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Make exact distance match for FTS phrase operator

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Phrase operator now requires exact distance betweens lexems instead of
less-or-equal.

Per discussion c19fcfec308e6ccd952cdde9e648b505@mail.gmail.com
This commit is contained in:
Teodor Sigaev
2016-06-27 20:41:00 +03:00
parent f1993038a4
commit 028350f619
4 changed files with 63 additions and 47 deletions
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6
doc/src/sgml/textsearch.sgml
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@ -346,10 +346,10 @@ SELECT to_tsvector('error is not fatal') @@ to_tsquery('fatal <-> error');
There is a more general version of the FOLLOWED BY operator having the
form <literal>&lt;<replaceable>N</>&gt;</literal>,
where <replaceable>N</> is an integer standing for the greatest distance
where <replaceable>N</> is an integer standing for the exact distance
allowed between the matching lexemes. <literal>&lt;1&gt;</literal> is
the same as <literal>&lt;-&gt;</>, while <literal>&lt;2&gt;</literal>
allows one other lexeme to optionally appear between the matches, and so
allows one other lexeme to appear between the matches, and so
on. The <literal>phraseto_tsquery</> function makes use of this
operator to construct a <literal>tsquery</> that can match a multi-word
phrase when some of the words are stop words. For example:
@ -1529,7 +1529,7 @@ SELECT to_tsquery('fat') &lt;-&gt; to_tsquery('cat | rat');
<para>
Returns a query that searches for a match to the first given query
followed by a match to the second given query at a distance of at
most <replaceable>distance</replaceable> lexemes, using
<replaceable>distance</replaceable> lexemes, using
the <literal>&lt;<replaceable>N</>&gt;</literal>
<type>tsquery</> operator. For example: