MDEV-13301 Optimize DROP INDEX, ADD INDEX into RENAME INDEX

Just rename index in data dictionary and in InnoDB cache when it's possible.
Introduce ALTER_INDEX_RENAME for that purpose so that engines can optimize
such operation.

Unused code between macro MYSQL_RENAME_INDEX was removed.

compare_keys_but_name(): compare index definitions except for index names

Alter_inplace_info::rename_keys:
ha_innobase_inplace_ctx::rename_keys: vector of rename indexes

fill_alter_inplace_info():: fills Alter_inplace_info::rename_keys

1 files changed, 3 insertions, 0 deletions

diff --git a/sql/mem_root_array.h b/sql/mem_root_array.h
index 5daeedadcba..bf266a60334 100644
--- a/sql/mem_root_array.h
+++ b/sql/mem_root_array.h
@@ -87,9 +87,11 @@ public:
 
   // Returns a pointer to the first element in the array.
   Element_type *begin() { return &m_array[0]; }
+  const Element_type *begin() const { return &m_array[0]; }
 
   // Returns a pointer to the past-the-end element in the array.
   Element_type *end() { return &m_array[size()]; }
+  const Element_type *end() const { return &m_array[size()]; }
 
   // Erases all of the elements. 
   void clear()
@@ -226,6 +228,7 @@ public:
   size_t element_size() const { return sizeof(Element_type); }
   bool   empty()        const { return size() == 0; }
   size_t size()         const { return m_size; }
+  const MEM_ROOT *mem_root() const { return m_root; }
 
 private:
   MEM_ROOT *const m_root;