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Constraints naming conventions

The most common option is to let Rails pick the name for database constraints and indexes or let PostgreSQL use the defaults (when applicable). However, when defining custom names in Rails, or working in Go applications where no ORM is used, it is important to follow strict naming conventions to improve consistency and discoverability.

The table below describes the naming conventions for custom PostgreSQL constraints. The intent is not to retroactively change names in existing databases but rather ensure consistency of future changes.

Type Syntax Notes Examples
Primary Key pk_<table name> pk_projects
Foreign Key fk_<table name>_<column name>[_and_<column name>]*_<foreign table name> fk_projects_group_id_groups
Index index_<table name>_on_<column name>[_and_<column name>]*[_and_<column name in partial clause>]* Index names must be all lowercase. index_repositories_on_group_id
Unique Constraint unique_<table name>_<column name>[_and_<column name>]* unique_projects_group_id_and_name
Check Constraint check_<table name>_<column name>[_and_<column name>]*[_<suffix>]? The optional suffix should denote the type of validation, such as length and enum. It can also be used to disambiguate multiple CHECK constraints on the same column. check_projects_name_length
Exclusion Constraint excl_<table name>_<column name>[_and_<column name>]*_[_<suffix>]? The optional suffix should denote the type of exclusion being performed. excl_reservations_start_at_end_at_no_overlap


  • Check db/structure.sql for conflicts.
  • Prefixes are preferred over suffices because they make it easier to identify the type of a given constraint quickly, as well as group them alphabetically;
  • The _and_ that joins column names can be omitted to keep the identifiers under the 63 characters' length limit defined by PostgreSQL. Additionally, the notation may be abbreviated to the best of our ability if struggling to keep under this limit.
  • For indexes added to solve a very specific problem, it may make sense for the name to reflect their use.