multi parent relationship for changes

lix/packages/sdk/src/change-queue.test.ts

@@ -37,7 +37,7 @@ test("should use queue and settled correctly", async () => {
 	const enc = new TextEncoder();
 	await lix.db
 		.insertInto("file")
-		.values({ id: "test", path: "test.txt", data: enc.encode("test") })
+		.values({ id: "test", path: "test.txt", data: enc.encode("insert text") })
 		.execute();
 
 	const internalFiles = await lix.db
@@ -85,19 +85,15 @@ test("should use queue and settled correctly", async () => {
 		.execute();
 
 	expect(changes).toEqual([
-		{
-			id: changes[0]?.id,
-			created_at: changes[0]?.created_at,
-			snapshot_id: changes[0]?.snapshot_id,
-			parent_id: null,
+		expect.objectContaining({
 			entity_id: "test",
 			type: "text",
 			file_id: "test",
 			plugin_key: "mock-plugin",
 			content: {
-				text: "test",
+				text: "insert text",
 			},
-		},
+		}),
 	]);
 
 	await lix.db
@@ -150,46 +146,46 @@ test("should use queue and settled correctly", async () => {
 		.select("snapshot.content")
 		.execute();
 
+	const updatedEdges = await lix.db
+		.selectFrom("change_edge")
+		.selectAll()
+		.execute();
+
 	expect(updatedChanges).toEqual([
-		{
-			id: updatedChanges[0]?.id,
-			created_at: updatedChanges[0]?.created_at,
-			snapshot_id: updatedChanges[0]?.snapshot_id,
-			parent_id: null,
+		expect.objectContaining({
 			entity_id: "test",
 			type: "text",
 			file_id: "test",
 			plugin_key: "mock-plugin",
 			content: {
-				text: "test",
+				text: "insert text",
 			},
-		},
-		{
+		}),
+		expect.objectContaining({
 			entity_id: "test",
-			created_at: updatedChanges[1]?.created_at,
-			snapshot_id: updatedChanges[1]?.snapshot_id,
 			file_id: "test",
-			id: updatedChanges[1]?.id,
-			parent_id: updatedChanges[0]?.id,
 			plugin_key: "mock-plugin",
 			type: "text",
 			content: {
 				text: "test updated text",
 			},
-		},
-		{
-			created_at: updatedChanges[2]?.created_at,
-			snapshot_id: updatedChanges[2]?.snapshot_id,
+		}),
+		expect.objectContaining({
 			file_id: "test",
-			id: updatedChanges[2]?.id,
-			parent_id: updatedChanges[1]?.id,
 			entity_id: "test",
 			plugin_key: "mock-plugin",
 			type: "text",
 			content: {
 				text: "test updated text second update",
 			},
-		},
+		}),
+	]);
+
+	expect(updatedEdges).toEqual([
+		// 0 is the parent of 1
+		// 1 is the parent of 2
+		{ parent_id: updatedChanges[0]?.id, child_id: updatedChanges[1]?.id },
+		{ parent_id: updatedChanges[1]?.id, child_id: updatedChanges[2]?.id },
 	]);
 });
 

lix/packages/sdk/src/database/applySchema.ts

@@ -28,7 +28,6 @@ export async function applySchema(args: { sqlite: SqliteDatabase }) {
 
   CREATE TABLE IF NOT EXISTS change (
     id TEXT PRIMARY KEY DEFAULT (uuid_v4()),
-    parent_id TEXT,
     entity_id TEXT NOT NULL,
     type TEXT NOT NULL,
     file_id TEXT NOT NULL,
@@ -37,7 +36,15 @@ export async function applySchema(args: { sqlite: SqliteDatabase }) {
     created_at TEXT DEFAULT CURRENT_TIMESTAMP NOT NULL
   ) strict;
 
-  CREATE INDEX IF NOT EXISTS idx_change_parent_id ON change (parent_id);
+  CREATE TABLE IF NOT EXISTS change_edge (
+    parent_id TEXT NOT NULL,
+    child_id TEXT NOT NULL,
+    PRIMARY KEY (parent_id, child_id),
+    FOREIGN KEY(parent_id) REFERENCES change(id),
+    FOREIGN KEY(child_id) REFERENCES change(id),
+    -- Prevent self referencing edges
+    CHECK (parent_id != child_id)
+  ) strict;
 
   CREATE TABLE IF NOT EXISTS snapshot (
     id TEXT GENERATED ALWAYS AS (sha256(content)) STORED UNIQUE,

lix/packages/sdk/src/database/initDb.test.ts

@@ -91,3 +91,26 @@ test("files should be able to have metadata", async () => {
 
 	expect(updatedFile.metadata?.primary_key).toBe("something-else");
 });
+
+test("change edges can't reference themselves", async () => {
+	const sqlite = await createInMemoryDatabase({
+		readOnly: false,
+	});
+	const db = initDb({ sqlite });
+
+	try {
+		await db
+			.insertInto("change_edge")
+			.values({
+				parent_id: "change1",
+				child_id: "change1",
+			})
+			.returningAll()
+			.execute();
+	} catch (error) {
+		// the sqite3 error is not exposed
+		expect((error as any).name).toBe("SQLite3Error");
+		// error code 275 = SQLITE_CONSTRAINT_CHECK
+		expect((error as any).resultCode).toBe(275);
+	}
+});

lix/packages/sdk/src/database/schema.ts

@@ -7,6 +7,7 @@ export type LixDatabaseSchema = {
 	change: ChangeTable;
 	file_internal: LixFileTable;
 	change_queue: ChangeQueueTable;
+	change_edge: ChangeEdgeTable;
 	conflict: ConflictTable;
 	snapshot: SnapshotTable;
 
@@ -42,7 +43,6 @@ export type Change = Selectable<ChangeTable>;
 export type NewChange = Insertable<ChangeTable>;
 type ChangeTable = {
 	id: Generated<string>;
-	parent_id: Generated<string> | null;
 	/**
 	 * The entity the change refers to.
 	 */
@@ -71,6 +71,13 @@ type ChangeTable = {
 	created_at: Generated<string>;
 };
 
+export type ChangeEdge = Selectable<ChangeEdgeTable>;
+export type NewChangeEdge = Insertable<ChangeEdgeTable>;
+type ChangeEdgeTable = {
+	parent_id: ChangeTable["id"];
+	child_id: ChangeTable["id"];
+};
+
 export type Snapshot = Selectable<SnapshotTable>;
 export type NewSnapshot = Insertable<SnapshotTable>;
 type SnapshotTable = {

lix/packages/sdk/src/file-handlers.ts

@@ -120,9 +120,11 @@ export async function handleFileChange(args: {
 			// heuristic to find the previous change
 			// there is no guarantee that the previous change is the leaf change
 			// because sorting by time is unreliable in a distributed system
-			const previousChange = await trx
+			const maybeParentChange = await trx
 				.selectFrom("change")
-				.selectAll()
+				.innerJoin("snapshot", "snapshot.id", "change.snapshot_id")
+				.selectAll("change")
+				.select("snapshot.content")
 				.where("file_id", "=", fileId)
 				.where("type", "=", detectedChange.type)
 				.where("entity_id", "=", detectedChange.entity_id)
@@ -132,11 +134,11 @@ export async function handleFileChange(args: {
 				.executeTakeFirst();
 
 			// get the leaf change of the assumed previous change
-			const leafChange = !previousChange
+			const parentChange = !maybeParentChange
 				? undefined
 				: await getLeafChange({
 						lix: { db: trx },
-						change: previousChange,
+						change: maybeParentChange,
 					});
 
 			const snapshot = await trx
@@ -155,17 +157,28 @@ export async function handleFileChange(args: {
 				.returning("id")
 				.executeTakeFirstOrThrow();
 
-			await trx
+			const insertedChange = await trx
 				.insertInto("change")
 				.values({
 					type: detectedChange.type,
 					file_id: fileId,
 					plugin_key: detectedChange.pluginKey,
 					entity_id: detectedChange.entity_id,
-					parent_id: leafChange?.id,
 					snapshot_id: snapshot.id,
 				})
-				.execute();
+				.returning("id")
+				.executeTakeFirstOrThrow();
+
+			// If a parent exists, the change is a child of the parent
+			if (parentChange) {
+				await trx
+					.insertInto("change_edge")
+					.values({
+						parent_id: parentChange.id,
+						child_id: insertedChange.id,
+					})
+					.execute();
+			}
 		}
 
 		await trx

lix/packages/sdk/src/merge/merge.test.ts

@@ -3,6 +3,7 @@ import { openLixInMemory } from "../open/openLixInMemory.js";
 import { newLixFile } from "../newLix.js";
 import { merge } from "./merge.js";
 import type {
+	ChangeEdge,
 	NewChange,
 	NewConflict,
 	NewSnapshot,
@@ -45,6 +46,8 @@ test("it should copy changes from the sourceLix into the targetLix that do not e
 		},
 	];
 
+	const mockEdges: ChangeEdge[] = [{ parent_id: "2", child_id: "3" }];
+
 	const mockPlugin: LixPlugin = {
 		key: "mock-plugin",
 		detectConflicts: vi.fn().mockResolvedValue([]),
@@ -76,6 +79,8 @@ test("it should copy changes from the sourceLix into the targetLix that do not e
 		.values([mockChanges[0]!, mockChanges[1]!, mockChanges[2]!])
 		.execute();
 
+	await sourceLix.db.insertInto("change_edge").values([mockEdges[0]]).execute();
+
 	await targetLix.db
 		.insertInto("snapshot")
 		.values(
@@ -119,6 +124,13 @@ test("it should copy changes from the sourceLix into the targetLix that do not e
 		mockSnapshots[2]?.id,
 	]);
 
+	const edges = await targetLix.db
+		.selectFrom("change_edge")
+		.selectAll()
+		.execute();
+
+	expect(edges).toEqual(mockEdges);
+
 	expect(mockPlugin.applyChanges).toHaveBeenCalledTimes(1);
 	expect(mockPlugin.detectConflicts).toHaveBeenCalledTimes(1);
 });
@@ -345,7 +357,6 @@ test("it should apply changes that are not conflicting", async () => {
 		},
 		{
 			id: "2",
-			parent_id: "1",
 			entity_id: "value1",
 			type: "mock",
 			snapshot_id: mockSnapshots[1]!.id,
@@ -354,6 +365,8 @@ test("it should apply changes that are not conflicting", async () => {
 		},
 	];
 
+	const edges: ChangeEdge[] = [{ parent_id: "1", child_id: "2" }];
+
 	const mockPlugin: LixPlugin = {
 		key: "mock-plugin",
 		applyChanges: async ({ changes }) => {
@@ -389,6 +402,8 @@ test("it should apply changes that are not conflicting", async () => {
 		.values([mockChanges[0]!, mockChanges[1]!])
 		.execute();
 
+	await sourceLix.db.insertInto("change_edge").values([edges[0]]).execute();
+
 	await targetLix.db
 		.insertInto("snapshot")
 		.values(
@@ -397,6 +412,7 @@ test("it should apply changes that are not conflicting", async () => {
 			}),
 		)
 		.execute();
+
 	await targetLix.db.insertInto("change").values([mockChanges[0]!]).execute();
 
 	await targetLix.db
@@ -657,7 +673,6 @@ test("it should copy discussion and related comments and mappings", async () =>
 			id: changes[0]?.id,
 			created_at: changes[0]?.created_at,
 			snapshot_id: changes[0]?.snapshot_id,
-			parent_id: null,
 			type: "text",
 			file_id: "test",
 			entity_id: "test",

lix/packages/sdk/src/merge/merge.ts

@@ -117,9 +117,14 @@ export async function merge(args: {
 		.selectAll()
 		.execute();
 
+	const sourceEdges = await args.sourceLix.db
+		.selectFrom("change_edge")
+		.selectAll()
+		.execute();
+
 	await args.targetLix.db.transaction().execute(async (trx) => {
 		if (sourceChangesWithSnapshot.length > 0) {
-			// 1. copy the snapshots from source
+			// copy the snapshots from source
 			await trx
 				.insertInto("snapshot")
 				.values(
@@ -146,7 +151,7 @@ export async function merge(args: {
 				.execute();
 		}
 
-		// 2. insert the conflicts of those changes
+		// insert the conflicts of those changes
 		if (conflicts.length > 0) {
 			await trx
 				.insertInto("conflict")
@@ -157,15 +162,25 @@ export async function merge(args: {
 		}
 
 		for (const [fileId, fileData] of Object.entries(changesPerFile)) {
-			// 3. update the file data with the applied changes
+			// update the file data with the applied changes
 			await trx
 				.updateTable("file_internal")
 				.set("data", fileData)
 				.where("id", "=", fileId)
 				.execute();
 		}
 
-		// 4. add discussions, comments and discsussion_change_mappings
+		// copy edges
+		if (sourceEdges.length > 0) {
+			await trx
+				.insertInto("change_edge")
+				.values(sourceEdges)
+				// ignore if already exists
+				.onConflict((oc) => oc.doNothing())
+				.execute();
+		}
+
+		// add discussions, comments and discsussion_change_mappings
 
 		if (sourceDiscussions.length > 0) {
 			await trx