Add nonblocking/asyn I/O operations

backend/db/notes.dao.js

@@ -1,12 +1,49 @@
-import { query } from './index.js';
+import QueryStream from 'pg-query-stream';
+import { pipeline } from 'node:stream/promises';
+import { Readable } from 'node:stream';
+import { query, getPool } from './index.js';
+import { batch } from '../lib/streams.js';
+
+const SELECT_NOTES = 'SELECT id, text, x, y, author, color FROM notes ORDER BY id';
+
+// Postgres caps a statement at 65535 bind parameters; six columns per note
+// leaves 10922 as the hard ceiling, so stay well under it.
+const INSERT_BATCH_SIZE = 1000;
 
 export const getAllNotes = async () => {
-  const { rows } = await query(
-    'SELECT id, text, x, y, author, color FROM notes ORDER BY id'
-  );
+  const { rows } = await query(SELECT_NOTES);
   return rows;
 };
 
+/**
+ * Streams every note as an object-mode Readable. The pooled client is checked
+ * out for the life of the stream and released once it ends, errors, or is
+ * destroyed early by a consumer.
+ *
+ * @returns {Promise<import('node:stream').Readable>}
+ */
+export const streamAllNotes = async () => {
+  const client = await getPool().connect();
+
+  let released = false;
+  const release = () => {
+    if (released) return;
+    released = true;
+    client.release();
+  };
+
+  try {
+    const rows = client.query(new QueryStream(SELECT_NOTES));
+    rows.once('end', release);
+    rows.once('error', release);
+    rows.once('close', release);
+    return rows;
+  } catch (err) {
+    release();
+    throw err;
+  }
+};
+
 export const getNoteById = async (id) => {
   const { rows } = await query(
     'SELECT id, text, x, y, author, color FROM notes WHERE id = $1',
@@ -25,7 +62,7 @@ export const createNote = async (note) => {
   return rows[0];
 };
 
-export const createNotes = async (notes) => {
+const insertNoteBatch = async (notes) => {
   const values = [];
   const placeholders = [];
 
@@ -52,3 +89,23 @@ export const createNotes = async (notes) => {
   );
   return rows;
 };
+
+export const createNotes = async (notes) => {
+  if (!notes || notes.length === 0) {
+    return [];
+  }
+
+  const inserted = [];
+
+  await pipeline(
+    Readable.from(notes, { objectMode: true }),
+    batch(INSERT_BATCH_SIZE),
+    async (batches) => {
+      for await (const chunk of batches) {
+        inserted.push(...await insertNoteBatch(chunk));
+      }
+    }
+  );
+
+  return inserted;
+};