Mike,
Would this select query be able to get our aggregated data?
query = select(func.max(DataModel.value)).select_from(_query
.subquery()).group_by(
func.date_format(DataModel.timestamp, "%Y-%m-%d %H")
)
We tried this route but are now getting this error
"errors": [
{
"message": "'Select' object has no attribute 'statement'",
"locations": [
{
"line": 2,
"column": 3
}
],
On Thursday, April 13, 2023 at 10:13:44 AM UTC-7 Peter Harrison wrote:
> Thanks Mike,
>
> Ideally we'd prefer to find a solution via Graphene-SQLAlchemy.
> Unfortunately we don't have the luxury of creating our own query when
> interacting with Graphene-SQLAlchemy.
>
> So the key question for us is, can you modify an existing
> sqlalchemy.orm.query.Query object to insert a "func.max(Data.value)" object
> into the select? This is what Graphene-SQLAlchemy is giving us.
> If this is possible, then the group_by part is easy. We have tested that
> frequently, the hard part is the modifying the original "select" object.
>
> 1. We have tried add_columns, but that adds in incompatible object type in
> the GraphQL results making it an unusable option.
> 2. We thought that modifying the select would be possible using data with
> "statement.froms" but can't figure out how to update the MetaData object in
> it
>
> If modifying the "select" after its creation is not possible, we need to
> start considering using a separate reporting table with hourly data.
>
> On Wednesday, April 12, 2023 at 3:12:46 PM UTC-7 Mike Bayer wrote:
>
>>
>>
>> On Wed, Apr 12, 2023, at 5:21 PM, Luis Del Rio IV wrote:
>>
>> I am currently using the following sqlalchemy code,
>>
>> _query = super().get_query(model, info, sort, **args)
>> query = _query.group_by(
>> func.date_format(DataModel.timestamp, "%Y-%m-%d %H")
>> )
>> return query
>>
>> I am trying to aggregate the the max value of a field from
>> DataModel.value utilizing the group by clause.
>>
>> In simple sql, you would do the following.
>>
>> SELECT max(data.value) AS data_value
>> from data
>> GROUP BY date_format(data.timestamp, "%Y-%m-%d %H")
>>
>> What would the proper way to express this? The various methods I have
>> tried somehow overwrite the original query and do not map to our attributes.
>>
>>
>> using legacy query style:
>>
>> q1 = session.query(func.max(Data.value)).group_by(
>> func.date_format(Data.timestamp, "%Y-%m-%d %H")
>> )
>>
>>
>> using 2.0 style select(), replace "session.query" with "select":
>>
>> s1 = select(func.max(Data.value)).group_by(
>> func.date_format(Data.timestamp, "%Y-%m-%d %H")
>> )
>>
>> POC script is at the bottom of this email.
>>
>>
>>
>> I have some additional context on the issue
>>
>> 1. We are using the graphene-sqlalchemy package.
>> 2. When you do a GraphQL web api query, the package creates a
>> sqlalchemy.orm.query.Query
>> object.
>> 3. We want to modify this standard query that the package creates so
>> that we can do the group_by action to help us get the maximum time series
>> value for every hour because this is not possible using GraphQL.
>> 4. Talking to the graphene-sqlalchemy team they told us the best
>> place to do the modification to the standardized query is in the
>> get_query
>> method (line 67) in this file: https://github.com/graphql-
>> python/graphene-sqlalchemy/blob/master/graphene_sqlalchemy/fields.py
>>
>> <https://github.com/graphql-python/graphene-sqlalchemy/blob/master/graphene_sqlalchemy/fields.py>
>> 5. The standardized query we need to modify translates to this SQL
>> statement:
>>
>> SELECT sy_data.oid_id, sy_data.rrd_timestamp, sy_data.cabinet_id, sy_data
>> .customer_id, sy_data.value, sy_data.active_flag, sy_data.timestamp
>> FROM sy_data
>> WHERE sy_data.rrd_timestamp >= %(rrd_timestamp_1)s AND
>> sy_data.rrd_timestamp <= %(rrd_timestamp_2)s AND (sy_data.oid_id =
>> %(oid_id_1)s OR sy_data.oid_id = %(o
>> id_id_2)s) ORDER BY sy_data.oid_id ASC, sy_data.rrd_timestamp ASC
>>
>> Therefore we need to find a way to insert a func.max for the values in
>> the first part of the SELECT statement, (before the FROM). It is easy for
>> us to apend the group_by like this.
>>
>>
>> if you have a Query which renders the above SQL, you can add group_by()
>> to it in place. but if these queries are being translated into GraphQL,
>> and GraphQL does not have any concept of GROUP BY, then it wont work, what
>> you want to do would not be possible unless a GraphQL query exists that
>> does what you need.
>>
>>
>> query.group_by(
>> func.date_format(DataModel.timestamp, "%Y-%m-%d %H")
>> )
>>
>> The big issue for us is to figure out how to insert the func.max
>>
>>
>> see func at
>> https://docs.sqlalchemy.org/en/20/core/sqlelement.html#sqlalchemy.sql.expression.func
>>
>>
>> from sqlalchemy import Column
>> from sqlalchemy import DateTime
>> from sqlalchemy import func
>> from sqlalchemy import Integer
>> from sqlalchemy import select
>> from sqlalchemy.orm import declarative_base
>> from sqlalchemy.orm import Session
>>
>> Base = declarative_base()
>>
>>
>> class Data(Base):
>> __tablename__ = "data"
>>
>> id = Column(Integer, primary_key=True)
>> value = Column(Integer)
>> timestamp = Column(DateTime)
>>
>>
>> s = Session()
>>
>> q1 = s.query(func.max(Data.value)).group_by(
>> func.date_format(Data.timestamp, "%Y-%m-%d %H")
>> )
>>
>> print(q1)
>>
>> s1 = select(func.max(Data.value)).group_by(
>> func.date_format(Data.timestamp, "%Y-%m-%d %H")
>> )
>>
>> print(s1)
>>
>>
--
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The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
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