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Fóntais allmhairithe sonraí Layermapping

Soláthraíonn an rang:class: LayerMapping bealach chun ábhar comhaid sonraí spásúla veicteora (m.sh. comhaid chruthach) a mhapáil i samhlacha GeoDjango.

D'fhás an fóntais seo as riachtanais phearsanta an údair chun deireadh a chur leis an athrá cód a chuaigh chun geoiméadraí agus réimsí a tharraingt as ciseal veicteora, ag tiontú go córas comhordaithe eile (m.sh. WGS84), agus ansin a chur isteach i samhail GeoDjango.

Sampla

  1. Teastaíonn foinse sonraí le tacaíocht ó GDAL uait, cosúil le comhaid chruthach (anseo táimid ag úsáid comhad cruth polygon simplí, test_poly.shp, le trí ghné):

Python console
>>> from django.contrib.gis.gdal import DataSource
>>> ds = DataSource("test_poly.shp")
>>> layer = ds[0]
>>> print(layer.fields)  # Exploring the fields in the layer, we only want the 'str' field.
['float', 'int', 'str']
>>> print(len(layer))  # getting the number of features in the layer (should be 3)
3
>>> print(layer.geom_type)  # Should be 'Polygon'
Polygon
>>> print(layer.srs)  # WGS84 in WKT
GEOGCS["GCS_WGS_1984",
    DATUM["WGS_1984",
        SPHEROID["WGS_1984",6378137,298.257223563]],
    PRIMEM["Greenwich",0],
    UNIT["Degree",0.017453292519943295]]

  1. Anois sainmhínímid ár samhail Django comhfhreagrach (déan cinnte go n-úsáidtear: djadmin: migrate):

    Code
    from django.contrib.gis.db import models


class TestGeo(models.Model):
    name = models.CharField(max_length=25)  # corresponds to the 'str' field
    poly = models.PolygonField(srid=4269)  # we want our model in a different SRID

    def __str__(self):
        return "Name: %s" % self.name

  2. Úsáid: aicme: LayerMapping chun na gnéithe go léir a bhaint agus iad a chur sa bhunachar sonraí:

Python console
>>> from django.contrib.gis.utils import LayerMapping
>>> from geoapp.models import TestGeo
>>> mapping = {
...     "name": "str",  # The 'name' model field maps to the 'str' layer field.
...     "poly": "POLYGON",  # For geometry fields use OGC name.
... }  # The mapping is a dictionary
>>> lm = LayerMapping(TestGeo, "test_poly.shp", mapping)
>>> lm.save(verbose=True)  # Save the layermap, imports the data.
Saved: Name: 1
Saved: Name: 2
Saved: Name: 3

Here, LayerMapping transformed the three geometries from the shapefile in their original spatial reference system (WGS84) to the spatial reference system of the GeoDjango model (NAD83). If no spatial reference system is defined for the layer, use the source_srs keyword with a SpatialReference object to specify one.

Sraith Maping API

class LayerMapping(model, data_source, mapping, layer=0, source_srs=None, encoding=None, transaction_mode='commit_on_success', transform=True, unique=True, using='default')

Is iad seo a leanas na hargóintí agus na heochairfhocail a d'fhéadfaí a úsáid le linn rudaí Layermapping` a chur isteach.

Argóint

Cur síos

``Samhail ``

An tsamhail gheografach, ní sampla.

foinse sonraí

The path to the OGR-supported data source file (e.g., a shapefile). Also accepts django.contrib.gis.gdal.DataSource instances.

mapaitheo

Foclóir: is teaghráin iad na heochracha a fhreagraíonn don réimse samhail, agus freagraíonn luachanna d'ainmneacha réimse teaghrán don ghné OGR, nó más réimse samhail is geografach é ansin ba chóir go bhfreagródh sé do chineál geoiméadrachta OGR, m.sh., `POINT, LINESTRING`, ``POLYGON'`.

Argóintí Eochair

sraithe

Innéacs an chiseal le húsáid ón bhFoinse Sonraí (réamhshocraithe go 0)

foinse_srs

Use this to specify the source SRS manually (for example, some shapefiles don't come with a '.prj' file). An integer SRID, WKT or PROJ strings, and django.contrib.gis.gdal.SpatialReference objects are accepted.

``ionchódú ``

Specifies the character set encoding of the strings in the OGR data source. For example, 'latin-1', 'utf-8', and 'cp437' are all valid encoding parameters.

mod_idirbhearta

D'fhéadfadh sé a bheith `commit_on_success' (réamhshocraithe) nó `'autochommit'.

`claochl

Setting this to False will disable coordinate transformations. In other words, geometries will be inserted into the database unmodified from their original state in the data source.

uath

Setting this to the name, or a tuple of names, from the given model will create models unique only to the given name(s). Geometries from each feature will be added into the collection associated with the unique model. Forces the transaction mode to be 'autocommit'.

`Úsáid

Socraíonn an bunachar sonraí le húsáid agus sonraí spásúla á iompórtá Is é réamhshocraithe ``'default' ``.

``save () ``Argóintí Eochairfhocal

LayerMapping.save(verbose=False, fid_range=False, step=False, progress=False, silent=False, stream=sys.stdout, strict=False)

The save() method also accepts keywords. These keywords are used for controlling output logging, error handling, and for importing specific feature ranges.

Argóintí Eochairfhocal

Cur síos

raon fid

May be set with a slice or tuple of (begin, end) feature ID's to map from the data source. In other words, this keyword enables the user to selectively import a subset range of features in the geographic data source.

`dul chun cinne

When this keyword is set, status information will be printed giving the number of features processed and successfully saved. By default, progress information will be printed every 1000 features processed, however, this default may be overridden by setting this keyword with an integer for the desired interval.

ciúna

De réir réamhshocraithe, clóitear fógraí earráide neamh-mharfach chuig sys.stdout`, ach féadfar an eochairfhocal seo a shocrú chun na fógraí seo a dhíchumasú.

céime

Má shocraítear é le sláimhir, tarlóidh idirbhearta ag gach eatramh céim. Mar shampla, má tharlódh sé step = 1000, tiomantas tar éis na 1,000ú gné, an 2,000ú gné srl.

sruth

Status information will be written to this file handle. Defaults to using sys.stdout, but any object with a write method is supported.

``docht ``

Execution of the model mapping will cease upon the first error encountered. The default value (False) behavior is to attempt to continue.

Verbose

Má shocraítear é, clófar faisnéis ina dhiaidh sin gach samhail sábháil a fhorghníomhú ar an mbunachar sonraí.

Fabhtcheartú

Rith as cuimhne

As noted in the warning at the top of this section, Django stores all SQL queries when DEBUG=True. Set DEBUG=False in your settings, and this should stop excessive memory use when running LayerMapping scripts.

MySQL: earráid max_allowed_packet

Má thagann tú ar an earráid seo a leanas agus tú ag úsáid LayerMapping agus MySQL:

Pytb
OperationalError: (1153, "Got a packet bigger than 'max_allowed_packet' bytes")

Then the solution is to increase the value of the max_allowed_packet setting in your MySQL configuration. For example, the default value may be something low like one megabyte -- the setting may be modified in MySQL's configuration file (my.cnf) in the [mysqld] section:

Ini
max_allowed_packet = 10M

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