Fix for BUG#16211: Stored function return type for strings is ignored.

Fix for BUG#16676: Database CHARSET not used for stored procedures

The problem in BUG#16211 is that CHARSET-clause of the return type for
stored functions is just ignored.

The problem in BUG#16676 is that if character set is not explicitly
specified for sp-variable, the server character set is used instead
of the database one.

The fix has two parts:

  - always store CHARSET-clause of the return type along with the
    type definition in mysql.proc.returns column. "Always" means that
    CHARSET-clause is appended even if it has not been explicitly
    specified in CREATE FUNCTION statement (this affects BUG#16211 only).

    Storing CHARSET-clause if it is not specified is essential to avoid
    changing character set if the database character set is altered in
    the future.

    NOTE: this change is not backward compatible with the previous releases.

  - use database default character set if CHARSET-clause is not explicitly
    specified (this affects both BUG#16211 and BUG#16676).

    NOTE: this also breaks backward compatibility.


mysql-test/r/mysqldump.result:
  Updated result file.
mysql-test/r/sp.result:
  Updated result file.
mysql-test/t/sp.test:
  Provided test cases for BUG#16211, BUG#16676.
sql/mysql_priv.h:
  Added two convenient functions for work with databases.
sql/sp.cc:
  1. Add CHARSET-clause to CREATE-statement if it has been explicitly specified.
  2. Polishing -- provided some comments.
sql/sp_head.cc:
  Use database charset as default charset of sp-variable.
sql/sp_head.h:
  Move init_sp_name() out of init_strings().
sql/sql_db.cc:
  Two new functions created:
    - load_db_opt_by_name();
    - check_db_dir_existence();
sql/sql_show.cc:
  Eliminate duplicated code by using
  check_db_dir_existence() and load_db_opt_by_name()
sql/sql_table.cc:
  Eliminate duplicated code by using
  check_db_dir_existence() and load_db_opt_by_name()
sql/sql_yacc.yy:
  Call sp_head::init_sp_name() to initialize stored routine name.

sql/sql_db.cc

@@ -295,7 +295,6 @@ static bool write_db_opt(THD *thd, const char *path, HA_CREATE_INFO *create)
   create	Where to store the read options
 
   DESCRIPTION
-    For now, only default-character-set is read.
 
   RETURN VALUES
   0	File found
@@ -383,6 +382,50 @@ err1:
 }
 
 
+/*
+  Retrieve database options by name. Load database options file or fetch from
+  cache.
+
+  SYNOPSIS
+    load_db_opt_by_name()
+    db_name         Database name
+    db_create_info  Where to store the database options
+
+  DESCRIPTION
+    load_db_opt_by_name() is a shortcut for load_db_opt().
+
+  NOTE
+    Although load_db_opt_by_name() (and load_db_opt()) returns status of
+    the operation, it is useless usually and should be ignored. The problem
+    is that there are 1) system databases ("mysql") and 2) virtual
+    databases ("information_schema"), which do not contain options file.
+    So, load_db_opt[_by_name]() returns FALSE for these databases, but this
+    is not an error.
+
+    load_db_opt[_by_name]() clears db_create_info structure in any case, so
+    even on failure it contains valid data. So, common use case is just
+    call load_db_opt[_by_name]() without checking return value and use
+    db_create_info right after that.
+
+  RETURN VALUES (read NOTE!)
+    FALSE   Success
+    TRUE    Failed to retrieve options
+*/
+
+bool load_db_opt_by_name(THD *thd, const char *db_name,
+                         HA_CREATE_INFO *db_create_info)
+{
+  char db_opt_path[FN_REFLEN];
+
+  strxnmov(db_opt_path, sizeof (db_opt_path) - 1, mysql_data_home, "/",
+           db_name, "/", MY_DB_OPT_FILE, NullS);
+
+  unpack_filename(db_opt_path, db_opt_path);
+
+  return load_db_opt(thd, db_opt_path, db_create_info);
+}
+
+
 /*
   Create a database
 
@@ -1126,8 +1169,6 @@ bool mysql_change_db(THD *thd, const char *name, bool no_access_check)
 {
   int path_length, db_length;
   char *db_name;
-  char	path[FN_REFLEN];
-  HA_CREATE_INFO create;
   bool system_db= 0;
 #ifndef NO_EMBEDDED_ACCESS_CHECKS
   ulong db_access;
@@ -1196,16 +1237,14 @@ bool mysql_change_db(THD *thd, const char *name, bool no_access_check)
     }
   }
 #endif
-  (void) sprintf(path,"%s/%s", mysql_data_home, db_name);
-  path_length= unpack_dirname(path, path);      // Convert if not UNIX
-  if (path_length && path[path_length-1] == FN_LIBCHAR)
-    path[path_length-1]= '\0';                  // remove ending '\'
-  if (my_access(path,F_OK))
+
+  if (check_db_dir_existence(db_name))
   {
     my_error(ER_BAD_DB_ERROR, MYF(0), db_name);
     my_free(db_name, MYF(0));
     DBUG_RETURN(1);
   }
+
 end:
   x_free(thd->db);
   DBUG_ASSERT(db_name == NULL || db_name[0] != '\0');
@@ -1221,8 +1260,10 @@ end:
   }
   else
   {
-    strmov(path+unpack_dirname(path,path), MY_DB_OPT_FILE);
-    load_db_opt(thd, path, &create);
+    HA_CREATE_INFO create;
+
+    load_db_opt_by_name(thd, db_name, &create);
+
     thd->db_charset= create.default_table_charset ?
       create.default_table_charset :
       thd->variables.collation_server;
@@ -1230,3 +1271,36 @@ end:
   }
   DBUG_RETURN(0);
 }
+
+
+/*
+  Check if there is directory for the database name.
+
+  SYNOPSIS
+    check_db_dir_existence()
+    db_name   database name
+
+  RETURN VALUES
+    FALSE   There is directory for the specified database name.
+    TRUE    The directory does not exist.
+*/
+
+bool check_db_dir_existence(const char *db_name)
+{
+  char db_dir_path[FN_REFLEN];
+  uint db_dir_path_len;
+
+  strxnmov(db_dir_path, sizeof (db_dir_path) - 1, mysql_data_home, "/",
+           db_name, NullS);
+
+  db_dir_path_len= unpack_dirname(db_dir_path, db_dir_path);
+
+  /* Remove trailing '/' or '\' if exists. */
+
+  if (db_dir_path_len && db_dir_path[db_dir_path_len - 1] == FN_LIBCHAR)
+    db_dir_path[db_dir_path_len - 1]= 0;
+
+  /* Check access. */
+
+  return my_access(db_dir_path, F_OK);
+}