X-Git-Url: https://git.notmuchmail.org/git?a=blobdiff_plain;f=lib%2Fnotmuch-private.h;h=5a0cf92540619ff5fa50951c5326c84e191051b8;hb=029830c1f130b3780684d056c01a73061090f15f;hp=f9774a4853e6dd561cbefe60bb0beaa44b852c12;hpb=98845fdbb2a4acaa0036f8e2e998e726b18e6b13;p=notmuch

diff --git a/lib/notmuch-private.h b/lib/notmuch-private.h
index f9774a48..5a0cf925 100644
--- a/lib/notmuch-private.h
+++ b/lib/notmuch-private.h
@@ -108,6 +108,16 @@ typedef enum {
  * programmatically. */
 #define NOTMUCH_TERM_MAX 245
 
+#define NOTMUCH_METADATA_THREAD_ID_PREFIX "thread_id_"
+
+/* For message IDs we have to be even more restrictive. Beyond fitting
+ * into the term limit, we also use message IDs to construct
+ * metadata-key values. And the documentation says that these should
+ * be restricted to about 200 characters. (The actual limit for the
+ * chert backend at least is 252.)
+ */
+#define NOTMUCH_MESSAGE_ID_MAX (200 - sizeof (NOTMUCH_METADATA_THREAD_ID_PREFIX))
+
 typedef enum _notmuch_private_status {
     /* First, copy all the public status values. */
     NOTMUCH_PRIVATE_STATUS_SUCCESS = NOTMUCH_STATUS_SUCCESS,