Allows upgrading geometries to include these dimensions, or
overwriting any existing Z/M values with a new value.
Intended mostly as a test run for QgsProcessingFeatureBasedAlgorithm
An abstract QgsProcessingAlgorithm base class for processing algorithms
which operate "feature-by-feature".
Feature based algorithms are algorithms which operate on individual
features in isolation. These are algorithms where one feature is
output for each input feature, and the output feature result
for each input feature is not dependent on any other features
present in the source.
For instance, algorithms like "centroids" and "buffers" are feature
based algorithms since the centroid or buffer of a feature is
calculated for each feature in isolation. An algorithm like "dissolve"
is NOT suitable for a feature based algorithm as the dissolved output
depends on multiple input features and these features cannot be
processed in isolation.
Using QgsProcessingFeatureBasedAlgorithm as the base class for feature
based algorithms allows shortcutting much of the common algorithm code
for handling iterating over sources and pushing features to output sinks.
It also allows the algorithm execution to be optimised in future
(for instance allowing automatic multi-thread processing of the
algorithm, or use of the algorithm in "chains", avoiding the need
for temporary outputs in multi-step models).
When methods are called that use GEOS to create new geometries, the
result geometries now contain information about what has gone wrong in
case of an error.
In practice, this means it's possible to give more detailed information
in place (and not only in the message log) when things like processing
algorithms fail.
This allows optional outputs (such as null geometry features detected
by the Remove Null Geometries algorithm) to be skipped by default
when desirable.
Enhancements:
- add a new optional output for null geometries, and make
the non-null geometry output optional. This allows the algorithm
to act as a router for features with null/not null geometries
inside of a model
Improvements:
- by default output a table with unique values, instead of a HTML
file. This allows the values to be more easily used in follow up
analysis (e.g. in a model). HTML output is still available, but
not output by default
Enhancements:
- support source/target layers in different CRS
- output layers with geometry (i.e. keep input point geometry - avoids
need to rejoin result back to original table to get geometry)
- keep original data types for id fields
- don't fire off many single feature requests - instead request
multiple features at once to improve speed
Improvements
- allow different CRS between layers
- instead of optionally allowing selection of a single field to keep from
both inputs, allow selection of multiple fields
