This commit adds a number of different forms of aggregates to
the expression engine.
1. Aggregates within the current layer, eg sum("passengers")
Supports sub expressions (ie sum("passengers"/2) ), group by
( sum("passengers", group_by:="line_segment") ), and optional
filters ( sum("passengers", filter:= "station_class" > 3 ) )
2. Relational aggregates, which calculate an aggregate over
all matching child features from a relation, eg
relation_aggregate( 'my_relation', 'mean', "some_child_field" )
3. A summary aggregate function, for calculating aggregates
on other layers. Eg aggregate('rail_station_layer','sum',"passengers")
The summary aggregate function supports an optional filter,
making it possible to calculate things like:
aggregate('rail_stations','sum',"passengers",
intersects(@atlas_geometry, $geometry ) )
for calculating the total number of passengers for the stations
inside the current atlas feature
In all cases the calculations are cached inside the expression
context, so they only need to be calculated once for each
set of expression evaluations.
Sponsored by Kanton of Zug, Switzerland
Rationale:
- there was a lot of large objects passed by value, so potentially
there's a speed bump from this
- even for implicitly shared classes like QString/QList there's still
a (small) cost for copying the objects when there's no reason to
- it's the right thing to do!
- Switch data defined properties from field index- to name-based
- Add routine to migrate properties to new keys: labeling/dataDefined/[enum name]
- Add QHash containing old-style data provider mapping of index to name for use in properties migration
- Update QgsLabelingGui, QgsMapToolLabel, QgsLabelPropertyDialog to work with name-based properties
Most important changes:
- introduced feature iterator for QgsVectorLayer
- vector editing moved to QgsVectorEditBuffer
- complete rework of undo/redo commands for vector layers
- geometry cache separated from editing (QgsVectorLayerCache)
- non-essential editing functionality moved to QgsVectorLayerEditUtils
Vector data provider now has getFeatures() method to access features.
select(), nextFeature(), featureAtId(), rewind() were removed resp. moved to provider's feature iterator implementations.
Providers that currently do not implement the new API were disabled.
- update methods of existing classes
- add comment to methods missing in the sip bindings
- split up collective sip files into single files and use
same directory structure in python/ as in src/
- add a lot of missing classes (some might not make sense because of
missing python methods in those classes)
- remove some non-existing methods from the header files
- add scripts/sipdiff
- replace some usages of std::vector and std::set with QVector/QSet
builder to report errors in where clauses from OGR and postgres provider).
git-svn-id: http://svn.osgeo.org/qgis/trunk@14935 c8812cc2-4d05-0410-92ff-de0c093fc19c
- QgsVectorLayer and QgsVectorDataProvider support iterating
- QgsFeature allows direct access to attributes (get/set/del)
git-svn-id: http://svn.osgeo.org/qgis/trunk@12878 c8812cc2-4d05-0410-92ff-de0c093fc19c
- add query support for OGR and spatialite layers (additional to postgres)
- QgsDataProvider::setSubsetString() now returns if the query is successful.
- add optional parameter to limit number of values returned from QgsVectorDataProvider::uniqueValues()
- rename QgsDbSourceSelect to QgsPgSourceSelect, use QgsVectorLayer for layer queries and make it wider
- QgsDataSourceURI: improve quoting
- fix relative path support for SpatiaLite on windows
- rename QgsPgQueryBuilder to QgsQueryBuilder and use QgsVectorLayer for
queries instead of postgres
cleanups:
- rename QgsServerSourceSelect to QgsWMSSourceSelect
git-svn-id: http://svn.osgeo.org/qgis/trunk@11762 c8812cc2-4d05-0410-92ff-de0c093fc19c
