| PostgreSQL 9.2.24 Documentation | ||||
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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.
The dictionary accepts two 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.
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;