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How to create a data change trigger in PostgreSQL?
Triggers on Data Changes A data change trigger is declared as a function with no arguments and a return type of trigger. Note that the function must be declared with no arguments even if it expects to receive some arguments specified in CREATE TRIGGER — such arguments are passed via TG_ARGV, as described below.
Do you have to declare function as event trigger in PostgreSQL?
PostgreSQL requires that a function that is to be called as an event trigger must be declared as a function with no arguments and a return type of event_trigger. When a PL/pgSQL function is called as an event trigger, several special variables are created automatically in the top-level block.
How to create a trigger function in pgSQL?
Triggers on Events. PL/pgSQL can be used to define trigger functions on data changes or database events. A trigger function is created with the CREATE FUNCTION command, declaring it as a function with no arguments and a return type of trigger (for data change triggers) or event_trigger (for database event triggers).
Why do you set schema for every function in PostgreSQL?
The SET SCHEMA option sets the schema search path that will be used for the duration of the function execution. Setting the search path for every function is a good practice, as it saves having to prefix database objects with a schema name and protects against certain vulnerabilities related to the search path.
How does read replication work in PostgreSQL database?
The read replica feature uses PostgreSQL physical replication, not logical replication. Streaming replication by using replication slots is the default operation mode. When necessary, log shipping is used to catch up.
How to update sensor data in postgresql-12?
I have 2 tables in PostgreSQL-12, SENSORS (receives timeseries data feed from sensors) and LABELS (contains sensor labels & meta-data). I am trying to create a PostgreSQL trigger to update the sensor data as they are inserted into SENSORS. Each row of sensor data will be updated with the corresponding label name from LABELS.
What are the triggers in PostgreSQL callback function?
PostgreSQL Triggers are database callback functions, which are automatically performed/invoked when a specified database event occurs. The following are important points about PostgreSQL triggers −