Intermediate LevelPostgreSQL

How do Event Triggers monitor and intercept DDL schema changes?

❓ Interview Prompt: Explain Event Triggers (`CREATE EVENT TRIGGER`), DDL event hooks (`ddl_command_start`, `ddl_command_end`, `sql_drop`), and schema auditing.

Unlike standard triggers that fire on DML row changes ('INSERT'/'UPDATE'), Event Triggers fire when DDL schema changes ('CREATE TABLE', 'ALTER TABLE', 'DROP') execute:

Use Cases:

•

Auditing DDL schema migrations.

•

Blocking unauthorized table drops in production databases.

Code Implementation Example

sql

CREATE OR REPLACE FUNCTION audit_ddl_changes()
RETURNS event_trigger AS $$
BEGIN
  RAISE NOTICE 'DDL Command Executed: %', tg_tag;
END;
$$ LANGUAGE plpgsql;

CREATE EVENT TRIGGER log_ddl_event 
ON ddl_command_end 
EXECUTE FUNCTION audit_ddl_changes();

💡Intercepting DDL schema changes via Event Triggers.

🎯 Interview Key Takeaway

Use Event Triggers to audit or restrict DDL schema modifications across production databases.

#Event Triggers#DDL#Auditing#Intermediate

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