MDEV-35307 Unexpected error WARN_SORTING_ON_TRUNCATED_LENGTH or assertion failure in diagnostics area #2

When strict mode is enabled, all warnings during `INSERT` are
converted to errors regardless of their actual severity.
`WARN_SORTING_ON_TRUNCATED_LENGTH` is not considered severe enough
to be elevated to the ERROR level, and this commit fixes that

mysql-test/suite/sys_vars/r/max_sort_length_func.result

@@ -513,6 +513,16 @@ select a from t1;
 a
 3
 drop table t1;
+#
+# MDEV-35307 Unexpected WARN_SORTING_ON_TRUNCATED_LENGTH or assertion
+#            failure in diagnostics area #2
+#
+create table t1 (a varchar(1024)) engine=innodb;
+insert into t1 values (repeat('a',1000)),(repeat('b',1000));
+insert into t1 (a) select a from t1 order by a;
+Warnings:
+Warning	4202	2 values were longer than max_sort_length. Sorting used only the first 70 bytes
+drop table t1;
 connection default;
 disconnect test_con1;
 disconnect test_con2;

mysql-test/suite/sys_vars/t/max_sort_length_func.test

@@ -303,6 +303,19 @@ select a from t1;
 
 drop table t1;
 
+--echo #
+--echo # MDEV-35307 Unexpected WARN_SORTING_ON_TRUNCATED_LENGTH or assertion
+--echo #            failure in diagnostics area #2
+--echo #
+
+--source include/have_innodb.inc
+
+create table t1 (a varchar(1024)) engine=innodb;
+insert into t1 values (repeat('a',1000)),(repeat('b',1000));
+insert into t1 (a) select a from t1 order by a;
+
+drop table t1;
+
 #
 # Cleanup
 #

sql/sql_class.cc

@@ -8632,6 +8632,32 @@ error:
 
 }
 
+
+/*
+  Push post-execution warnings, which may be some kinds of aggregate messages
+  like number of times max_sort_length was reached during sorting/grouping
+*/
+void THD::push_final_warnings()
+{
+  if (num_of_strings_sorted_on_truncated_length)
+  {
+    /*
+      WARN_SORTING_ON_TRUNCATED_LENGTH is not considered important enough to be
+      elevated to the ERROR level, so reset abort_on_warning flag before pushing
+    */
+    bool saved_abort_on_warning= abort_on_warning;
+    abort_on_warning= false;
+    push_warning_printf(this, Sql_condition::WARN_LEVEL_WARN,
+                        WARN_SORTING_ON_TRUNCATED_LENGTH,
+                        ER_THD(this, WARN_SORTING_ON_TRUNCATED_LENGTH),
+                        num_of_strings_sorted_on_truncated_length,
+                        variables.max_sort_length);
+    num_of_strings_sorted_on_truncated_length= 0;
+    abort_on_warning= saved_abort_on_warning;
+  }
+}
+
+
 void AUTHID::copy(MEM_ROOT *mem_root, const LEX_CSTRING *user_name,
                                       const LEX_CSTRING *host_name)
 {

sql/sql_class.h

@@ -6067,23 +6067,7 @@ public:
   bool need_report_unit_results();
   bool report_collected_unit_results();
   bool init_collecting_unit_results();
-
+  void push_final_warnings();
-  /*
-    Push post-execution warnings, which may be some kinds of aggregate messages
-    like number of times max_sort_length was reached during sorting/grouping
-  */
-  void push_final_warnings()
-  {
-    if (num_of_strings_sorted_on_truncated_length)
-    {
-      push_warning_printf(this, Sql_condition::WARN_LEVEL_WARN,
-                          WARN_SORTING_ON_TRUNCATED_LENGTH,
-                          ER_THD(this, WARN_SORTING_ON_TRUNCATED_LENGTH),
-                          num_of_strings_sorted_on_truncated_length,
-                          variables.max_sort_length);
-      num_of_strings_sorted_on_truncated_length= 0;
-    }
-  }
 };