MDEV-17761: Odd optimizer choice with ORDER BY LIMIT and condition selectivity

Make the "ORDER BY ... LIMIT n" optimizer take into account condition
selectivity data from EITS (not just from potential range accesses).

1 files changed, 17 insertions, 0 deletions

diff --git a/mysql-test/main/range_vs_index_merge.test b/mysql-test/main/range_vs_index_merge.test
index 84b87579e85..762fb481b39 100644
--- a/mysql-test/main/range_vs_index_merge.test
+++ b/mysql-test/main/range_vs_index_merge.test
@@ -718,6 +718,23 @@ SELECT * FROM City
 ORDER BY Population LIMIT 5;
 SHOW STATUS LIKE 'Handler_read_%';
 
+set @tmp_mdev585=@@optimizer_use_condition_selectivity;
+set optimizer_use_condition_selectivity=1;
+--replace_column 9 #
+EXPLAIN 
+SELECT * FROM City
+  WHERE ((Name > 'Ca' AND Name < 'Cf') OR (Country > 'E' AND Country < 'H'))
+        AND (Population >= 100000 AND Population < 120000)
+ORDER BY Population LIMIT 5;
+
+FLUSH STATUS;
+SELECT * FROM City
+  WHERE ((Name > 'Ca' AND Name < 'Cf') OR (Country > 'E' AND Country < 'H'))
+        AND (Population >= 100000 AND Population < 120000)
+ORDER BY Population LIMIT 5;
+SHOW STATUS LIKE 'Handler_read_%';
+
+set optimizer_use_condition_selectivity=@tmp_mdev585;
 
 set optimizer_switch='index_merge=off';