fix(controlplane): force DuckLake transpile mode in multitenant remote backend (#550)

Sessions on the multitenant control plane are always backed by DuckLake
workers, but the per-org metadata store comes from configstore so the
global server.Config.DuckLake.MetadataStore stays empty. The transpiler
was gated on that field alone, so the DDL transform never registered
in MTCP — meaning Fivetran's ALTER TABLE ... ADD PRIMARY KEY (and
ON CONFLICT, DuckLake-aware pg_catalog/info_schema rewrites) flowed
straight through to the worker, which rejects them with
"Adding indexes or constraints is not supported in DuckLake".

Add server.Config.AlwaysDuckLake and set it from the remote-backend
control plane. Tests cover the bare ADD PRIMARY KEY / UNIQUE / FK
forms (the existing test only exercised the named-constraint path).

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: fuziontech

controlplane/control.go

@@ -375,6 +375,15 @@ func RunControlPlane(cfg ControlPlaneConfig) {
 		cfg.K8s.SharedWarmTarget = k8sSharedWarmTarget
 	}
 
+	// In remote (multitenant) mode the global DuckLake.MetadataStore is empty
+	// because metadata stores are per-org (loaded from configstore), but every
+	// worker is DuckLake-backed. Force the transpiler into DuckLake mode so
+	// DDL stripping (e.g. ALTER TABLE ADD PRIMARY KEY → no-op) and the other
+	// DuckLake-aware transforms still run.
+	if cfg.WorkerBackend == "remote" {
+		cfg.AlwaysDuckLake = true
+	}
+
 	// Create a minimal server for cancel request routing
 	srv := &server.Server{}
 	server.InitMinimalServer(srv, cfg.Config, nil)

server/conn.go

@@ -188,7 +188,7 @@ type clientConn struct {
 // newTranspiler creates a transpiler configured for this connection.
 func (c *clientConn) newTranspiler(convertPlaceholders bool) *transpiler.Transpiler {
 	return transpiler.New(transpiler.Config{
-		DuckLakeMode:        c.server.cfg.DuckLake.MetadataStore != "",
+		DuckLakeMode:        c.server.cfg.DuckLake.MetadataStore != "" || c.server.cfg.AlwaysDuckLake,
 		LogicalDatabaseName: c.database,
 		PhysicalCatalogName: "ducklake",
 		ConvertPlaceholders: convertPlaceholders,

server/server.go

@@ -225,6 +225,13 @@ type Config struct {
 	// DuckLake configuration
 	DuckLake DuckLakeConfig
 
+	// AlwaysDuckLake forces the SQL transpiler into DuckLake mode for every
+	// session even when the global DuckLake.MetadataStore is empty. The
+	// multitenant control plane sets this because metadata stores are
+	// per-org (loaded from configstore), so the global field stays empty
+	// even though every worker is DuckLake-backed.
+	AlwaysDuckLake bool
+
 	// Graceful shutdown timeout (default: 30s)
 	ShutdownTimeout time.Duration
 

transpiler/transpiler_test.go

@@ -886,6 +886,9 @@ func TestTranspile_DDL_NoOps(t *testing.T) {
 		{"GRANT", "GRANT SELECT ON users TO public", "GRANT"},
 		{"REVOKE", "REVOKE SELECT ON users FROM public", "REVOKE"},
 		{"ALTER TABLE ADD CONSTRAINT", "ALTER TABLE users ADD CONSTRAINT pk_users PRIMARY KEY (id)", "ALTER TABLE"},
+		{"ALTER TABLE ADD PRIMARY KEY (Fivetran form)", `/*Fivetran*/ALTER TABLE "billing_public"."billing_usagereport" ADD PRIMARY KEY ("id")`, "ALTER TABLE"},
+		{"ALTER TABLE ADD UNIQUE", "ALTER TABLE users ADD UNIQUE (email)", "ALTER TABLE"},
+		{"ALTER TABLE ADD FOREIGN KEY", "ALTER TABLE orders ADD FOREIGN KEY (user_id) REFERENCES users(id)", "ALTER TABLE"},
 		{"ALTER TABLE SET NOT NULL", "ALTER TABLE users ALTER COLUMN name SET NOT NULL", "ALTER TABLE"},
 		{"ALTER TABLE DROP NOT NULL", "ALTER TABLE users ALTER COLUMN name DROP NOT NULL", "ALTER TABLE"},
 		{"ALTER TABLE SET DEFAULT", "ALTER TABLE users ALTER COLUMN status SET DEFAULT 'active'", "ALTER TABLE"},