A review comment for the fix for Bug#46672.

Remove unnecessary need_reopen loops.

1 files changed, 57 insertions, 3 deletions

diff --git a/sql/sql_handler.cc b/sql/sql_handler.cc
index 3afeb4164bd..f4db3f21db7 100644
--- a/sql/sql_handler.cc
+++ b/sql/sql_handler.cc
@@ -405,6 +405,56 @@ bool mysql_ha_close(THD *thd, TABLE_LIST *tables)
 }
 
 
+/**
+  A helper class to process an error from mysql_lock_tables().
+  HANDLER READ statement's attempt to lock the subject table
+  may get aborted if there is a pending DDL. In that case
+  we close the table, reopen it, and try to read again.
+  This is implicit and obscure, since HANDLER position
+  is lost in the process, but it's the legacy server
+  behaviour we should preserve.
+*/
+
+class Sql_handler_lock_error_handler: public Internal_error_handler
+{
+public:
+  virtual
+  bool handle_condition(THD *thd,
+                        uint sql_errno,
+                        const char *sqlstate,
+                        MYSQL_ERROR::enum_warning_level level,
+                        const char* msg,
+                        MYSQL_ERROR **cond_hdl);
+
+  bool need_reopen() const { return m_need_reopen; };
+  void init() { m_need_reopen= FALSE; };
+private:
+  bool m_need_reopen;
+};
+
+
+/**
+  Handle an error from mysql_lock_tables().
+  Ignore ER_LOCK_ABORTED errors.
+*/
+
+bool
+Sql_handler_lock_error_handler::
+handle_condition(THD *thd,
+                 uint sql_errno,
+                 const char *sqlstate,
+                 MYSQL_ERROR::enum_warning_level level,
+                 const char* msg,
+                 MYSQL_ERROR **cond_hdl)
+{
+  *cond_hdl= NULL;
+  if (sql_errno == ER_LOCK_ABORTED)
+    m_need_reopen= TRUE;
+
+  return m_need_reopen;
+}
+
+
 /*
   Read from a HANDLER table.
 
@@ -442,7 +492,7 @@ bool mysql_ha_read(THD *thd, TABLE_LIST *tables,
   uint          num_rows;
   uchar		*UNINIT_VAR(key);
   uint		UNINIT_VAR(key_len);
-  bool          need_reopen;
+  Sql_handler_lock_error_handler sql_handler_lock_error;
   DBUG_ENTER("mysql_ha_read");
   DBUG_PRINT("enter",("'%s'.'%s' as '%s'",
                       tables->db, tables->table_name, tables->alias));
@@ -506,8 +556,12 @@ retry:
   thd->open_tables= hash_tables->table;
 
 
-  lock= mysql_lock_tables(thd, &thd->open_tables, 1, 0, &need_reopen);
+  sql_handler_lock_error.init();
+  thd->push_internal_handler(&sql_handler_lock_error);
+
+  lock= mysql_lock_tables(thd, &thd->open_tables, 1, 0);
 
+  thd->pop_internal_handler();
   /*
     In 5.1 and earlier, mysql_lock_tables() could replace the TABLE
     object with another one (reopen it). This is no longer the case
@@ -517,7 +571,7 @@ retry:
   /* Restore previous context. */
   thd->open_tables= backup_open_tables;
 
-  if (need_reopen)
+  if (sql_handler_lock_error.need_reopen())
   {
     mysql_ha_close_table(thd, hash_tables);
     goto retry;