Add note clarifying that indexes that support ordered scans had better

allow clauseless scans.

diff --git a/doc/src/sgml/indexam.sgml b/doc/src/sgml/indexam.sgml
index ef1e37a82605644e08f538233ff71cabe1da6781..9a84509f749aba91bada4777fec2df50d63b89e0 100644 (file)
--- a/doc/src/sgml/indexam.sgml
+++ b/doc/src/sgml/indexam.sgml
@@ -1,5 +1,5 @@
 
 
 
@@ -109,7 +109,8 @@ $PostgreSQL: pgsql/doc/src/sgml/indexam.sgml,v 2.3 2005/03/27 23:52:51 tgl Exp $
    such a scan should include null rows.  In practice this means that
    indexes that support ordered scans (have amorderstrategy
    nonzero) must index nulls, since the planner might decide to use such a
-   scan as a substitute for sorting.  Another restriction is that an index
+   scan as a substitute for sorting.  Such indexes must also be willing to
+   run a scan with no scan keys at all.  Another restriction is that an index
    access method that supports multiple index columns must
    support indexing null values in columns after the first, because the planner
    will assume the index can be used for queries on just the first