MDEV-17067 Server crash in write_block_record

Problem was that Create_field::create_length_to_internal_length()
calculated a different pack_length for NEWDECIMAL compared to
Field_new_decimal constructor which lead to some unused bytes
in the middle of the record, which Aria didn't like.

mysql-test/suite/maria/create.result

@@ -24,3 +24,10 @@ INSERT IGNORE INTO t1 (f1,f2,f3,f4,f5,f6,f7,f8,f9,f10,f11,f12) VALUES
 Warnings:
 Note	1265	Data truncated for column 'f1' at row 1
 DROP TABLE t1;
+CREATE OR REPLACE TABLE t1 (a INT(45));
+INSERT IGNORE INTO t1 VALUES (1),(2);
+CREATE OR REPLACE TABLE t2 ENGINE=Aria AS SELECT SUM(a) AS f1, IFNULL( 'qux', ExtractValue( 'foo', 'bar' ) ) AS f2 FROM t1;
+select * from t2;
+f1	f2
+3	qux
+DROP TABLE t1, t2;

mysql-test/suite/maria/create.test

@@ -29,3 +29,14 @@ CREATE OR REPLACE TABLE t1 (
 INSERT IGNORE INTO t1 (f1,f2,f3,f4,f5,f6,f7,f8,f9,f10,f11,f12) VALUES
  (0.8,'16:01:46',NULL,'2006-03-01 12:44:34','2029-10-10 21:27:53','a','foo','1989-12-24','bar',9,1975,b'1');
 DROP TABLE t1;
+
+#
+# MDEV-17067 Server crash in write_block_record
+#
+
+CREATE OR REPLACE TABLE t1 (a INT(45));
+INSERT IGNORE INTO t1 VALUES (1),(2);
+
+CREATE OR REPLACE TABLE t2 ENGINE=Aria AS SELECT SUM(a) AS f1, IFNULL( 'qux', ExtractValue( 'foo', 'bar' ) ) AS f2 FROM t1;
+select * from t2;
+DROP TABLE t1, t2;

sql/field.cc

@@ -9065,13 +9065,18 @@ void Create_field::create_length_to_internal_length(void)
     }
     break;
   case MYSQL_TYPE_NEWDECIMAL:
-    key_length= pack_length=
-      my_decimal_get_binary_size(my_decimal_length_to_precision(length,
-								decimals,
-								flags &
-								UNSIGNED_FLAG),
-				 decimals);
+  {
+    /*
+      This code must be identical to code in
+      Field_new_decimal::Field_new_decimal as otherwise the record layout
+      gets out of sync.
+    */
+    uint precision= my_decimal_length_to_precision(length, decimals,
+                                                   flags & UNSIGNED_FLAG);
+    set_if_smaller(precision, DECIMAL_MAX_PRECISION);
+    key_length= pack_length= my_decimal_get_binary_size(precision, decimals);
     break;
+  }
   default:
     key_length= pack_length= calc_pack_length(sql_type, length);
     break;