Develop Reference

SQLAlchemy/Postgres: Intermittent Error Serializing Object After Commit

I have a Flask application that uses SQLAlchemy (with some Marshmallow for serialization and deserialization).
I'm currently encountering some intermittent issues when trying to dump an object post-commit.
To give an example, let's say I have implemented a (multi-tenant) system for tracking system faults of some sort. This information is contained in a fault table:
class Fault(Base):
__tablename__ = "fault"
fault_id = Column(BIGINT, primary_key=True)
workspace_id = Column(Integer, ForeignKey('workspace.workspace_id'))
local_fault_id = Column(Integer)
name = Column(String)
description = Column(String)
I've removed a number of columns in the interest of simplicity, but this is the core of the model. The columns should be largely self explanatory, with workspace_id effectively representing tenant, and local_fault_id representing a tenant-specific fault sequence number, which is handled via a separate fault_sequence table.
This fault_sequence table holds a counter against workspace, and is updated by means of a simple on_fault_created() function that is executed by a trigger:
CREATE TRIGGER fault_created
AFTER INSERT
ON "fault"
FOR EACH ROW
EXECUTE PROCEDURE on_fault_created();
So - the problem:
I have a Flask endpoint for fault creation, where we create an instance of a Fault entity, add this via a scoped session (session.add(fault)), then call session.commit().
It seems that this is always successful in creating the desired entities in the database, executing the sequence update trigger etc. However, when I then try to interrogate the fault object for updated fields (after commit()), around 10% of the time I find that each key/field just points to an Exception:
psycopg2.errors.InFailedSqlTransaction: current transaction is aborted, commands ignored until end of transaction block
Which seems to boil down to the following:
(psycopg2.errors.InvalidTextRepresentation) invalid input syntax for integer: ""
[SQL: SELECT fault.fault_id AS fault_fault_id, fault.workspace_id AS fault_workspace_id, fault.local_fault_id AS fault_local_fault_id, fault.name as fault_name, fault.description as fault_description
FROM fault
WHERE fault.fault_id = %(param_1)s]
[parameters: {'param_1': 166}]
(Background on this error at: http://sqlalche.me/e/13/2j8
My question, then, is what do we think could be causing this?
I think it smells like a race condition, with the update trigger not being complete before SQLAlchemy has tried to get the updated data; perhaps local_fault_id is null, and this is resulting in the invalid input syntax error.
That said, I have very low confidence on this. Any guidance here would be amazing, as I could really do with retrieving that sequence number that's incremented/handled by the update trigger.
Thanks
Edit 1:
Some more info:
I have tried removing the update trigger, in the hope of eliminating that as a suspect. This behaviour is still intermittently evident, so I don't think it's related to that.
I have tried adopting usage of flush and refresh before the commit, and this allows me to get the values that I need - though commit still appears to 'break' the fault object.
Edit 2:
So it really seems to be more postgres than anything else. When I interrogate my database logs, this is the weirdest thing. I can copy and paste the command it says is failing, and I struggle to see how this integer value in the WHERE clause is possibly evaluating to an empty string.
This same error is reproducible with SELECT ... FROM fault WHERE fault.fault_id = '', which in no way seems to be the query making to the DB.
I am stumped.

Your sentence "This same error is reproducible with SELECT ... FROM fault WHERE fault.fault_id = '', which in no way seems to be the query making to the DB." seems to indicate that you are trying to access an object that does not have the database primary key "fault_id".
I guess, given that you did not provide the code, that you are adding the object to your session (session.add), committing (session.commit) and then using the object. As fault_id is autogenerated by the database, the fault object in the session (in memory) does not have fault_id.
I believe you can correct this with:
session.add(fault)
session.commit()
session.refresh(fault)
The refresh needs to be AFTER commit to refresh the fault object and retrieve fault_id.
If you are using async, you need
session.add(fault)
await session.commit()
await session.refresh(fault)

How to fetch warnings from a django mysql query?

I'm trying to get a list of warnings after a mySQL query, using Django admin. I can see from the documentation here that it's possible to record warnings by setting connection.get_warnings to true. But I can't find anything explaining how to read those warnings.
I do not want to throw an exception - I am deleting items from the database using a DELETE IGNORE statement and want to get all instances of deletions that failed (due to external keys, etc.)
I've tried returning the result of the execute function itself (just gave me a number) and calling fetchwarnings() on the cursor (threw a "Cursor object has no attribute fetchwarnings" error).
I'm still new to both Python and Django. I'm looking through all the documentation I can find but can't find anything that works.
from django.db import connection
query = "{query here}"
connection.get_warnings = True
with connection.cursor() as cursor:
cursor.execute(query) <-- Returns a number
return cursor.fetchwarnings() <-- Throws an error

SQLite3 incorrect number of bindings on second query

Using Python and SQlite3 where c is a cursor this code...
print("vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv")
print("SQL and parameters:",sql,parm)
c.execute(sql,parm)
# Get the row
print("Executed OK")
response = c.fetchone()
# If not successful return null
if not response:
return None
#
print("and produced ", response)
print("^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^")
give this output:
vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
SQL and parameters: select * from Links where LinkNum = ? (301,)
Executed OK
and produced (301, 'Index', 'The Independent', 'https://www.independent.co.uk/', 6, 0)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
SQL and parameters: select * from Links where LinkNum = ? (301,)
Encountered exception of type ProgrammingError with arguments ('Incorrect number of bindings supplied. The current statement uses 1, and there are 6 supplied.',)
The application will close
Two identical statements. 1 works and the next throws the exception. As can be seen the row I'm trying to retrieve has 6 columns but that's the only hint/clue I can see. Can anyone help with tracking down the problem? Thanks.

Whatever was causing SQLite to have a fit I remedied the problem by retrieving the second row/object out side the Links object and passing it as an argument to the method I was calling, rather than have that method attempt to retrieve the object.
The problem would still be there but must be deep within the internals of Python instantiation and/or SQLite. Whatever, this problem is solved with some less fancy code.

Error Message when trying to delete features in Feature Service Python API 1.7 for ArcGIS

I am trying to delete features using the delete_features method on the FeatureLayer Object and I keep getting the following error: "This SqlTransaction has completed; it is no longer usable."
The code is below. The error message seems to populate in the last line where="OBJECTID >=0", but I'm not a 100 sure if this is the problem. Unfortunately I'm not very good at programming.
gis = arcgis.GIS("http://gfcgis.maps.arcgis.com", "UserName", "Password")
feature_layer_item = gis.content.search(FeatureLayer, item_type = 'Feature Service')[0]
flayers = feature_layer_item.layers
flayer = flayers[0]
flayer.delete_features(where="OBJECTID >= 0", rollback_on_failure=True)
Any help would be greatly appreciated.
Michael

This sounds like a zombie transaction. Check with your DBA if there's a query, most likely a Stored Procedure, which is being called when your code runs. This message usually shows up when the application code tries to do a commit on the DB after the SP has already committed.
That's the SQL Transaction which has already completed.

Come to find out, it was a simple syntax error causing the issue. I didn't put quotations around 'True' for the rollback_on_failure parameter.

How to execute query in Odoo-8 from Python?

I have the following function in the class hr_evaluation_interview:
#api.onchange('evaluation_id')
def onchange_evalID(self):
self.deadline=self.env.cr.execute('SELECT date FROM hr_evaluation_evaluation where id=119')
Note: I'm just giving id=119 in the query for testing purposes.
When I give self.deadline=datetime.now.strftime(%Y-%m-%d %H:%M:%S") it works fine and changes the value of field deadline when the value of field evaluation_id changes. Again for just testing.
What I really need is to execute a query similar to what I mentioned. However when I execute this query nothing is printing on the deadline field. When I check the log I see this warning:
WARNING db_name openerp.models: Cannot execute name_search, no _rec_name defined on hr_evaluation.evaluation
I tried checking online why this warning, but got no help. Am I doing something wrong? How exactly can I execute query from within #api.onchange(self)?

As Hardik said, cr.execute() doesn't return directly you result. You need to fetch the values from the cursor after executing the query. Try like this:
#api.onchange('evaluation_id')
def onchange_evalID(self):
self.env.cr.execute('SELECT date '
'FROM hr_evaluation_evaluation where id=119')
self.deadline = self.env.cr.fetchone()[0]

If evaluation_id is m2o field of hr.evaluation.evaluation model you can try below code. you don't need to execute query at all.
#api.onchange('evaluation_id')
def onchange_evalID(self):
if self.evaluation_id and self.evaluation_id.date:
self.date = self.evaluation_id.date