# 51.56. pg\_trigger

The catalog `pg_trigger` stores triggers on tables and views. See [CREATE TRIGGER](https://www.postgresql.org/docs/10/static/sql-createtrigger.html) for more information.

**Table 51.56. `pg_trigger` Columns**

| Name             | Type           | References                                                                                   | Description                                                                                                                                                                                                                                                                                                                 |
| ---------------- | -------------- | -------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `oid`            | `oid`          |                                                                                              | Row identifier (hidden attribute; must be explicitly selected)                                                                                                                                                                                                                                                              |
| `tgrelid`        | `oid`          | [`pg_class`](https://www.postgresql.org/docs/10/static/catalog-pg-class.html).oid            | The table this trigger is on                                                                                                                                                                                                                                                                                                |
| `tgname`         | `name`         |                                                                                              | Trigger name (must be unique among triggers of same table)                                                                                                                                                                                                                                                                  |
| `tgfoid`         | `oid`          | [`pg_proc`](https://www.postgresql.org/docs/10/static/catalog-pg-proc.html).oid              | The function to be called                                                                                                                                                                                                                                                                                                   |
| `tgtype`         | `int2`         |                                                                                              | Bit mask identifying trigger firing conditions                                                                                                                                                                                                                                                                              |
| `tgenabled`      | `char`         |                                                                                              | Controls in which [session\_replication\_role](https://www.postgresql.org/docs/10/static/runtime-config-client.html#GUC-SESSION-REPLICATION-ROLE) modes the trigger fires. `O` = trigger fires in “origin” and “local” modes, `D` = trigger is disabled, `R` = trigger fires in “replica” mode, `A` = trigger fires always. |
| `tgisinternal`   | `bool`         |                                                                                              | True if trigger is internally generated (usually, to enforce the constraint identified by `tgconstraint`)                                                                                                                                                                                                                   |
| `tgconstrrelid`  | `oid`          | [`pg_class`](https://www.postgresql.org/docs/10/static/catalog-pg-class.html).oid            | The table referenced by a referential integrity constraint                                                                                                                                                                                                                                                                  |
| `tgconstrindid`  | `oid`          | [`pg_class`](https://www.postgresql.org/docs/10/static/catalog-pg-class.html).oid            | The index supporting a unique, primary key, referential integrity, or exclusion constraint                                                                                                                                                                                                                                  |
| `tgconstraint`   | `oid`          | [`pg_constraint`](https://www.postgresql.org/docs/10/static/catalog-pg-constraint.html).oid  | The `pg_constraint` entry associated with the trigger, if any                                                                                                                                                                                                                                                               |
| `tgdeferrable`   | `bool`         |                                                                                              | True if constraint trigger is deferrable                                                                                                                                                                                                                                                                                    |
| `tginitdeferred` | `bool`         |                                                                                              | True if constraint trigger is initially deferred                                                                                                                                                                                                                                                                            |
| `tgnargs`        | `int2`         |                                                                                              | Number of argument strings passed to trigger function                                                                                                                                                                                                                                                                       |
| `tgattr`         | `int2vector`   | [`pg_attribute`](https://www.postgresql.org/docs/10/static/catalog-pg-attribute.html).attnum | Column numbers, if trigger is column-specific; otherwise an empty array                                                                                                                                                                                                                                                     |
| `tgargs`         | `bytea`        |                                                                                              | Argument strings to pass to trigger, each NULL-terminated                                                                                                                                                                                                                                                                   |
| `tgqual`         | `pg_node_tree` |                                                                                              | Expression tree (in `nodeToString()` representation) for the trigger's `WHEN` condition, or null if none                                                                                                                                                                                                                    |
| `tgoldtable`     | `name`         |                                                                                              | `REFERENCING` clause name for `OLD TABLE`, or null if none                                                                                                                                                                                                                                                                  |
| `tgnewtable`     | `name`         |                                                                                              | `REFERENCING` clause name for `NEW TABLE`, or null if none                                                                                                                                                                                                                                                                  |

Currently, column-specific triggering is supported only for `UPDATE` events, and so `tgattr` is relevant only for that event type. `tgtype` might contain bits for other event types as well, but those are presumed to be table-wide regardless of what is in `tgattr`.

## Note

When `tgconstraint` is nonzero, `tgconstrrelid`, `tgconstrindid`, `tgdeferrable`, and `tginitdeferred` are largely redundant with the referenced `pg_constraint` entry. However, it is possible for a non-deferrable trigger to be associated with a deferrable constraint: foreign key constraints can have some deferrable and some non-deferrable triggers.

## Note

`pg_class.relhastriggers` must be true if a relation has any triggers in this catalog.