reduce length of dashboard columns used in compound indexes (#8507)

pkg/services/sqlstore/migrations/dashboard_mig.go

@@ -8,7 +8,7 @@ func addDashboardMigration(mg *Migrator) {
 		Columns: []*Column{
 			{Name: "id", Type: DB_BigInt, IsPrimaryKey: true, IsAutoIncrement: true},
 			{Name: "version", Type: DB_Int, Nullable: false},
-			{Name: "slug", Type: DB_NVarchar, Length: 190, Nullable: false},
+			{Name: "slug", Type: DB_NVarchar, Length: 189, Nullable: false},
 			{Name: "title", Type: DB_NVarchar, Length: 255, Nullable: false},
 			{Name: "data", Type: DB_Text, Nullable: false},
 			{Name: "account_id", Type: DB_BigInt, Nullable: false},
@@ -114,7 +114,7 @@ func addDashboardMigration(mg *Migrator) {
 
 	// add column to store plugin_id
 	mg.AddMigration("Add column plugin_id in dashboard", NewAddColumnMigration(dashboardV2, &Column{
-		Name: "plugin_id", Type: DB_NVarchar, Nullable: true, Length: 255,
+		Name: "plugin_id", Type: DB_NVarchar, Nullable: true, Length: 189,
 	}))
 
 	mg.AddMigration("Add index for plugin_id in dashboard", NewAddIndexMigration(dashboardV2, &Index{
@@ -129,7 +129,7 @@ func addDashboardMigration(mg *Migrator) {
 	mg.AddMigration("Update dashboard table charset", NewTableCharsetMigration("dashboard", []*Column{
 		{Name: "slug", Type: DB_NVarchar, Length: 189, Nullable: false},
 		{Name: "title", Type: DB_NVarchar, Length: 255, Nullable: false},
-		{Name: "plugin_id", Type: DB_NVarchar, Nullable: true, Length: 255},
+		{Name: "plugin_id", Type: DB_NVarchar, Nullable: true, Length: 189},
 		{Name: "data", Type: DB_MediumText, Nullable: false},
 	}))