diff --git a/doc/src/sgml/textsearch.sgml b/doc/src/sgml/textsearch.sgml index a83582a39c..71e29dbfcb 100644 --- a/doc/src/sgml/textsearch.sgml +++ b/doc/src/sgml/textsearch.sgml @@ -1,4 +1,4 @@ - + Full Text Search @@ -1770,7 +1770,7 @@ LIMIT 10; hword Hyphenated word, all letters - político-militar + lógico-matemática numhword @@ -1780,14 +1780,13 @@ LIMIT 10; hword_asciipart Hyphenated word part, all ASCII - militar in the context - político-militar, or postgresql in the context postgresql-beta1 + postgresql in the context postgresql-beta1 hword_part Hyphenated word part, all letters - físico or químico - in the context físico-químico + lógico or matemática + in the context lógico-matemática hword_numpart @@ -1902,12 +1901,12 @@ SELECT alias, description, token FROM ts_debug('foo-bar-beta1'); instructive example: -SELECT alias, description, token FROM ts_debug('http://foo.com/stuff/index.html'); - alias | description | token -----------+---------------+-------------------------- +SELECT alias, description, token FROM ts_debug('http://example.com/stuff/index.html'); + alias | description | token +----------+---------------+------------------------------ protocol | Protocol head | http:// - url | URL | foo.com/stuff/index.html - host | Host | foo.com + url | URL | example.com/stuff/index.html + host | Host | example.com uri | URI | /stuff/index.html @@ -3093,8 +3092,9 @@ SELECT plainto_tsquery('supernovae stars'); - A GiST index is lossy, meaning it is necessary - to check the actual table row to eliminate false matches. + A GiST index is lossy, meaning that the index + may produce false matches, and it is necessary + to check the actual table row to eliminate such false matches. PostgreSQL does this automatically; for example, in the query plan below, the Filter: line indicates the index output will be rechecked: @@ -3112,14 +3112,15 @@ EXPLAIN SELECT * FROM apod WHERE textsearch @@ to_tsquery('supernovae'); index by a fixed-length signature. The signature is generated by hashing each word into a random bit in an n-bit string, with all these bits OR-ed together to produce an n-bit document signature. When two words hash to - the same bit position there will be a false match, and if all words in + the same bit position there will be a false match. If all words in the query have matches (real or false) then the table row must be retrieved to see if the match is correct. - Lossiness causes performance degradation since random access to table - records is slow; this limits the usefulness of GiST indexes. The + Lossiness causes performance degradation due to useless fetches of table + records that turn out to be false matches. Since random access to table + records is slow, this limits the usefulness of GiST indexes. The likelihood of false matches depends on several factors, in particular the number of unique words, so using dictionaries to reduce this number is recommended.