MDEV-23644 Assertion on evaluating foreign referential action for self-reference in system versioned table

First part of the fix (row0mysql.cc) addresses external columns when adding history
row on referential action. The full data must be retrieved before the
row is inserted.

Second part of the fix (the rest) avoids duplicate primary key error between
the history row generated on referential action and the history row
generated by SQL command. Both command and referential action can
happen on same table since foreign key can be self-reference (parent
and child tables are same). Moreover, the self-reference can refer
multiple rows when the key is non-unique. In such case history is
generated by referential action occured on first row but processed all
rows by a matched key. The second round is when the next row is
processed by a command but history already exists. In such case we
check TRX_ID of existing history row and if it is the same we assume
the above situation and skip adding one more history row or failing
the command.

1 files changed, 9 insertions, 1 deletions

diff --git a/sql/sql_delete.cc b/sql/sql_delete.cc
index 929455977e6..0857c4e5457 100644
--- a/sql/sql_delete.cc
+++ b/sql/sql_delete.cc
@@ -246,7 +246,15 @@ int TABLE::delete_row()
 
   store_record(this, record[1]);
   vers_update_end();
-  return file->ha_update_row(record[1], record[0]);
+  int err= file->ha_update_row(record[1], record[0]);
+  /*
+     MDEV-23644: we get HA_ERR_FOREIGN_DUPLICATE_KEY iff we already got history
+     row with same trx_id which is the result of foreign key action, so we
+     don't need one more history row.
+  */
+  if (err == HA_ERR_FOREIGN_DUPLICATE_KEY)
+    return file->ha_delete_row(record[0]);
+  return err;
 }