remove from tail of filelist on modern postgres

Modern postgres actually uses array as List implementation. Therefore, removing element from head is quite expensive.

Author: funny-falcon

ptrack.c

@@ -402,12 +402,21 @@ ptrack_filelist_getnext(PtScanCtx * ctx)
 if (list_length(ctx->filelist) == 0)
 return -1;
 
+#ifdef foreach_current_index
+/* Get first file from the head */
+cell = list_tail(ctx->filelist);
+pfl = (PtrackFileList_i *) lfirst(cell);
+
+/* Remove this file from the list */
+ctx->filelist = list_delete_last(ctx->filelist);
+#else
 /* Get first file from the head */
 cell = list_head(ctx->filelist);
 pfl = (PtrackFileList_i *) lfirst(cell);
 
 /* Remove this file from the list */
 ctx->filelist = list_delete_first(ctx->filelist);
+#endif
 
 if (pfl->segno > 0)
 {