Storage: Support drop vector index defined on ColumnInfo when column …

…is dropped (pingcap#283)

dbms/src/Common/FailPoint.cpp

@@ -71,6 +71,7 @@ namespace DB
     M(force_remote_read_for_batch_cop_once)                       \
     M(exception_new_dynamic_thread)                               \
     M(force_wait_index_timeout)                                   \
+    M(force_not_support_vector_index)                             \
     M(sync_schema_request_failure)
 
 #define APPLY_FOR_FAILPOINTS(M)                              \

dbms/src/Storages/DeltaMerge/DeltaMergeStore.cpp

@@ -1967,25 +1967,32 @@ void DeltaMergeStore::applySchemaChanges(TableInfo & table_info)
     original_table_columns.swap(new_original_table_columns);
     store_columns.swap(new_store_columns);
 
-    // Get a snapshot on the local_index_infos to check whether any new index is created
-    LocalIndexInfosSnapshot local_index_infos_snap = getLocalIndexInfosSnapshot();
-
     std::atomic_store(&original_table_header, std::make_shared<Block>(toEmptyBlock(original_table_columns)));
 
     // release the lock because `applyLocalIndexChange` will try to acquire the lock
     // and generate tasks on segments
     lock.unlock();
 
-    auto new_local_index_infos = generateLocalIndexInfos(local_index_infos_snap, table_info, log);
-    if (new_local_index_infos)
+    applyLocalIndexChange(table_info);
+}
+
+void DeltaMergeStore::applyLocalIndexChange(const TiDB::TableInfo & new_table_info)
+{
+    // Get a snapshot on the local_index_infos to check whether any new index is created
+    auto new_local_index_infos = generateLocalIndexInfos(getLocalIndexInfosSnapshot(), new_table_info, log);
+
+    // no index is created or dropped
+    if (!new_local_index_infos)
+        return;
+
     {
-        {
-            // new index created, update the info in-memory thread safety between `getLocalIndexInfosSnapshot`
-            std::unique_lock index_write_lock(mtx_local_index_infos);
-            local_index_infos.swap(new_local_index_infos);
-        }
-        checkAllSegmentsLocalIndex();
-    } // else no new index is created
+        // new index created, update the info in-memory thread safety between `getLocalIndexInfosSnapshot`
+        std::unique_lock index_write_lock(mtx_local_index_infos);
+        local_index_infos.swap(new_local_index_infos);
+    }
+
+    // generate async tasks for building local index for all segments
+    checkAllSegmentsLocalIndex();
 }
 
 SortDescription DeltaMergeStore::getPrimarySortDescription() const

dbms/src/Storages/DeltaMerge/DeltaMergeStore.h

@@ -575,6 +575,18 @@ class DeltaMergeStore
         bool keep_order,
         const PushDownFilterPtr & filter);
 
+    // Get a snap of local_index_infos for checking.
+    // Note that this is just a shallow copy of `local_index_infos`, do not
+    // modify the local indexes inside the snapshot.
+    LocalIndexInfosSnapshot getLocalIndexInfosSnapshot() const
+    {
+        std::shared_lock index_read_lock(mtx_local_index_infos);
+        if (!local_index_infos || local_index_infos->empty())
+            return nullptr;
+        // only make a shallow copy on the shared_ptr is OK
+        return local_index_infos;
+    }
+
 public:
     /// Methods mainly used by region split.
 
@@ -856,18 +868,6 @@ class DeltaMergeStore
         const SegmentPtr & old_segment,
         const SegmentPtr & new_segment);
 
-    // Get a snap of local_index_infos for checking.
-    // Note that this is just a shallow copy of `local_index_infos`, do not
-    // modify the local indexes inside the snapshot.
-    LocalIndexInfosSnapshot getLocalIndexInfosSnapshot() const
-    {
-        std::shared_lock index_read_lock(mtx_local_index_infos);
-        if (!local_index_infos || local_index_infos->empty())
-            return nullptr;
-        // only make a shallow copy on the shared_ptr is OK
-        return local_index_infos;
-    }
-
     /**
      * Check whether there are new local indexes should be built for all segments.
      */
@@ -887,6 +887,9 @@ class DeltaMergeStore
 #else
 public:
 #endif
+
+    void applyLocalIndexChange(const TiDB::TableInfo & new_table_info);
+
     /**
      * Wait until the segment has stable index.
      * If the index is ready or no need to build, it will return immediately.

dbms/src/Storages/DeltaMerge/File/DMFileIndexWriter.cpp

@@ -42,6 +42,9 @@ DMFileIndexWriter::LocalIndexBuildInfo DMFileIndexWriter::getLocalIndexBuildInfo
     assert(index_infos != nullptr);
     static constexpr double VECTOR_INDEX_SIZE_FACTOR = 1.2;
 
+    // TODO(vector-index): Now we only generate the build info when new index is added.
+    //    The built indexes will be dropped (lazily) after the segment instance is updated.
+    //    We can support dropping the vector index more quickly later.
     LocalIndexBuildInfo build;
     build.indexes_to_build = std::make_shared<LocalIndexInfos>();
     build.file_ids.reserve(dm_files.size());