mnoGoSearch 3.2.39 reference manual: Full-featured search engine software
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# Tags

Tag is a special parameter which can be given for a set of documents. The main purpose of tags is to join a number of documents into one group and then, while doing a search, to select a group of documents to search through.

You can use the Tag command in `indexer.conf` to give some tag value for a server or server subset. While doing a search you can specify a tag value to search through documents whose tag match a given parameter with the t=xxx syntax, which can be passed from an HTML form. Take a look into Tag, `indexer.conf-dist` and `search.htm-dist` for more explanations and examples.

## Tags in SQL version

Starting from version 3.1.x, tag type was changed from INT to CHAR. The CHAR type provides the use of some nice features. Due to the fact that, since 3.1.x, the tag is tested against the SQL LIKE operator, you can use '_' and '%' LIKE wildcards in the tag parameter when doing a search. It makes it possible for a tag, like a category, to support an idea of nesting. For example, documents with tag value "AB" can be found with both "A%" and "AB" tag limits.

Tags also provide a way to make an URL a member of multiple tag selections. Playing with LIKE wildcards you can easily create two or more groups.

For example, tag "ABCDE" is the member of at least these selections:

    _BCDE
    A_CDE
    AB_DE
    ABC_E
    ABCD_

> Note: If you have a database big enough and often use tag limits, it is useful to create an index by field "tag" in the "server" table. This index is not created by default.

>     CREATE INDEX srv_tag ON "server" ("tag");

> By default, the length of the tag field in the url table is limited to 16 characters. If you need more, increase this length before creating the database.

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