MDEV-18478 ANALYZE for statement should show selectivity of ICP, part#3

Fix the previous patch:
- Only enable handler_stats if thd->should_collect_handler_stats()==true.
- Make handler_index_cond_check() work when handler_stats are not enabled.

sql/handler.cc

@@ -6995,7 +6995,6 @@ extern "C" check_result_t handler_index_cond_check(void* h_arg)
  check_result_t res;
 
  DEBUG_SYNC(thd, "handler_index_cond_check");
- DBUG_ASSERT(h->handler_stats);
 
  enum thd_kill_levels killed= thd_kill_level(thd);
  if (unlikely(killed != THD_IS_NOT_KILLED))
@@ -7009,13 +7008,15 @@ extern "C" check_result_t handler_index_cond_check(void* h_arg)
  if (unlikely(h->end_range) && h->compare_key2(h->end_range) > 0)
  return CHECK_OUT_OF_RANGE;
  h->increment_statistics(&SSV::ha_icp_attempts);
- h->handler_stats->icp_attempts++;
+ if (unlikely(h->handler_stats))
+ h->handler_stats->icp_attempts++;
  res= CHECK_NEG;
  if (h->pushed_idx_cond->val_int())
  {
  res= CHECK_POS;
  h->fast_increment_statistics(&SSV::ha_icp_match);
- h->handler_stats->icp_match++;
+ if (unlikely(h->handler_stats))
+ h->handler_stats->icp_match++;
  }
  return res;
 }

sql/table.cc

@@ -5871,7 +5871,11 @@ void TABLE::init(THD *thd, TABLE_LIST *tl)
  (*f_ptr)->cond_selectivity= 1.0;
  }
 
- file->ha_handler_stats_reset();
+ /* enable and clear or disable engine query statistics */
+ if (thd->should_collect_handler_stats())
+ file->ha_handler_stats_reset();
+ else
+ file->ha_handler_stats_disable();
 
  notnull_cond= 0;
  DBUG_ASSERT(!file->keyread_enabled());