fix a stupid case of intersecting parts

src/Storages/MergeTree/MergeTreeData.cpp

@@ -3985,8 +3985,12 @@ MergeTreeData::PartsToRemoveFromZooKeeper MergeTreeData::removePartsInRangeFromW
     /// FIXME refactor removePartsFromWorkingSet(...), do not remove parts twice
     removePartsFromWorkingSet(txn, parts_to_remove, clear_without_timeout, lock);
 
+    /// We can only create a covering part for a blocks range that starts with 0 (otherwise we may get "intersecting parts").
+    /// Maybe we could do it by incrementing mutation version to get a name for the empty covering part,
+    /// but it's okay to simply avoid creating it for DROP PART
+    bool is_drop_part = drop_range.min_block;
     bool is_new_syntax = format_version >= MERGE_TREE_DATA_MIN_FORMAT_VERSION_WITH_CUSTOM_PARTITIONING;
-    if (create_empty_part && !parts_to_remove.empty() && is_new_syntax)
+    if (create_empty_part && !parts_to_remove.empty() && is_new_syntax && !is_drop_part)
     {
         /// We are going to remove a lot of parts from zookeeper just after returning from this function.
         /// And we will remove parts from disk later (because some queries may use them).
@@ -3995,12 +3999,9 @@ MergeTreeData::PartsToRemoveFromZooKeeper MergeTreeData::removePartsInRangeFromW
         /// We don't need to commit it to zk, and don't even need to activate it.
 
         MergeTreePartInfo empty_info = drop_range;
-        empty_info.level = empty_info.mutation = 0;
-        if (!empty_info.min_block)
-            empty_info.min_block = MergeTreePartInfo::MAX_BLOCK_NUMBER;
+        empty_info.min_block = empty_info.level = empty_info.mutation = 0;
         for (const auto & part : parts_to_remove)
         {
-            empty_info.min_block = std::min(empty_info.min_block, part->info.min_block);
             empty_info.level = std::max(empty_info.level, part->info.level);
             empty_info.mutation = std::max(empty_info.mutation, part->info.mutation);
         }

tests/queries/0_stateless/02486_truncate_and_unexpected_parts.reference

@@ -13,3 +13,5 @@
 5	rmt2
 7	rmt2
 9	rmt2
+1
+3

tests/queries/0_stateless/02486_truncate_and_unexpected_parts.sql

@@ -50,3 +50,19 @@ system sync replica rmt1;
 system sync replica rmt2;
 
 select *, _table from merge(currentDatabase(), '') order by _table, (*,);
+
+
+create table rmt3 (n int) engine=ReplicatedMergeTree('/test/02468/{database}3', '1') order by tuple() settings replicated_max_ratio_of_wrong_parts=0, max_suspicious_broken_parts=0, max_suspicious_broken_parts_bytes=0;
+set insert_keeper_fault_injection_probability=0;
+insert into rmt3 values (1);
+insert into rmt3 values (2);
+insert into rmt3 values (3);
+
+system stop cleanup rmt3;
+alter table rmt3 drop part 'all_1_1_0';
+optimize table rmt3 final;
+
+detach table rmt3 sync;
+attach table rmt3;
+
+select * from rmt3 order by n;