QGIS API Documentation  3.17.0-Master (a035f434f4)
qgsvectorlayercache.h
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1 /***************************************************************************
2  qgsvectorlayercache.h
3  Cache features of a vector layer
4  -------------------
5  begin : January 2013
6  copyright : (C) Matthias Kuhn
7  email : matthias at opengis dot ch
8 
9  ***************************************************************************
10  * *
11  * This program is free software; you can redistribute it and/or modify *
12  * it under the terms of the GNU General Public License as published by *
13  * the Free Software Foundation; either version 2 of the License, or *
14  * (at your option) any later version. *
15  * *
16  ***************************************************************************/
17 
18 
19 #ifndef QgsVectorLayerCache_H
20 #define QgsVectorLayerCache_H
21 
22 #include "qgis_core.h"
23 #include "qgis_sip.h"
24 #include "qgsfield.h"
25 #include "qgsfeaturerequest.h"
26 #include "qgsfeatureiterator.h"
27 
28 #include <QCache>
29 
30 class QgsVectorLayer;
31 class QgsFeature;
34 
45 class CORE_EXPORT QgsVectorLayerCache : public QObject
46 {
47  Q_OBJECT
48 
49  private:
50 
56  class QgsCachedFeature
57  {
58  public:
59 
66  QgsCachedFeature( const QgsFeature &feat, QgsVectorLayerCache *vlCache )
67  : mCache( vlCache )
68  {
69  mFeature = new QgsFeature( feat );
70  }
71 
72  ~QgsCachedFeature()
73  {
74  // That's the reason we need this wrapper:
75  // Inform the cache that this feature has been removed
76  mCache->featureRemoved( mFeature->id() );
77  delete mFeature;
78  }
79 
80  inline const QgsFeature *feature() { return mFeature; }
81 
82  private:
83  QgsFeature *mFeature = nullptr;
84  QgsVectorLayerCache *mCache = nullptr;
85 
86  friend class QgsVectorLayerCache;
87  Q_DISABLE_COPY( QgsCachedFeature )
88  };
89 
90  public:
91  QgsVectorLayerCache( QgsVectorLayer *layer, int cacheSize, QObject *parent SIP_TRANSFERTHIS = nullptr );
92  ~QgsVectorLayerCache() override;
93 
100  void setCacheSize( int cacheSize );
101 
109  int cacheSize();
110 
117  void setCacheGeometry( bool cacheGeometry );
118 
124  bool cacheGeometry() const { return mCacheGeometry; }
125 
131  void setCacheSubsetOfAttributes( const QgsAttributeList &attributes );
132 
139  void setCacheAddedAttributes( bool cacheAddedAttributes );
140 
154  void setFullCache( bool fullCache );
155 
163  bool hasFullCache() const { return mFullCache; }
164 
174 
185 
189  inline QgsFeatureIterator getFeatures( const QString &expression )
190  {
191  return getFeatures( QgsFeatureRequest( expression ) );
192  }
193 
199  {
200  QgsFeature feature;
201  getFeatures( QgsFeatureRequest( fid ) ).nextFeature( feature );
202  return feature;
203  }
204 
209  {
210  return getFeatures( QgsFeatureRequest( fids ) );
211  }
212 
216  inline QgsFeatureIterator getFeatures( const QgsRectangle &rectangle )
217  {
218  return getFeatures( QgsFeatureRequest( rectangle ) );
219  }
220 
227  bool isFidCached( QgsFeatureId fid ) const;
228 
234  QgsFeatureIds cachedFeatureIds() const { return qgis::listToSet( mCache.keys() ); }
235 
243  bool featureAtId( QgsFeatureId featureId, QgsFeature &feature, bool skipCache = false );
244 
250  bool removeCachedFeature( QgsFeatureId fid );
251 
256 
261 
265  QgsFields fields() const;
266 
270  QgsWkbTypes::Type wkbType() const;
271 
272 #ifdef SIP_RUN
273 
278  int __len__() const;
279  % MethodCode
280  sipRes = sipCpp->featureCount();
281  % End
282 
284  int __bool__() const;
285  % MethodCode
286  sipRes = true;
287  % End
288 #endif
289 
294  long featureCount() const;
295 
296  protected:
297 
306  void requestCompleted( const QgsFeatureRequest &featureRequest, const QgsFeatureIds &fids );
307 
315  void featureRemoved( QgsFeatureId fid );
316 
327  bool checkInformationCovered( const QgsFeatureRequest &featureRequest );
328 
329 
330  signals:
331 
341  void progress( int i, bool &cancel ) SIP_SKIP;
342 
346  void finished();
347 
353  void cachedLayerDeleted();
354 
359  void attributeValueChanged( QgsFeatureId fid, int field, const QVariant &value );
360 
368  void featureAdded( QgsFeatureId fid );
369 
375  void invalidated();
376 
377  private slots:
378  void onAttributeValueChanged( QgsFeatureId fid, int field, const QVariant &value );
379  void onJoinAttributeValueChanged( QgsFeatureId fid, int field, const QVariant &value );
380  void featureDeleted( QgsFeatureId fid );
381  void onFeatureAdded( QgsFeatureId fid );
382  void attributeAdded( int field );
383  void attributeDeleted( int field );
384  void geometryChanged( QgsFeatureId fid, const QgsGeometry &geom );
385  void layerDeleted();
386  void invalidate();
387 
388  private:
389 
390  void connectJoinedLayers() const;
391 
392  inline void cacheFeature( QgsFeature &feat )
393  {
394  QgsCachedFeature *cachedFeature = new QgsCachedFeature( feat, this );
395  mCache.insert( feat.id(), cachedFeature );
396  }
397 
398  QgsVectorLayer *mLayer = nullptr;
399  QCache< QgsFeatureId, QgsCachedFeature > mCache;
400 
401  bool mCacheGeometry = true;
402  bool mFullCache = false;
403  QList<QgsAbstractCacheIndex *> mCacheIndices;
404 
405  QgsAttributeList mCachedAttributes;
406 
409  friend class QgsCachedFeature;
410 
419  bool canUseCacheForRequest( const QgsFeatureRequest &featureRequest, QgsFeatureIterator &it );
420 
421  friend class TestVectorLayerCache;
422 };
423 #endif // QgsVectorLayerCache_H
QgsFeatureIterator getFeatures(const QString &expression)
Query the layer for features matching a given expression.
QgsFeatureId id
Definition: qgsfeature.h:64
Wrapper for iterator of features from vector data provider or vector layer.
A rectangle specified with double values.
Definition: qgsrectangle.h:41
QSet< QgsFeatureId > QgsFeatureIds
Definition: qgsfeatureid.h:37
QgsVectorLayerCache(QgsVectorLayer *layer, int cacheSize, QObject *parent=nullptr)
#define SIP_TRANSFERTHIS
Definition: qgis_sip.h:53
QgsFeatureIterator getFeatures(const QgsFeatureIds &fids)
Query the layer for the features with the given ids.
void invalidated()
The cache has been invalidated and cleared.
bool cacheGeometry() const
Returns true if the cache will fetch and cache feature geometries.
bool removeCachedFeature(QgsFeatureId fid)
Removes the feature identified by fid from the cache if present.
qint64 QgsFeatureId
64 bit feature ids negative numbers are used for uncommitted/newly added features ...
Definition: qgsfeatureid.h:28
Container of fields for a vector layer.
Definition: qgsfields.h:44
A geometry is the spatial representation of a feature.
Definition: qgsgeometry.h:123
void requestCompleted(const QgsFeatureRequest &featureRequest, const QgsFeatureIds &fids)
Gets called, whenever the full list of feature ids for a certain request is known.
QgsVectorLayer * layer()
Returns the layer to which this cache belongs.
The feature class encapsulates a single feature including its id, geometry and a list of field/values...
Definition: qgsfeature.h:55
void attributeValueChanged(QgsFeatureId fid, int field, const QVariant &value)
Emitted when an attribute is changed.
void setCacheSubsetOfAttributes(const QgsAttributeList &attributes)
Set the subset of attributes to be cached.
void featureAdded(QgsFeatureId fid)
Emitted when a new feature has been added to the layer and this cache.
Type
The WKB type describes the number of dimensions a geometry has.
Definition: qgswkbtypes.h:69
bool isFidCached(QgsFeatureId fid) const
Check if a certain feature id is cached.
Uses another iterator as backend and writes features to the cache.
QgsCoordinateReferenceSystem sourceCrs() const
Returns the coordinate reference system for features in the cache.
#define SIP_SKIP
Definition: qgis_sip.h:126
QgsFeatureIds cachedFeatureIds() const
Returns the set of feature IDs for features which are cached.
void progress(int i, bool &cancel)
When filling the cache, this signal gets emitted periodically to notify about the progress and to be ...
#define SIP_TRANSFER
Definition: qgis_sip.h:36
This class wraps a request for features to a vector layer (or directly its vector data provider)...
QgsFields fields() const
Returns the fields associated with features in the cache.
void cachedLayerDeleted()
Is emitted when the cached layer is deleted.
bool checkInformationCovered(const QgsFeatureRequest &featureRequest)
Checks if the information required to complete the request is cached.
This class caches features of a given QgsVectorLayer.
long featureCount() const
Returns the number of features contained in the source, or -1 if the feature count is unknown...
Abstract base class for cache indices.
Definition: qgscacheindex.h:31
void setCacheGeometry(bool cacheGeometry)
Enable or disable the caching of geometries.
void setFullCache(bool fullCache)
This enables or disables full caching.
bool featureAtId(QgsFeatureId featureId, QgsFeature &feature, bool skipCache=false)
Gets the feature at the given feature id.
void setCacheSize(int cacheSize)
Sets the maximum number of features to keep in the cache.
This class represents a coordinate reference system (CRS).
QgsWkbTypes::Type wkbType() const
Returns the geometry type for features in the cache.
QgsFeatureIterator getFeatures(const QgsRectangle &rectangle)
Query the layer for the features which intersect the specified rectangle.
Delivers features from the cache.
void featureRemoved(QgsFeatureId fid)
Gets called, whenever a feature has been removed.
int cacheSize()
Returns the maximum number of features this cache will hold.
QgsFeature getFeature(QgsFeatureId fid)
Query the layer for the feature with the given id.
QList< int > QgsAttributeList
Definition: qgsfield.h:26
bool nextFeature(QgsFeature &f)
void addCacheIndex(QgsAbstractCacheIndex *cacheIndex)
Adds a QgsAbstractCacheIndex to this cache.
Represents a vector layer which manages a vector based data sets.
QgsFeatureIterator getFeatures(const QgsFeatureRequest &featureRequest=QgsFeatureRequest())
Query this VectorLayerCache for features.
void finished()
When filling the cache, this signal gets emitted once the cache is fully initialized.
bool hasFullCache() const
Returns true if the cache is complete, ie it contains all features.
const QgsField & field
Definition: qgsfield.h:471
void setCacheAddedAttributes(bool cacheAddedAttributes)
If this is enabled, the subset of cached attributes will automatically be extended to also include ne...