MDEV-22401: Optimizer trace: multi-component range is not printed correctly

KEY_MULTI_RANGE::range_flag does not have correct flag bits for
per-endpoint flags (NEAR_MIN, NEAR_MAX, NO_MIN_RANGE, NO_MAX_RANGE).
It only has bits for flags that describe both endpoints.
So
- Document this.
- Switch optimizer trace to using {start|end}_key.flag values, instead.
  This fixes the bug.
- Switch records_in_column_ranges() to doing that too. (This used to
  work, because KEY_MULTI_RANGE::range_flag had correct flag value
  for the last key component, and EITS only uses one-component
  pseudo-indexes)

1 files changed, 1 insertions, 1 deletions

diff --git a/sql/opt_range_mrr.cc b/sql/opt_range_mrr.cc
index 4afa06a7ca0..267d764bb3b 100644
--- a/sql/opt_range_mrr.cc
+++ b/sql/opt_range_mrr.cc
@@ -262,7 +262,6 @@ walk_up_n_right:
   else
   {
     max_key_parts= MY_MAX(cur->min_key_parts, cur->max_key_parts);
-    range->range_flag= cur->min_key_flag | cur->max_key_flag;
     
     range->start_key.key=    seq->param->min_key;
     range->start_key.length= (uint)(cur->min_key - seq->param->min_key);
@@ -298,6 +297,7 @@ walk_up_n_right:
         !memcmp(seq->param->min_key, seq->param->max_key,    // (2)
                 range->start_key.length);
 
+    range->range_flag= 0;
     if (is_eq_range_pred)
     {
       range->range_flag = EQ_RANGE;