[docs from cvs HEAD]
I found the text-search documentation a little unclear about 'prefix search';
specifically, the
examples do not show that the so-called 'prefix' is first stemmed, before it is
used as prefix.
For instance, the following can be a little surprising:
SELECT to_tsvector( 'postgraduate' ) @@ to_tsquery( 'postgres:*' );
?column?
----------
t
(1 row)
Because prefix search is such an important functionality I think this should be
better explained,
which I hope the attached doc-patch does.
(In textsearch.sgml is another mention + example of prefix search, perhaps it
should be extended a
little there too - which I'm happy to do as well, but I first wanted to see if
you agree that it
is a little too obscure as it stands)
Erik Rijkers
--- doc/src/sgml/datatype.sgml.orig 2010-08-31 22:35:20.000000000 +0200
+++ doc/src/sgml/datatype.sgml 2010-08-31 23:27:51.000000000 +0200
@@ -3842,7 +3842,25 @@
'super':*
</programlisting>
This query will match any word in a <type>tsvector</> that begins
- with <quote>super</>.
+ with <quote>super</>. Note that the 'prefix' term will be stemmed
+ first, which means that this will match:
+<programlisting>
+SELECT to_tsvector( 'postgraduate' ) @@ to_tsquery( 'postgres:*' );
+ ?column?
+----------
+ t
+(1 row)
+</programlisting>
+ because 'postgres' gets stemmed into 'postgr':
+<programlisting>
+SELECT to_tsquery('postgres:*');
+ to_tsquery
+------------
+ 'postgr':*
+(1 row)
+</programlisting>
+ which then of course also matches 'postgraduate'.
+
</para>
<para>
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