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, 7 insertions, 1 deletions

diff --git a/include/my_base.h b/include/my_base.h
index 68b3aaa6a13..44af7b45075 100644
--- a/include/my_base.h
+++ b/include/my_base.h
@@ -632,7 +632,13 @@ typedef struct st_key_multi_range
   key_range start_key;
   key_range end_key;
   range_id_t ptr;                 /* Free to use by caller (ptr to row etc) */
-  uint  range_flag;           /* key range flags see above */
+  /*
+    A set of range flags that describe both endpoints: UNIQUE_RANGE,
+    NULL_RANGE, EQ_RANGE, GEOM_FLAG.
+    (Flags that describe one endpoint, NO_{MIN|MAX}_RANGE, NEAR_{MIN|MAX} will
+     not be set here)
+  */
+  uint  range_flag;
 } KEY_MULTI_RANGE;