Iterate through all documents¶
Sometimes you want to access all the documents in a Xapian database. This can actually be done in two ways:
The Xapian::Query::MatchAll query is a special static query which will match all documents in the database. If you run this query on its own, with appropriate start and end parameters, you could retrieve all the documents. However be aware that even if you paged through the result sets, when you try to access a page deep in the result set a lot of processing and memory will be used even if the page is small, so running a plain MatchAll query is rarely a good idea.
However, this method is appropriate if you’re constructing a complicated query, and one of the components of that query should be all the documents. In particular, since Xapian doesn’t support a unary NOT operator, if you want to run a “pure NOT” query to retrieve all documents which do not contain a given term, this can be only be done using a MatchAll query and the binary NOT operator.
Iterating through all documents¶
If you do need access to all the documents in the database, it is better to use a “posting list iterator”. Such an iterator, which returns all documents in the database, can be created using:
In Xapian, a postlist is a list of the documents in which a term exists. Here, we’re again using the special “empty” term, which implicitly matches all documents, to get an iterator over all documents.
The iterator can be dereferenced to get the document IDs; to get the actual documents, the
xapian.Database.get_document() method should be used.