PostgreSQL Triggers for Incremental Config Changes

On an INSERT or UPDATE on each row of a "main configuration tables", as
listed in the ConfigSet Go struct, the changed_at column field will
automatically be bumped to the current timestamp.

Furthermore, the "relationship tables" will update the changed_at field
in its referred row in the main table for INSERT, UPDATE or DELETE.

schema/pgsql/schema.sql

@@ -26,6 +26,68 @@ CREATE OR REPLACE FUNCTION anynonarrayliketext(anynonarray, text)
     $$;
 CREATE OPERATOR ~~ (LEFTARG=anynonarray, RIGHTARG=text, PROCEDURE=anynonarrayliketext);
 
+-- incr_cfg_bump_changed_at is a BEFORE TRIGGER for INSERT/UPDATE, setting changed_at to the current timestamp.
+CREATE FUNCTION incr_cfg_bump_changed_at()
+    RETURNS trigger
+    LANGUAGE plpgsql
+    AS $$
+        BEGIN
+            NEW.changed_at = EXTRACT(EPOCH FROM NOW()) * 1000;
+            RETURN NEW;
+        END;
+    $$;
+
+-- incr_cfg_bump_changed_at_relation is an AFTER TRIGGER updating the changed_at column of another table. This function
+-- might be used on relationship tables to bump the changed_at of their "main" table. It expects the foreign key table
+-- name as its parameter. Due to our convention, the foreign key field will be "${foreign_table}_id", being accessed.
+CREATE FUNCTION incr_cfg_bump_changed_at_relation() -- foreign_tbl text
+    RETURNS trigger
+    LANGUAGE plpgsql
+    AS $$
+    DECLARE
+        foreign_tbl TEXT := TG_ARGV[0];
+        update_id BIGINT;
+    BEGIN
+        IF (TG_OP = 'DELETE') THEN
+            update_id := row_to_json(OLD)->>format('%s_id', foreign_tbl);
+        ELSE
+            update_id := row_to_json(NEW)->>format('%s_id', foreign_tbl);
+        END IF;
+        EXECUTE format('
+         UPDATE %s
+         SET changed_at = EXTRACT(EPOCH FROM NOW()) * 1000
+         WHERE id = %s', foreign_tbl, update_id);
+        RETURN NULL;
+    END;
+    $$;
+
+-- incr_cfg_bump_changed_at_relation_2nd is similar to incr_cfg_bump_changed_at_relation, just allowing one additional
+-- relationship table in between, like: $tbl -> $join_tbl -> $foreign_tbl. Thus, it has two arguments: first the name of
+-- the join table, which is referenced from the table having the trigger attached, and second the destination or foreign
+-- table where changed_at should be bumped.
+CREATE FUNCTION incr_cfg_bump_changed_at_relation_2nd() -- join_tbl text, foreign_tbl text
+    RETURNS trigger
+    LANGUAGE plpgsql
+    AS $$
+    DECLARE
+        join_tbl          TEXT := TG_ARGV[0];
+        foreign_tbl       TEXT := TG_ARGV[1];
+        join_update_id    BIGINT;
+    BEGIN
+        IF (TG_OP = 'DELETE') THEN
+            join_update_id := row_to_json(OLD)->>format('%s_id', join_tbl);
+        ELSE
+            join_update_id := row_to_json(NEW)->>format('%s_id', join_tbl);
+        END IF;
+        EXECUTE format('
+             UPDATE %1$s
+             SET changed_at = EXTRACT(EPOCH FROM NOW()) * 1000
+             WHERE id IN (SELECT %1$s_id FROM %2$s WHERE id = %3s)',
+             foreign_tbl, join_tbl, join_update_id);
+        RETURN NULL;
+    END;
+    $$;
+
 CREATE TABLE available_channel_type (
     type text NOT NULL,
     name text NOT NULL,
@@ -52,14 +114,19 @@ CREATE TABLE channel (
 
 CREATE INDEX idx_channel_changed_at ON channel(changed_at);
 
+CREATE TRIGGER trg_channel_incr_cfg_update
+    BEFORE INSERT OR UPDATE ON channel
+    FOR EACH ROW
+    EXECUTE FUNCTION incr_cfg_bump_changed_at();
+
 CREATE TABLE contact (
     id bigserial,
     full_name text NOT NULL,
     username text, -- reference to web user
     default_channel_id bigint NOT NULL REFERENCES channel(id),
     color varchar(7) NOT NULL, -- hex color codes e.g #000000
 
-    changed_at bigint NOT NULL DEFAULT extract(epoch from now()) * 1000,
+    changed_at bigint NOT NULL DEFAULT EXTRACT(EPOCH FROM NOW()) * 1000,
     deleted boolenum NOT NULL DEFAULT 'n',
 
     CONSTRAINT pk_contact PRIMARY KEY (id),
@@ -68,13 +135,18 @@ CREATE TABLE contact (
 
 CREATE INDEX idx_contact_changed_at ON contact(changed_at);
 
+CREATE TRIGGER trg_contact_incr_cfg_update
+    BEFORE INSERT OR UPDATE ON contact
+    FOR EACH ROW
+    EXECUTE FUNCTION incr_cfg_bump_changed_at();
+
 CREATE TABLE contact_address (
     id bigserial,
     contact_id bigint NOT NULL REFERENCES contact(id),
     type text NOT NULL, -- 'phone', 'email', ...
     address text NOT NULL, -- phone number, email address, ...
 
-    changed_at bigint NOT NULL DEFAULT extract(epoch from now()) * 1000,
+    changed_at bigint NOT NULL DEFAULT EXTRACT(EPOCH FROM NOW()) * 1000,
     deleted boolenum NOT NULL DEFAULT 'n',
 
     CONSTRAINT pk_contact_address PRIMARY KEY (id),
@@ -83,19 +155,29 @@ CREATE TABLE contact_address (
 
 CREATE INDEX idx_contact_address_changed_at ON contact_address(changed_at);
 
+CREATE TRIGGER trg_contact_address_incr_cfg_update
+    BEFORE INSERT OR UPDATE ON contact_address
+    FOR EACH ROW
+    EXECUTE FUNCTION incr_cfg_bump_changed_at();
+
 CREATE TABLE contactgroup (
     id bigserial,
     name text NOT NULL,
     color varchar(7) NOT NULL, -- hex color codes e.g #000000
 
-    changed_at bigint NOT NULL DEFAULT extract(epoch from now()) * 1000,
+    changed_at bigint NOT NULL DEFAULT EXTRACT(EPOCH FROM NOW()) * 1000,
     deleted boolenum NOT NULL DEFAULT 'n',
 
     CONSTRAINT pk_contactgroup PRIMARY KEY (id)
 );
 
 CREATE INDEX idx_contactgroup_changed_at ON contactgroup(changed_at);
 
+CREATE TRIGGER trg_contactgroup_incr_cfg_update
+    BEFORE INSERT OR UPDATE ON contactgroup
+    FOR EACH ROW
+    EXECUTE FUNCTION incr_cfg_bump_changed_at();
+
 -- Changes to contactgroup_member should be notified by an updated contactgroup.changed_at.
 CREATE TABLE contactgroup_member (
     contactgroup_id bigint NOT NULL REFERENCES contactgroup(id),
@@ -104,30 +186,45 @@ CREATE TABLE contactgroup_member (
     CONSTRAINT pk_contactgroup_member PRIMARY KEY (contactgroup_id, contact_id)
 );
 
+CREATE TRIGGER trg_contactgroup_member_changed_at_relation
+    AFTER INSERT OR UPDATE OR DELETE ON contactgroup_member
+    FOR EACH ROW
+    EXECUTE FUNCTION incr_cfg_bump_changed_at_relation('contactgroup');
+
 CREATE TABLE schedule (
     id bigserial,
     name text NOT NULL,
 
-    changed_at bigint NOT NULL DEFAULT extract(epoch from now()) * 1000,
+    changed_at bigint NOT NULL DEFAULT EXTRACT(EPOCH FROM NOW()) * 1000,
     deleted boolenum NOT NULL DEFAULT 'n',
 
     CONSTRAINT pk_schedule PRIMARY KEY (id)
 );
 
 CREATE INDEX idx_schedule_changed_at ON schedule(changed_at);
 
+CREATE TRIGGER trg_schedule_incr_cfg_update
+    BEFORE INSERT OR UPDATE ON schedule
+    FOR EACH ROW
+    EXECUTE FUNCTION incr_cfg_bump_changed_at();
+
 CREATE TABLE timeperiod (
     id bigserial,
     owned_by_schedule_id bigint REFERENCES schedule(id), -- nullable for future standalone timeperiods
 
-    changed_at bigint NOT NULL DEFAULT extract(epoch from now()) * 1000,
+    changed_at bigint NOT NULL DEFAULT EXTRACT(EPOCH FROM NOW()) * 1000,
     deleted boolenum NOT NULL DEFAULT 'n',
 
     CONSTRAINT pk_timeperiod PRIMARY KEY (id)
 );
 
 CREATE INDEX idx_timeperiod_changed_at ON timeperiod(changed_at);
 
+CREATE TRIGGER trg_timeperiod_incr_cfg_update
+    BEFORE INSERT OR UPDATE ON timeperiod
+    FOR EACH ROW
+    EXECUTE FUNCTION incr_cfg_bump_changed_at();
+
 -- Changes to timeperiod_entry should be notified by an updated timeperiod.changed_at.
 CREATE TABLE timeperiod_entry (
     id bigserial,
@@ -147,6 +244,11 @@ CREATE TABLE timeperiod_entry (
     CONSTRAINT pk_timeperiod_entry PRIMARY KEY (id)
 );
 
+CREATE TRIGGER trg_timeperiod_entry_changed_at_relation
+    AFTER INSERT OR UPDATE OR DELETE ON timeperiod_entry
+    FOR EACH ROW
+    EXECUTE FUNCTION incr_cfg_bump_changed_at_relation('timeperiod');
+
 -- Changes to schedule_member should be notified by an updated schedule.changed_at.
 CREATE TABLE schedule_member (
     schedule_id bigint NOT NULL REFERENCES schedule(id),
@@ -164,6 +266,11 @@ CREATE TABLE schedule_member (
     CHECK (num_nonnulls(contact_id, contactgroup_id) = 1)
 );
 
+CREATE TRIGGER trg_schedule_member_changed_at_relation
+    AFTER INSERT OR UPDATE OR DELETE ON schedule_member
+    FOR EACH ROW
+    EXECUTE FUNCTION incr_cfg_bump_changed_at_relation('schedule');
+
 CREATE TABLE source (
     id bigserial,
     -- The type "icinga2" is special and requires (at least some of) the icinga2_ prefixed columns.
@@ -189,7 +296,7 @@ CREATE TABLE source (
     icinga2_common_name text,
     icinga2_insecure_tls boolenum NOT NULL DEFAULT 'n',
 
-    changed_at bigint NOT NULL DEFAULT extract(epoch from now()) * 1000,
+    changed_at bigint NOT NULL DEFAULT EXTRACT(EPOCH FROM NOW()) * 1000,
     deleted boolenum NOT NULL DEFAULT 'n',
 
     -- The hash is a PHP password_hash with PASSWORD_DEFAULT algorithm, defaulting to bcrypt. This check roughly ensures
@@ -203,6 +310,11 @@ CREATE TABLE source (
 
 CREATE INDEX idx_source_changed_at ON source(changed_at);
 
+CREATE TRIGGER trg_source_incr_cfg_update
+    BEFORE INSERT OR UPDATE ON source
+    FOR EACH ROW
+    EXECUTE FUNCTION incr_cfg_bump_changed_at();
+
 CREATE TABLE object (
     id bytea NOT NULL, -- SHA256 of identifying tags and the source.id
     source_id bigint NOT NULL REFERENCES source(id),
@@ -252,14 +364,19 @@ CREATE TABLE rule (
     object_filter text,
     is_active boolenum NOT NULL DEFAULT 'y',
 
-    changed_at bigint NOT NULL DEFAULT extract(epoch from now()) * 1000,
+    changed_at bigint NOT NULL DEFAULT EXTRACT(EPOCH FROM NOW()) * 1000,
     deleted boolenum NOT NULL DEFAULT 'n',
 
     CONSTRAINT pk_rule PRIMARY KEY (id)
 );
 
 CREATE INDEX idx_rule_changed_at ON rule(changed_at);
 
+CREATE TRIGGER trg_rule_incr_cfg_update
+    BEFORE INSERT OR UPDATE ON rule
+    FOR EACH ROW
+    EXECUTE FUNCTION incr_cfg_bump_changed_at();
+
 -- Changes to rule_escalation should be notified by an updated rule.changed_at.
 CREATE TABLE rule_escalation (
     id bigserial,
@@ -275,6 +392,11 @@ CREATE TABLE rule_escalation (
     CHECK (NOT (condition IS NOT NULL AND fallback_for IS NOT NULL))
 );
 
+CREATE TRIGGER trg_rule_escalation_changed_at_relation
+    AFTER INSERT OR UPDATE OR DELETE ON rule_escalation
+    FOR EACH ROW
+    EXECUTE FUNCTION incr_cfg_bump_changed_at_relation('rule');
+
 -- Changes to rule_escalation_recipient should be notified by an updated rule.changed_at via rule_escalation.rule_id.
 CREATE TABLE rule_escalation_recipient (
     id bigserial,
@@ -289,6 +411,11 @@ CREATE TABLE rule_escalation_recipient (
     CHECK (num_nonnulls(contact_id, contactgroup_id, schedule_id) = 1)
 );
 
+CREATE TRIGGER trg_rule_escalation_recipient_changed_at_relation
+    AFTER INSERT OR UPDATE OR DELETE ON rule_escalation_recipient
+    FOR EACH ROW
+    EXECUTE FUNCTION incr_cfg_bump_changed_at_relation_2nd('rule_escalation', 'rule');
+
 CREATE TABLE incident (
     id bigserial,
     object_id bytea NOT NULL REFERENCES object(id),