我正在尝试做简单的查询:
entity = DeviceLocation.query(ndb.StringProperty('deviceID') == data['deviceID']).order(-DeviceLocation.timestamp).get()
每次它引发下一个错误:
NeedIndexError: no matching index found. recommended index is:
- kind: DeviceLocation
properties:
- name: deviceID
- name: timestamp
问题是，即使我正在尝试创建索引(以此为指导 - https://cloud.google.com/appengine/docs/python/datastore/indexes)，部署命令 (gcloud app deloy index.yaml) 也返回了这个:
ERROR: (gcloud.app.deploy) Server responded with code [400]:
Bad Request Unexpected HTTP status 400.
Creating a composite index failed for entity_type: "DeviceLocation"
ancestor: false
Property {
name: "timestamp"
direction: 2
}
: This index:
IndexDef{form=SCANNER_BUILTIN_SINGLE_PROPERTY, kind=DeviceLocation, isAncestor=false, propertyDefs=[PropertyDef{path=timestamp, direction=DESCENDING, mode=null}]}
is not necessary, since single-property indices are built in. Please remove it from your index file and upgrade to the latest version of the SDK, if you haven't already.
据我理解，错误之间存在矛盾。这与 group_by 和 projection 相关。
目前，无法运行任何复杂的查询，这使我无法取得任何进展。
请您参考如下方法:
实际上这不是一个“简单查询”，因为您是按 deviceID 过滤并按 timestamp 排序。
GAE 指导您创建一个复合索引，这是您必须附加到您的 index.yaml 文件的内容:
- kind: DeviceLocation
properties:
- name: deviceID
- name: timestamp
确保在此特定顺序中包含这两个属性(deviceID 和 timestamp)。
最后要改进的是按属性过滤的方式:
DeviceLocation.deviceID == data['deviceID']
