Fix for BUG#5117:

 * Renamed handler::estimate_number_of_rows to handler::estimate_rows_upper_bound function, which can also return "unknown"
 * made filesort to use full sort buffer if number of rows to sort is not known.

1 files changed, 9 insertions, 1 deletions

diff --git a/sql/handler.h b/sql/handler.h
index 4bb1d66eef3..073bb688077 100644
--- a/sql/handler.h
+++ b/sql/handler.h
@@ -300,7 +300,15 @@ public:
   virtual const key_map *keys_to_use_for_scanning() { return &key_map_empty; }
   virtual bool has_transactions(){ return 0;}
   virtual uint extra_rec_buf_length() { return 0; }
-  virtual ha_rows estimate_number_of_rows() { return records+EXTRA_RECORDS; }
+  
+  /*
+    Return upper bound of current number of records in the table
+    (max. of how many records one will retrieve when doing a full table scan)
+    If upper bound is not known, HA_POS_ERROR should be returned as a max
+    possible upper bound.
+  */
+  virtual ha_rows estimate_rows_upper_bound()
+  { return records+EXTRA_RECORDS; }
 
   virtual const char *index_type(uint key_number) { DBUG_ASSERT(0); return "";}