Alerting: Fix migration pauses all alert rules on PostgreSQL (#63951)

This commit fixes a serious bug in Grafana 9.4.1 where on upgrade
a migration would pause all existing alert rules and change the
default value of the column to true.

pkg/services/sqlstore/migrations/ualert/tables.go

@@ -290,6 +290,11 @@ func addAlertRuleMigrations(mg *migrator.Migrator, defaultIntervalSeconds int64)
 			Default:  "0",
 		},
 	))
+
+	// This migration fixes a bug where "false" for the default value created a column with default "true" in PostgreSQL databases
+	mg.AddMigration("fix is_paused column for alert_rule table", migrator.NewRawSQLMigration("").
+		Postgres(`ALTER TABLE alert_rule ALTER COLUMN is_paused SET DEFAULT false;
+UPDATE alert_rule SET is_paused = false;`))
 }
 
 func addAlertRuleVersionMigrations(mg *migrator.Migrator) {
@@ -354,6 +359,11 @@ func addAlertRuleVersionMigrations(mg *migrator.Migrator) {
 			Default:  "0",
 		},
 	))
+
+	// This migration fixes a bug where "false" for the default value created a column with default "true" in PostgreSQL databases
+	mg.AddMigration("fix is_paused column for alert_rule_version table", migrator.NewRawSQLMigration("").
+		Postgres(`ALTER TABLE alert_rule_version ALTER COLUMN is_paused SET DEFAULT false;
+UPDATE alert_rule_version SET is_paused = false;`))
 }
 
 func addAlertmanagerConfigMigrations(mg *migrator.Migrator) {