capsite/toybox: mount lookups in SQL, not a scan in JS

Each request parsed every mount's labels and searched them in JS. Labels
now sit one per row in mount_label, indexed on (key, value): a lookup
joins the request's labels (json_each) on the index and keeps the vat
whose every label matched. The overlap check at registration is SQL too.

mount.labels keeps the whole set as JSON; mounts stored before
mount_label get their rows filled in when the schema runs. The SQL lives
in mounts-sql.js, tested on node:sqlite, old-shape state included.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

toybox/supervisor.js

@@ -4,7 +4,8 @@ import { DurableObject, WorkerEntrypoint } from "cloudflare:workers";
 import { RpcTarget, newWebSocketRpcSession, newWorkersRpcResponse } from "capnweb";
 import { E, Far } from "@endo/far";
 import { makeClient, swissnumFromBytes } from "@endo/ocapn";
-import { carries, conflict, mergeLabels, urlLabels } from "./labels.js";
+import { mergeLabels, urlLabels } from "./labels.js";
+import { LOOKUP, MOUNT, MOUNT_LABELS, MOUNT_SCHEMA, OVERLAP, UNMOUNT, UNMOUNT_LABELS } from "./mounts-sql.js";
 import { locationOf, makeRpcNetLayer } from "./netlayer.js";
 import VAT_RUNTIME from "vat-runtime.txt";
 
@@ -282,14 +283,7 @@ export class Router extends WorkerEntrypoint {
 export class Directory extends DurableObject {
 	constructor(ctx, env) {
 		super(ctx, env);
-		ctx.storage.sql.exec("CREATE TABLE IF NOT EXISTS mount (vat TEXT PRIMARY KEY, labels TEXT)");
-	}
-
-	#mounts() {
-		return this.ctx.storage.sql
-			.exec("SELECT vat, labels FROM mount")
-			.toArray()
-			.map(({ vat, labels }) => ({ vat, labels: JSON.parse(labels) }));
+		for (const statement of MOUNT_SCHEMA) ctx.storage.sql.exec(statement);
 	}
 
 	/**
@@ -299,22 +293,28 @@ export class Directory extends DurableObject {
 	 * @param {Record<string, string> | null} labels
 	 */
 	mount(vat, labels) {
-		if (labels) {
-			const overlap = this.#mounts().find((m) => m.vat !== vat && !conflict(m.labels, labels));
-			if (overlap) throw new Error("mount overlaps another: add a label whose value tells them apart");
-			this.ctx.storage.sql.exec("INSERT OR REPLACE INTO mount VALUES (?, ?)", vat, JSON.stringify(labels));
-		} else {
-			this.ctx.storage.sql.exec("DELETE FROM mount WHERE vat = ?", vat);
-		}
+		const { sql } = this.ctx.storage;
+		this.ctx.storage.transactionSync(() => {
+			sql.exec(UNMOUNT_LABELS, vat);
+			if (!labels) return void sql.exec(UNMOUNT, vat);
+			const json = JSON.stringify(labels);
+			if (sql.exec(OVERLAP, json, vat).toArray().length) {
+				throw new Error("mount overlaps another: add a label whose value tells them apart");
+			}
+			sql.exec(MOUNT, vat, json);
+			sql.exec(MOUNT_LABELS, vat, json);
+		});
 	}
 
 	/**
-	 * The mount whose labels `request` carries, if any.
+	 * The mount whose labels `request` carries, if any. Registration keeps
+	 * mounts pairwise conflicting, so at most one can match.
 	 *
 	 * @param {Record<string, string>} request
 	 */
 	lookup(request) {
-		return this.#mounts().find((m) => carries(m.labels, request)) ?? null;
+		const [row] = this.ctx.storage.sql.exec(LOOKUP, JSON.stringify(request)).toArray();
+		return row ? { vat: row.vat, labels: JSON.parse(row.labels) } : null;
 	}
 }