TrackerDecorator: Tracker Miner Library Reference Manual

## TrackerDecorator TrackerDecorator — A miner tasked with listening for DB resource changes and extracting metadata |

## Functions

GQuark | tracker_decorator_error_quark ()
const gchar * | tracker_decorator_get_data_source ()
const gchar ** | tracker_decorator_get_class_names ()
guint | tracker_decorator_get_n_items ()
void | tracker_decorator_prepend_id ()
void | tracker_decorator_delete_id ()
void | tracker_decorator_next ()
TrackerDecoratorInfo * | tracker_decorator_next_finish ()
void | tracker_decorator_set_priority_rdf_types ()
TrackerDecoratorInfo * | tracker_decorator_info_ref ()
void | tracker_decorator_info_unref ()
const gchar * | tracker_decorator_info_get_urn ()
const gchar * | tracker_decorator_info_get_url ()
const gchar * | tracker_decorator_info_get_mimetype ()
GTask * | tracker_decorator_info_get_task ()
TrackerSparqlBuilder * | tracker_decorator_info_get_sparql ()

## Properties

GStrv | class-names | Read / Write
gint | commit-batch-size | Read / Write
gchar * | data-source | Read / Write / Construct Only
GStrv | priority-rdf-types | Write

## Signals

void | finished | Run Last
void | items-available | Run Last

## Types and Values

struct | TrackerDecorator
struct | TrackerDecoratorClass
enum | TrackerDecoratorError

## Object Hierarchy

        GObject
        ╰── TrackerMiner
            ╰── TrackerDecorator
                ╰── TrackerDecoratorFS

## Implemented Interfaces

TrackerDecorator implements GInitable.

## Includes

    #include <libtracker-miner/tracker-miner.h>

## Description

TrackerDecorator watches for signal updates based on content changes in the database. When new files are added initially, only simple metadata exists, for example, name, size, mtime, etc. The TrackerDecorator queues files for extended metadata extraction (i.e. for tracker-extract to fetch metadata specific to the file type) for example 'nmm:whiteBalance' for a picture.

## Functions

### tracker_decorator_error_quark ()

    GQuark
    tracker_decorator_error_quark (void);

Gives the caller the GQuark used to identify TrackerDecorator errors in GError structures. The GQuark is used as the domain for the error.

#### Returns

the GQuark used for the domain of a GError.

Since: 0.18.

### tracker_decorator_get_data_source ()

    const gchar *
    tracker_decorator_get_data_source (TrackerDecorator *decorator);

The unique string identifying this TrackerDecorator that has extracted the extended metadata. This is essentially an identifier so it's clear WHO has extracted this extended metadata.

#### Parameters

decorator | a TrackerDecorator. |

#### Returns

a const gchar* or NULL if an error happened.

Since: 0.18.

### tracker_decorator_get_class_names ()

    const gchar **
    tracker_decorator_get_class_names (TrackerDecorator *decorator);

This function returns a string list of class names which are being updated with extended metadata. An example would be 'nfo:Document'.

#### Parameters

decorator | a TrackerDecorator. |

#### Returns

a const gchar** or NULL.

[transfer none]

Since: 0.18.

### tracker_decorator_get_n_items ()

    guint
    tracker_decorator_get_n_items (TrackerDecorator *decorator);

Get the number of items left in the queue to be processed. This indicates content that may already exist in Tracker but is waiting to be further flurished with metadata with a 2nd pass extraction or index.

#### Parameters

decorator | a TrackerDecorator |

#### Returns

the number of items queued to be processed, always >= 0.

Since: 0.18.

### tracker_decorator_prepend_id ()

    void
    tracker_decorator_prepend_id (TrackerDecorator *decorator,
                                  gint id,
                                  gint class_name_id);

Adds resource needing extended metadata extraction to the queue. `id` is the same IDs emitted by tracker-store when the database is updated for consistency. For details, see the GraphUpdated signal.

#### Parameters

decorator | a TrackerDecorator. |
id | the ID of the resource ID. |
class_name_id | the ID of the resource's class. |

Since: 0.18.

### tracker_decorator_delete_id ()

    void
    tracker_decorator_delete_id (TrackerDecorator *decorator,
                                 gint id);

Deletes resource needing extended metadata extraction from the queue. `id` is the same IDs emitted by tracker-store when the database is updated for consistency. For details, see the GraphUpdated signal.

#### Parameters

decorator | a TrackerDecorator. |
id | an ID. |

Since: 0.18.

### tracker_decorator_next ()

    void
    tracker_decorator_next (TrackerDecorator *decorator,
                            GCancellable *cancellable,
                            GAsyncReadyCallback callback,
                            gpointer user_data);

Processes the next resource in the queue to have extended metadata extracted. If the item in the queue has been completed already, it signals it's completion instead.

This function will give a GError if the miner is paused at the time it is called.

#### Parameters

decorator | a TrackerDecorator. |
cancellable | a GCancellable. |
callback | a GAsyncReadyCallback. |
user_data | user_data for `callback` . |

Since: 0.18.

### tracker_decorator_next_finish ()

    TrackerDecoratorInfo *
    tracker_decorator_next_finish (TrackerDecorator *decorator,
                                   GAsyncResult *result,
                                   GError **error);

Should be called in the callback function provided to `tracker_decorator_next()` to return the result of the task be it an error or not.

#### Parameters

decorator | a TrackerDecorator. |
result | a GAsyncResult. |
error | return location for a GError, or NULL. |

#### Returns

a TrackerDecoratorInfo on success or NULL on error. Free with `tracker_decorator_info_unref()`.

[transfer full]

Since: 0.18.

### tracker_decorator_set_priority_rdf_types ()

    void
    tracker_decorator_set_priority_rdf_types
                                   (TrackerDecorator *decorator,
                                    const gchar * const *rdf_types);

Re-evaluate the priority queues internally to ensure that `rdf_types` are handled before all other content. This is useful for applications that need their content available sooner than the standard time it would take to index content.

#### Parameters

decorator | a TrackerDecorator |
rdf_types | a string array of rdf types |

Since: 0.18.

### tracker_decorator_info_ref ()

    TrackerDecoratorInfo *
    tracker_decorator_info_ref (TrackerDecoratorInfo *info);

Increases the reference count of `info` by 1.

#### Parameters

info | a TrackerDecoratorInfo |

#### Returns

the same `info` passed in, or `NULL` on error.

Since: 0.18.

### tracker_decorator_info_unref ()

    void
    tracker_decorator_info_unref (TrackerDecoratorInfo *info);

Decreases the reference count of `info` by 1 and frees it when the reference count reaches 0.

#### Parameters

info | a TrackerDecoratorInfo |

Since: 0.18.

### tracker_decorator_info_get_urn ()

    const gchar *
    tracker_decorator_info_get_urn (TrackerDecoratorInfo *info);

A URN is a Uniform Resource Name and should be a unique identifier for a resource in the database.

#### Parameters

info | a TrackerDecoratorInfo. |

#### Returns

the URN for TrackerDecoratorInfo on success or NULL on error.

Since: 0.18.

### tracker_decorator_info_get_url ()

    const gchar *
    tracker_decorator_info_get_url (TrackerDecoratorInfo *info);

A URL is a Uniform Resource Locator and should be a location associated with a resource in the database. For example, 'file:///tmp/foo.txt'.

#### Parameters

info | a TrackerDecoratorInfo. |

#### Returns

the URL for TrackerDecoratorInfo on success or NULL on error.

Since: 0.18.

### tracker_decorator_info_get_mimetype ()

    const gchar *
    tracker_decorator_info_get_mimetype (TrackerDecoratorInfo *info);

A MIME¹ type is a way of describing the content type of a file or set of data. An example would be 'text/plain' for a clear text document or file.

¹: http://en.wikipedia.org/wiki/MIME

#### Parameters

info | a TrackerDecoratorInfo. |

#### Returns

the MIME type for TrackerDecoratorInfo on success or NULL on error.

Since: 0.18.

### tracker_decorator_info_get_task ()

    GTask *
    tracker_decorator_info_get_task (TrackerDecoratorInfo *info);

Get the GTask associated with retrieving extended metadata and information for a URN in Tracker.

#### Parameters

info | a TrackerDecoratorInfo. |

#### Returns

the GTask for TrackerDecoratorInfo on success or NULL if there is no existing GTask.

[transfer none]

Since: 0.18.

### tracker_decorator_info_get_sparql ()

    TrackerSparqlBuilder *
    tracker_decorator_info_get_sparql (TrackerDecoratorInfo *info);

A TrackerSparqlBuilder allows the caller to extract the final SPARQL used to insert the extracted metadata into the database for the resource being processed.

This function calls `g_task_get_task_data()` on the return value of `tracker_decorator_info_get_task()`.

#### Parameters

info | a TrackerDecoratorInfo. |

#### Returns

a TrackerSparqlBuilder on success or NULL on error.

[transfer none]

Since: 0.18.

## Types and Values

### struct TrackerDecorator

    struct TrackerDecorator;

Abstract miner object for passive extended metadata indexing, i.e. data past the basic information such as file name, size, etc.

### struct TrackerDecoratorClass

    struct TrackerDecoratorClass {
    	TrackerMinerClass parent_class;

    	void (* items_available) (TrackerDecorator *decorator);
    	void (* finished)        (TrackerDecorator *decorator);

    	/* <Private> */
    	gpointer padding[10];
    };

An implementation that takes care of extracting extra metadata specific to file types by talking to tracker-extract.

Based on TrackerMinerClass.

#### Members

TrackerMinerClass `parent_class`; | parent object class. |
`items_available` () | Called when there are resources to be processed. |
`finished` () | Called when all resources have been processed. |
gpointer `padding`[10]; | Reserved for future API improvements. |

### enum TrackerDecoratorError

Possible errors returned when calling `tracker_decorator_next_finish()`.

#### Members

TRACKER_DECORATOR_ERROR_EMPTY | There is no item to be processed next. It is entirely possible to have a ::items_available signal emitted and then have this error when calling `tracker_decorator_next_finish()` because the signal may apply to a class which we're not interested in. For example, a new nmo:Email might have been added to Tracker, but we might only be interested in nfo:Document. This case would give this error. |
TRACKER_DECORATOR_ERROR_PAUSED | No work was done or will be done because the miner is currently paused. |

## Property Details

### The `“class-names”` property

      “class-names”              GStrv

rdfs:Class objects to listen to for changes.

Flags: Read / Write

### The `“commit-batch-size”` property

      “commit-batch-size”        gint

Number of items per update batch.

Flags: Read / Write

Allowed values: >= 0

Default value: 200

### The `“data-source”` property

      “data-source”              gchar *

nie:DataSource to use in this decorator.

Flags: Read / Write / Construct Only

Default value: NULL

### The `“priority-rdf-types”` property

      “priority-rdf-types”       GStrv

rdf:type that needs to be extracted first.

Flags: Write

## Signal Details

### The `“finished”` signal

    void
    user_function (TrackerDecorator *decorator,
                   gpointer          user_data)

The ::finished signal will be emitted whenever the TrackerDecorator has finished extracted extended metadata for resources in the database.

#### Parameters

decorator | the TrackerDecorator |
user_data | user data set when the signal handler was connected. |

Flags: Run Last

Since: 0.18.

### The `“items-available”` signal

    void
    user_function (TrackerDecorator *decorator,
                   gpointer          user_data)

The ::items-available signal will be emitted whenever the TrackerDecorator sees resources that are available for extended metadata extraction.

#### Parameters

decorator | the TrackerDecorator |
user_data | user data set when the signal handler was connected. |

Flags: Run Last

Since: 0.18.

## See Also

TrackerDecoratorFS