Ignore all DDL executed by pgroll (#890)

Set a session-level setting `pgroll.internal` to `TRUE` on connections
used by `pgroll` (`pgroll` uses two connections, one to execute
migrations and one for its internal state).

Use the `pgroll.internal` setting to prevent schema changes made by
`pgroll` itself being captured by the `raw_migration()` event trigger
function.

DDL changes made in schema `s` are already ignored by `raw_migration()`
if there is an active migration period in progress for schema `s`. The
change in this commit ensures that *all* DDL changes in *all* schema at
*all* times made by `pgroll` are ignored by `raw_migration()`, including
version schema creation and the creation of views within those schema.

This reverts PR #823 which removed
a `pgroll.internal` setting that was set using `SET LOCAL` outside a
transaction block. That PR assumed that setting `pgroll.internal` with
`SET LOCAL` outside a transaction had no effect, but it did have an
effect (the setting was set to an empty string, which was sufficient
given how it was used in`raw_migration()`). This PR uses the same
setting but sets it with `SET` (instead of `SET LOCAL`) to make it more
obvious what is happening.

Add a test to verify that version schema creation does not create
inferred migrations.

Author: andrew-farries

pkg/roll/execute_test.go

@@ -880,6 +880,37 @@ func TestStartFailsWithExistingSchemaWithoutHistory(t *testing.T) {
 	})
 }
 
+func TestVersionSchemaCreationIsNotCapturedAsAnInferredMigration(t *testing.T) {
+	t.Parallel()
+
+	testutils.WithMigratorAndConnectionToContainer(t, func(m *roll.Roll, db *sql.DB) {
+		ctx := context.Background()
+
+		// Apply a migration
+		err := m.Start(ctx, &migrations.Migration{
+			Name:       "01_create_table",
+			Operations: migrations.Operations{createTableOp("new_table")},
+		}, backfill.NewConfig())
+		require.NoError(t, err)
+		err = m.Complete(ctx)
+		require.NoError(t, err)
+
+		// Ensure that the version schema has been created
+		versionSchema := roll.VersionedSchemaName("public", "01_create_table")
+		require.True(t, schemaExists(t, db, versionSchema))
+
+		// Get the schema history **for the version schema**
+		hist, err := m.State().SchemaHistory(ctx, versionSchema)
+		require.NoError(t, err)
+
+		// Ensure that there are no inferred migrations recorded for the version
+		// schema; the DDL statements that `pgroll` executes to create the version
+		// schema and the views inside it should be ignored by the event trigger
+		// that captures inferred migrations.
+		require.Len(t, hist, 0)
+	})
+}
+
 func addColumnOp(tableName string) *migrations.OpAddColumn {
 	return &migrations.OpAddColumn{
 		Table: tableName,

pkg/roll/roll.go

@@ -105,6 +105,11 @@ func setupConn(ctx context.Context, pgURL, schema string, options options) (*sql
 		return nil, err
 	}
 
+	_, err = conn.ExecContext(ctx, "SET pgroll.internal TO 'TRUE'")
+	if err != nil {
+		return nil, fmt.Errorf("unable to set pgroll.internal to true: %w", err)
+	}
+
 	if options.lockTimeoutMs > 0 {
 		_, err = conn.ExecContext(ctx, fmt.Sprintf("SET lock_timeout to '%dms'", options.lockTimeoutMs))
 		if err != nil {

pkg/state/init.sql

@@ -331,6 +331,10 @@ DECLARE
     schemaname text;
     migration_id text;
 BEGIN
+    -- Ignore schema changes made by pgroll
+    IF (pg_catalog.current_setting('pgroll.internal', TRUE) = 'TRUE') THEN
+        RETURN;
+    END IF;
     IF tg_event = 'sql_drop' AND tg_tag = 'DROP SCHEMA' THEN
         -- Take the schema name from the drop schema command
         SELECT

pkg/state/state.go

@@ -47,6 +47,11 @@ func New(ctx context.Context, pgURL, stateSchema string, opts ...StateOpt) (*Sta
 		return nil, err
 	}
 
+	_, err = conn.ExecContext(ctx, "SET pgroll.internal TO 'TRUE'")
+	if err != nil {
+		return nil, fmt.Errorf("unable to set pgroll.internal to true: %w", err)
+	}
+
 	st := &State{
 		pgConn:        conn,
 		pgrollVersion: "development",