App Engine搜索API - 排序结果

Question

I have several entities that I am searching across that include dates, and the Search API works great across all of them except for one thing - sorting.

Here's the data model for one of my entities (simplified of course):

class DepositReceipt(ndb.Expando):
    #Sets creation date
    creation_date = ndb.DateTimeProperty(auto_now_add=True)

---

And the code to create the search.Document where de is an instance of the entity:

document = search.Document(doc_id=de.key.urlsafe(),
    fields=[search.TextField(name='deposit_key', value=de.key.urlsafe()),
            search.DateField(name='created', value=de.creation_date),
            search.TextField(name='settings', value=de.settings.urlsafe()),
            ])

This returns a valid document.

---

And finally the problem line. I took this snippet from the official GAE Search API tutorial and just changed the direction of the sort to DESCENDING and changed the search expression to created (the date property from the Document above).

expr_list = [search.SortExpression(
    expression="created", default_value='',
    direction=search.SortExpression.DESCENDING)]

---

I don't think this is important, but the rest of the search code looks like this:

sort_opts = search.SortOptions(expressions=expr_list)

query_options = search.QueryOptions(
    cursor=query_cursor,
    limit=_NUM_RESULTS,
    sort_options=sort_opts)  

query_obj = search.Query(query_string=query, options=query_options)

search_results = search.Index(name=index_name).search(query=query_obj)

---

In production, I get this error message:

InvalidRequest: Failed to parse search request "settings:ag5zfmdoaWRvbmF0aW9uc3IQCxIIU2V0dGluZ3MYmewDDA"; failed to parse date

Changing the expression="created" to anything else works perfectly fine. This also happens across my other entity types that use dates, so I have no idea what's going on. Advice?

Answer 1

我认为default_value需要是一个有效的日期，而不是''你拥有它”。