Bug#21172963 ASSERTION `PARAM.SORT_LENGTH != 0' FAILED IN SQL/FILESORT.CC:361

Tor Didriksen · Tor Didriksen · commit 7effb0f844d4 · 2015-06-16T15:50:59.000+02:00
This affects debug versions only.
The bug was fixed (for order-by-with-limit) by the patch for
Bug #19660891 HANDLE_FATAL_SIGNAL (SIG=11) IN QUEUE_INSERT

Merge-sort uses the same compare function,
and *does* handle zero-length keys during merge sort.
So the DBUG_ASSERT is wrong.
diff --git a/sql/filesort.cc b/sql/filesort.cc
@@ -365,9 +365,6 @@ ha_rows filesort(THD *thd, TABLE *table, Filesort *filesort,
   }
   else
   {
-    /* filesort cannot handle zero-length records during merge. */
-    DBUG_ASSERT(param.sort_length != 0);
-
     if (table_sort.buffpek && table_sort.buffpek_len < maxbuffer)
     {
       my_free(table_sort.buffpek);

Original file line number	Diff line number	Diff line change
`@@ -365,9 +365,6 @@ ha_rows filesort(THD thd, TABLE table, Filesort *filesort,`
`365`	`365`	`}`
`366`	`366`	`else`
`367`	`367`	`{`
`368`		`- /* filesort cannot handle zero-length records during merge. */`
`369`		`- DBUG_ASSERT(param.sort_length != 0);`
`370`		`-`
`371`	`368`	`if (table_sort.buffpek && table_sort.buffpek_len < maxbuffer)`
`372`	`369`	`{`
`373`	`370`	`my_free(table_sort.buffpek);`