Bug#31590: Wrong error message on sort buffer being too small.

The out of memory error was thrown when the sort buffer size were too small.
This led to a user confusion.

Now filesort throws the error message about sort buffer being too small.

mysql-test/r/order_by.result

@@ -1064,3 +1064,15 @@ a	b
 10	00:00:10
 0	00:00:00
 DROP TABLE t1;
+#
+# Bug#31590: Wrong error message on sort buffer being too small.
+#
+create table t1(a int, b tinytext);
+insert into t1 values (1,2),(3,2);
+set session sort_buffer_size= 30000;
+Warnings:
+Warning	1292	Truncated incorrect sort_buffer_size value: '30000'
+set session max_sort_length= 2180;
+select * from t1 order by b;
+ERROR HY001: Out of sort memory; increase server sort buffer size
+drop table t1;

mysql-test/t/order_by.test

@@ -726,3 +726,15 @@ SELECT a, b FROM t1 ORDER BY b DESC;
 SELECT a, b FROM t1 ORDER BY SEC_TO_TIME(a) DESC;
 
 DROP TABLE t1;
+
+--echo #
+--echo # Bug#31590: Wrong error message on sort buffer being too small.
+--echo #
+create table t1(a int, b tinytext);
+insert into t1 values (1,2),(3,2);
+set session sort_buffer_size= 30000;
+set session max_sort_length= 2180;
+--error 1038
+select * from t1 order by b;
+drop table t1;
+

sql/filesort.cc

@@ -215,8 +215,7 @@ ha_rows filesort(THD *thd, TABLE *table, SORT_FIELD *sortorder, uint s_length,
   sort_keys= table_sort.sort_keys;
   if (memavl < min_sort_memory)
   {
-    my_error(ER_OUTOFMEMORY,MYF(ME_ERROR+ME_WAITTANG),
-	     thd->variables.sortbuff_size);
+    my_error(ER_OUT_OF_SORTMEMORY,MYF(ME_ERROR+ME_WAITTANG));
     goto err;
   }
   if (open_cached_file(&buffpek_pointers,mysql_tmpdir,TEMP_PREFIX,