Simplify replication of table removal

src/realm/group.cpp

@@ -833,29 +833,23 @@ void Group::remove_table(size_t table_ndx, TableKey key)
     // columns of other tables, however, to do that, we would have to
     // automatically remove the "offending" link columns from those other
     // tables. Such a behaviour is deemed too obscure, and we shall therefore
-    // require that a removed table does not contain foreigh origin backlink
+    // require that a removed table does not contain foreign origin backlink
     // columns.
     if (table->is_cross_table_link_target())
         throw CrossTableLinkTarget(table->get_name());
 
-    // There is no easy way for Group::TransactAdvancer to handle removal of
-    // tables that contain foreign target table link columns, because that
-    // involves removal of the corresponding backlink columns. For that reason,
-    // we start by removing all columns, which will generate individual
-    // replication instructions for each column removal with sufficient
-    // information for Group::TransactAdvancer to handle them.
-    size_t n = table->get_column_count();
-    Replication* repl = *get_repl();
-    if (repl) {
-        // This will prevent sync instructions for column removals to be generated
-        repl->prepare_erase_class(key);
-    }
-    for (size_t i = n; i > 0; --i) {
-        ColKey col_key = table->spec_ndx2colkey(i - 1);
-        table->remove_column(col_key);
+    {
+        // We don't want to replicate the individual column removals along the
+        // way as they're covered by the table removal
+        Table::DisableReplication dr(*table);
+        for (size_t i = table->get_column_count(); i > 0; --i) {
+            ColKey col_key = table->spec_ndx2colkey(i - 1);
+            table->remove_column(col_key);
+        }
     }
 
     size_t prior_num_tables = m_tables.size();
+    Replication* repl = *get_repl();
     if (repl)
         repl->erase_class(key, prior_num_tables); // Throws
 

src/realm/replication.hpp

@@ -49,7 +49,6 @@ class Replication {
     virtual void add_class(TableKey table_key, StringData table_name, Table::Type table_type);
     virtual void add_class_with_primary_key(TableKey, StringData table_name, DataType pk_type, StringData pk_field,
                                             bool nullable, Table::Type table_type);
-    virtual void prepare_erase_class(TableKey table_key);
     virtual void erase_class(TableKey table_key, size_t num_tables);
     virtual void rename_class(TableKey table_key, StringData new_name);
     virtual void insert_column(const Table*, ColKey col_key, DataType type, StringData name, Table* target_table);
@@ -494,8 +493,6 @@ inline void Replication::select_collection(const CollectionBase& list)
     }
 }
 
-inline void Replication::prepare_erase_class(TableKey) {}
-
 inline void Replication::erase_class(TableKey table_key, size_t)
 {
     unselect_all();

src/realm/sync/instruction_replication.cpp

@@ -298,12 +298,6 @@ void SyncReplication::create_object_with_primary_key(const Table* table, ObjKey
 }
 
 
-void SyncReplication::prepare_erase_class(TableKey table_key)
-{
-    REALM_ASSERT(!m_table_being_erased);
-    m_table_being_erased = table_key;
-}
-
 void SyncReplication::erase_class(TableKey table_key, size_t num_tables)
 {
     Replication::erase_class(table_key, num_tables);
@@ -312,15 +306,10 @@ void SyncReplication::erase_class(TableKey table_key, size_t num_tables)
 
     bool is_class = m_transaction->table_is_public(table_key);
 
-    if (is_class) {
-        REALM_ASSERT(table_key == m_table_being_erased);
-        m_table_being_erased = TableKey();
-
-        if (!m_short_circuit) {
-            Instruction::EraseTable instr;
-            instr.table = emit_class_name(table_name);
-            emit(instr);
-        }
+    if (is_class && !m_short_circuit) {
+        Instruction::EraseTable instr;
+        instr.table = emit_class_name(table_name);
+        emit(instr);
     }
 
     m_last_table = nullptr;
@@ -385,11 +374,6 @@ void SyncReplication::erase_column(const Table* table, ColKey col_ndx)
     Replication::erase_column(table, col_ndx);
 
     if (select_table(*table)) {
-        if (table->get_key() == m_table_being_erased) {
-            // Ignore any EraseColumn instructions generated by Core as part of
-            // EraseTable.
-            return;
-        }
         // Not allowed to remove PK/OID columns!
         REALM_ASSERT(col_ndx != table->get_primary_key_column());
         Instruction::EraseColumn instr;

src/realm/sync/instruction_replication.hpp

@@ -51,7 +51,6 @@ class SyncReplication : public Replication {
     void create_object(const Table*, GlobalKey) final;
     void create_object_with_primary_key(const Table*, ObjKey, Mixed) final;
 
-    void prepare_erase_class(TableKey tk) final;
     void erase_class(TableKey table_key, size_t num_tables) final;
     void rename_class(TableKey table_key, StringData new_name) final;
     void insert_column(const Table*, ColKey col_key, DataType type, StringData name, Table* target_table) final;
@@ -105,8 +104,6 @@ class SyncReplication : public Replication {
     ChangesetEncoder m_encoder;
     Transaction* m_transaction;
 
-    TableKey m_table_being_erased;
-
     template <class T>
     void emit(T instruction);