MDEV-20611: MRR scan over partitioned InnoDB table produces "Out of memory" error

Fix partitioning and DS-MRR to work together

- In ha_partition::index_end(): take into account that ha_innobase (and
  other engines using DS-MRR) will have inited=RND when initialized for
  DS-MRR scan.
- In ha_partition::multi_range_read_next(): if the MRR scan is using
  HA_MRR_NO_ASSOCIATION mode, it is not guaranteed that the partition's
  handler will store anything into *range_info.
- In DsMrr_impl::choose_mrr_impl(): ha_partition will inquire partitions
  about how much memory their MRR implementation needs by passing
  *buffer_size=0. DS-MRR code didn't know about this (actually it used
  uint for buffer size calculation and would have an under-flow).
  Returning *buffer_size=0 made ha_partition assume that partitions do
  not need MRR memory and pass the same buffer to each of them.

  Now, this is fixed. If DS-MRR gets *buffer_size=0, it will return
  the amount of buffer space needed, but not more than about
  @@mrr_buffer_size.

* Fix ha_{innobase,maria,myisam}::clone. If ha_partition uses MRR on its
  partitions, and partition use DS-MRR, the code will call handler->clone
  with TABLE (*NOT partition*) name as an argument.
  DS-MRR has no way of knowing the partition name, so the solution was
  to have the ::clone() function for the affected storage engine to ignore
  the name argument and get it elsewhere.

1 files changed, 12 insertions, 2 deletions

diff --git a/sql/ha_partition.cc b/sql/ha_partition.cc
index ccda01de6b7..09664deb458 100644
--- a/sql/ha_partition.cc
+++ b/sql/ha_partition.cc
@@ -5478,6 +5478,13 @@ int ha_partition::index_end()
       if ((tmp= (*file)->ha_index_end()))
         error= tmp;
     }
+    else if ((*file)->inited == RND)
+    {
+      // Possible due to MRR
+      int tmp;
+      if ((tmp= (*file)->ha_rnd_end()))
+        error= tmp;
+    }
   } while (*(++file));
   destroy_record_priority_queue();
   DBUG_RETURN(error);
@@ -6519,8 +6526,11 @@ int ha_partition::multi_range_read_next(range_id_t *range_info)
     else if (unlikely((error= handle_unordered_next(table->record[0], FALSE))))
       DBUG_RETURN(error);
 
-    *range_info=
-      ((PARTITION_KEY_MULTI_RANGE *) m_range_info[m_last_part])->ptr;
+    if (!(m_mrr_mode & HA_MRR_NO_ASSOCIATION))
+    {
+      *range_info=
+        ((PARTITION_KEY_MULTI_RANGE *) m_range_info[m_last_part])->ptr;
+    }
   }
   DBUG_RETURN(0);
 }