From 09ce891438c8d4ca2bf45b492fff84f004ad8df8 Mon Sep 17 00:00:00 2001
From: Andrey Zvonov <32552679+zvonand@users.noreply.github.com>
Date: Fri, 22 May 2026 22:42:55 +0200
Subject: [PATCH] Merge pull request #1738 from
 Altinity/backports/25.8.16/95597
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25.8.16 Backport of #95597 - Fix zero‑copy unlock check before part dir move
---
 src/Storages/MergeTree/DataPartStorageOnDiskBase.cpp | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/src/Storages/MergeTree/DataPartStorageOnDiskBase.cpp b/src/Storages/MergeTree/DataPartStorageOnDiskBase.cpp
index 9d0e0bf9dd43..f71d5437a7d0 100644
--- a/src/Storages/MergeTree/DataPartStorageOnDiskBase.cpp
+++ b/src/Storages/MergeTree/DataPartStorageOnDiskBase.cpp
@@ -754,6 +754,11 @@ void DataPartStorageOnDiskBase::remove(
             return;
         }
 
+        /// Evaluate can_remove_callback before moving the directory so zero-copy reference checks
+        /// use the current (existing) path. We intentionally don't update part_dir to avoid races.
+        if (!can_remove_description)
+            can_remove_description.emplace(can_remove_callback());
+
         try
         {
             disk->moveDirectory(from, to);
@@ -766,9 +771,6 @@ void DataPartStorageOnDiskBase::remove(
             if (e.code() == ErrorCodes::FILE_DOESNT_EXIST)
             {
                 LOG_ERROR(log, "Directory {} (part to remove) doesn't exist or one of nested files has gone. Most likely this is due to manual removing. This should be discouraged. Ignoring.", fullPath(disk, from));
-                /// We will never touch this part again, so unlocking it from zero-copy
-                if (!can_remove_description)
-                    can_remove_description.emplace(can_remove_callback());
                 return;
             }
             throw;
@@ -779,10 +781,6 @@ void DataPartStorageOnDiskBase::remove(
             {
                 LOG_ERROR(log, "Directory {} (part to remove) doesn't exist or one of nested files has gone. "
                           "Most likely this is due to manual removing. This should be discouraged. Ignoring.", fullPath(disk, from));
-                /// We will never touch this part again, so unlocking it from zero-copy
-                if (!can_remove_description)
-                    can_remove_description.emplace(can_remove_callback());
-
                 return;
             }
             throw;