Implement MarkM optimization request to avoid redundnat packet exchange

in cursors.


libmysql/libmysql.c:
  - reset_stmt_handle(): don't reset the server side just because we have 
    an open cursor: the server will close the cursor automatically if 
    needed
sql/sql_prepare.cc:
  - implement Prepared_statement::close_cursor,
  - implicitly close an open cursor in mysql_stmt_execute instead of 
    issuing an error (to reduce the need to explicitly close cursors
    and save network bandwidth).
  - cleanup
sql/sql_select.cc:
  Remove a destructor: cursor destruction can not be done by simply
  calling a destructor, because of cross-references between cursor
  and statement memory.
sql/sql_select.h:
  - add an empty Cursor destructor
tests/mysql_client_test.c:
  - remove a test for dropped functionality

1 files changed, 2 insertions, 3 deletions

diff --git a/libmysql/libmysql.c b/libmysql/libmysql.c
index 2074abd0f85..a896460beeb 100644
--- a/libmysql/libmysql.c
+++ b/libmysql/libmysql.c
@@ -4907,13 +4907,12 @@ static my_bool reset_stmt_handle(MYSQL_STMT *stmt, uint flags)
   {
     MYSQL *mysql= stmt->mysql;
     MYSQL_DATA *result= &stmt->result;
-    my_bool has_cursor= stmt->read_row_func == stmt_read_row_from_cursor;
 
     /*
       Reset stored result set if so was requested or it's a part
       of cursor fetch.
     */
-    if (result->data && (has_cursor || (flags & RESET_STORE_RESULT)))
+    if (result->data && (flags & RESET_STORE_RESULT))
     {
       /* Result buffered */
       free_root(&result->alloc, MYF(MY_KEEP_PREALLOC));
@@ -4944,7 +4943,7 @@ static my_bool reset_stmt_handle(MYSQL_STMT *stmt, uint flags)
           mysql->status= MYSQL_STATUS_READY;
         }
       }
-      if (has_cursor || (flags & RESET_SERVER_SIDE))
+      if (flags & RESET_SERVER_SIDE)
       {
         /*
           Reset the server side statement and close the server side