cleanup: dead code, comments, avoid current_thd

sql/handler.cc

@@ -4860,7 +4860,7 @@ handler::ha_rename_table(const char *from, const char *to)
 int
 handler::ha_delete_table(const char *name)
 {
-  if (ha_check_if_updates_are_ignored(current_thd, ht, "DROP"))
+  if (ha_check_if_updates_are_ignored(ha_thd(), ht, "DROP"))
     return 0;                                   // Simulate dropped
   mark_trx_read_write();
   return delete_table(name);
@@ -4880,7 +4880,7 @@ void
 handler::ha_drop_table(const char *name)
 {
   DBUG_ASSERT(m_lock_type == F_UNLCK);
-  if (ha_check_if_updates_are_ignored(current_thd, ht, "DROP"))
+  if (ha_check_if_updates_are_ignored(ha_thd(), ht, "DROP"))
     return;
 
   mark_trx_read_write();

sql/handler.h

@@ -1729,10 +1729,14 @@ handlerton *ha_default_tmp_handlerton(THD *thd);
 /* can be replicated by wsrep replication provider plugin */
 #define HTON_WSREP_REPLICATION (1 << 13)
 
-/* Shared storage on slave. Ignore on slave any CREATE TABLE, DROP or updates */
+/*
+  Set this on the *slave* that's connected to a shared with a master storage.
+  The slave will ignore any CREATE TABLE, DROP or updates for this engine.
+*/
 #define HTON_IGNORE_UPDATES (1 << 14)
 
 /*
+  Set this on the *master* that's connected to a shared with a slave storage.
   The table may not exists on the slave. The effects of having this flag are:
   - ALTER TABLE that changes engine from this table to another engine will
     be replicated as CREATE + INSERT

sql/sql_table.cc

@@ -5686,7 +5686,7 @@ bool mysql_create_like_table(THD* thd, TABLE_LIST* table,
   int res= 1;
   bool is_trans= FALSE;
   bool do_logging= FALSE;
-  bool force_generated_create;
+  bool force_generated_create= false;
   uint not_used;
   int create_res;
   DBUG_ENTER("mysql_create_like_table");
@@ -5838,6 +5838,7 @@ bool mysql_create_like_table(THD* thd, TABLE_LIST* table,
   if (thd->is_current_stmt_binlog_disabled())
     goto err;
 
+#ifdef ENABLE_WHEN_S3_CAN_CREATE_TABLES
   /*
     If we do a create based on a shared table, log the full create of the
     resulting table. This is needed as a shared table may look different
@@ -5847,6 +5848,7 @@ bool mysql_create_like_table(THD* thd, TABLE_LIST* table,
     (((src_table->table->s->db_type()->flags &
        HTON_TABLE_MAY_NOT_EXIST_ON_SLAVE) &&
       src_table->table->s->db_type() != local_create_info.db_type));
+#endif
 
   if (thd->is_current_stmt_binlog_format_row() || force_generated_create)
   {