How to add the index_elements to the on_conflict_do_update() method

[Chaozy Z]

Hi there, I just started to learn SQLAlchemy. 0

I have a `on_conflict_do_update` command as follows:

```

insert_stmt = insert(MessageSymbol).values(message_id=12345, symbol_id=1)

do_update_stmt = insert_stmt.on_conflict_do_update( index_elements=['message_id'], set_=dict( symbol_id=123 ) )

```

and my MessageSymbol is defined as follow:

```

class MessageSymbol(Base):

 __tablename__ = "message_symbol" 

message_id = Column(BigInteger, primary_key=True, nullable=False) 

symbol_id = Column(BigInteger, nullable=False)

```

When the command is executed it throws the error:

```

sqlalchemy.exc.ProgrammingError: (psycopg2.errors.InvalidColumnReference) there is no unique or exclusion constraint matching the ON CONFLICT specification

[SQL: INSERT INTO message_symbol (message_id, symbol_id) VALUES (%(message_id)s, %(symbol_id)s) ON CONFLICT (message_id) DO UPDATE SET symbol_id = %(param_1)s]
[parameters: {'message_id': 12345, 'symbol_id': 1, 'param_1': 123}]

```

Since I have defined the `message_id` as the primary key I assume it should be a unique constraint. I am wondering what else is being missing? 

Chaozy

[Chaozy Z]

I also tried to add unique=True to the column message_id but still fail with the same error

[Simon King]

Does the table definition in postgres match your SQLAlchemy
definition? Adding "unique=True" to the SQLAlchemy table definition
will not automatically add an index to an existing table in the
database.

If you connect to the database using "psql" and run "\d
message_symbol", does it show the primary key and/or unique index?

Simon

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[Chaozy Z]

Many thanks your suggestion!  I checked the properties of the table and it turns that the primary key is actually the composite of both the message_id and the symbol_id. Problem solved by simply adding the symbol_id into the index_elements. Thank you again for your time and assistance!

Chaozy