Fixes and test cases for Bug#8880 "Commands out of sync error with cursors"

 and Bug#9159 "Server crash during mysql_stmt_close".
The patch adds support for single-row result sets in cursors.


libmysql/libmysql.c:
  If we wanted a cursor, and the server wasn't able to create one,
  buffer all rows on client. Currently this is possible only for
  single row result sets and some SHOW commands.
sql/sql_prepare.cc:
  Properly free resources if there was a request to open a cursor which
  wasn't fullfilled.
  Give error on attempt to open a cursor for a statement not returning
  a result set.
sql/sql_select.h:
  Initialize Item_arena of Cursor object. A case when a cursor object
  is created but not used is possible with single-row result sets.
tests/mysql_client_test.c:
  Test cases for Bug#8880 and Bug#9159

1 files changed, 11 insertions, 0 deletions

diff --git a/libmysql/libmysql.c b/libmysql/libmysql.c
index 9746cb222fa..47a15dd3fe3 100644
--- a/libmysql/libmysql.c
+++ b/libmysql/libmysql.c
@@ -2862,6 +2862,17 @@ int STDCALL mysql_stmt_execute(MYSQL_STMT *stmt)
       mysql->status= MYSQL_STATUS_READY;
       stmt->read_row_func= stmt_read_row_from_cursor;
     }
+    else if (stmt->flags & CURSOR_TYPE_READ_ONLY)
+    {
+      /*
+        This is a single-row result set, a result set with no rows, EXPLAIN,
+        SHOW VARIABLES, or some other command which either a) bypasses the
+        cursors framework in the server and writes rows directly to the
+        network or b) is more efficient if all (few) result set rows are
+        precached on client and server's resources are freed.
+      */
+      DBUG_RETURN(mysql_stmt_store_result(stmt));
+    }
     else
     {
       stmt->mysql->unbuffered_fetch_owner= &stmt->unbuffered_fetch_cancelled;