PostgreSQL 9.0.9 Documentation
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# 45.38. `pg_trigger`

The catalog `pg_trigger` stores triggers on tables. See CREATE TRIGGER for more information.

Table 45-38. `pg_trigger` Columns

Name | Type | References | Description
--- | --- | --- | ---
`tgrelid` | `oid` | ``pg_class`.oid` | The table this trigger is on
`tgname` | `name` |  | Trigger name (must be unique among triggers of same table)
`tgfoid` | `oid` | ``pg_proc`.oid` | The function to be called
`tgtype` | `int2` |  | Bit mask identifying trigger conditions
`tgenabled` | `char` |  | Controls in which 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`.oid` | The table referenced by a referential integrity constraint
`tgconstrindid` | `oid` | ``pg_class`.oid` | The index supporting a unique, primary key, or referential integrity constraint
`tgconstraint` | `oid` | ``pg_constraint`.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`.attnum` | Column numbers, if trigger is column-specific; otherwise an empty array
`tgargs` | `bytea` |  | Argument strings to pass to trigger, each NULL-terminated
`tgqual` | `text` |  | Expression tree (in `nodeToString()` representation) for the trigger's `WHEN` condition, 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 table has any triggers in this catalog.

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