From c7b10200379b54a0cd99bd03d0a266514cf3fd70 Mon Sep 17 00:00:00 2001
From: Lei Zhang <27994433+SWJTU-ZhangLei@users.noreply.github.com>
Date: Fri, 23 Aug 2024 12:20:40 +0800
Subject: [PATCH] [opt](fe) Use `table.readLock` in `TabletStatMgr` for
 updating statistics (#39612)

---
 .../main/java/org/apache/doris/catalog/Table.java    |  9 +++++++++
 .../java/org/apache/doris/catalog/TabletStatMgr.java | 12 +++---------
 2 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/fe/fe-core/src/main/java/org/apache/doris/catalog/Table.java b/fe/fe-core/src/main/java/org/apache/doris/catalog/Table.java
index 862d6c1878e026..389be51d57af91 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/catalog/Table.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/catalog/Table.java
@@ -174,6 +174,15 @@ public void readLock() {
         }
     }
 
+    public boolean readLockIfExist() {
+        readLock();
+        if (isDropped) {
+            readUnlock();
+            return false;
+        }
+        return true;
+    }
+
     public boolean tryReadLock(long timeout, TimeUnit unit) {
         try {
             boolean res = this.rwLock.readLock().tryLock(timeout, unit);
diff --git a/fe/fe-core/src/main/java/org/apache/doris/catalog/TabletStatMgr.java b/fe/fe-core/src/main/java/org/apache/doris/catalog/TabletStatMgr.java
index b9093dcd83828d..7224d66ad44e91 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/catalog/TabletStatMgr.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/catalog/TabletStatMgr.java
@@ -34,7 +34,6 @@
 import java.util.List;
 import java.util.Map;
 import java.util.concurrent.ForkJoinPool;
-import java.util.concurrent.TimeUnit;
 
 /*
  * TabletStatMgr is for collecting tablet(replica) statistics from backends.
@@ -114,13 +113,7 @@ protected void runAfterCatalogReady() {
 
                 Long tableRowCount = 0L;
 
-                // Use try write lock to avoid such cases
-                //    Time1: Thread1 hold read lock for 5min
-                //    Time2: Thread2 want to add write lock, then it will be the first element in lock queue
-                //    Time3: Thread3 want to add read lock, but it will not, because thread 2 want to add write lock
-                // In this case, thread 3 has to wait more than 5min, because it has to wait thread 2 to add
-                // write lock and release write lock and thread 2 has to wait thread 1 to release read lock
-                if (!table.tryWriteLockIfExist(3000, TimeUnit.MILLISECONDS)) {
+                if (!table.readLockIfExist()) {
                     continue;
                 }
                 try {
@@ -193,6 +186,7 @@ protected void runAfterCatalogReady() {
                         } // end for indices
                     } // end for partitions
 
+                    // this is only one thread to update table statistics, readLock is enough
                     olapTable.setStatistics(new OlapTable.Statistics(db.getName(), table.getName(),
                             tableDataSize, tableTotalReplicaDataSize,
                             tableRemoteDataSize, tableReplicaCount, tableRowCount, 0L, 0L));
@@ -202,7 +196,7 @@ protected void runAfterCatalogReady() {
                                  table.getName(), db.getFullName());
                     }
                 } finally {
-                    table.writeUnlock();
+                    table.readUnlock();
                 }
             }
         }