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What do you need to know about triggers in PostgreSQL?
A “trigger” is defined as any event that sets a course of action in a motion. In PostgreSQL, if you want to take action on specific database events, such as INSERT, UPDATE, DELETE, or TRUNCATE, then trigger functionality can be useful as it will invoke the required function on defined events.
Are there Postgres notifications from inside stored procedures?
Postgres does not support them inside stored procedures/functions, and the behaviour you are seeing is correct – the (implicit) transaction does not complete until the procedure completes. This page discusses the issue in detail along with potential workarounds.
How are stored functions configured in PostgreSQL?
Also, in PostgreSQL stored functions can be configured to execute code at a higher privilege level than the session user, which admits some powerful capabilities. We’ll do some examples later.
Can you use the same name for both the trigger and the stored function?
The exact same name can be used for both the trigger and the associated stored function, which is completely permissible in PostgreSQL because the RDBMS keeps track of triggers and stored functions separately by the respective purposes, and the context in which the item name is used makes clear which item the name refers to.
When does a row level fire in PostgreSQL?
Row-level BEFORE triggers fire immediately before a particular row is operated on, while row-level AFTER triggers fire at the end of the statement (but before any statement-level AFTER triggers). These types of triggers may only be defined on tables.
How are constraint triggers the same as regular triggers?
This is the same as a regular trigger except that the timing of the trigger firing can be adjusted using SET CONSTRAINTS. Constraint triggers are expected to raise an exception when the constraints they implement are violated. The basic syntax of creating a trigger is as follows −
When to use a nonnull return value in PostgreSQL?
A nonnull return value is used to signal that the trigger performed the necessary data modifications in the view. This will cause the count of the number of rows affected by the command to be incremented. For INSERT and UPDATE operations, the trigger may modify the NEW row before returning it.