL
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H.5. plpgsql_check — static code analysis for PL/pgSQL

H.5.1. Features
H.5.2. Usage
H.5.3. Function Arguments
H.5.4. Configuration Settings
H.5.5. Author

This extension is a full linter for PL/pgSQL for Postgres Pro. It leverages only the internal Postgres Pro parser/evaluator so you see exactly the errors would occur at runtime. Furthermore, it parses the SQL inside your routines and finds errors not usually found during the CREATE PROCEDURE/FUNCTION command. You can control the levels of many warnings and hints. Finally, you can add PRAGMA type markers to turn off/on many aspects allowing you to hide messages you already know about or to remind you to come back for deeper cleaning later.

plpgsql_check is provided with Postgres Pro Enterprise as a separate pre-built package plpgsql-check-ent-15 (for the detailed installation instructions, see Chapter 17).

H.5.1. Features

Checks fields of referenced database objects and types inside embedded SQL.
Validates you are using the correct types for function parameters.
Identifies unused variables and function arguments, unmodified OUT arguments.
Partially detects dead code (code after a RETURN command).
Detects missing RETURN command in function (common after exception handlers, complex logic).
Tries to identify unwanted hidden casts, which can be a performance issue like unused indexes.
Can collect relations and functions used by function.
Can check EXECUTE statements against SQL injection vulnerability.

H.5.2. Usage

The SQL statements inside PL/pgSQL functions are checked by the validator for semantic errors. These errors can be found by calling the plpgsql_check_function function. See Section H.5.3 for the list of the function arguments. The only mandatory function argument is funcoid. All the other arguments listed in Section H.5.3 are optional.

H.5.2.1. Active Mode

postgres=# CREATE EXTENSION plpgsql_check;
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(); -- execution doesn't find a bug due to empty table t1
  f1
 ────

 (1 row)

postgres=# \x
Expanded display is on.
postgres=# select * from plpgsql_check_function_tb('f1()');
─[ RECORD 1 ]───────────────────────────
functionid │ f1
lineno     │ 6
statement  │ RAISE
sqlstate   │ 42703
message    │ record "r" has no field "c"
detail     │ [null]
hint       │ [null]
level      │ error
position   │ 0
query      │ [null]

postgres=# \sf+ f1
    CREATE OR REPLACE FUNCTION public.f1()
     RETURNS void
     LANGUAGE plpgsql
1       AS $function$
2       DECLARE r record;
3       BEGIN
4         FOR r IN SELECT * FROM t1
5         LOOP
6           RAISE NOTICE '%', r.c; -- there is bug - table t1 missing "c" column
7         END LOOP;
8       END;
9       $function$

Function plpgsql_check_function() has three possible output formats: text, json or xml

select * from plpgsql_check_function('f1()', fatal_errors := false);
                         plpgsql_check_function
------------------------------------------------------------------------
 error:42703:4:SQL statement:column "c" of relation "t1" does not exist
 Query: update t1 set c = 30
 --                   ^
 error:42P01:7:RAISE:missing FROM-clause entry for table "r"
 Query: SELECT r.c
 --            ^
 error:42601:7:RAISE:too few parameters specified for RAISE
(7 rows)

postgres=# select * from plpgsql_check_function('fx()', format:='xml');
                 plpgsql_check_function
────────────────────────────────────────────────────────────────
 <Function oid="16400">
   <Issue>
     <Level>error</level>
     <Sqlstate>42P01</Sqlstate>
     <Message>relation "foo111" does not exist</Message>
     <Stmt lineno="3">RETURN</Stmt>
     <Query position="23">SELECT (select a from foo111)</Query>
   </Issue>
  </Function>
 (1 row)

H.5.2.1.1. Triggers

When you want to check any trigger, you have to enter a relation that will be used together with trigger function

CREATE TABLE bar(a int, b int);

postgres=# \sf+ foo_trg
    CREATE OR REPLACE FUNCTION public.foo_trg()
         RETURNS trigger
         LANGUAGE plpgsql
1       AS $function$
2       BEGIN
3         NEW.c := NEW.a + NEW.b;
4         RETURN NEW;
5       END;
6       $function$

Missing relation specification

postgres=# select * from plpgsql_check_function('foo_trg()');
ERROR:  missing trigger relation
HINT:  Trigger relation oid must be valid

Correct trigger checking (with specified relation)

postgres=# select * from plpgsql_check_function('foo_trg()', 'bar');
                 plpgsql_check_function
--------------------------------------------------------
 error:42703:3:assignment:record "new" has no field "c"
(1 row)

For triggers with transitive tables you can set the oldtable and newtable parameters:

create or replace function footab_trig_func()
returns trigger as $$
declare x int;
begin
  if false then
    -- should be ok;
    select count(*) from newtab into x;

    -- should fail;
    select count(*) from newtab where d = 10 into x;
  end if;
  return null;
end;
$$ language plpgsql;

select * from plpgsql_check_function('footab_trig_func','footab', newtable := 'newtab');

H.5.2.1.2. In-Comment Options

plpgsql_check allows persistent setting written in comments. These options are taken from function's source code before checking. The syntax is:

@plpgsql_check_option: optioname [=] value [, optname [=] value ...]

The settings from comment options have top high priority, but generally it can be disabled by setting use_incomment_options to false.

Example:

create or replace function fx(anyelement)
returns text as $$
begin
  /*
   * rewrite default polymorphic type to text
   * @plpgsql_check_options: anyelementtype = text
   */
  return $1;
end;
$$ language plpgsql;

H.5.2.1.3. Checking All of Your Code

You can use the plpgsql_check_function function for mass checking of functions/procedures and mass checking of triggers. Please, test following queries:

-- check all nontrigger plpgsql functions
SELECT p.oid, p.proname, plpgsql_check_function(p.oid)
   FROM pg_catalog.pg_namespace n
   JOIN pg_catalog.pg_proc p ON pronamespace = n.oid
   JOIN pg_catalog.pg_language l ON p.prolang = l.oid
  WHERE l.lanname = 'plpgsql' AND p.prorettype <> 2279;

-- check all trigger plpgsql functions
SELECT p.proname, tgrelid::regclass, cf.*
   FROM pg_proc p
        JOIN pg_trigger t ON t.tgfoid = p.oid
        JOIN pg_language l ON p.prolang = l.oid
        JOIN pg_namespace n ON p.pronamespace = n.oid,
        LATERAL plpgsql_check_function(p.oid, t.tgrelid, oldtable=>t.tgoldtable, newtable=>t.tgnewtable) cf
  WHERE n.nspname = 'public' and l.lanname = 'plpgsql';

-- check all plpgsql functions (functions or trigger functions with defined triggers)
SELECT
    (pcf).functionid::regprocedure, (pcf).lineno, (pcf).statement,
    (pcf).sqlstate, (pcf).message, (pcf).detail, (pcf).hint, (pcf).level,
    (pcf)."position", (pcf).query, (pcf).context
FROM
(
    SELECT
        plpgsql_check_function_tb(pg_proc.oid, COALESCE(pg_trigger.tgrelid, 0),
                                  oldtable=>pg_trigger.tgoldtable,
                                  newtable=>pg_trigger.tgnewtable) AS pcf
    FROM pg_proc
    LEFT JOIN pg_trigger
        ON (pg_trigger.tgfoid = pg_proc.oid)
    WHERE
        prolang = (SELECT lang.oid FROM pg_language lang WHERE lang.lanname = 'plpgsql') AND
        pronamespace <> (SELECT nsp.oid FROM pg_namespace nsp WHERE nsp.nspname = 'pg_catalog') AND
        -- ignore unused triggers
        (pg_proc.prorettype <> (SELECT typ.oid FROM pg_type typ WHERE typ.typname = 'trigger') OR
         pg_trigger.tgfoid IS NOT NULL)
    OFFSET 0
) ss
ORDER BY (pcf).functionid::regprocedure::text, (pcf).lineno;

H.5.2.2. Passive Mode

This mode is only recommended for development or preproduction.

Functions can be checked upon execution — plpgsql_check module must be loaded (via postgresql.conf).

To configure passive mode, choose values for plpgsql_check.mode and plpgsql_check.fatal_errors configuration settings and set plpgsql_check.show_nonperformance_warnings and plpgsql_check.show_performance_warnings to false.

You can enable passive mode as follows:

load 'plpgsql'; -- 1.1 and higher doesn't need it
load 'plpgsql_check';
set plpgsql_check.mode = 'every_start';  -- This scans all code before it is executed

SELECT fx(10); -- run functions - function is checked before runtime starts it

H.5.2.3. Compatibility Warnings

H.5.2.3.1. Assigning String to refcursor Variable

Postgres Pro cursor's and refcursor's variables are enhanced string variables that hold unique name of related portal (internal structure of PostgreSQL that is used for cursor's implementation). Until PostgreSQL 16, the portal had same name like name of cursor variable. PostgreSQL 16 and higher change this mechanism and by default related portal will be named by some unique name. It solves some issues with cursors in nested blocks or when cursor is used in recursive called function.

With mentioned change, the refcursor's variable should take value from another refcursor variable or from some cursor variable (when cursor is opened).

-- obsolete pattern
DECLARE
  cur CURSOR FOR SELECT 1;
  rcur refcursor;
BEGIN
  rcur := 'cur';
  OPEN cur;
  ...

-- new pattern
DECLARE
  cur CURSOR FOR SELECT 1;
  rcur refcursor;
BEGIN
  OPEN cur;
  rcur := cur;
  ...

When the plpgsql_check_function function flag compatibility_warnings is active, then plpgsql_check tries to identify some fishy assigning to refcursor's variable or returning of refcursor's values:

CREATE OR REPLACE FUNCTION public.foo()
 RETURNS refcursor
AS $$
declare
   c cursor for select 1;
   r refcursor;
begin
  open c;
  r := 'c';
  return r;
end;
$$ LANGUAGE plpgsql;

select * from plpgsql_check_function('foo', extra_warnings =>false, compatibility_warnings => true);
┌───────────────────────────────────────────────────────────────────────────────────┐
│                              plpgsql_check_function                               │
╞═══════════════════════════════════════════════════════════════════════════════════╡
│ compatibility:00000:6:assignment:obsolete setting of refcursor or cursor variable │
│ Detail: Internal name of cursor should not be specified by users.                 │
│ Context: at assignment to variable "r" declared on line 3                         │
└───────────────────────────────────────────────────────────────────────────────────┘
(3 rows)

H.5.2.4. Limits

plpgsql_check should find almost all errors on really static code. When developers use PL/pgSQL 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_check 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_check TO false;

Warning

Usage of plpgsql_check adds a small overhead (when passive mode is enabled) and you should use that setting only in development or preproduction environments.

H.5.2.4.1. Dynamic SQL

This module doesn't check queries that are assembled in runtime. It is not possible to identify results of dynamic queries — so plpgsql_check cannot set correct type to record variables and cannot check dependent SQL statements and expressions.

When type of record's variable is not known, you can assign it explicitly with pragma type:

DECLARE r record;
BEGIN
  EXECUTE format('SELECT * FROM %I', _tablename) INTO r;
  PERFORM plpgsql_check_pragma('type: r (id int, processed bool)');
  IF NOT r.processed THEN
    ...

Warning

The SQL injection check can detect only some SQL injection vulnerabilities. This tool cannot be used for security audit. Some issues will not be detected. This check can raise false alarms too — probably when variable is sanitized by other command or when the value is of some composite type.

H.5.2.4.2. Refcursors

plpgsql_check cannot be used to detect structure of referenced cursors. A reference on cursor in PL/pgSQL is implemented as name of global cursor. In check time, the name is not known (not in all possibilities), and global cursor doesn't exist. It is a significant issue for any static analysis. PL/pgSQL cannot know how to set the correct type for the record variables and cannot check the dependent SQL statements and expressions. A solution is the same for dynamic SQL. Don't use record variable as target when you use refcursor type or disable plpgsql_check for these functions.

CREATE OR REPLACE FUNCTION foo(refcur_var refcursor)
RETURNS void AS $$
DECLARE
  rec_var record;
BEGIN
  FETCH refcur_var INTO rec_var; -- this is STOP for plpgsql_check
  RAISE NOTICE '%', rec_var;     -- record rec_var is not assigned yet error

In this case a record type should not be used (use known rowtype instead):

CREATE OR REPLACE FUNCTION foo(refcur_var refcursor)
RETURNS void AS $$
DECLARE
  rec_var some_rowtype;
BEGIN
  FETCH refcur_var INTO rec_var;
  RAISE NOTICE '%', rec_var;

H.5.2.4.3. Temporary Tables

plpgsql_check cannot verify queries over temporary tables that are created in PL/pgSQL function runtime. For this use case it is necessary to create a fake temp table or disable plpgsql_check for this function.

In reality temp tables are stored in own (per user) schema with higher priority than persistent tables. So you can do (with following trick safely):

CREATE OR REPLACE FUNCTION public.disable_dml()
RETURNS trigger
LANGUAGE plpgsql AS $function$
BEGIN
  RAISE EXCEPTION SQLSTATE '42P01'
     USING message = format('this instance of %I table doesn''t allow any DML operation', TG_TABLE_NAME),
           hint = format('you should use "CREATE TEMP TABLE %1$I(LIKE %1$I INCLUDING ALL);" statement',
                         TG_TABLE_NAME);
  RETURN NULL;
END;
$function$;

CREATE TABLE foo(a int, b int); -- doesn't hold data, ever
CREATE TRIGGER foo_disable_dml
   BEFORE INSERT OR UPDATE OR DELETE ON foo
   EXECUTE PROCEDURE disable_dml();

postgres=# INSERT INTO  foo VALUES(10,20);
ERROR:  this instance of foo table doesn't allow any DML operation
HINT:  you should to run "CREATE TEMP TABLE foo(LIKE foo INCLUDING ALL);" statement
postgres=#

CREATE TABLE
postgres=# INSERT INTO  foo VALUES(10,20);
INSERT 0 1

This trick emulates GLOBAL TEMP tables partially and it allows a statical validation. Other possibility is using a template foreign data wrapper.

You can use pragma table and create ephemeral table:

BEGIN
   CREATE TEMP TABLE xxx(a int);
   PERFORM plpgsql_check_pragma('table: xxx(a int)');
   INSERT INTO xxx VALUES(10);
   PERFORM plpgsql_check_pragma('table: [pg_temp].zzz(like schemaname.table1 including all)');
   ...

H.5.2.5. Dependency List

The function plpgsql_show_dependency_tb will show all functions, operators and relations used inside processed function:

postgres=# select * from plpgsql_show_dependency_tb('testfunc(int,float)');
┌──────────┬───────┬────────┬─────────┬────────────────────────────┐
│   type   │  oid  │ schema │  name   │           params           │
╞══════════╪═══════╪════════╪═════════╪════════════════════════════╡
│ FUNCTION │ 36008 │ public │ myfunc1 │ (integer,double precision) │
│ FUNCTION │ 35999 │ public │ myfunc2 │ (integer,double precision) │
│ OPERATOR │ 36007 │ public │ **      │ (integer,integer)          │
│ RELATION │ 36005 │ public │ myview  │                            │
│ RELATION │ 36002 │ public │ mytable │                            │
└──────────┴───────┴────────┴─────────┴────────────────────────────┘
(4 rows)

Optional arguments of plpgsql_show_dependency_tb are relid, anyelementtype, anyenumtype, anyrangetype, anycompatibletype, and anycompatiblerangetype.

H.5.2.6. Profiler

plpgsql_check contains simple profiler of PL/pgSQL functions and procedures. It can work with/without access to shared memory. It depends on shared_preload_libraries config. When plpgsql_check is initialized by shared_preload_libraries, then it can allocate shared memory, and function's profiles are stored there. When plpgsql_check cannot allocate shared memory, the profile is stored in session memory.

Due to dependencies, shared_preload_libraries should contain plpgsql first.

postgres=# show shared_preload_libraries ;
┌──────────────────────────┐
│ shared_preload_libraries │
╞══════════════════════════╡
│ plpgsql,plpgsql_check    │
└──────────────────────────┘
(1 row)

The profiler is active when the configuration setting plpgsql_check.profiler is on. The profiler doesn't require shared memory, but if there is not enough shared memory, then the profiler is limited just to active session. The profiler can be activated by calling function plpgsql_check_profiler(true) and disabled by calling same function with false argument (or with literals on, off).

The plpgsql_check should be initialized before any PL/pgSQL function is executed. Only early initialization ensures correct work of profiler and tracer. When you don't use shared_preloaded_libraries, you can use command load 'plpgsql_check' instead.

When plpgsql_check is initialized by shared_preload_libraries, another configutration setting is available to configure the amount of shared memory used by the profiler: plpgsql_check.profiler_max_shared_chunks.

The profiler will also retrieve the query identifier for each instruction that contains an expression or optimizable statement. Note that this requires pg_stat_statements, or another similar third-party extension, to be installed. There are some limitations to the query identifier retrieval:

If a PL/pgSQL expression contains underlying statements, only the top level query identifier will be retrieved
The profiler doesn't compute query identifier by itself but relies on external extension, such as pg_stat_statements, for that. It means that depending on the external extension behavior, you may not be able to see a query identifier for some statements. That's for instance the case with DDL statements, as pg_stat_statements doesn't expose the query identifier for such queries.
A query identifier is retrieved only for instructions containing expressions. This means that plpgsql_profiler_function_tb() function can report less query identifiers than instructions on a single line.

Warning

An update of shared profiles can decrease performance on servers under higher load.

The profile can be displayed by function plpgsql_profiler_function_tb:

postgres=# select lineno, avg_time, source from plpgsql_profiler_function_tb('fx(int)');
┌────────┬──────────┬───────────────────────────────────────────────────────────────────┐
│ lineno │ avg_time │                              source                               │
╞════════╪══════════╪═══════════════════════════════════════════════════════════════════╡
│      1 │          │                                                                   │
│      2 │          │ declare result int = 0;                                           │
│      3 │    0.075 │ begin                                                             │
│      4 │    0.202 │   for i in 1..$1 loop                                             │
│      5 │    0.005 │     select result + i into result; select result + i into result; │
│      6 │          │   end loop;                                                       │
│      7 │        0 │   return result;                                                  │
│      8 │          │ end;                                                              │
└────────┴──────────┴───────────────────────────────────────────────────────────────────┘
(9 rows)

The times in the result are in milliseconds.

The profile per statements (not per line) can be displayed by function plpgsql_profiler_function_statements_tb:

        CREATE OR REPLACE FUNCTION public.fx1(a integer)
         RETURNS integer
         LANGUAGE plpgsql
1       AS $function$
2       begin
3         if a > 10 then
4           raise notice 'ahoj';
5           return -1;
6         else
7           raise notice 'nazdar';
8           return 1;
9         end if;
10      end;
11      $function$

postgres=# select stmtid, parent_stmtid, parent_note, lineno, exec_stmts, stmtname
             from plpgsql_profiler_function_statements_tb('fx1');
┌────────┬───────────────┬─────────────┬────────┬────────────┬─────────────────┐
│ stmtid │ parent_stmtid │ parent_note │ lineno │ exec_stmts │    stmtname     │
╞════════╪═══════════════╪═════════════╪════════╪════════════╪═════════════════╡
│      0 │             ∅ │ ∅           │      2 │          0 │ statement block │
│      1 │             0 │ body        │      3 │          0 │ IF              │
│      2 │             1 │ then body   │      4 │          0 │ RAISE           │
│      3 │             1 │ then body   │      5 │          0 │ RETURN          │
│      4 │             1 │ else body   │      7 │          0 │ RAISE           │
│      5 │             1 │ else body   │      8 │          0 │ RETURN          │
└────────┴───────────────┴─────────────┴────────┴────────────┴─────────────────┘
(6 rows)

All stored profiles can be displayed by calling function plpgsql_profiler_functions_all:

postgres=# select * from plpgsql_profiler_functions_all();
┌───────────────────────┬────────────┬────────────┬──────────┬─────────────┬──────────┬──────────┐
│        funcoid        │ exec_count │ total_time │ avg_time │ stddev_time │ min_time │ max_time │
╞═══════════════════════╪════════════╪════════════╪══════════╪═════════════╪══════════╪══════════╡
│ fxx(double precision) │          1 │       0.01 │     0.01 │        0.00 │     0.01 │     0.01 │
└───────────────────────┴────────────┴────────────┴──────────┴─────────────┴──────────┴──────────┘
(1 row)

There are two functions for cleaning stored profiles: plpgsql_profiler_reset_all() and plpgsql_profiler_reset(regprocedure).

H.5.2.6.1. Coverage Metrics

plpgsql_check provides two functions:

plpgsql_coverage_statements(name)
plpgsql_coverage_branches(name)

H.5.2.6.2. Third-Party Profiler

There is another very good PL/pgSQL profiler — https://github.com/glynastill/plprofiler.

plpgsql_check is designed to be simple for use and practical.

plprofiler is more complex. It builds call graphs and from this graph it can create flame graph of execution times.

Both extensions can be used together with the builtin Postgres Pro's feature — tracking functions.

set track_functions to 'pl';
...
select * from pg_stat_user_functions;

H.5.2.7. Tracer

plpgsql_check provides a tracing possibility. You can specify the tracer verbosity by means of the plpgsql_check.tracer_verbosity configuration setting.

postgres=# do $$ begin perform fx(10,null, 'now', e'stehule'); end; $$;
NOTICE:  #0 ->> start of inline_code_block (Oid=0)
NOTICE:  #2   ->> start of function fx(integer,integer,date,text) (Oid=16405)
NOTICE:  #2        call by inline_code_block line 1 at PERFORM
NOTICE:  #2       "a" => '10', "b" => null, "c" => '2020-08-03', "d" => 'stehule'
NOTICE:  #4     ->> start of function fx(integer) (Oid=16404)
NOTICE:  #4          call by fx(integer,integer,date,text) line 1 at PERFORM
NOTICE:  #4         "a" => '10'
NOTICE:  #4     <<- end of function fx (elapsed time=0.098 ms)
NOTICE:  #2   <<- end of function fx (elapsed time=0.399 ms)
NOTICE:  #0 <<- end of block (elapsed time=0.754 ms)

The number after # is an execution frame counter (this number is related to depth of error context stack). It allows you to pair start and end of function.

Note

The initial depth of error context stack can be different in dependency on environment (and used protocol).

Tracing is activated by setting plpgsql_check.tracer to on. The tracer can also be activated by calling function plpgsql_check_tracer(true) and disabled by calling same function with false argument (or with literals on, off).

Warning

Enabling this behaviour has significant negative impact on performance (unlike the profiler).

You can configure the level for output used by tracer by means of the plpgsql_check.tracer_errlevel configuration setting. The output content is limited by length specified by plpgsql_check.tracer_variable_max_length configuration setting.

First, the usage of tracer should be explicitly enabled by superuser by setting plpgsql-check.enable-tracer to on on the command line or in postgresql.conf. This is a security safeguard. The tracer shows content of PL/pgSQL's variables, and then some security sensitive information can be displayed to an unprivileged user (when he runs security definer function). Second, the extension plpgsql_check should be loaded. It can be done by execution of some plpgsql_check function or explicitly by command load 'plpgsql_check';. You can use configuration's option shared_preload_libraries, local_preload_libraries or session_preload_libraries.

Caution

Tracer prints content of variables or function arguments. For security definer function, this content can hold security sensitive data. This is reason why tracer is disabled by default and should be enabled only by setting plpgsql-check.enable-tracer with superuser rights.

In terse verbosity mode the output is reduced:

postgres=# set plpgsql_check.tracer_verbosity TO terse;
SET
postgres=# do $$ begin perform fx(10,null, 'now', e'stehule'); end; $$;
NOTICE:  #0 start of inline code block (oid=0)
NOTICE:  #2 start of fx (oid=16405)
NOTICE:  #4 start of fx (oid=16404)
NOTICE:  #4 end of fx
NOTICE:  #2 end of fx
NOTICE:  #0 end of inline code block

In verbose mode the output is extended about statement details:

postgres=# do $$ begin perform fx(10,null, 'now', e'stehule'); end; $$;
NOTICE:  #0            ->> start of block inline_code_block (oid=0)
NOTICE:  #0.1       1  --> start of PERFORM
NOTICE:  #2              ->> start of function fx(integer,integer,date,text) (oid=16405)
NOTICE:  #2                   call by inline_code_block line 1 at PERFORM
NOTICE:  #2                  "a" => '10', "b" => null, "c" => '2020-08-04', "d" => 'stehule'
NOTICE:  #2.1       1    --> start of PERFORM
NOTICE:  #2.1                "a" => '10'
NOTICE:  #4                ->> start of function fx(integer) (oid=16404)
NOTICE:  #4                     call by fx(integer,integer,date,text) line 1 at PERFORM
NOTICE:  #4                    "a" => '10'
NOTICE:  #4.1       6      --> start of assignment
NOTICE:  #4.1                  "a" => '10', "b" => '20'
NOTICE:  #4.1              <-- end of assignment (elapsed time=0.076 ms)
NOTICE:  #4.1                  "res" => '130'
NOTICE:  #4.2       7      --> start of RETURN
NOTICE:  #4.2                  "res" => '130'
NOTICE:  #4.2              <-- end of RETURN (elapsed time=0.054 ms)
NOTICE:  #4                <<- end of function fx (elapsed time=0.373 ms)
NOTICE:  #2.1            <-- end of PERFORM (elapsed time=0.589 ms)
NOTICE:  #2              <<- end of function fx (elapsed time=0.727 ms)
NOTICE:  #0.1          <-- end of PERFORM (elapsed time=1.147 ms)
NOTICE:  #0            <<- end of block (elapsed time=1.286 ms)

A special feature of tracer is tracing of the ASSERT statement when plpgsql_check.trace_assert is on. The verbosilty of this feature is specified by the plpgsql_check.trace_assert_verbosity configuration setting. This behaviour is independent of the plpgsql.check_asserts value. It can be used, although the assertions are disabled in PL/pgSQL runtime.

postgres=# set plpgsql_check.tracer to off;
postgres=# set plpgsql_check.trace_assert_verbosity TO verbose;

postgres=# do $$ begin perform fx(10,null, 'now', e'stehule'); end; $$;
NOTICE:  #4 PLpgSQL assert expression (false) on line 12 of fx(integer) is false
NOTICE:   "a" => '10', "res" => null, "b" => '20'
NOTICE:  #2 PL/pgSQL function fx(integer,integer,date,text) line 1 at PERFORM
NOTICE:   "a" => '10', "b" => null, "c" => '2020-08-05', "d" => 'stehule'
NOTICE:  #0 PL/pgSQL function inline_code_block line 1 at PERFORM
ERROR:  assertion failed
CONTEXT:  PL/pgSQL function fx(integer) line 12 at ASSERT
SQL statement "SELECT fx(a)"
PL/pgSQL function fx(integer,integer,date,text) line 1 at PERFORM
SQL statement "SELECT fx(10,null, 'now', e'stehule')"
PL/pgSQL function inline_code_block line 1 at PERFORM

postgres=# set plpgsql.check_asserts to off;
SET
postgres=# do $$ begin perform fx(10,null, 'now', e'stehule'); end; $$;
NOTICE:  #4 PLpgSQL assert expression (false) on line 12 of fx(integer) is false
NOTICE:   "a" => '10', "res" => null, "b" => '20'
NOTICE:  #2 PL/pgSQL function fx(integer,integer,date,text) line 1 at PERFORM
NOTICE:   "a" => '10', "b" => null, "c" => '2020-08-05', "d" => 'stehule'
NOTICE:  #0 PL/pgSQL function inline_code_block line 1 at PERFORM
DO

Tracer can show usage of subtransaction buffer ID (nxids). The displayed tnl number is transaction nesting level number (for PL/pgSQL it depends on depth of blocks with exception's handlers).

H.5.2.7.1. Detection of Unclosed Cursors

PL/pgSQL cursors are just names of SQL cursors. The life cycle of SQL cursors is not joined with scope of related plpgsql's cursor variable. SQL cursors are closed by self at transaction end, but for long transaction and too much opened cursors it can be too late. It is better to close cursor explicitly when cursor is not necessary (by CLOSE statement). Without it the significant memory issues are possible.

When OPEN statement tries to use cursor that is not closed yet, the warning is raised. This feature can be disabled by setting plpgsql_check.cursors_leaks to off. This check is not active, when routine is called recusively.

The unclosed cursors can be checked immediately when function is finished. This check is disabled by default, and should be enabled by setting plpgsql_check.strict_cursors_leaks to on.

Any unclosed cursor is reported once.

H.5.2.7.2. Using with plugin_debugger

If you use plugin_debugger (PL/pgSQL debugger) together with plpgsql_check, then plpgsql_check should be initialized after plugin_debugger (because plugin_debugger doesn't support the sharing of PL/pgSQL's debug API). For example (postgresql.conf):

shared_preload_libraries = 'plugin_debugger,plpgsql,plpgsql_check'

H.5.2.8. pragma

You can configure plpgsql_check behaviour inside a checked function with “pragma” function. This is an analogy of PL/SQL or ADA language of PRAGMA feature. PL/pgSQL doesn't support PRAGMA, but plpgsql_check detects function named plpgsql_check_pragma and takes options from the parameters of this function. These plpgsql_check options are valid to the end of this group of statements.

CREATE OR REPLACE FUNCTION test()
RETURNS void AS $$
BEGIN
  ...
  -- for following statements disable check
  PERFORM plpgsql_check_pragma('disable:check');m
  ...
  -- enable check again
  PERFORM plpgsql_check_pragma('enable:check');
  ...
END;
$$ LANGUAGE plpgsql;

The function plpgsql_check_pragma is immutable function that returns one. It is defined by plpgsql_check extension. You can declare alternative plpgsql_check_pragma function like:

CREATE OR REPLACE FUNCTION plpgsql_check_pragma(VARIADIC args[])
RETURNS int AS $$
SELECT 1
$$ LANGUAGE sql IMMUTABLE;

Using pragma function in declaration part of top block sets options on function level too.

CREATE OR REPLACE FUNCTION test()
RETURNS void AS $$
DECLARE
  aux int := plpgsql_check_pragma('disable:extra_warnings');
  ...

Shorter syntax for pragma is supported too:

CREATE OR REPLACE FUNCTION test()
RETURNS void AS $$
DECLARE r record;
BEGIN
  PERFORM 'PRAGMA:TYPE:r (a int, b int)';
  PERFORM 'PRAGMA:TABLE: x (like pg_class)';
  ...

H.5.2.8.1. Supported Pragmas

echo:str — print string (for testing). Inside string, there can be used “variables”: @@id, @@name, @@signature.
status:check,status:tracer, status:other_warnings, status:performance_warnings, status:extra_warnings,status:security_warnings This outputs the current value (e.g. other_warnings enabled).
enable:check,enable:tracer, enable:other_warnings, enable:performance_warnings, enable:extra_warnings,enable:security_warnings.
disable:check, disable:tracer, disable:other_warnings, disable:performance_warnings, disable:extra_warnings, disable:security_warnings This can be used to disable the Hint in returning from an anyelement function. Just put the pragma before the RETURN statement.
type:varname typename or type:varname (fieldname type, ...) — set type to variable of record type.
table: name (column_name type, ...) or table: name (like tablename) — create ephemeral temporary table (if you want to specify schema, then only pg_temp schema is allowed).
sequence: name — create ephemeral temporary sequence.
assert-schema: varname — check-time assertation — ensure that schema specified by variable is valid.
assert-table: [ varname_schema, ] , varname — ensure that table name specified by variables (by constant tracing) is valid.
assert-column: [varname_schema, ], varname_table , varname — ensure that column specified by variables is valid.

H.5.3. Function Arguments

The following list explains the meaning of arguments of some plpgsql_check functions, specifically, of plpgsql_check_function:

funcoid oid: Function name or function signature. Functions require a function specification. Any function in Postgres Pro can be specified by OID or by name or by signature. When you know OID or complete function's signature, you can use a regprocedure type parameter like 'fx()'::regprocedure or 16799::regprocedure. Possible alternative is using a name only, when function's name is unique — like 'fx'. When the name is not unique or the function doesn't exist, an error is raised.
relid oid DEFAULT 0: OID of relation assigned with trigger function. It is necessary to check any trigger function. You are sending the table in which the trigger operates on.
fatal_errors boolean DEFAULT true: Stop on first error (prevents massive error reports).
other_warnings boolean DEFAULT true: Show warnings like different attributes number in assignment on left and right side, variable overlaps function's parameter, unused variables, unwanted casting, etc.
extra_warnings boolean DEFAULT true: Show warnings like missing RETURN, shadowed variables, dead code, never read (unused) function's parameter, unmodified variables, modified auto variables, etc.
performance_warnings boolean DEFAULT false: Performance-related warnings like declared type with type modifier, casting, implicit casts in WHERE clause (can be the reason why an index is not used), etc.
security_warnings boolean DEFAULT false: Security-related checks like SQL injection vulnerability detection.
compatibility_warnings boolean DEFAULT false: Compatibility-related checks like obsolete explicit setting of internal cursor names in refcursor's or cursor's variables.
anyelementtype regtype DEFAULT 'int': An actual type to be used when testing the anyelement type.
anyenumtype regtype DEFAULT '-': An actual type to be used when testing the anyenum type.
anyrangetype regtype DEFAULT 'int4range': An actual type to be used when testing the anyrange type.
anycompatibletype DEFAULT 'int': An actual type to be used when testing the anycompatible type.
anycompatiblerangetype DEFAULT 'int4range': An actual type to be used when testing the anycompatible range type.
without_warnings boolean DEFAULT false: Disable all warnings (Ignores all xxxx_warning parameters, a quick override).
all_warnings boolean DEFAULT false: Enable all warnings (Ignores other xxx_warning parameters, a quick positive).
newtable text DEFAULT NULL: The name of NEW transition table. This parameter is required when transition tables are used in trigger functions.
oldtable text DEFAULT NULL: The name of OLD transition table. This parameter is required when transition tables are used in trigger functions.
use_incomment_options boolean DEFAULT true: When it is true, then in-comment options are active.
incomment_options_usage_warning boolean DEFAULT false: When it is true, then the warning is raised when in-comment option is used.
constant_tracing boolean DEFAULT true: When it is true, then the variable that holds some constant content can be used like constant (it works only in some simple cases, and the content of variable should not be ambigonuous).

H.5.4. Configuration Settings

The following is the list of plpgsql-check configuration settings:

plpgsql_check.mode = disabled | by_function | fresh_start | every_start: plpgsql_check mode. Default mode is by_function, which means that the enhanced check is done only in active mode — by calling plpgsql_check_function. fresh_start means cold start (first the function is called).
plpgsql_check.fatal_errors = yes | no: Whether to check for fatal errors.
plpgsql_check.show_nonperformance_warnings = true | false: Whether to show non-performance warnings.
plpgsql_check.show_performance_warnings = true | false: Whether to show performance warnings.
plpgsql_check.profiler = on | off: Whether the profiler is active.
plpgsql_check.profiler_max_shared_chunks: Defines the maximum number of statement chunks that can be stored in shared memory. For each PL/pgSQL function (or procedure), the whole content is split into chunks of 30 statements. If needed, multiple chunks can be used to store the whole content of a single function. A single chunk is 1704 bytes. The default value for this setting is 15000, which should be enough for big projects containing hundreds of thousands of statements in PL/pgSQL, and will consume about 24MB of memory. If your project doesn't require that large number of chunks, you can set this parameter to a smaller number in order to decrease the memory usage. The minimum value is 50 (which should consume about 83kB of memory), and the maximum value is 100000 (which should consume about 163MB of memory). Changing this parameter requires a Postgres Pro restart.
plpgsql_check.enable_tracer = on | off: Enables the use of the tracer. Setting of this variable requires superuser permissions.
plpgsql_check.tracer = on | off: Whether the tracer is active.
plpgsql_check.tracer_verbosity = terse | default | verbose: The tracer verbosity. With the terse and default verbosity, you can see notices on start or end of functions. With the verbose verbosity, you can see start or end of statements. For default and verbose verbosity, the content of function arguments is displayed. The contents of related variables are displayed when verbosity is verbose.
plpgsql_check.tracer_errlevel: The error level in the tracer output. The default is notice.
plpgsql_check.tracer_variable_max_length: The limit for the tracer output content.
plpgsql_check.trace_assert = on | off: Trace the ASSERT statement.
plpgsql_check.trace_assert_verbosity = default | verbose: The verbosity when tracing the ASSERT statement. If the value is default, then all function's or procedure's variables are displayed when the assert expression is false. If the value is verbose then all variables from all PL/pgSQL frames are displayed.
plpgsql_check.cursors_leaks = on | off: Raise a warning when an OPEN statement tries to use cursor that is not closed yet. The default is on.
plpgsql_check.strict_cursors_leaks = on | off: Check unclosed cursors immediately when function is finished. The default is off.

H.5.5. Author

Pavel Stehule <pavel.stehule@gmail.com>

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