LayerMappingLink to this heading#Kelas LayerMapping menyediakan sebuah cara untuk memetakan isi dari berkas-berkas data spasial vektor (misalnya, shapefiles) kedalam model GeoDjango.
Kegunaan ini tumbuh dari kebutuhan pribadi penulis untuk menhilangkan perulangan kode yang masuk menarik geometri dan bidang diluar lapisan vektor, merubah ke sistem kordinat lain (misalnya WGS84), dan kemudian memasukkan kedalam model GeoDjango.
\n\n\nYou need a GDAL-supported data source, like a shapefile (here we're using\na simple polygon shapefile, test_poly.shp, with three features):
>>> from django.contrib.gis.gdal import DataSource\n>>> ds = DataSource("test_poly.shp")\n>>> layer = ds[0]\n>>> print(layer.fields) # Exploring the fields in the layer, we only want the 'str' field.\n['float', 'int', 'str']\n>>> print(len(layer)) # getting the number of features in the layer (should be 3)\n3\n>>> print(layer.geom_type) # Should be 'Polygon'\nPolygon\n>>> print(layer.srs) # WGS84 in WKT\nGEOGCS["GCS_WGS_1984",\n DATUM["WGS_1984",\n SPHEROID["WGS_1984",6378137,298.257223563]],\n PRIMEM["Greenwich",0],\n UNIT["Degree",0.017453292519943295]]\nSekarang kami menentukan model Django yang sesuai (pastikan menggunakan migrate):
from django.contrib.gis.db import models\n\n\nclass TestGeo(models.Model):\n name = models.CharField(max_length=25) # corresponds to the 'str' field\n poly = models.PolygonField(srid=4269) # we want our model in a different SRID\n\n def __str__(self):\n return "Name: %s" % self.name\nUse LayerMapping to extract all the features and place them in the\ndatabase:
>>> from django.contrib.gis.utils import LayerMapping\n>>> from geoapp.models import TestGeo\n>>> mapping = {\n... "name": "str", # The 'name' model field maps to the 'str' layer field.\n... "poly": "POLYGON", # For geometry fields use OGC name.\n... } # The mapping is a dictionary\n>>> lm = LayerMapping(TestGeo, "test_poly.shp", mapping)\n>>> lm.save(verbose=True) # Save the layermap, imports the data.\nSaved: Name: 1\nSaved: Name: 2\nSaved: Name: 3\nHere, LayerMapping transformed the three geometries from the shapefile\nin their original spatial reference system (WGS84) to the spatial reference\nsystem of the GeoDjango model (NAD83). If no spatial reference system is\ndefined for the layer, use the source_srs keyword with a\nSpatialReference object to specify one.
LayerMappingLink to this heading#Berikut adalah argumen dan kata kunci yang mungkin digunakan selama penginstansiasi dari obyek LayerMapping.
Argument | \nDeskripsi | \n
|---|---|
| \nModel geografis, bukan sebuah instance. | \n
| \nThe path to the OGR-supported data source file\n(e.g., a shapefile). Also accepts\n | \n
| \nSebuah dictionary: kunci-kunci adalah string berhubungan pada bidang model, dan nilai-nilai sesuai pada nama-nama bidang string untuk fitur OGR, atau jika bidang model adalah sebuah geografik lalu itu harus sesuai pada jenis geometri OGR, misalnya, | \n
Argumen Katakunci | \n\n |
|---|---|
| \nIndeks dari lapisan untuk digunaan dari Data Source (awalan adalah 0) | \n
| \nUse this to specify the source SRS manually (for\nexample, some shapefiles don't come with a | \n
| \nSpecifies the character set encoding of the strings\nin the OGR data source. For example, | \n
| \nMungkin | \n
| \nSetting this to False will disable coordinate\ntransformations. In other words, geometries will\nbe inserted into the database unmodified from their\noriginal state in the data source. | \n
| \nSetting this to the name, or a tuple of names,\nfrom the given model will create models unique\nonly to the given name(s). Geometries from\neach feature will be added into the collection\nassociated with the unique model. Forces\nthe transaction mode to be | \n
| \nSetel basisdata yang digunakan ketika mengimpor data spasial. Awalan adalah | \n
save()Link to this heading#The save() method also accepts keywords. These keywords are\nused for controlling output logging, error handling, and for importing\nspecific feature ranges.
Simpan Argumen Kata Kunci | \nDeskripsi | \n
|---|---|
| \nMay be set with a slice or tuple of\n(begin, end) feature ID's to map from\nthe data source. In other words, this\nkeyword enables the user to selectively\nimport a subset range of features in the\ngeographic data source. | \n
| \nWhen this keyword is set, status information\nwill be printed giving the number of features\nprocessed and successfully saved. By default,\nprogress information will be printed every 1000\nfeatures processed, however, this default may\nbe overridden by setting this keyword with an\ninteger for the desired interval. | \n
| \nSecara awalan, pemberitahuan kesalahan bukan-penting dicetak pada | \n
| \nJika disetel dengan integer, transaksi akan muncul pada setiap jangka waktu langkah. Sebagai contoh, jika | \n
| \nStatus information will be written to this file\nhandle. Defaults to using | \n
| \nExecution of the model mapping will cease upon\nthe first error encountered. The default value\n( | \n
| \nJika disetel, informasi akan dicetak selanjutnya pada setiap model simpan dijalankan pada basisdata. | \n
As noted in the warning at the top of this section, Django stores all SQL\nqueries when DEBUG=True. Set DEBUG=False in your settings, and this\nshould stop excessive memory use when running LayerMapping scripts.
max_allowed_packetLink to this heading#If you encounter the following error when using LayerMapping and MySQL:
OperationalError: (1153, "Got a packet bigger than 'max_allowed_packet' bytes")\nThen the solution is to increase the value of the max_allowed_packet\nsetting in your MySQL configuration. For example, the default value may\nbe something low like one megabyte -- the setting may be modified in MySQL's\nconfiguration file (my.cnf) in the [mysqld] section:
max_allowed_packet = 10M\n