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[FEATURE][processing] New algorithm to truncate tables

Irretrievably deletes all features from a table... use with caution!
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nyalldawson committed Jan 6, 2017
1 parent bce716c commit e5e0ec51eb306761d7b4e0900902f31f451f6acf
@@ -540,6 +540,11 @@ qgis:texttofloat: >
qgis:translate: >
This algorithm moves the geometries within a layer, by offsetting them with a specified x and y displacement.

qgis:truncatetable: >
This algorithm truncates a layer, by deleting all features from within the layer.

Warning - this algorithm modifies the layer in place, and deleted features cannot be restored!

qgis:union: >
This algorithm creates a layer containing all the features from both input layers. In the case of polygon layers, separate features are created for overlapping and non-overlapping features. The attribute table of the union layer contains attribute values from the respective input layer for non-overlapping features, and attribute values from both input layers for overlapping features.

@@ -187,6 +187,7 @@
from .ShortestPathLayerToPoint import ShortestPathLayerToPoint
from .ServiceAreaFromPoint import ServiceAreaFromPoint
from .ServiceAreaFromLayer import ServiceAreaFromLayer
from .TruncateTable import TruncateTable

pluginPath = os.path.normpath(os.path.join(
os.path.split(os.path.dirname(__file__))[0], os.pardir))
@@ -255,7 +256,7 @@ def __init__(self):
RasterCalculator(), Heatmap(), Orthogonalize(),
ShortestPathPointToPoint(), ShortestPathPointToLayer(),
ShortestPathLayerToPoint(), ServiceAreaFromPoint(),
ServiceAreaFromLayer(), TruncateTable()

if hasMatplotlib:
@@ -0,0 +1,59 @@
# -*- coding: utf-8 -*-

Date : January 2017
Copyright : (C) 2017 by Nyall Dawson
Email : nyall dot dawson at gmail dot com
* *
* This program is free software; you can redistribute it and/or modify *
* it under the terms of the GNU General Public License as published by *
* the Free Software Foundation; either version 2 of the License, or *
* (at your option) any later version. *
* *

__author__ = 'Nyall Dawson'
__date__ = 'January 2017'
__copyright__ = '(C) 2017, Nyall Dawson'

# This will get replaced with a git SHA1 when you do a git archive

__revision__ = '$Format:%H$'

from processing.core.GeoAlgorithm import GeoAlgorithm
from processing.core.parameters import ParameterTable
from processing.core.outputs import OutputVector
from processing.core.GeoAlgorithmExecutionException import GeoAlgorithmExecutionException
from import dataobjects

class TruncateTable(GeoAlgorithm):


def defineCharacteristics(self):, self.i18n_name = self.trAlgorithm('Truncate table')
self.tags ='empty,delete,layer,clear,features'), self.i18n_group = self.trAlgorithm('Vector general tools')

self.addParameter(ParameterTable(self.INPUT,'Input Layer')))
self.addOutput(OutputVector(self.OUTPUT,'Truncated layer'), True))

def processAlgorithm(self, progress):
file_name = self.getParameterValue(self.INPUT)
layer = dataobjects.getObjectFromUri(file_name)
provider = layer.dataProvider()

if not provider.truncate():
raise GeoAlgorithmExecutionException('Could not truncate table.'))

self.setOutputValue(self.OUTPUT, file_name)
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@@ -0,0 +1 @@
GEOGCS["WGS 84",DATUM["WGS_1984",SPHEROID["WGS 84",6378137,298.257223563,AUTHORITY["EPSG","7030"]],AUTHORITY["EPSG","6326"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNIT["degree",0.0174532925199433,AUTHORITY["EPSG","9122"]],AUTHORITY["EPSG","4326"]]
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@@ -2118,3 +2118,15 @@ tests:
type: vector
in_place_result: true

- algorithm: qgis:truncatetable
name: Truncate table
name: custom/points.shp
type: vector
in_place: true
name: expected/truncated.shp
type: vector
in_place_result: true

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