F.11. dict_int
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.
F.11.1. Configuration
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. Ifrejectlong
isfalse
(the default), the dictionary returns the firstmaxlen
digits of the integer. Ifrejectlong
istrue
, 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.
F.11.2. Usage
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;
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https://www.postgresql.org/docs/11/dict-int.html