docs: Add short "cover density" description

Also, previous commit 1420f3a982 to fix ts_rank_cd() for stripped lexemes was from a patch created by Alex Hill.
12 years ago · 0b5c0f3bc7
parent 1420f3a982
commit 0b5c0f3bc7
1 changed files with 3 additions and 1 deletions
--- a/doc/src/sgml/textsearch.sgml
+++ b/doc/src/sgml/textsearch.sgml
@ -885,7 +885,9 @@ SELECT plainto_tsquery('english', 'The Fat &amp; Rats:C');
        ranking for the given document vector and query, as described in
        Clarke, Cormack, and Tudhope's "Relevance Ranking for One to Three
        Term Queries" in the journal "Information Processing and Management",
-        1999.
+        1999.  Cover density is similar to <function>ts_rank</> ranking
+        except that the proximity of matching lexemes to each other is
+        taken into consideration.
       </para>

       <para>