--- a/src/imap/cmd-thread.c	Fri Jun 20 04:41:03 2008 +0300
+++ b/src/imap/cmd-thread.c	Fri Jun 20 05:29:19 2008 +0300
@@ -141,15 +141,7 @@
 	}
 
 	str = IMAP_ARG_STR(args);
-	if (strcasecmp(str, "REFERENCES") == 0)
-		thread_type = MAIL_THREAD_REFERENCES;
-	else if (strcasecmp(str, "X-REFERENCES2") == 0)
-		thread_type = MAIL_THREAD_REFERENCES2;
-	else if (strcasecmp(str, "ORDEREDSUBJECT") == 0) {
-		client_send_command_error(cmd,
-			"ORDEREDSUBJECT threading is currently not supported.");
-		return TRUE;
-	} else {
+	if (!mail_thread_type_parse(str, &thread_type)) {
 		client_send_command_error(cmd, "Unknown thread algorithm.");
 		return TRUE;
 	}

--- a/src/lib-storage/index/index-thread.c	Fri Jun 20 04:41:03 2008 +0300
+++ b/src/lib-storage/index/index-thread.c	Fri Jun 20 05:29:19 2008 +0300
@@ -8,6 +8,7 @@
 #include "mail-index-private.h"
 #include "mail-index-sync-private.h"
 #include "mail-search.h"
+#include "mail-search-build.h"
 #include "index-storage.h"
 #include "index-thread-private.h"
 
@@ -41,6 +42,17 @@
 static MODULE_CONTEXT_DEFINE_INIT(mail_thread_storage_module,
 				  &mail_storage_module_register);
 
+bool mail_thread_type_parse(const char *str, enum mail_thread_type *type_r)
+{
+	if (strcasecmp(str, "REFERENCES") == 0)
+		*type_r = MAIL_THREAD_REFERENCES;
+	else if (strcasecmp(str, "X-REFERENCES2") == 0)
+		*type_r = MAIL_THREAD_REFERENCES2;
+	else
+		return FALSE;
+	return TRUE;
+}
+
 static unsigned int mail_thread_hash_key(const void *key)
 {
 	const struct msgid_search_key *key_rec = key;
@@ -413,6 +425,13 @@
 
 	i_assert(tbox->ctx == NULL);
 
+	if (args != NULL)
+		mail_search_args_ref(args);
+	else {
+		args = mail_search_build_init();
+		mail_search_build_add_all(args);
+	}
+
 	ctx = i_new(struct mail_thread_context, 1);
 	tbox->ctx = &ctx->thread_ctx;
 	ctx->box = box;
@@ -421,6 +440,9 @@
 	while ((ret = mail_thread_update(ctx, reset)) < 0) {
 		if (ctx->thread_ctx.hash == tbox->hash) {
 			/* failed with in-memory hash */
+			mail_storage_set_critical(box->storage,
+				"Threading mailbox %s failed unexpectedly",
+				box->name);
 			mail_thread_deinit(&ctx);
 			return -1;
 		}
@@ -436,15 +458,6 @@
 	return 0;
 }
 
-struct mail_thread_iterate_context *
-mail_thread_iterate_init(struct mail_thread_context *ctx,
-			 enum mail_thread_type thread_type, bool write_seqs)
-{
-	return mail_thread_iterate_init_full(ctx->thread_ctx.tmp_mail,
-					     ctx->thread_ctx.hash_trans,
-					     thread_type, write_seqs);
-}
-
 void mail_thread_deinit(struct mail_thread_context **_ctx)
 {
 	struct mail_thread_context *ctx = *_ctx;
@@ -468,9 +481,20 @@
 
 	array_free(&ctx->thread_ctx.msgid_cache);
 	pool_unref(&ctx->thread_ctx.msgid_pool);
- 
+	mail_search_args_unref(&ctx->search_args);
+
  	i_assert(!tbox->ctx->syncing);
  	tbox->ctx = NULL;
+	i_free(ctx);
+}
+
+struct mail_thread_iterate_context *
+mail_thread_iterate_init(struct mail_thread_context *ctx,
+			 enum mail_thread_type thread_type, bool write_seqs)
+{
+	return mail_thread_iterate_init_full(ctx->thread_ctx.tmp_mail,
+					     ctx->thread_ctx.hash_trans,
+					     thread_type, write_seqs);
 }
 
 static bool

--- a/src/lib-storage/mail-thread.h	Fri Jun 20 04:41:03 2008 +0300
+++ b/src/lib-storage/mail-thread.h	Fri Jun 20 05:29:19 2008 +0300
@@ -1,6 +1,8 @@
 #ifndef MAIL_THREAD_H
 #define MAIL_THREAD_H
 
+struct mailbox;
+struct mail_search_args;
 struct mail_thread_context;
 
 enum mail_thread_type {
@@ -20,8 +22,12 @@
 };
 ARRAY_DEFINE_TYPE(mail_thread_child_node, struct mail_thread_child_node);
 
+/* Convert thread type string to enum. Returns TRUE if ok, FALSE if type is
+   unknown. */
+bool mail_thread_type_parse(const char *str, enum mail_thread_type *type_r);
+
 /* Build thread from given search arguments. If reset=TRUE, build a new thread
-   tree to memory even if thread index exists. */
+   tree to memory even if thread index exists. args=NULL searches everything. */
 int mail_thread_init(struct mailbox *box, bool reset,
 		     struct mail_search_args *args,
 		     struct mail_thread_context **ctx_r);