{"title":"Conas imirce bunachar sonraí a chruthú","version":"5.2","locale":"ga","docname":"howto/writing-migrations","url":"/ga/5.2/howto/writing-migrations/","canonical":"https://djangodocs.dev/ga/5.2/howto/writing-migrations/","summary":"Míníonn an doiciméad seo conas imirce bunachar sonraí a struchtúrú agus a scríobh do chásanna éagsúla a d'fhéad Le haghaidh ábhar tosaigh maidir le himirce,…","html":"

Conas imirce bunachar sonraí a chruthúLink to this heading#

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Míníonn an doiciméad seo conas imirce bunachar sonraí a struchtúrú agus a scríobh do chásanna éagsúla a d'fhéad Le haghaidh ábhar tosaigh maidir le himirce, féach:doc: `an treoir ábhair `</topics/migrations>.

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Imirce sonraí agus bunachair sonraí iolrachaLink to this heading#

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Agus bunachair sonraí iolracha á úsáid agat, b'fhéidir go mbeidh ort a fháil amach cibé acu imirce a reáchtáil i gcoinne bunachar sonraí áirithe nó Mar shampla, b'fhéidir gur mhaith leat imirce a reáchtáil** ar bhunachar sonraí áirithe.

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D'fhonn é sin a dhéanamh is féidir leat ainm an nasc bunachar sonraí a sheiceáil taobh istigh d'oibríocht RunPython trí fhéachaint ar an tréith schema_editor.connection.alias`:

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Code
from django.db import migrations\n\n\ndef forwards(apps, schema_editor):\n    if schema_editor.connection.alias != "default":\n        return\n    # Your migration code goes here\n\n\nclass Migration(migrations.Migration):\n    dependencies = [\n        # Dependencies to other migrations\n    ]\n\n    operations = [\n        migrations.RunPython(forwards),\n    ]\n
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Is féidir leat leideanna a sholáthar freisin a chuirfear ar aghaidh chuig an modh:meth: allow_migration () `de ródairí bunachar sonraí mar `**hints`:

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myapp/dbrouters.py
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Python
class MyRouter:\n    def allow_migrate(self, db, app_label, model_name=None, **hints):\n        if "target_db" in hints:\n            return db == hints["target_db"]\n        return True\n
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Ansin, chun é seo a ghiaráil i do imirce, déan an méid seo a leanas:

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Code
from django.db import migrations\n\n\ndef forwards(apps, schema_editor):\n    # Your migration code goes here\n    ...\n\n\nclass Migration(migrations.Migration):\n    dependencies = [\n        # Dependencies to other migrations\n    ]\n\n    operations = [\n        migrations.RunPython(forwards, hints={"target_db": "default"}),\n    ]\n
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Mura ndéanann d'oibríocht `` RunPython`` nó `` RunSQL`` difear ach do mhúnla amháin, is dea-chleachtas é `` model_name`` a chur ar aghaidh mar leid chun é a dhéanamh chomh trédhearcach agus is féidir don ródaire. Tá sé seo tábhachtach go háirithe maidir le haipeanna ath-inúsáidte agus tríú páirtí.

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Imirce a chuireann réimsí uathúla leisLink to this heading#

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Má chuirtear ascnamh “gnáth” i bhfeidhm a chuireann réimse uathúil neamh-neamhnithe le tábla le sraitheanna atá ann cheana féin, ardófar earráid mar ní ghintear an luach a úsáidtear chun sraitheanna atá ann cheana a líonadh ach uair amháin, rud a bhriseann an srian uathúil.

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Dá bhrí sin, ba chóir na céimeanna seo a leanas a dhéanamh. Sa sampla seo, cuirfimid neamh-nullable:class: ~django.db.models.uuidfield le luach réamhshocraithe. Athraigh an réimse faoi seach de réir do riachtanas.

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Imirce neamh-adamhachaLink to this heading#

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Ar bhunachair sonraí a thacaíonn le hidirbhearta DDL (SQLite agus PostgreSQL), rithfidh imirce taobh istigh d'idirbheart de réir réamhshocraithe. Maidir le cásanna úsáide mar imirce sonraí a dhéanamh ar tháblaí móra, b'fhéidir gur mhaith leat imirce a chosc ó rith in idirbheart tríd an tréith atomic` a shocrú do `False:

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Code
from django.db import migrations\n\n\nclass Migration(migrations.Migration):\n    atomic = False\n
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Laistigh d'imirce den sórt sin, reáchtáiltear gach oibríocht gan idirbheart. Is féidir codanna den imirce a fhorghníomhú taobh istigh d'idirbheart ag baint úsáid:func: ~django.db.transaction.atomic () `nó trí `Atomic=True` a chur chuig RunPython`.

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Seo sampla d'imirce sonraí neamh-adamhacha a nuashonraíonn tábla mór i mbaisceanna níos lú:

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Code
import uuid\n\nfrom django.db import migrations, transaction\n\n\ndef gen_uuid(apps, schema_editor):\n    MyModel = apps.get_model("myapp", "MyModel")\n    while MyModel.objects.filter(uuid__isnull=True).exists():\n        with transaction.atomic():\n            for row in MyModel.objects.filter(uuid__isnull=True)[:1000]:\n                row.uuid = uuid.uuid4()\n                row.save()\n\n\nclass Migration(migrations.Migration):\n    atomic = False\n\n    operations = [\n        migrations.RunPython(gen_uuid),\n    ]\n
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Níl éifeacht ag an tréith atomic ar bhunachair sonraí nach dtacaíonn le hidirbhearta DDL (m.sh. MySQL, Oracle). (Tagraíonn “tacaíocht ráiteas DDL adamhach” MySQL < https://dev.mysql.com/doc/refman/en/atomic-ddl.html> do ráitis aonair seachas ráitis iolracha atá fillte in idirbheart is féidir a rolladh ar ais.)

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Ord na n-imirce a rialúLink to this heading#

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Cinneann Django an t-ord ina gcaithfear imirce a chur i bhfeidhm ní trí ainm comhaid gach imirce, ach trí graf a thógáil ag baint úsáide as dhá airíonna ar an aicme Imigration: dependencies` agus ``run_before ``.

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Má d'úsáid tú an t-ordú:djadmin: makemigrations is dócha go bhfaca tú dependencies i ngníomh cheana féin toisc go bhfuil sé seo sainmhínithe ag imirce uathoibríoch mar chuid dá bpróiseas cruthaithe.

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Dearbhaítear an maoin `spleáchais ``mar seo:

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Code
from django.db import migrations\n\n\nclass Migration(migrations.Migration):\n    dependencies = [\n        ("myapp", "0123_the_previous_migration"),\n    ]\n
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De ghnáth beidh sé seo go leor, ach ó am go ham b'fhéidir go gcaithfidh tú a chinntiú go ritheann d'imirce* roim* imirce eile. Tá sé seo úsáideach, mar shampla, chun imirce feidhmchláir tríú páirtí a reáchtáil* tar éis d'athsholáthar your:setting: AUTH_USER_MODEL.

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Chun é seo a bhaint amach, cuir na himirce go léir ar chóir a bheith ag brath ar leatsa sa tréith run_before ``ar do rang ``Immigration:

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Code
class Migration(migrations.Migration):\n    ...\n\n    run_before = [\n        ("third_party_app", "0001_do_awesome"),\n    ]\n
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Is fearr leat dependencies a úsáid seachas run_before ``nuair is féidir. Níor cheart duit ``run_before ``a úsáid ach mura bhfuil sé inmhianaithe nó neamhphraiticiúil ``spleáchais a shonrú san imirce a theastaíonn uait a reáchtáil tar éis an ceann atá á scríobh agat.

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Sonraí a imirce idir apps tríú páirtíLink to this heading#

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Is féidir leat imirce sonraí a úsáid chun sonraí a aistriú ó fheidhmchlár tríú páirtí amháin go ceann eile.

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Má tá sé ar intinn agat an sean-aip a bhaint níos déanaí, beidh ort an maoin spleáchais ``a shocrú bunaithe ar cibé an bhfuil an sean-aip suiteáilte nó nach bhfuil. Seachas sin, beidh spleáchais in easnamh agat nuair a dhíshuiteálann tú an sean-aip. Ar an gcaoi chéanna, beidh ort: exc: `LookuPerror a ghabháil sa ghlao ``apps.get_model () ``a aisghabhann samhlacha ón sean-aip. Ligeann an cur chuige seo duit do thionscadal a imscaradh áit ar bith gan an sean-aip a shuiteáil agus ansin a dhíshuiteáil.

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Seo imirce samplach:

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myapp/imirceach/0124_move_old_app_to_new_app.py
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Python
from django.apps import apps as global_apps\nfrom django.db import migrations\n\n\ndef forwards(apps, schema_editor):\n    try:\n        OldModel = apps.get_model("old_app", "OldModel")\n    except LookupError:\n        # The old app isn't installed.\n        return\n\n    NewModel = apps.get_model("new_app", "NewModel")\n    NewModel.objects.bulk_create(\n        NewModel(new_attribute=old_object.old_attribute)\n        for old_object in OldModel.objects.all()\n    )\n\n\nclass Migration(migrations.Migration):\n    operations = [\n        migrations.RunPython(forwards, migrations.RunPython.noop),\n    ]\n    dependencies = [\n        ("myapp", "0123_the_previous_migration"),\n        ("new_app", "0001_initial"),\n    ]\n\n    if global_apps.is_installed("old_app"):\n        dependencies.append(("old_app", "0001_initial"))\n
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Smaoinigh freisin ar cad ba mhaith leat a tharlóidh nuair nach gcuirtear an imirce i bhfeidhm. D'fhéadfá aon rud a dhéanamh (mar atá sa sampla thuas) nó cuid de na sonraí nó go léir a bhaint as an bhfeidhmchlár nua. Coigeartaigh an dara argóint den oibríocht: mod: ~django.db.migrations.operations.runpython dá réir.

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Athrú `ManyTomanyField chun samhail ``trí ``a úsáidLink to this heading#

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If you change a ManyToManyField to use a through\nmodel, the default migration will delete the existing table and create a new\none, losing the existing relations. To avoid this, you can use\nSeparateDatabaseAndState to rename the existing table to the new\ntable name while telling the migration autodetector that the new model has\nbeen created. You can check the existing table name and constraint name through\nsqlmigrate or dbshell. You can check the new table name\nwith the through model's _meta.db_table property. Your new through\nmodel should use the same names for the ForeignKeys as Django did. Also if\nit needs any extra fields, they should be added in operations after\nSeparateDatabaseAndState.

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Mar shampla, dá mbeadh samhail Leabhar againn le ManyTomanyField ag nascadh le Author ``, d'fhéadfaimis samhail tríd ``Authorbook a chur leis le réimse nua is_primary, mar shampla:

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Code
from django.db import migrations, models\nimport django.db.models.deletion\n\n\nclass Migration(migrations.Migration):\n    dependencies = [\n        ("core", "0001_initial"),\n    ]\n\n    operations = [\n        migrations.SeparateDatabaseAndState(\n            database_operations=[\n                # Old table name from checking with sqlmigrate, new table\n                # name from AuthorBook._meta.db_table.\n                migrations.RunSQL(\n                    sql="ALTER TABLE core_book_authors RENAME TO core_authorbook",\n                    reverse_sql="ALTER TABLE core_authorbook RENAME TO core_book_authors",\n                ),\n            ],\n            state_operations=[\n                migrations.CreateModel(\n                    name="AuthorBook",\n                    fields=[\n                        (\n                            "id",\n                            models.AutoField(\n                                auto_created=True,\n                                primary_key=True,\n                                serialize=False,\n                                verbose_name="ID",\n                            ),\n                        ),\n                        (\n                            "author",\n                            models.ForeignKey(\n                                on_delete=django.db.models.deletion.DO_NOTHING,\n                                to="core.Author",\n                            ),\n                        ),\n                        (\n                            "book",\n                            models.ForeignKey(\n                                on_delete=django.db.models.deletion.DO_NOTHING,\n                                to="core.Book",\n                            ),\n                        ),\n                    ],\n                    options={\n                        "constraints": [\n                            models.UniqueConstraint(\n                                fields=["author", "book"],\n                                name="unique_author_book",\n                            )\n                        ],\n                    },\n                ),\n                migrations.AlterField(\n                    model_name="book",\n                    name="authors",\n                    field=models.ManyToManyField(\n                        to="core.Author",\n                        through="core.AuthorBook",\n                    ),\n                ),\n            ],\n        ),\n        migrations.AddField(\n            model_name="authorbook",\n            name="is_primary",\n            field=models.BooleanField(default=False),\n        ),\n    ]\n
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Samhail neamh-bhainistithe a athrú go bainistitheLink to this heading#

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Más mian leat samhail neamhbhainistithe (:attr: managed=false <django.db.models.Options.managed>) a athrú go bainistithe, ní mór duit Managed = False` a bhaint agus imirce a ghiniúint sula ndéanann tú athruithe eile a bhaineann le scéim ar an tsamhail, ós rud é nach féidir athruithe scéime atá le feiceáil san imirce ina bhfuil an oibríocht chun `Meta.Managed ``a athrú.

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