How to create trigger for all table in postgresql?

Question

I have a trigger, but I need to associate with all tables of the my postgres. Is there a command like this below?

CREATE TRIGGER delete_data_alldb
BEFORE DELETE
ON ALL DATABASE
FOR EACH ROW
EXECUTE PROCEDURE delete_data();

Answer 1

Well there is no database-wide trigger creation but for all such bulk-admin-operations you could use PostgreSQL system tables to generate queries for you instead of writing them by hand. In this case you could run:

SELECT
    'CREATE TRIGGER '
    || tab_name
    || ' BEFORE DELETE ON ALL DATABASE FOR EACH ROW EXECUTE PROCEDURE delete_data();' AS trigger_creation_query
FROM (
    SELECT
        quote_ident(table_schema) || '.' || quote_ident(table_name) as tab_name
    FROM
        information_schema.tables
    WHERE
        table_schema NOT IN ('pg_catalog', 'information_schema')
        AND table_schema NOT LIKE 'pg_toast%'
) tablist;

This will get you set of strings which are SQL commands like:

CREATE TRIGGER schema1.table1 BEFORE DELETE ON ALL DATABASE FOR EACH ROW EXECUTE PROCEDURE delete_data();
CREATE TRIGGER schema1.table2 BEFORE DELETE ON ALL DATABASE FOR EACH ROW EXECUTE PROCEDURE delete_data();
CREATE TRIGGER schema1.table3 BEFORE DELETE ON ALL DATABASE FOR EACH ROW EXECUTE PROCEDURE delete_data();
CREATE TRIGGER schema2.table1 BEFORE DELETE ON ALL DATABASE FOR EACH ROW EXECUTE PROCEDURE delete_data();
CREATE TRIGGER schema2."TABLE2" BEFORE DELETE ON ALL DATABASE FOR EACH ROW EXECUTE PROCEDURE delete_data();
...
etc

You just need to run them at once (either by psql or pgAdmin).

Now some explanation:

• I select names of tables in my database using information_schema.tables system table. Because there are data of literally all tables, remember to exclude pg_catalog and information_schema schemas and toast tables from your select.
• I use quote_ident(text) function which will put string inside double quote signs ("") if necessary (ie. names with spaces or capital letters require that).
• When I have list of tables names I just concatenate them with some static strings to get my SQL commands.
• I write that command using sub-query because I want you to get better idea of what's going on here. You may write a single query by putting quote_ident(table_schema) || '.' || quote_ident(table_name) in place of tab_name.