Cleanup: Remove handler::update_table_comment()

The only call of the virtual member function
handler::update_table_comment() was removed in
commit 82d28fad (MySQL 5.5.53)
but the implementation was not removed.

The only non-trivial implementation was for InnoDB. The information
is now returned via handler::get_foreign_key_create_info() and
ha_statistics::delete_length.

sql/ha_partition.cc

 /*
   Copyright (c) 2005, 2019, Oracle and/or its affiliates.
-  Copyright (c) 2009, 2019, MariaDB
+  Copyright (c) 2009, 2021, MariaDB
 
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
@@ -2244,25 +2244,6 @@ void ha_partition::change_table_ptr(TABLE *table_arg, TABLE_SHARE *share)
   }
 }
 
-/*
-  Change comments specific to handler
-
-  SYNOPSIS
-    update_table_comment()
-    comment                       Original comment
-
-  RETURN VALUE
-    new comment 
-
-  DESCRIPTION
-    No comment changes so far
-*/
-
-char *ha_partition::update_table_comment(const char *comment)
-{
-  return (char*) comment;                       /* Nothing to change */
-}
-
 
 /**
   Handle delete and rename table

sql/ha_partition.h

@@ -3,7 +3,7 @@
 
 /*
    Copyright (c) 2005, 2012, Oracle and/or its affiliates.
-   Copyright (c) 2009, 2013, Monty Program Ab & SkySQL Ab.
+   Copyright (c) 2009, 2021, MariaDB Corporation.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -314,10 +314,6 @@ class ha_partition :public handler
     Meta data routines to CREATE, DROP, RENAME table and often used at
     ALTER TABLE (update_create_info used from ALTER TABLE and SHOW ..).
 
-    update_table_comment is used in SHOW TABLE commands to provide a
-    chance for the handler to add any interesting comments to the table
-    comments not provided by the users comment.
-
     create_partitioning_metadata is called before opening a new handler object
     with openfrm to call create. It is used to create any local handler
     object needed in opening the object in openfrm
@@ -330,7 +326,6 @@ class ha_partition :public handler
   virtual int create_partitioning_metadata(const char *name,
                                    const char *old_name, int action_flag);
   virtual void update_create_info(HA_CREATE_INFO *create_info);
-  virtual char *update_table_comment(const char *comment);
   virtual int change_partitions(HA_CREATE_INFO *create_info,
                                 const char *path,
                                 ulonglong * const copied,

sql/handler.h

@@ -2,7 +2,7 @@
 #define HANDLER_INCLUDED
 /*
    Copyright (c) 2000, 2019, Oracle and/or its affiliates.
-   Copyright (c) 2009, 2019, MariaDB
+   Copyright (c) 2009, 2021, MariaDB
 
    This program is free software; you can redistribute it and/or
    modify it under the terms of the GNU General Public License
@@ -3363,8 +3363,6 @@ class handler :public Sql_alloc
   /* end of the list of admin commands */
 
   virtual int indexes_are_disabled(void) {return 0;}
-  virtual char *update_table_comment(const char * comment)
-  { return (char*) comment;}
   virtual void append_create_info(String *packet) {}
   /**
     If index == MAX_KEY then a check for table is made and if index <

storage/innobase/handler/ha_innodb.cc

@@ -15190,68 +15190,6 @@ ha_innobase::check(
 	DBUG_RETURN(is_ok ? HA_ADMIN_OK : HA_ADMIN_CORRUPT);
 }
 
-/*************************************************************//**
-Adds information about free space in the InnoDB tablespace to a table comment
-which is printed out when a user calls SHOW TABLE STATUS. Adds also info on
-foreign keys.
-@return	table comment + InnoDB free space + info on foreign keys */
-UNIV_INTERN
-char*
-ha_innobase::update_table_comment(
-/*==============================*/
-	const char*	comment)/*!< in: table comment defined by user */
-{
-	uint	length = (uint) strlen(comment);
-	char*	str=0;
-	size_t	flen;
-	std::string fk_str;
-
-	/* We do not know if MySQL can call this function before calling
-	external_lock(). To be safe, update the thd of the current table
-	handle. */
-
-	if (length > 64000 - 3) {
-		return((char*) comment); /* string too long */
-	}
-
-	update_thd(ha_thd());
-
-	m_prebuilt->trx->op_info = "returning table comment";
-
-#define SSTR( x ) reinterpret_cast< std::ostringstream & >(		\
-        ( std::ostringstream() << std::dec << x ) ).str()
-
-	fk_str.append("InnoDB free: ");
-	fk_str.append(SSTR(fsp_get_available_space_in_free_extents(
-				m_prebuilt->table->space)));
-
-	fk_str.append(dict_print_info_on_foreign_keys(
-			FALSE, m_prebuilt->trx,
-			m_prebuilt->table));
-
-	flen = fk_str.length();
-
-	if (length + flen + 3 > 64000) {
-		flen = 64000 - 3 - length;
-	}
-	/* allocate buffer for the full string */
-	str = (char*) my_malloc(length + flen + 3, MYF(0));
-	if (str) {
-		char* pos	= str + length;
-		if (length) {
-			memcpy(str, comment, length);
-			*pos++ = ';';
-			*pos++ = ' ';
-		}
-		memcpy(pos, fk_str.c_str(), flen);
-		pos[flen] = 0;
-	}
-
-	m_prebuilt->trx->op_info = (char*)"";
-
-	return(str ? str : (char*) comment);
-}
-
 /*******************************************************************//**
 Gets the foreign key create info for a table stored in InnoDB.
 @return own: character string in the form which can be inserted to the

storage/innobase/handler/ha_innodb.h

@@ -221,7 +221,6 @@ class ha_innobase: public handler
 	int rename_table(const char* from, const char* to);
 	inline int defragment_table(const char* name);
 	int check(THD* thd, HA_CHECK_OPT* check_opt);
-	char* update_table_comment(const char* comment);
 
 	char* get_foreign_key_create_info();