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Aggregation Operation in JSON Column #301

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Menda0 opened this Issue Oct 9, 2017 · 1 comment

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Menda0 commented Oct 9, 2017

Hi I am trying to execute the following query:

select((o.label,avg(o.properties["Output"])) for o in Object if o.repid.id == 2 and o.object_class.name == "Application Service")

However I an getting the following error:

Function 'AVG' expects argument of numeric type, got 'Json' in avg(o.properties['Throughput'])

I tried to execute an aggregation operation in non JSON columns with no problem.

Does pony orm not support aggregation operation in JSON columns or there is any way do solve this problem?

Regards,
Marco Mendão

@kozlovsky kozlovsky self-assigned this Oct 9, 2017

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kozlovsky commented Oct 9, 2017

Hi, I think we need to fix it. Currently it is not working because Pony does not know the type of JSON expression - is it int, str or something else, and may be different in different rows. Probably we can implicitly case such JSON expressions to float, it should be what user expects in most cases.

Also, we need to add support of float function to allow explicit conversion of any expression to the float type

@kozlovsky kozlovsky added this to the 0.7.4 milestone Mar 14, 2018

@kozlovsky kozlovsky closed this in 5183c44 Mar 14, 2018

kozlovsky added a commit that referenced this issue Jul 23, 2018

Pony ORM Release 0.7.4 (2018-07-23)
# Major features

* Hybrid methods and properties added: https://docs.ponyorm.com/entities.html#hybrid-methods-and-properties
* Allow to base queries on another queries: `select(x.a for x in prev_query if x.b)`
* Added support of Python 3.7
* Added support of PyPy
* `group_concat()` aggregate function added
* pony.flask subpackage added for integration with Flask

# Other features

* `distinct` option added to aggregate functions
* Support of explicit casting to `float` and `bool` in queries

# Improvements

* Apply @cut_traceback decorator only when pony.MODE is 'INTERACTIVE'

# Bugfixes

* In SQLite3 `LIKE` is case sensitive now
* #249: Fix incorrect mixin used for Timedelta
* #251: correct dealing with qualified table names
* #301: Fix aggregation over JSON Column
* #306: Support of frozenset constants added
* #308: Fixed an error when assigning JSON attribute value to the same attribute: obj.json_attr = obj.json_attr
* #313: Fix missed retry on exception raised during db_session.__exit__
* #314: Fix AttributeError: 'NoneType' object has no attribute 'seeds'
* #315: Fix attribute lifting for JSON attributes
* #321: Fix KeyError on obj.delete()
* #325: duplicating percentage sign in raw SQL queries without parameters
* #331: Overriding __len__ in entity fails
* #336: entity declaration serialization
* #357: reconnect after PostgreSQL server closed the connection unexpectedly
* Fix Python implementation of between() function and rename arguments: between(a, x, y) -> between(x, a, b)
* Fix retry handling: in PostgreSQL and Oracle an error can be raised during commit
* Fix optimistic update checks for composite foreign keys
* Don't raise OptimisticCheckError if db_session is not optimistic
* Handling incorrect datetime values in MySQL
* Improved ImportError exception messages when MySQLdb, pymysql, psycopg2 or psycopg2cffi driver was not found
* desc() function fixed to allow reverse its effect by calling desc(desc(x))
* __contains__ method should check if objects belong to the same db_session
* Fix pony.MODE detection; mod_wsgi detection according to official doc
* A lot of inner fixes
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