Attributes are additional values associated with each document that can be used to perform additional filtering and sorting during search.
It is often desired to additionally process full-text search results based not only on matching document ID and its rank, but on a number of other per-document values as well. For instance, one might need to sort news search results by date and then relevance, or search through products within specified price range, or limit blog search to posts made by selected users, or group results by month. To do that efficiently, Manticore allows to attach a number of additional attributes to each document, and store their values in the full-text index. It’s then possible to use stored values to filter, sort, or group full-text matches.
Attributes, unlike the fields, are not full-text indexed. They are stored in the index, but it is not possible to search them as full-text, and attempting to do so results in an error.
For example, it is impossible to use the extended matching mode
@column 1 to match documents where column is 1, if column
is an attribute, and this is still true even if the numeric digits are
Attributes can be used for filtering, though, to restrict returned rows, as well as sorting or result grouping; it is entirely possible to sort results purely based on attributes, and ignore the search relevance tools. Additionally, attributes are returned from the search daemon, while the indexed text is not.
A good example for attributes would be a forum posts table. Assume that only title and content fields need to be full-text searchable - but that sometimes it is also required to limit search to a certain author or a sub-forum (ie. search only those rows that have some specific values of author_id or forum_id columns in the SQL table); or to sort matches by post_date column; or to group matching posts by month of the post_date and calculate per-group match counts.
This can be achieved by specifying all the mentioned columns (excluding title and content, that are full-text fields) as attributes, indexing them, and then using API calls to setup filtering, sorting, and grouping. Here as an example.
Example sphinx.conf part:¶
... sql_query = SELECT id, title, content, \ author_id, forum_id, post_date FROM my_forum_posts sql_attr_uint = author_id sql_attr_uint = forum_id sql_attr_timestamp = post_date ...
Example application code (in PHP):¶
// only search posts by author whose ID is 123 $cl->SetFilter ( "author_id", array ( 123 ) ); // only search posts in sub-forums 1, 3 and 7 $cl->SetFilter ( "forum_id", array ( 1,3,7 ) ); // sort found posts by posting date in descending order $cl->SetSortMode ( SPH_SORT_ATTR_DESC, "post_date" );
Attributes are named. Attribute names are case insensitive. Attributes are not full-text indexed; they are stored in the index as is. Currently supported attribute types are:
- unsigned integers (1-bit to 32-bit wide);
- signed big integers (64-bit wide);
- UNIX timestamps;
- floating point values (32-bit, IEEE 754 single precision);
- MVA, multi-value attributes (variable-length lists of 32-bit unsigned or 64-bit signed integers).
The complete set of per-document attribute values is sometimes referred
to as docinfo. Docinfos are stored separately from the main full-text
index data in
A copy of
.spa file (with all the
attribute values for all the documents) is kept in RAM by
all times (via mmap()). This is for performance reasons; random disk I/O may be too slow otherwise
in most cases.