ProgrammingError - sqlalchemy - on_conflict_do_update - sqlalchemy

Question

Following this question:
As Ilja Everilä mentioned in his answer, I created a table object:
from sqlalchemy import *
metadata = MetaData()
idTagTable = Table('id_tag', metadata,
Column('id', String(255), primary_key = True),
Column('category', String(20), nullable = False),
Column('createddate', Date, nullable = False),
Column('updatedon', Date, nullable = False)
)
After creating a table object, I changed insert and update statements:
insert_statement = sqlalchemy.dialects.postgresql.insert(idTagTable)
upsert_statement = insert_statement.on_conflict_do_update(
constraint=PrimaryKeyConstraint('id'),
set_={"updatedon": insert_statement.excluded.updateon,
"category":insert_statement.excluded.category}
)
insert_values = df.to_dict(orient='records')
conn.execute(upsert_statement, insert_values)
Now I am getting Programming Error:
Traceback (most recent call last):
File "<ipython-input-66-0fc6a1bf9c6b>", line 7, in <module>
conn.execute(upsert_statement, insert_values)
File "/home/ubuntu/anaconda2/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 945, in execute
return meth(self, multiparams, params)
File "/home/ubuntu/anaconda2/lib/python2.7/site-packages/sqlalchemy/sql/elements.py", line 263, in _execute_on_connection
return connection._execute_clauseelement(self, multiparams, params)
File "/home/ubuntu/anaconda2/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 1053, in _execute_clauseelement
compiled_sql, distilled_params
File "/home/ubuntu/anaconda2/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 1189, in _execute_context
context)
File "/home/ubuntu/anaconda2/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 1402, in _handle_dbapi_exception
exc_info
File "/home/ubuntu/anaconda2/lib/python2.7/site-packages/sqlalchemy/util/compat.py", line 203, in raise_from_cause
reraise(type(exception), exception, tb=exc_tb, cause=cause)
File "/home/ubuntu/anaconda2/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 1159, in _execute_context
context)
File "/home/ubuntu/anaconda2/lib/python2.7/site-packages/sqlalchemy/engine/default.py", line 467, in do_executemany
cursor.executemany(statement, parameters)
ProgrammingError: (psycopg2.ProgrammingError) syntax error at or near
")"
LINE 1: ...category) VALUES ('sports') ON CONFLICT () DO UPDAT...
^
Not Able to understand why I am getting this error.

Answer 1

The PrimaryKeyConstraint object you're using as constraint= argument is not bound to any table and would seem to produce nothing when rendered, as seen in ON CONFLICT (). Instead pass the primary key(s) of your table as the conflict_target and Postgresql will perform unique index inference:
upsert_statement = insert_statement.on_conflict_do_update(
constraint=idTagTable.primary_key,
set_={"updatedon": insert_statement.excluded.updateon,
"category":insert_statement.excluded.category}
)