diff --git a/include/mysql/plugin_audit.h.pp b/include/mysql/plugin_audit.h.pp
index 6122aa4029a..4ede09a0d41 100644
--- a/include/mysql/plugin_audit.h.pp
+++ b/include/mysql/plugin_audit.h.pp
@@ -314,22 +314,22 @@ struct st_mysql_const_lex_string
 };
 typedef struct st_mysql_const_lex_string MYSQL_CONST_LEX_STRING;
 extern struct thd_alloc_service_st {
-  void *(*thd_alloc_func)(THD*, size_t);
-  void *(*thd_calloc_func)(THD*, size_t);
-  char *(*thd_strdup_func)(THD*, const char *);
-  char *(*thd_strmake_func)(THD*, const char *, size_t);
-  void *(*thd_memdup_func)(THD*, const void*, size_t);
-  MYSQL_CONST_LEX_STRING *(*thd_make_lex_string_func)(THD*,
+  void *(*thd_alloc_func)(const THD*, size_t);
+  void *(*thd_calloc_func)(const THD*, size_t);
+  char *(*thd_strdup_func)(const THD*, const char *);
+  char *(*thd_strmake_func)(const THD*, const char *, size_t);
+  void *(*thd_memdup_func)(const THD*, const void*, size_t);
+  MYSQL_CONST_LEX_STRING *(*thd_make_lex_string_func)(const THD*,
                                         MYSQL_CONST_LEX_STRING *,
                                         const char *, size_t, int);
 } *thd_alloc_service;
-void *thd_alloc(THD* thd, size_t size);
-void *thd_calloc(THD* thd, size_t size);
-char *thd_strdup(THD* thd, const char *str);
-char *thd_strmake(THD* thd, const char *str, size_t size);
-void *thd_memdup(THD* thd, const void* str, size_t size);
+void *thd_alloc(const THD* thd, size_t size);
+void *thd_calloc(const THD* thd, size_t size);
+char *thd_strdup(const THD* thd, const char *str);
+char *thd_strmake(const THD* thd, const char *str, size_t size);
+void *thd_memdup(const THD* thd, const void* str, size_t size);
 MYSQL_CONST_LEX_STRING
-*thd_make_lex_string(THD* thd, MYSQL_CONST_LEX_STRING *lex_str,
+*thd_make_lex_string(const THD* thd, MYSQL_CONST_LEX_STRING *lex_str,
                      const char *str, size_t size,
                      int allocate_lex_string);
 }
diff --git a/include/mysql/plugin_auth.h.pp b/include/mysql/plugin_auth.h.pp
index 4f42e693a16..ab32177fbb0 100644
--- a/include/mysql/plugin_auth.h.pp
+++ b/include/mysql/plugin_auth.h.pp
@@ -314,22 +314,22 @@ struct st_mysql_const_lex_string
 };
 typedef struct st_mysql_const_lex_string MYSQL_CONST_LEX_STRING;
 extern struct thd_alloc_service_st {
-  void *(*thd_alloc_func)(THD*, size_t);
-  void *(*thd_calloc_func)(THD*, size_t);
-  char *(*thd_strdup_func)(THD*, const char *);
-  char *(*thd_strmake_func)(THD*, const char *, size_t);
-  void *(*thd_memdup_func)(THD*, const void*, size_t);
-  MYSQL_CONST_LEX_STRING *(*thd_make_lex_string_func)(THD*,
+  void *(*thd_alloc_func)(const THD*, size_t);
+  void *(*thd_calloc_func)(const THD*, size_t);
+  char *(*thd_strdup_func)(const THD*, const char *);
+  char *(*thd_strmake_func)(const THD*, const char *, size_t);
+  void *(*thd_memdup_func)(const THD*, const void*, size_t);
+  MYSQL_CONST_LEX_STRING *(*thd_make_lex_string_func)(const THD*,
                                         MYSQL_CONST_LEX_STRING *,
                                         const char *, size_t, int);
 } *thd_alloc_service;
-void *thd_alloc(THD* thd, size_t size);
-void *thd_calloc(THD* thd, size_t size);
-char *thd_strdup(THD* thd, const char *str);
-char *thd_strmake(THD* thd, const char *str, size_t size);
-void *thd_memdup(THD* thd, const void* str, size_t size);
+void *thd_alloc(const THD* thd, size_t size);
+void *thd_calloc(const THD* thd, size_t size);
+char *thd_strdup(const THD* thd, const char *str);
+char *thd_strmake(const THD* thd, const char *str, size_t size);
+void *thd_memdup(const THD* thd, const void* str, size_t size);
 MYSQL_CONST_LEX_STRING
-*thd_make_lex_string(THD* thd, MYSQL_CONST_LEX_STRING *lex_str,
+*thd_make_lex_string(const THD* thd, MYSQL_CONST_LEX_STRING *lex_str,
                      const char *str, size_t size,
                      int allocate_lex_string);
 }
diff --git a/include/mysql/plugin_data_type.h.pp b/include/mysql/plugin_data_type.h.pp
index d8788f5d4e0..34b8dadd75e 100644
--- a/include/mysql/plugin_data_type.h.pp
+++ b/include/mysql/plugin_data_type.h.pp
@@ -314,22 +314,22 @@ struct st_mysql_const_lex_string
 };
 typedef struct st_mysql_const_lex_string MYSQL_CONST_LEX_STRING;
 extern struct thd_alloc_service_st {
-  void *(*thd_alloc_func)(THD*, size_t);
-  void *(*thd_calloc_func)(THD*, size_t);
-  char *(*thd_strdup_func)(THD*, const char *);
-  char *(*thd_strmake_func)(THD*, const char *, size_t);
-  void *(*thd_memdup_func)(THD*, const void*, size_t);
-  MYSQL_CONST_LEX_STRING *(*thd_make_lex_string_func)(THD*,
+  void *(*thd_alloc_func)(const THD*, size_t);
+  void *(*thd_calloc_func)(const THD*, size_t);
+  char *(*thd_strdup_func)(const THD*, const char *);
+  char *(*thd_strmake_func)(const THD*, const char *, size_t);
+  void *(*thd_memdup_func)(const THD*, const void*, size_t);
+  MYSQL_CONST_LEX_STRING *(*thd_make_lex_string_func)(const THD*,
                                         MYSQL_CONST_LEX_STRING *,
                                         const char *, size_t, int);
 } *thd_alloc_service;
-void *thd_alloc(THD* thd, size_t size);
-void *thd_calloc(THD* thd, size_t size);
-char *thd_strdup(THD* thd, const char *str);
-char *thd_strmake(THD* thd, const char *str, size_t size);
-void *thd_memdup(THD* thd, const void* str, size_t size);
+void *thd_alloc(const THD* thd, size_t size);
+void *thd_calloc(const THD* thd, size_t size);
+char *thd_strdup(const THD* thd, const char *str);
+char *thd_strmake(const THD* thd, const char *str, size_t size);
+void *thd_memdup(const THD* thd, const void* str, size_t size);
 MYSQL_CONST_LEX_STRING
-*thd_make_lex_string(THD* thd, MYSQL_CONST_LEX_STRING *lex_str,
+*thd_make_lex_string(const THD* thd, MYSQL_CONST_LEX_STRING *lex_str,
                      const char *str, size_t size,
                      int allocate_lex_string);
 }
diff --git a/include/mysql/plugin_encryption.h.pp b/include/mysql/plugin_encryption.h.pp
index 5624c6d6f61..449ee46d585 100644
--- a/include/mysql/plugin_encryption.h.pp
+++ b/include/mysql/plugin_encryption.h.pp
@@ -314,22 +314,22 @@ struct st_mysql_const_lex_string
 };
 typedef struct st_mysql_const_lex_string MYSQL_CONST_LEX_STRING;
 extern struct thd_alloc_service_st {
-  void *(*thd_alloc_func)(THD*, size_t);
-  void *(*thd_calloc_func)(THD*, size_t);
-  char *(*thd_strdup_func)(THD*, const char *);
-  char *(*thd_strmake_func)(THD*, const char *, size_t);
-  void *(*thd_memdup_func)(THD*, const void*, size_t);
-  MYSQL_CONST_LEX_STRING *(*thd_make_lex_string_func)(THD*,
+  void *(*thd_alloc_func)(const THD*, size_t);
+  void *(*thd_calloc_func)(const THD*, size_t);
+  char *(*thd_strdup_func)(const THD*, const char *);
+  char *(*thd_strmake_func)(const THD*, const char *, size_t);
+  void *(*thd_memdup_func)(const THD*, const void*, size_t);
+  MYSQL_CONST_LEX_STRING *(*thd_make_lex_string_func)(const THD*,
                                         MYSQL_CONST_LEX_STRING *,
                                         const char *, size_t, int);
 } *thd_alloc_service;
-void *thd_alloc(THD* thd, size_t size);
-void *thd_calloc(THD* thd, size_t size);
-char *thd_strdup(THD* thd, const char *str);
-char *thd_strmake(THD* thd, const char *str, size_t size);
-void *thd_memdup(THD* thd, const void* str, size_t size);
+void *thd_alloc(const THD* thd, size_t size);
+void *thd_calloc(const THD* thd, size_t size);
+char *thd_strdup(const THD* thd, const char *str);
+char *thd_strmake(const THD* thd, const char *str, size_t size);
+void *thd_memdup(const THD* thd, const void* str, size_t size);
 MYSQL_CONST_LEX_STRING
-*thd_make_lex_string(THD* thd, MYSQL_CONST_LEX_STRING *lex_str,
+*thd_make_lex_string(const THD* thd, MYSQL_CONST_LEX_STRING *lex_str,
                      const char *str, size_t size,
                      int allocate_lex_string);
 }
diff --git a/include/mysql/plugin_ftparser.h.pp b/include/mysql/plugin_ftparser.h.pp
index 46f4e6fc1fe..42c3e093150 100644
--- a/include/mysql/plugin_ftparser.h.pp
+++ b/include/mysql/plugin_ftparser.h.pp
@@ -314,22 +314,22 @@ struct st_mysql_const_lex_string
 };
 typedef struct st_mysql_const_lex_string MYSQL_CONST_LEX_STRING;
 extern struct thd_alloc_service_st {
-  void *(*thd_alloc_func)(THD*, size_t);
-  void *(*thd_calloc_func)(THD*, size_t);
-  char *(*thd_strdup_func)(THD*, const char *);
-  char *(*thd_strmake_func)(THD*, const char *, size_t);
-  void *(*thd_memdup_func)(THD*, const void*, size_t);
-  MYSQL_CONST_LEX_STRING *(*thd_make_lex_string_func)(THD*,
+  void *(*thd_alloc_func)(const THD*, size_t);
+  void *(*thd_calloc_func)(const THD*, size_t);
+  char *(*thd_strdup_func)(const THD*, const char *);
+  char *(*thd_strmake_func)(const THD*, const char *, size_t);
+  void *(*thd_memdup_func)(const THD*, const void*, size_t);
+  MYSQL_CONST_LEX_STRING *(*thd_make_lex_string_func)(const THD*,
                                         MYSQL_CONST_LEX_STRING *,
                                         const char *, size_t, int);
 } *thd_alloc_service;
-void *thd_alloc(THD* thd, size_t size);
-void *thd_calloc(THD* thd, size_t size);
-char *thd_strdup(THD* thd, const char *str);
-char *thd_strmake(THD* thd, const char *str, size_t size);
-void *thd_memdup(THD* thd, const void* str, size_t size);
+void *thd_alloc(const THD* thd, size_t size);
+void *thd_calloc(const THD* thd, size_t size);
+char *thd_strdup(const THD* thd, const char *str);
+char *thd_strmake(const THD* thd, const char *str, size_t size);
+void *thd_memdup(const THD* thd, const void* str, size_t size);
 MYSQL_CONST_LEX_STRING
-*thd_make_lex_string(THD* thd, MYSQL_CONST_LEX_STRING *lex_str,
+*thd_make_lex_string(const THD* thd, MYSQL_CONST_LEX_STRING *lex_str,
                      const char *str, size_t size,
                      int allocate_lex_string);
 }
diff --git a/include/mysql/plugin_function.h.pp b/include/mysql/plugin_function.h.pp
index 750f94cbf5d..2e78d23ae2e 100644
--- a/include/mysql/plugin_function.h.pp
+++ b/include/mysql/plugin_function.h.pp
@@ -314,22 +314,22 @@ struct st_mysql_const_lex_string
 };
 typedef struct st_mysql_const_lex_string MYSQL_CONST_LEX_STRING;
 extern struct thd_alloc_service_st {
-  void *(*thd_alloc_func)(THD*, size_t);
-  void *(*thd_calloc_func)(THD*, size_t);
-  char *(*thd_strdup_func)(THD*, const char *);
-  char *(*thd_strmake_func)(THD*, const char *, size_t);
-  void *(*thd_memdup_func)(THD*, const void*, size_t);
-  MYSQL_CONST_LEX_STRING *(*thd_make_lex_string_func)(THD*,
+  void *(*thd_alloc_func)(const THD*, size_t);
+  void *(*thd_calloc_func)(const THD*, size_t);
+  char *(*thd_strdup_func)(const THD*, const char *);
+  char *(*thd_strmake_func)(const THD*, const char *, size_t);
+  void *(*thd_memdup_func)(const THD*, const void*, size_t);
+  MYSQL_CONST_LEX_STRING *(*thd_make_lex_string_func)(const THD*,
                                         MYSQL_CONST_LEX_STRING *,
                                         const char *, size_t, int);
 } *thd_alloc_service;
-void *thd_alloc(THD* thd, size_t size);
-void *thd_calloc(THD* thd, size_t size);
-char *thd_strdup(THD* thd, const char *str);
-char *thd_strmake(THD* thd, const char *str, size_t size);
-void *thd_memdup(THD* thd, const void* str, size_t size);
+void *thd_alloc(const THD* thd, size_t size);
+void *thd_calloc(const THD* thd, size_t size);
+char *thd_strdup(const THD* thd, const char *str);
+char *thd_strmake(const THD* thd, const char *str, size_t size);
+void *thd_memdup(const THD* thd, const void* str, size_t size);
 MYSQL_CONST_LEX_STRING
-*thd_make_lex_string(THD* thd, MYSQL_CONST_LEX_STRING *lex_str,
+*thd_make_lex_string(const THD* thd, MYSQL_CONST_LEX_STRING *lex_str,
                      const char *str, size_t size,
                      int allocate_lex_string);
 }
diff --git a/include/mysql/plugin_password_validation.h.pp b/include/mysql/plugin_password_validation.h.pp
index 376df1dd330..138422e2b3e 100644
--- a/include/mysql/plugin_password_validation.h.pp
+++ b/include/mysql/plugin_password_validation.h.pp
@@ -314,22 +314,22 @@ struct st_mysql_const_lex_string
 };
 typedef struct st_mysql_const_lex_string MYSQL_CONST_LEX_STRING;
 extern struct thd_alloc_service_st {
-  void *(*thd_alloc_func)(THD*, size_t);
-  void *(*thd_calloc_func)(THD*, size_t);
-  char *(*thd_strdup_func)(THD*, const char *);
-  char *(*thd_strmake_func)(THD*, const char *, size_t);
-  void *(*thd_memdup_func)(THD*, const void*, size_t);
-  MYSQL_CONST_LEX_STRING *(*thd_make_lex_string_func)(THD*,
+  void *(*thd_alloc_func)(const THD*, size_t);
+  void *(*thd_calloc_func)(const THD*, size_t);
+  char *(*thd_strdup_func)(const THD*, const char *);
+  char *(*thd_strmake_func)(const THD*, const char *, size_t);
+  void *(*thd_memdup_func)(const THD*, const void*, size_t);
+  MYSQL_CONST_LEX_STRING *(*thd_make_lex_string_func)(const THD*,
                                         MYSQL_CONST_LEX_STRING *,
                                         const char *, size_t, int);
 } *thd_alloc_service;
-void *thd_alloc(THD* thd, size_t size);
-void *thd_calloc(THD* thd, size_t size);
-char *thd_strdup(THD* thd, const char *str);
-char *thd_strmake(THD* thd, const char *str, size_t size);
-void *thd_memdup(THD* thd, const void* str, size_t size);
+void *thd_alloc(const THD* thd, size_t size);
+void *thd_calloc(const THD* thd, size_t size);
+char *thd_strdup(const THD* thd, const char *str);
+char *thd_strmake(const THD* thd, const char *str, size_t size);
+void *thd_memdup(const THD* thd, const void* str, size_t size);
 MYSQL_CONST_LEX_STRING
-*thd_make_lex_string(THD* thd, MYSQL_CONST_LEX_STRING *lex_str,
+*thd_make_lex_string(const THD* thd, MYSQL_CONST_LEX_STRING *lex_str,
                      const char *str, size_t size,
                      int allocate_lex_string);
 }
diff --git a/include/mysql/service_thd_alloc.h b/include/mysql/service_thd_alloc.h
index 0be4687b8e6..e85a8e8c4e0 100644
--- a/include/mysql/service_thd_alloc.h
+++ b/include/mysql/service_thd_alloc.h
@@ -50,12 +50,12 @@ struct st_mysql_const_lex_string
 typedef struct st_mysql_const_lex_string MYSQL_CONST_LEX_STRING;
 
 extern struct thd_alloc_service_st {
-  void *(*thd_alloc_func)(MYSQL_THD, size_t);
-  void *(*thd_calloc_func)(MYSQL_THD, size_t);
-  char *(*thd_strdup_func)(MYSQL_THD, const char *);
-  char *(*thd_strmake_func)(MYSQL_THD, const char *, size_t);
-  void *(*thd_memdup_func)(MYSQL_THD, const void*, size_t);
-  MYSQL_CONST_LEX_STRING *(*thd_make_lex_string_func)(MYSQL_THD,
+  void *(*thd_alloc_func)(const MYSQL_THD, size_t);
+  void *(*thd_calloc_func)(const MYSQL_THD, size_t);
+  char *(*thd_strdup_func)(const MYSQL_THD, const char *);
+  char *(*thd_strmake_func)(const MYSQL_THD, const char *, size_t);
+  void *(*thd_memdup_func)(const MYSQL_THD, const void*, size_t);
+  MYSQL_CONST_LEX_STRING *(*thd_make_lex_string_func)(const MYSQL_THD,
                                         MYSQL_CONST_LEX_STRING *,
                                         const char *, size_t, int);
 } *thd_alloc_service;
@@ -92,23 +92,23 @@ extern struct thd_alloc_service_st {
 
   @see alloc_root()
 */
-void *thd_alloc(MYSQL_THD thd, size_t size);
+void *thd_alloc(const MYSQL_THD thd, size_t size);
 /**
   @see thd_alloc()
 */
-void *thd_calloc(MYSQL_THD thd, size_t size);
+void *thd_calloc(const MYSQL_THD thd, size_t size);
 /**
   @see thd_alloc()
 */
-char *thd_strdup(MYSQL_THD thd, const char *str);
+char *thd_strdup(const MYSQL_THD thd, const char *str);
 /**
   @see thd_alloc()
 */
-char *thd_strmake(MYSQL_THD thd, const char *str, size_t size);
+char *thd_strmake(const MYSQL_THD thd, const char *str, size_t size);
 /**
   @see thd_alloc()
 */
-void *thd_memdup(MYSQL_THD thd, const void* str, size_t size);
+void *thd_memdup(const MYSQL_THD thd, const void* str, size_t size);
 
 /**
   Create a LEX_STRING in this connection's local memory pool
@@ -124,7 +124,7 @@ void *thd_memdup(MYSQL_THD thd, const void* str, size_t size);
   @see thd_alloc()
 */
 MYSQL_CONST_LEX_STRING
-*thd_make_lex_string(MYSQL_THD thd, MYSQL_CONST_LEX_STRING *lex_str,
+*thd_make_lex_string(const MYSQL_THD thd, MYSQL_CONST_LEX_STRING *lex_str,
                      const char *str, size_t size,
                      int allocate_lex_string);
 
diff --git a/sql/sql_class.cc b/sql/sql_class.cc
index 17225f7decd..1e6ce05bb72 100644
--- a/sql/sql_class.cc
+++ b/sql/sql_class.cc
@@ -1138,31 +1138,31 @@ ret:
 }
 
 extern "C"
-void *thd_alloc(MYSQL_THD thd, size_t size)
+void *thd_alloc(const MYSQL_THD thd, size_t size)
 {
   return thd->alloc(size);
 }
 
 extern "C"
-void *thd_calloc(MYSQL_THD thd, size_t size)
+void *thd_calloc(const MYSQL_THD thd, size_t size)
 {
   return thd->calloc(size);
 }
 
 extern "C"
-char *thd_strdup(MYSQL_THD thd, const char *str)
+char *thd_strdup(const MYSQL_THD thd, const char *str)
 {
   return thd->strdup(str);
 }
 
 extern "C"
-char *thd_strmake(MYSQL_THD thd, const char *str, size_t size)
+char *thd_strmake(const MYSQL_THD thd, const char *str, size_t size)
 {
   return thd->strmake(str, size);
 }
 
 extern "C"
-LEX_CSTRING *thd_make_lex_string(THD *thd, LEX_CSTRING *lex_str,
+LEX_CSTRING *thd_make_lex_string(const THD *thd, LEX_CSTRING *lex_str,
                                 const char *str, size_t size,
                                 int allocate_lex_string)
 {
@@ -1171,7 +1171,7 @@ LEX_CSTRING *thd_make_lex_string(THD *thd, LEX_CSTRING *lex_str,
 }
 
 extern "C"
-void *thd_memdup(MYSQL_THD thd, const void* str, size_t size)
+void *thd_memdup(const MYSQL_THD thd, const void* str, size_t size)
 {
   return thd->memdup(str, size);
 }
@@ -2345,7 +2345,7 @@ void THD::cleanup_after_query()
 
 bool THD::convert_string(LEX_STRING *to, CHARSET_INFO *to_cs,
 			 const char *from, size_t from_length,
-			 CHARSET_INFO *from_cs)
+			 CHARSET_INFO *from_cs) const
 {
   DBUG_ENTER("THD::convert_string");
   size_t new_length= to_cs->mbmaxlen * from_length;
@@ -2382,7 +2382,7 @@ bool THD::convert_string(LEX_STRING *to, CHARSET_INFO *to_cs,
 */
 
 bool THD::reinterpret_string_from_binary(LEX_CSTRING *to, CHARSET_INFO *cs,
-                                         const char *str, size_t length)
+                                         const char *str, size_t length) const
 {
   /*
     When reinterpreting from binary to tricky character sets like
@@ -2424,7 +2424,7 @@ bool THD::reinterpret_string_from_binary(LEX_CSTRING *to, CHARSET_INFO *cs,
 */
 bool THD::convert_fix(CHARSET_INFO *dstcs, LEX_STRING *dst,
                       CHARSET_INFO *srccs, const char *src, size_t src_length,
-                      String_copier *status)
+                      String_copier *status) const
 {
   DBUG_ENTER("THD::convert_fix");
   size_t dst_length= dstcs->mbmaxlen * src_length;
@@ -2442,7 +2442,7 @@ bool THD::convert_fix(CHARSET_INFO *dstcs, LEX_STRING *dst,
 */
 bool THD::copy_fix(CHARSET_INFO *dstcs, LEX_STRING *dst,
                    CHARSET_INFO *srccs, const char *src, size_t src_length,
-                   String_copier *status)
+                   String_copier *status) const
 {
   DBUG_ENTER("THD::copy_fix");
   size_t dst_length= dstcs->mbmaxlen * src_length;
@@ -2474,7 +2474,7 @@ public:
 
 bool THD::convert_with_error(CHARSET_INFO *dstcs, LEX_STRING *dst,
                              CHARSET_INFO *srccs,
-                             const char *src, size_t src_length)
+                             const char *src, size_t src_length) const
 {
   String_copier_with_error status;
   return convert_fix(dstcs, dst, srccs, src, src_length, &status) ||
@@ -2484,7 +2484,7 @@ bool THD::convert_with_error(CHARSET_INFO *dstcs, LEX_STRING *dst,
 
 bool THD::copy_with_error(CHARSET_INFO *dstcs, LEX_STRING *dst,
                           CHARSET_INFO *srccs,
-                          const char *src, size_t src_length)
+                          const char *src, size_t src_length) const
 {
   String_copier_with_error status;
   return copy_fix(dstcs, dst, srccs, src, src_length, &status) ||
@@ -2507,7 +2507,8 @@ bool THD::copy_with_error(CHARSET_INFO *dstcs, LEX_STRING *dst,
    !0   out of memory
 */
 
-bool THD::convert_string(String *s, CHARSET_INFO *from_cs, CHARSET_INFO *to_cs)
+bool THD::convert_string(String *s, CHARSET_INFO *from_cs,
+                         CHARSET_INFO *to_cs)
 {
   uint dummy_errors;
   if (unlikely(convert_buffer.copy(s->ptr(), s->length(), from_cs, to_cs,
@@ -2539,7 +2540,8 @@ bool THD::check_string_for_wellformedness(const char *str,
 }
 
 
-bool THD::to_ident_sys_alloc(Lex_ident_sys_st *to, const Lex_ident_cli_st *ident)
+bool THD::to_ident_sys_alloc(Lex_ident_sys_st *to,
+                             const Lex_ident_cli_st *ident) const
 {
   if (ident->is_quoted())
   {
diff --git a/sql/sql_class.h b/sql/sql_class.h
index 8d0cef4a650..b9716ae943a 100644
--- a/sql/sql_class.h
+++ b/sql/sql_class.h
@@ -1221,21 +1221,21 @@ public:
   inline bool is_conventional() const
   { return state == STMT_CONVENTIONAL_EXECUTION; }
 
-  inline void* alloc(size_t size) { return alloc_root(mem_root,size); }
-  inline void* calloc(size_t size)
+  inline void* alloc(size_t size) const { return alloc_root(mem_root,size); }
+  inline void* calloc(size_t size) const
   {
     void *ptr;
     if (likely((ptr=alloc_root(mem_root,size))))
       bzero(ptr, size);
     return ptr;
   }
-  inline char *strdup(const char *str)
+  inline char *strdup(const char *str) const
   { return strdup_root(mem_root,str); }
-  inline char *strmake(const char *str, size_t size)
+  inline char *strmake(const char *str, size_t size) const
   { return strmake_root(mem_root,str,size); }
-  inline void *memdup(const void *str, size_t size)
+  inline void *memdup(const void *str, size_t size) const
   { return memdup_root(mem_root,str,size); }
-  inline void *memdup_w_gap(const void *str, size_t size, size_t gap)
+  inline void *memdup_w_gap(const void *str, size_t size, size_t gap) const
   {
     void *ptr;
     if (likely((ptr= alloc_root(mem_root,size+gap))))
@@ -2695,7 +2695,7 @@ public:
   Protocol_binary protocol_binary;	// Binary protocol
   HASH    user_vars;			// hash for user variables
   String  packet;			// dynamic buffer for network I/O
-  String  convert_buffer;               // buffer for charset conversions
+  String  convert_buffer;		// buffer for charset conversions
   struct  my_rnd_struct rand;		// used for authentication
   struct  system_variables variables;	// Changeable local variables
   struct  system_status_var status_var; // Per thread statistic vars
@@ -4148,24 +4148,25 @@ public:
   {
     return !stmt_arena->is_stmt_prepare();
   }
-  inline void* trans_alloc(size_t size)
+  inline void* trans_alloc(size_t size) const
   {
     return alloc_root(&transaction->mem_root,size);
   }
 
-  LEX_CSTRING strmake_lex_cstring(const char *str, size_t length)
+  LEX_CSTRING strmake_lex_cstring(const char *str, size_t length) const
   {
     const char *tmp= strmake_root(mem_root, str, length);
     if (!tmp)
       return {0,0};
     return {tmp, length};
   }
-  LEX_CSTRING strmake_lex_cstring(const LEX_CSTRING &from)
+  LEX_CSTRING strmake_lex_cstring(const LEX_CSTRING &from) const
   {
     return strmake_lex_cstring(from.str, from.length);
   }
 
-  LEX_STRING *make_lex_string(LEX_STRING *lex_str, const char* str, size_t length)
+  LEX_STRING *make_lex_string(LEX_STRING *lex_str, const char* str,
+                              size_t length) const
   {
     if (!(lex_str->str= strmake_root(mem_root, str, length)))
     {
@@ -4175,7 +4176,8 @@ public:
     lex_str->length= length;
     return lex_str;
   }
-  LEX_CSTRING *make_lex_string(LEX_CSTRING *lex_str, const char* str, size_t length)
+  LEX_CSTRING *make_lex_string(LEX_CSTRING *lex_str, const char* str,
+                               size_t length) const
   {
     if (!(lex_str->str= strmake_root(mem_root, str, length)))
     {
@@ -4186,7 +4188,8 @@ public:
     return lex_str;
   }
   // Remove double quotes:  aaa""bbb -> aaa"bbb
-  bool quote_unescape(LEX_CSTRING *dst, const LEX_CSTRING *src, char quote)
+  bool quote_unescape(LEX_CSTRING *dst, const LEX_CSTRING *src,
+                      char quote) const
   {
     const char *tmp= src->str;
     const char *tmpend= src->str + src->length;
@@ -4206,7 +4209,7 @@ public:
     return false;
   }
 
-  LEX_CSTRING *make_clex_string(const char* str, size_t length)
+  LEX_CSTRING *make_clex_string(const char* str, size_t length) const
   {
     LEX_CSTRING *lex_str;
     char *tmp;
@@ -4221,13 +4224,13 @@ public:
     lex_str->length= length;
     return lex_str;
   }
-  LEX_CSTRING *make_clex_string(const LEX_CSTRING from)
+  LEX_CSTRING *make_clex_string(const LEX_CSTRING from) const
   {
     return make_clex_string(from.str, from.length);
   }
 
   // Allocate LEX_STRING for character set conversion
-  bool alloc_lex_string(LEX_STRING *dst, size_t length)
+  bool alloc_lex_string(LEX_STRING *dst, size_t length) const
   {
     if (likely((dst->str= (char*) alloc(length))))
       return false;
@@ -4236,12 +4239,13 @@ public:
   }
   bool convert_string(LEX_STRING *to, CHARSET_INFO *to_cs,
 		      const char *from, size_t from_length,
-		      CHARSET_INFO *from_cs);
+		      CHARSET_INFO *from_cs) const;
   bool reinterpret_string_from_binary(LEX_CSTRING *to, CHARSET_INFO *to_cs,
-                                      const char *from, size_t from_length);
+                                      const char *from, size_t from_length)
+                                      const;
   bool convert_string(LEX_CSTRING *to, CHARSET_INFO *to_cs,
                       const char *from, size_t from_length,
-                      CHARSET_INFO *from_cs)
+                      CHARSET_INFO *from_cs) const
   {
     LEX_STRING tmp;
     bool rc= convert_string(&tmp, to_cs, from, from_length, from_cs);
@@ -4251,7 +4255,7 @@ public:
   }
   bool convert_string(LEX_CSTRING *to, CHARSET_INFO *tocs,
                       const LEX_CSTRING *from, CHARSET_INFO *fromcs,
-                      bool simple_copy_is_possible)
+                      bool simple_copy_is_possible) const
   {
     if (!simple_copy_is_possible)
       return unlikely(convert_string(to, tocs, from->str, from->length, fromcs));
@@ -4267,7 +4271,7 @@ public:
   */
   bool convert_fix(CHARSET_INFO *dstcs, LEX_STRING *dst,
                    CHARSET_INFO *srccs, const char *src, size_t src_length,
-                   String_copier *status);
+                   String_copier *status) const;
 
   /*
     Same as above, but additionally sends ER_INVALID_CHARACTER_STRING
@@ -4275,7 +4279,7 @@ public:
   */
   bool convert_with_error(CHARSET_INFO *dstcs, LEX_STRING *dst,
                           CHARSET_INFO *srccs,
-                          const char *src, size_t src_length);
+                          const char *src, size_t src_length) const;
   /*
     If either "dstcs" or "srccs" is &my_charset_bin,
     then performs native copying using copy_fix().
@@ -4283,16 +4287,18 @@ public:
   */
   bool copy_fix(CHARSET_INFO *dstcs, LEX_STRING *dst,
                 CHARSET_INFO *srccs, const char *src, size_t src_length,
-                String_copier *status);
+                String_copier *status) const;
 
   /*
     Same as above, but additionally sends ER_INVALID_CHARACTER_STRING
     in case of bad byte sequences or Unicode conversion problems.
   */
   bool copy_with_error(CHARSET_INFO *dstcs, LEX_STRING *dst,
-                       CHARSET_INFO *srccs, const char *src, size_t src_length);
+                       CHARSET_INFO *srccs, const char *src, size_t src_length)
+                       const;
 
-  bool convert_string(String *s, CHARSET_INFO *from_cs, CHARSET_INFO *to_cs);
+  bool convert_string(String *s, CHARSET_INFO *from_cs,
+                      CHARSET_INFO *to_cs);
 
   /*
     Check if the string is wellformed, raise an error if not wellformed.
@@ -4303,7 +4309,8 @@ public:
                                        size_t length,
                                        CHARSET_INFO *cs) const;
 
-  bool to_ident_sys_alloc(Lex_ident_sys_st *to, const Lex_ident_cli_st *from);
+  bool to_ident_sys_alloc(Lex_ident_sys_st *to,
+                          const Lex_ident_cli_st *from) const;
 
   /*
     Create a string literal with optional client->connection conversion.
@@ -4313,7 +4320,8 @@ public:
   */
   Item_basic_constant *make_string_literal(const char *str, size_t length,
                                            my_repertoire_t repertoire);
-  Item_basic_constant *make_string_literal(const Lex_string_with_metadata_st &str)
+  Item_basic_constant *
+  make_string_literal(const Lex_string_with_metadata_st &str)
   {
     my_repertoire_t repertoire= str.repertoire(variables.character_set_client);
     return make_string_literal(str.str, str.length, repertoire);
diff --git a/sql/sql_lex.cc b/sql/sql_lex.cc
index 3fe08ba658f..0b36b604126 100644
--- a/sql/sql_lex.cc
+++ b/sql/sql_lex.cc
@@ -9683,18 +9683,18 @@ Item *LEX::create_item_qualified_asterisk(THD *thd,
 }
 
 
-bool Lex_ident_sys_st::copy_ident_cli(THD *thd, const Lex_ident_cli_st *str)
+bool Lex_ident_sys_st::copy_ident_cli(const THD *thd, const Lex_ident_cli_st *str)
 {
   return thd->to_ident_sys_alloc(this, str);
 }
 
-bool Lex_ident_sys_st::copy_keyword(THD *thd, const Lex_ident_cli_st *str)
+bool Lex_ident_sys_st::copy_keyword(const THD *thd, const Lex_ident_cli_st *str)
 {
   return thd->make_lex_string(static_cast<LEX_CSTRING*>(this),
                               str->str, str->length) == NULL;
 }
 
-bool Lex_ident_sys_st::copy_or_convert(THD *thd,
+bool Lex_ident_sys_st::copy_or_convert(const THD *thd,
                                        const Lex_ident_cli_st *src,
                                        CHARSET_INFO *cs)
 {
@@ -9704,7 +9704,7 @@ bool Lex_ident_sys_st::copy_or_convert(THD *thd,
 }
 
 
-bool Lex_ident_sys_st::copy_sys(THD *thd, const LEX_CSTRING *src)
+bool Lex_ident_sys_st::copy_sys(const THD *thd, const LEX_CSTRING *src)
 {
   if (thd->check_string_for_wellformedness(src->str, src->length,
                                            system_charset_info))
@@ -9713,7 +9713,7 @@ bool Lex_ident_sys_st::copy_sys(THD *thd, const LEX_CSTRING *src)
 }
 
 
-bool Lex_ident_sys_st::convert(THD *thd,
+bool Lex_ident_sys_st::convert(const THD *thd,
                                const LEX_CSTRING *src, CHARSET_INFO *cs)
 {
   LEX_STRING tmp;
diff --git a/sql/sql_lex.h b/sql/sql_lex.h
index 6f80d54fe66..0e1de54cf95 100644
--- a/sql/sql_lex.h
+++ b/sql/sql_lex.h
@@ -148,11 +148,12 @@ public:
 struct Lex_ident_sys_st: public LEX_CSTRING
 {
 public:
-  bool copy_ident_cli(THD *thd, const Lex_ident_cli_st *str);
-  bool copy_keyword(THD *thd, const Lex_ident_cli_st *str);
-  bool copy_sys(THD *thd, const LEX_CSTRING *str);
-  bool convert(THD *thd, const LEX_CSTRING *str, CHARSET_INFO *cs);
-  bool copy_or_convert(THD *thd, const Lex_ident_cli_st *str, CHARSET_INFO *cs);
+  bool copy_ident_cli(const THD *thd, const Lex_ident_cli_st *str);
+  bool copy_keyword(const THD *thd, const Lex_ident_cli_st *str);
+  bool copy_sys(const THD *thd, const LEX_CSTRING *str);
+  bool convert(const THD *thd, const LEX_CSTRING *str, CHARSET_INFO *cs);
+  bool copy_or_convert(const THD *thd, const Lex_ident_cli_st *str,
+                       CHARSET_INFO *cs);
   bool is_null() const { return str == NULL; }
   bool to_size_number(ulonglong *to) const;
   void set_valid_utf8(const LEX_CSTRING *name)
@@ -167,7 +168,7 @@ public:
 class Lex_ident_sys: public Lex_ident_sys_st
 {
 public:
-  Lex_ident_sys(THD *thd, const Lex_ident_cli_st *str)
+  Lex_ident_sys(const THD *thd, const Lex_ident_cli_st *str)
   {
     if (copy_ident_cli(thd, str))
       ((LEX_CSTRING &) *this)= null_clex_str;