Django ORM阵列字段错误

尝试运行migrate命令时出现此错误

文件“/usr/local/lib/python3.4/dist-packages/django/db/backends/utils.py”，第64行，执行返回self.cursor.execute（sql，params）psycopg2.ProgrammingError：operator class “varchar_pattern_ops”不接受数据类型字符变化[]

我在模型中有一个ArrayField . 当我删除ArrayField时，一切正常

我正在使用django 1.8，python 3.4和postgresql 9.4

models

from django.db import models
from django.contrib.postgres.fields import ArrayField
from django.contrib.auth.models import User


class Post(models.Model):

    author = models.ForeignKey(User)
    title = models.CharField(max_length=512)
    slug = models.SlugField(unique=True, db_index=True)
    summary = models.TextField(blank=True, null=True)
    content = models.TextField()
    tags = ArrayField(models.CharField(max_length=256), blank=True, db_index=True)
    is_published = models.BooleanField(default=True)
    has_comments = models.BooleanField(default=True)
    created_on = models.DateTimeField(auto_now_add=True)
    updated_on = models.DateTimeField(auto_now=True)

    def __str__(self):
        return self.title


class Comment(models.Model):

    post = models.ForeignKey(Post, db_index=True)
    name = models.CharField(max_length=256)
    email = models.EmailField()
    content = models.TextField()
    is_published = models.BooleanField(default=False)
    created_on = models.DateTimeField(auto_now_add=True)
    updated_on = models.DateTimeField(auto_now=True)

    def __str__(self):
        return self.name

migrations

from __future__ import unicode_literals

from django.db import models, migrations
import django.contrib.postgres.fields
from django.conf import settings


class Migration(migrations.Migration):

    dependencies = [
        migrations.swappable_dependency(settings.AUTH_USER_MODEL),
    ]

    operations = [
        migrations.CreateModel(
            name='Comment',
            fields=[
                ('id', models.AutoField(verbose_name='ID', serialize=False, auto_created=True, primary_key=True)),
                ('name', models.CharField(max_length=256)),
                ('email', models.EmailField(max_length=254)),
                ('content', models.TextField()),
                ('is_published', models.BooleanField(default=False)),
                ('created_on', models.DateTimeField(auto_now_add=True)),
                ('updated_on', models.DateTimeField(auto_now=True)),
            ],
        ),
        migrations.CreateModel(
            name='Post',
            fields=[
                ('id', models.AutoField(verbose_name='ID', serialize=False, auto_created=True, primary_key=True)),
                ('title', models.CharField(max_length=512)),
                ('slug', models.SlugField(unique=True)),
                ('summary', models.TextField(null=True, blank=True)),
                ('content', models.TextField()),
                ('tags', django.contrib.postgres.fields.ArrayField(blank=True, size=None, base_field=models.CharField(max_length=256), db_index=True)),
                ('is_published', models.BooleanField(default=True)),
                ('has_comments', models.BooleanField(default=True)),
                ('created_on', models.DateTimeField(auto_now_add=True)),
                ('updated_on', models.DateTimeField(auto_now=True)),
                ('author', models.ForeignKey(to=settings.AUTH_USER_MODEL)),
            ],
        ),
        migrations.AddField(
            model_name='comment',
            name='post',
            field=models.ForeignKey(to='posts.Post'),
        ),
    ]