MDEV-38809 RBR fails upon DML with XML type.

Add Field_xmltype::rpl_conv_type_from() function to control
replication data types.

Author: Alexey Botchkov

plugin/type_xmltype/mysql-test/type_xmltype/type_xmltype_rpl.result

@@ -0,0 +1,11 @@
+include/master-slave.inc
+[connection master]
+CREATE TABLE t1 (a xmltype);
+INSERT INTO t1 VALUES ('<a></a>');
+connection slave;
+SELECT * from t1;
+a
+<a></a>
+connection master;
+DROP TABLE t1;
+include/rpl_end.inc

plugin/type_xmltype/mysql-test/type_xmltype/type_xmltype_rpl.test

@@ -0,0 +1,15 @@
+--source include/have_binlog_format_row.inc
+--source include/master-slave.inc
+ 
+CREATE TABLE t1 (a xmltype);
+INSERT INTO t1 VALUES ('<a></a>');
+ 
+--sync_slave_with_master
+ 
+SELECT * from t1;
+
+--connection master
+DROP TABLE t1;
+ 
+--source include/rpl_end.inc
+

plugin/type_xmltype/sql_type_xmltype.cc

@@ -217,6 +217,37 @@ int Field_xmltype::store(const char *from, size_t length, CHARSET_INFO *cs)
 }
 
 
+/*
+  We allow any string input into the XMLTYPE,
+  as it can fit into LONG BLOB without any loss.
+  But in any case values themselves can be invalid XML-s.
+
+  TODO: when the replication start sending UDT informatio,
+  we should only return CONV_TYPE_PRECISE for the XMLTYPE.
+*/
+enum_conv_type
+Field_xmltype::rpl_conv_type_from(const Conv_source &source,
+                                  const Relay_log_info *rli,
+                                  const Conv_param &param) const
+{
+  const Type_handler *th= source.type_handler();
+  if (th == &type_handler_tiny_blob ||
+      th == &type_handler_medium_blob ||
+      th == &type_handler_long_blob ||
+      th == &type_handler_blob ||
+      th == &type_handler_blob_compressed ||
+      th == &type_handler_string ||
+      th == &type_handler_var_string ||
+      th == &type_handler_varchar ||
+      th == &type_handler_varchar_compressed)
+  {
+    return CONV_TYPE_PRECISE;
+  }
+
+  return CONV_TYPE_IMPOSSIBLE;
+}
+
+
 class Item_xmltype_typecast_func_handler: public Item_handled_func::Handler_str
 {
 public:

plugin/type_xmltype/sql_type_xmltype.h

@@ -119,6 +119,9 @@ class Field_xmltype :public Field_blob
   uint size_of() const  override { return sizeof(*this); }
   int  store(const char *to, size_t length, CHARSET_INFO *charset) override;
   using Field_str::store;
+  enum_conv_type rpl_conv_type_from(const Conv_source &source,
+                                    const Relay_log_info *rli,
+                                    const Conv_param &param) const override;
 };