dict_int is an example of an add-on dictionary template
for full-text search. The motivation for this example dictionary is to
control the indexing of integers (signed and unsigned), allowing such
numbers to be indexed while preventing excessive growth in the number of
unique words, which greatly affects the performance of searching.
This module is considered “trusted”, that is, it can be
installed by non-superusers who have CREATE privilege
on the current database.
The dictionary accepts three options:
The maxlen parameter specifies the maximum number of
digits allowed in an integer word. The default value is 6.
The rejectlong parameter specifies whether an overlength
integer should be truncated or ignored. If rejectlong is
false (the default), the dictionary returns the first
maxlen digits of the integer. If rejectlong is
true, the dictionary treats an overlength integer as a stop
word, so that it will not be indexed. Note that this also means that
such an integer cannot be searched for.
The absval parameter specifies whether leading
“+” or “-”
signs should be removed from integer words. The default
is false. When true, the sign is
removed before maxlen is applied.
Installing the dict_int extension creates a text search
template intdict_template and a dictionary intdict
based on it, with the default parameters. You can alter the
parameters, for example
mydb# ALTER TEXT SEARCH DICTIONARY intdict (MAXLEN = 4, REJECTLONG = true); ALTER TEXT SEARCH DICTIONARY
or create new dictionaries based on the template.
To test the dictionary, you can try
mydb# select ts_lexize('intdict', '12345678');
ts_lexize
-----------
{123456}
but real-world usage will involve including it in a text search configuration as described in Chapter 12. That might look like this:
ALTER TEXT SEARCH CONFIGURATION english
ALTER MAPPING FOR int, uint WITH intdict;