Bug #32374 crash with filesort when selecting from federated table and view.

filesort() uses file->estimate_rows_upper_bound() call to allocate
internal buffers. If this function returns a value smaller than
a number of row that will be returned later in find_all_keys(),
that can cause server crash.
Fixed by implementing ha_federated::estimate_rows_upper_bound() to
return maximum possible number of rows.
Present estimation for FEDERATED always returns 0 if the linked to the VIEW.


mysql-test/r/federated.result:
  Bug #32374 crash with filesort when selecting from federated table and view.
  
  test result
mysql-test/t/federated.test:
  Bug #32374 crash with filesort when selecting from federated table and view.
  
  test case
sql/ha_federated.cc:
  Bug #32374 crash with filesort when selecting from federated table and view.
  
  ha_federated::estimate_rows_upper_bound() implemented
sql/ha_federated.h:
  Bug #32374 crash with filesort when selecting from federated table and view.
  
  ha_federated::estimate_rows_upper_bound() interface

1 files changed, 18 insertions, 0 deletions

diff --git a/sql/ha_federated.cc b/sql/ha_federated.cc
index d7f2309657b..ac1e0962ffb 100644
--- a/sql/ha_federated.cc
+++ b/sql/ha_federated.cc
@@ -2166,6 +2166,24 @@ error:
 }
 
 
+/*
+  This method is used exlusevely by filesort() to check if we
+  can create sorting buffers of necessary size.
+  If the handler returns more records that it declares
+  here server can just crash on filesort().
+  We cannot guarantee that's not going to happen with
+  the FEDERATED engine, as we have records==0 always if the
+  client is a VIEW, and for the table the number of
+  records can inpredictably change during execution.
+  So we return maximum possible value here.
+*/
+
+ha_rows ha_federated::estimate_rows_upper_bound()
+{
+  return HA_POS_ERROR;
+}
+
+
 /* Initialized at each key walk (called multiple times unlike rnd_init()) */
 
 int ha_federated::index_init(uint keynr)