The Python indexing API

Python indexing interface methods
Query data access for external indexers

There are two parts in the indexing interface:

  • Methods inside the recoll module allow the foreign indexer to update the index.

  • An interface based on scripts execution is defined for executing the indexer (from recollindex) and to allow either the GUI or the rclextract module to access original document data for previewing or editing.

Two sample scripts are included with the Recoll source and described in more detail a bit further.

Python indexing interface methods

The update methods are part of the recoll module. The connect() method is used with a writable=true parameter to obtain a writable Db object. The following Db object methods are then available.

addOrUpdate(udi, doc, parent_udi=None)

Add or update index data for a given document. The udi string must define a unique id for the document. It is an opaque interface element and not interpreted inside Recoll. doc is a Doc object, created from the data to be indexed (the main text should be in doc.text). If parent_udi is set, this is a unique identifier for the top-level container, the document for which needUpdate() would be called (e.g. for the filesystem indexer, this would be the one which is an actual file). The doc url and possibly ipath fields should also be set to allow access to the actual document after a query. Other fields should also be set to allow further access to the data, see the description further down: rclbes, sig, mimetype. Of course, any standard or custom Recoll field can also be added.

delete(udi)

Purge the index from all data for udi, and all documents (if any) which have udi as parent_udi.

needUpdate(udi, sig)

Test if the index needs to be updated for the document identified by udi. If this call is to be used, the doc.sig field should contain a signature value when calling addOrUpdate(). The needUpdate() call then compares its parameter value with the stored sig for udi. sig is an opaque value, compared as a string.

The filesystem indexer uses a concatenation of the decimal string values for file size and update time, but a hash of the contents could also be used.

As a side effect, if the return value is false (the index is up to date), the call will set the existence flag for the document (and any subdocument defined by its parent_udi), so that a later purge() call will preserve them.

The use of needUpdate() and purge() is optional, and the indexer may use another method for checking the need to reindex or to delete stale entries.

preparePurge(backend_name)

Mark all documents which do *not* belong to backend_name. backend_name is the value chosen for the rclbes field for the indexer documents (e.g. "MBOX", "JOPLIN"... for the samples). This is a mandatory call before starting an update if the index is shared with other backends and you are going to call purge() after the update, else all documents for other backends will be deleted from the index by the purge.

purge()

Delete all documents that were not touched during the just finished indexing pass (since preparePurge()). These are the documents for which the needUpdate() call was not performed, indicating that they no longer exist in the storage system.

createStemDbs(lang|sequence of langs)

Create stemming dictionaries for query stemming expansion. Note that this is not needed at all if the indexing is done from the recollindex program, as it will perform this action after calling all the external indexers. Should be called when done updating the index. Available only after Recoll 1.34.3. As an alternative, you can close the index and execute: 

recollindex -c <confdir> -s <lang(s)>

The Python module currently has no interface to the Aspell speller functions, so the same approach can be used for creating the spelling dictionary (with option -S) (again, not needed if recollindex is driving the indexing).

Query data access for external indexers

Recoll has internal methods to access document data for its internal (filesystem) indexer. An external indexer needs to provide data access methods if it needs integration with the GUI (e.g. preview function), or support for the rclextract module.

An external indexer needs to provide two commands, for fetching data (typically for previewing) and for computing the document signature (for up-to-date checks when opening or previewing). The sample MBOX and JOPLIN implementations use the same script with different parameters to perform both operations, but this is just a choice. A third command must be provided for performing the indexing proper.

The "fetch" and "makesig" scripts are called with three additional arguments: udi, url, ipath. These were set by the indexer and stored with the document by the addOrUpdate() call described above. Not all arguments are needed in all cases, the script will use what it needs to perform the requested operation. The caller expects the result data on stdout.

recollindex will set the RECOLL_CONFDIR environment variable when executing the scripts, so that the configuration can be created as 

rclconf = rclconfig.RclConfig()

if needed, and the configuration directory obtained as 

confdir = rclconf.getConfDir()
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