MDEV-11245 Move prepare_create_field and sp_prepare_create_field() as methods to Column_definition

Some upcoming tasks, e.g.:
- MDEV-10577 sql_mode=ORACLE: %TYPE in variable declarations
- MDEV-10914 ROW data type for stored routine variables

will need to reuse the code implemented in prepare_create_field(),
sp_prepare_create_field(), prepare_blob_field().

Before reusing this code, it's a good idea to move these global functions
as methods to Column_definition.

This patch:
- actually moves prepare_create_field(), sp_prepare_create_field(),
  prepare_blob_field() as methods to Column_definition
- makes sp_prepare_create_field() call prepare_create_field() at the end,
  to avoid duplicate code in MDEV-10577 and MDEV-10914.
- changes the return data type for prepare_create_field() from int to bool,
  to make it consistent with all other functions returning "ok" or "error".
- moves the implementation sp_head::fill_field_definition() from sp_head.cc
  to sp_head.h, as it now uses globally visible Column_definition methods,
  and is very simple, so inlining is now possible.
- removes the unused "LEX*" argument from sp_head::fill_field_definition()

sql/field.h

@@ -3872,6 +3872,13 @@ class Column_definition: public Sql_alloc
     set_if_smaller(length, MAX_FIELD_WIDTH - 1);
     DBUG_RETURN(false);
   }
+
+  bool prepare_blob_field(THD *thd);
+
+  bool sp_prepare_create_field(THD *thd, MEM_ROOT *mem_root);
+
+  bool prepare_create_field(uint *blob_columns, longlong table_flags);
+
   bool check(THD *thd);
 
   bool stored_in_db() const { return !vcol_info || vcol_info->stored_in_db; }

sql/sp_head.cc

@@ -23,8 +23,6 @@
 #include "probes_mysql.h"
 #include "sql_show.h"                           // append_identifier
 #include "sql_db.h"            // mysql_opt_change_db, mysql_change_db
-#include "sql_table.h"         // sp_prepare_create_field,
-                               // prepare_create_field
 #include "sql_acl.h"           // *_ACL
 #include "sql_array.h"         // Dynamic_array
 #include "log_event.h"         // Query_log_event
@@ -2287,40 +2285,6 @@ sp_head::backpatch(sp_label *lab)
   DBUG_VOID_RETURN;
 }
 
-/**
-  Prepare an instance of Column_definition for field creation
-  (fill all necessary attributes).
-
-  @param[in]  thd          Thread handle
-  @param[in]  lex          Yacc parsing context
-  @param[out] field_def    An instance of create_field to be filled
-
-  @retval
-    FALSE  on success
-  @retval
-    TRUE   on error
-*/
-
-bool
-sp_head::fill_field_definition(THD *thd, LEX *lex,
-                               Column_definition *field_def)
-{
-  uint unused1= 0;
-
-  if (field_def->check(thd))
-    return TRUE;
-
-  if (sp_prepare_create_field(thd, mem_root, field_def))
-    return true;
-
-  if (prepare_create_field(field_def, &unused1, HA_CAN_GEOMETRY))
-  {
-    return TRUE;
-  }
-
-  return FALSE;
-}
-
 
 int
 sp_head::new_cont_backpatch(sp_instr_opt_meta *i)

sql/sp_head.h

@@ -417,9 +417,23 @@ class sp_head :private Query_arena
   Field *create_result_field(uint field_max_length, const char *field_name,
                              TABLE *table);
 
-  bool fill_field_definition(THD *thd, LEX *lex,
-                             Column_definition *field_def);
 
+  /**
+    Check and prepare an instance of Column_definition for field creation
+    (fill all necessary attributes).
+
+    @param[in]  thd          Thread handle
+    @param[in]  lex          Yacc parsing context
+    @param[out] field_def    An instance of create_field to be filled
+
+    @retval false on success
+    @retval true  on error
+  */
+  bool fill_field_definition(THD *thd, Column_definition *field_def)
+  {
+    return field_def->check(thd) ||
+           field_def->sp_prepare_create_field(thd, mem_root);
+  }
   void set_info(longlong created, longlong modified,
 		st_sp_chistics *chistics, sql_mode_t sql_mode);
 

sql/sql_table.h

@@ -251,11 +251,6 @@ bool quick_rm_table(THD *thd, handlerton *base, const char *db,
                     const char *table_name, uint flags,
                     const char *table_path=0);
 void close_cached_table(THD *thd, TABLE *table);
-bool sp_prepare_create_field(THD *thd, MEM_ROOT *mem_root,
-                             Column_definition *sql_field);
-int prepare_create_field(Column_definition *sql_field,
-			 uint *blob_columns,
-			 longlong table_flags);
 CHARSET_INFO* get_sql_field_charset(Create_field *sql_field,
                                     HA_CREATE_INFO *create_info);
 bool mysql_write_frm(ALTER_PARTITION_PARAM_TYPE *lpt, uint flags);

sql/sql_yacc.yy

@@ -3009,7 +3009,7 @@ sp_param_name_and_type:
             LEX *lex= Lex;
             sp_variable *spvar= $<spvar>2;
 
-            if (lex->sphead->fill_field_definition(thd, lex, lex->last_field))
+            if (lex->sphead->fill_field_definition(thd, lex->last_field))
             {
               MYSQL_YYABORT;
             }
@@ -3121,8 +3121,7 @@ sp_decl:
               spvar->default_value= dflt_value_item;
               spvar->field_def.field_name= spvar->name.str;
             
-              if (lex->sphead->fill_field_definition(thd, lex,
-                                                     &spvar->field_def))
+              if (lex->sphead->fill_field_definition(thd, &spvar->field_def))
               {
                 MYSQL_YYABORT;
               }
@@ -16715,7 +16714,7 @@ sf_tail:
           }
           type_with_opt_collate /* $11 */
           { /* $12 */
-            if (Lex->sphead->fill_field_definition(thd, Lex, Lex->last_field))
+            if (Lex->sphead->fill_field_definition(thd, Lex->last_field))
               MYSQL_YYABORT;
           }
           sp_c_chistics /* $13 */