Explicit locking

Query goal:

PostgreSQL uses Multi-version Concurrency Control (MVCC) and thus, sometimes, one has to explicitly lock certain rows or entire table. One has to use LOCK TABLE or SELECT … FOR UPDATE statements for that.

Notes about the query:

Refers to the column pg_proc.prokind and thus works starting from PostgreSQL 11. In the returned body of routine the query replaces each newline character with the line break (br) tag for the better readability in case the query result is displayed in a web browser. There could be multiple routines with the same name but with different parameters in the same schema (overloading). Thus, for the unique identification of the routine it is necessary to present also its parameters in addition to the schema name and routine name.

Query type:

General (Overview of some aspect of the database.)

Query license:

MIT License

Data source:

INFORMATION_SCHEMA+system catalog

SQL query:

Click on query to copy it

SELECT 
  pg_namespace.nspname AS routine_schema, 
  pg_proc.proname AS routine_name, 
  pg_get_function_identity_arguments(pg_proc.oid) AS parameters,
  CASE WHEN pg_proc.prokind='f' THEN 'FUNCTION'
  WHEN pg_proc.prokind='p' THEN 'PROCEDURE'
  WHEN pg_proc.prokind='w' THEN 'WINDOW FUNCTION' END AS routine_type,  
  regexp_replace(
  regexp_replace( regexp_replace(pg_get_functiondef(pg_proc.oid),'<','&lt','g'),'[\r\n]','<br>','g'),
  '(LOCK|FOR[[:space:]]+UPDATE)','<b>\1</b>','g') AS routine_src
FROM 
  pg_catalog.pg_proc, 
  pg_catalog.pg_namespace
WHERE 
  pg_proc.pronamespace = pg_namespace.oid
  AND pg_proc.prokind<>'a'
 AND pg_proc.proname NOT IN ('f_assume_you_must_use_files', 'f_check_format_comma_separated_list', 'f_check_password', 'f_default_value_with_no_match') AND
pg_namespace.nspname NOT IN (SELECT schema_name
FROM INFORMATION_SCHEMA.schemata
WHERE schema_name<>'public' AND
schema_owner='postgres' AND schema_name IS NOT NULL) AND
pg_get_functiondef(pg_proc.oid)~*'([[:space:]]*LOCK[[:space:]]|[[:space:]]*FOR[[:space:]]+UPDATE)' 
ORDER BY routine_schema, routine_name, parameters;

Collections where the query belongs to

Collection name	Collection description
Find problems by overview	Queries that results point to different aspects of database that might have problems. A human reviewer has to decide based on the results as to whether there are problems or not .

Collection name

Collection description

Find problems by overview

Queries that results point to different aspects of database that might have problems. A human reviewer has to decide based on the results as to whether there are problems or not .

Categories where the query belongs to

Category name	Category description
Concurrency control	Queries of this category provide information about concurrency control.
Does not work in some earlier PostgreSQL version	Queries of this category provide information that was not available in some earlier PostgreSQL version
Transactions	Queries of this catergory provide information about the use of transactions.
User-defined routines	Queries of this category provide information about the user-defined routines

Category name

Category description

Concurrency control

Queries of this category provide information about concurrency control.

Does not work in some earlier PostgreSQL version

Queries of this category provide information that was not available in some earlier PostgreSQL version

Transactions

Queries of this catergory provide information about the use of transactions.

User-defined routines

Queries of this category provide information about the user-defined routines

Reference materials for further reading

Reference
https://devcenter.heroku.com/articles/postgresql-concurrency

Reference

https://devcenter.heroku.com/articles/postgresql-concurrency