python – ArrayField中的Django JSONField

我在使用带有JSONField的ArrayField插入字段时遇到问题.

models.py

locations = ArrayField(JSONField(null = True,blank = True), blank=True, null = True)

插入

location_arr = [{"locations" : "loc1","amount":Decimal(100.00)},{"locations" : "loc2","amount":Decimal(200.25)}]
instance.locations = location_arr
instance.save()

当我这样做时,我得到了

column “locations” is of type jsonb[] but expression is of type text[]

LINE 1: …d” = 2517, “locations” = ARRAY[‘{“loc…

Hint: You will need to rewrite or cast the expression.

所以我尝试使用以下方式转储它：

import json
location_arr = [{"locations" : "loc1","amount":Decimal(100.00)},{"locations" : "loc2","amount":Decimal(200.25)}]
instance.locations = json.dumps(location_arr)
instance.save()

然后我得到了这个

LINE 1: …d” = 2517, “locations” = ‘[{“loc”:…

DETAIL: “[” must introduce explicitly-specified array dimensions.

我在用：

> Django 1.9
> Python 2.7
> Postgres 9.4.10
> psycopg2 2.6.2

解决方法:

数组

首先,让我们仔细看看Postgresql Arrays文档中的这个重要文本.

Tip: Arrays are not sets; searching for specific array elements can be
a sign of database misdesign. Consider using a separate table with a
row for each item that would be an array element. This will be easier
to search, and is likely to scale better for a large number of
elements.

大多数情况下,您不应该使用数组.

JSONB

JSONB在Django中可用作JSONField类型.该字段比数组字段更具可伸缩性和灵活性,可以更有效地进行搜索.但是,如果您发现自己一直在JSONB字段内搜索上面关于Arrays的声明对JSONB同样有效.

现在你的系统有什么？一个包含JSONB字段的数组.这是一场等待发生的灾难.请规范化您的数据.

概括

so when to use ArrayField?

在极少数情况下,您不需要在该列中进行搜索,并且您不需要使用该列进行连接.