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POHow to query for a Computed Property inside a Structured Property in GAE Python
 

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  1. POHow to query for a Computed Property inside a Structured Property in GAE Python
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    <pre><code>class Name_score(ndb.Model): def get_value_of_name(self, name, date): # concatenate "X" and date before returning return_text = "X"+name+str(date) return return_text date = ndb.DateTimeProperty() name = ndb.StringProperty() # Computed values name_value_computed = ndb.ComputedProperty(lambda e: e.get_value_of_name(e.name, e.date)) class Activity_db(ndb.Model): # contains many properties # removed the not relevant ones here name_set = ndb.StructuredProperty(Name_score, repeated=True) hobby = ndb.StringProperty() </code></pre> <p>There are many entries in the NDB. I want to get the records where on particular dates, the "name_value_computed" matches the data provided in the query.<br> To query for all such entries with specific "name_value_computed" and "date" value(example below), what would be the query. </p> <p>Example(algorithm for condition):<br> ("hobby" is "tennis") AND ((if on "date" "18/01/1900", "name_value_computed" is "XJohn18/01/1900") OR (if on "date" "22/04/1910", "name_value_computed" is "XBran22/04/1910"))<br> Is the below one correct: </p> <pre><code>date_1 = datetime.strptime("18/01/1900", '%d/%m/%Y') name_computed_value_1 = "XJohn18/01/1900" date_2 = datetime.strptime("22/04/1910", '%d/%m/%Y') name_computed_value_2 = "XBran22/04/1910" qry_1 = Activity_db.query(ndb.OR(Activity_db.name_set==Name_score(date=date_1, name_value_computed=name_computed_value_1), Activity_db.name_set==Name_score(date=date_2, name_value_computed=name_computed_value_2)), Activity_db.hobby=="tennis") record_list = qry_1.fetch() </code></pre> <p>I got the below error: </p> <pre><code>File "C:\Program Files (x86)\Google\google_appengine\google\appengine\ext\ndb\model.py", line 2745, in __init__ self._set_attributes(kwds) File "C:\Program Files (x86)\Google\google_appengine\google\appengine\ext\ndb\model.py", line 2791, in _set_attributes prop._set_value(self, value) File "C:\Program Files (x86)\Google\google_appengine\google\appengine\ext\ndb\model.py", line 2612, in _set_value raise ComputedPropertyError("Cannot assign to a ComputedProperty") ComputedPropertyError: Cannot assign to a ComputedProperty </code></pre> <p>I referred <a href="https://developers.google.com/appengine/docs/python/ndb/queries#filtering_structured_properties" rel="nofollow">this section</a> of the Google Python GAE page </p>
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    1. USgsinha
    1. USgsinha
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      1. POHow to query for a Computed Property inside a Structured Property in GAE Python
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    1. COIIRC, it should be something like `qry_1 = Activity_db.query(ndb.AND(Activity_db.name_set.date == date_1, Activity_db.name_set.name_value_computed == "nhoJ1"), Activity_db.hobby = "tennis")`. Actually, the call to `ndb.AND` is superfluous here since all your conditions are "and"ed together...
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      1. USmgilson
    2. COThanks mgilson for you reply. You correctly pointed out the unnecessary "ndb.AND" over here(removed now). My actual query contains several more conditions. But, i tried to provide a smaller version(of both class and query) of it here to only focus on the problematic part of it. I have tried to make my question more clear now
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      1. USgsinha
    3. CO@mgilson Be careful with just using AND though. From the documentation an AND between two sub-properties of a repeated field do not behave as desired here, since it could match two separate properties.
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      1. POHow to query for a Computed Property inside a Structured Property in GAE Python
      1. USPatrick Costello
 

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