From 57470e5a7f363b78d11f007f874036e7338948fc Mon Sep 17 00:00:00 2001
From: Dragory <2606411+Dragory@users.noreply.github.com>
Date: Sun, 12 Sep 2021 22:09:29 +0300
Subject: [PATCH] Potential optimization to message deletion loop

---
 backend/src/data/cleanup/messages.ts | 66 +++++++++++++++++++---------
 1 file changed, 46 insertions(+), 20 deletions(-)

diff --git a/backend/src/data/cleanup/messages.ts b/backend/src/data/cleanup/messages.ts
index 0a5d038b..3dd094ff 100644
--- a/backend/src/data/cleanup/messages.ts
+++ b/backend/src/data/cleanup/messages.ts
@@ -11,7 +11,7 @@ import { SavedMessage } from "../entities/SavedMessage";
 const RETENTION_PERIOD = 1 * DAYS;
 const BOT_MESSAGE_RETENTION_PERIOD = 30 * MINUTES;
 const DELETED_MESSAGE_RETENTION_PERIOD = 5 * MINUTES;
-const CLEAN_PER_LOOP = 500;
+const CLEAN_PER_LOOP = 200;
 
 export async function cleanupMessages(): Promise<number> {
   let cleaned = 0;
@@ -25,38 +25,64 @@ export async function cleanupMessages(): Promise<number> {
   // SELECT + DELETE messages in batches
   // This is to avoid deadlocks that happened frequently when deleting with the same criteria as the select below
   // when a message was being inserted at the same time
-  let rows;
+  let ids: string[];
   do {
-    rows = await connection.query(
+    const deletedMessageRows = await connection.query(
       `
       SELECT id
       FROM messages
       WHERE (
-          deleted_at IS NOT NULL
-          AND deleted_at <= ?
-        )
-         OR (
-          posted_at <= ?
-          AND is_permanent = 0
-        )
-         OR (
-          is_bot = 1
-          AND posted_at <= ?
-          AND is_permanent = 0
-        )
+        deleted_at IS NOT NULL
+        AND deleted_at <= ?
+      )
       LIMIT ${CLEAN_PER_LOOP}
     `,
-      [deletedAtThreshold, postedAtThreshold, botPostedAtThreshold],
+      [deletedAtThreshold],
     );
 
-    if (rows.length > 0) {
+    const oldPostedRows = await connection.query(
+      `
+      SELECT id
+      FROM messages
+      WHERE (
+        posted_at <= ?
+        AND is_permanent = 0
+      )
+      LIMIT ${CLEAN_PER_LOOP}
+    `,
+      [postedAtThreshold],
+    );
+
+    const oldBotPostedRows = await connection.query(
+      `
+      SELECT id
+      FROM messages
+      WHERE (
+        is_bot = 1
+        AND posted_at <= ?
+        AND is_permanent = 0
+      )
+      LIMIT ${CLEAN_PER_LOOP}
+    `,
+      [botPostedAtThreshold],
+    );
+
+    ids = Array.from(
+      new Set([
+        ...deletedMessageRows.map((r) => r.id),
+        ...oldPostedRows.map((r) => r.id),
+        ...oldBotPostedRows.map((r) => r.id),
+      ]),
+    );
+
+    if (ids.length > 0) {
       await messagesRepository.delete({
-        id: In(rows.map((r) => r.id)),
+        id: In(ids),
       });
     }
 
-    cleaned += rows.length;
-  } while (rows.length === CLEAN_PER_LOOP);
+    cleaned += ids.length;
+  } while (ids.length > 0);
 
   return cleaned;
 }