feat: record the source namespace in a materialized view definition (#4098)

A view definition recorded its source by bare name and refresh resolved
that name at the root, so declaring a view over a namespaced source was
refused outright -- materialized views were root-only for every caller.

The definition now carries `source_namespace`, and refresh opens the
source at that coordinate. `plan` takes the namespace too: refresh
re-plans the stored definition and persists the result when it migrates,
so defaulting it there would strand the view on its next rebuild.

The stored kind is the version boundary. Root definitions keep the
`select` form byte-for-byte, so everything written before this change
reads exactly as it always did. A namespaced source is stored as
`namespaced_select`: released readers drop unknown fields and resolve a
`select` source at the root, so keeping the old kind would let a
rolled-back worker refresh a view from a same-name root table -- the new
kind routes them to their existing unrecognized-kind refusal instead.
The Python and Node definition parsers learn the new kind alongside the
Rust core.

nodejs/__test__/materialized_view.test.ts

@@ -48,6 +48,28 @@ describe("materialized views", () => {
     expect(definitionFromMetadata(safe, "v").limit).toBe(42);
   });
 
+  it("reads the namespaced select kind and refuses unknown kinds", () => {
+    // "namespaced_select" is the namespaced form of "select": same shape, a
+    // separate kind so readers that predate it refuse instead of resolving
+    // the source at the root.
+    const namespaced = new Map([
+      [
+        DEFINITION_META_KEY,
+        '{"kind":"namespaced_select","source_table":"people","source_namespace":["ns"]}',
+      ],
+    ]);
+    const definition = definitionFromMetadata(namespaced, "v");
+    expect(definition.sourceTable).toBe("people");
+    expect(definition.sourceNamespace).toEqual(["ns"]);
+
+    const unknown = new Map([
+      [DEFINITION_META_KEY, '{"kind":"select_v3","source_table":"people"}'],
+    ]);
+    expect(() => definitionFromMetadata(unknown, "v")).toThrow(
+      /cannot refresh/,
+    );
+  });
+
   it("creates, refreshes and queries a view", async () => {
     const view = await db.createMaterializedView("adults", "people", {
       select: ["name", ["shout", "upper(name)"]],

nodejs/lancedb/materialized_view.ts

@@ -19,6 +19,8 @@ export interface MaterializedViewDefinition {
   limit?: number;
   /** Source columns the projections and filter read. */
   inputs: string[];
+  /** Namespace holding the source table; empty is the root namespace. */
+  sourceNamespace: string[];
 }
 
 /**
@@ -78,7 +80,8 @@ export function definitionFromMetadata(
   }
   // biome-ignore lint/suspicious/noExplicitAny: raw JSON
   const value: any = JSON.parse(raw);
-  if (value.kind !== "select") {
+  // "namespaced_select" keeps older readers from resolving the source at root.
+  if (value.kind !== "select" && value.kind !== "namespaced_select") {
     throw new Error(
       `materialized view '${name}' is defined by '${value.kind}', which this ` +
         "version of lancedb cannot refresh",
@@ -103,6 +106,7 @@ export function definitionFromMetadata(
     filter: value.filter ?? undefined,
     limit,
     inputs: value.inputs ?? [],
+    sourceNamespace: value.source_namespace ?? [],
   };
 }