Fix Bug#30423 "InnoDBs treatment of NULL in index stats causes bad

"rows examined" estimates". This change implements "innodb_stats_method"
with options of "nulls_equal", "nulls_unequal" and "null_ignored".
      
rb://553 approved by Marko

1 files changed, 6 insertions, 0 deletions

diff --git a/storage/innobase/include/dict0mem.h b/storage/innobase/include/dict0mem.h
index 2f2a7441478..83dbf65ea41 100644
--- a/storage/innobase/include/dict0mem.h
+++ b/storage/innobase/include/dict0mem.h
@@ -222,6 +222,12 @@ struct dict_index_struct{
 				for this index, for each n-column prefix
 				where n <= dict_get_n_unique(index); we
 				periodically calculate new estimates */
+	ib_longlong*	stat_n_non_null_key_vals;
+				/* approximate number of non-null key values
+				for this index, for each column where
+				n < dict_get_n_unique(index); This
+				is used when innodb_stats_method is
+				"nulls_ignored". */
 	ulint		stat_index_size;
 				/* approximate index size in database pages */
 	ulint		stat_n_leaf_pages;