search: note why we do not support FLAG_PURE_NOT

Perhaps this can be optionally enabled in the future for smaller
sites.

diff --git a/lib/PublicInbox/Search.pm b/lib/PublicInbox/Search.pm
index 1874ee9df6d4a6d7ef92881def30abc2aee7a44f..b6e71da0120fb9425e5d1d78af5b2ed2d345372d 100644 (file)
--- a/lib/PublicInbox/Search.pm
+++ b/lib/PublicInbox/Search.pm
@@ -28,6 +28,9 @@ use constant {
        # 8 - remove redundant/unneeded document data
        # 9 - disable Message-ID compression
        SCHEMA_VERSION => 9,
+
+       # n.b. FLAG_PURE_NOT is expensive not suitable for a public website
+       # as it could become a denial-of-service vector
        QP_FLAGS => FLAG_PHRASE|FLAG_BOOLEAN|FLAG_LOVEHATE|FLAG_WILDCARD,
 };