bk commit into 5.0 tree (sergefp:1.2008) BUG#15204

[Sergey Petrunia]

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5.0 repository of psergey. When psergey does a push these changes will
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ChangeSet
  1.2008 05/11/25 12:31:47 sergefp@stripped +1 -0
  BUG#15204: in get_best_covering_ror_intersect(), return NULL if we've discovered the the

  first index is already covering (and don't try to construct index_merge index
intersection
  from one index scan). There is no testcase as the bug is not reproducible on small
dataset.

  sql/opt_range.cc
    1.199 05/11/25 12:31:42 sergefp@stripped +4 -4
    BUG#15204: in get_best_covering_ror_intersect(), return NULL if we've discovered the
the 
    first index is already covering (and don't try to construct index_merge index
intersection
    from one index scan)

# This is a BitKeeper patch.  What follows are the unified diffs for the
# set of deltas contained in the patch.  The rest of the patch, the part
# that BitKeeper cares about, is below these diffs.
# User:	sergefp
# Host:	newbox.mylan
# Root:	/home/psergey/mysql-5.0-bug15204

--- 1.198/sql/opt_range.cc	2005-11-20 21:47:00 +03:00
+++ 1.199/sql/opt_range.cc	2005-11-25 12:31:42 +03:00
@@ -3136,10 +3136,10 @@
     /* F=F-covered by first(I) */
     bitmap_union(&covered_fields, &(*ror_scan_mark)->covered_fields);
     all_covered= bitmap_is_subset(&param->needed_fields, &covered_fields);
-  } while (!all_covered && (++ror_scan_mark < ror_scans_end));
-
-  if (!all_covered)
-    DBUG_RETURN(NULL); /* should not happen actually */
+  } while ((++ror_scan_mark < ror_scans_end) && !all_covered);
+  
+  if (!all_covered || (ror_scan_mark - tree->ror_scans) == 1)
+    DBUG_RETURN(NULL);
 
   /*
     Ok, [tree->ror_scans .. ror_scan) holds covering index_intersection with