SQLAlchemy + Postgres: "You might need to add explicit type casts" on merge

Question

I have an app that uses SQLAlchemy, and it worked fine when I used SQLite. However, when I moved to PostgreSQL, I found myself unable to even do the merge. Here's the model that I use for the table I am unable to merge items with:

class Item(db.Model):
    __tablename__ = "prices"
    defindex = db.Column(db.Integer, primary_key=True)
    quality = db.Column(db.Integer, primary_key=True)
    craftable = db.Column(db.Boolean, primary_key=True)
    tradeable = db.Column(db.Boolean, primary_key=True)
    item_metadata = db.Column(db.String(70), primary_key=True)
    name = db.Column(db.String(70), primary_key=True)
    currency = db.Column(db.String(70))
    price = db.Column(db.Float)
    price_high = db.Column(db.Float)

And here is how I am trying to do the merge (assume all variables do have proper values assigned):

    new_item = Item(defindex=int(defindex), quality=int(quality), craftable=bool(is_craft),
                tradeable=bool(is_trade), item_metadata=int(priceindex), currency=str(currency),
                price=float(price), price_high=float(price), name=str(name))

But on this call, I get an error:

sqlalchemy.exc.ProgrammingError: (psycopg2.ProgrammingError) operator does not exist: character varying = integer
LINE 3: ... prices.tradeable = true AND prices.item_metadata = 0 AND pr...
                                                         ^
HINT:  No operator matches the given name and argument type(s). You might need to add explicit type casts.
[SQL: 'SELECT prices.defindex AS prices_defindex, prices.quality AS prices_quality, prices.craftable AS prices_craftable, prices.tradeable AS prices_tradeable, prices.item_metadata AS prices_item_metadata, prices.name AS prices_name, prices.currency AS prices_currency, prices.price AS prices_price, prices.price_high AS prices_price_high \nFROM prices \nWHERE prices.defindex = %(param_1)s AND prices.quality = %(param_2)s AND prices.craftable = %(param_3)s AND prices.tradeable = %(param_4)s AND prices.item_metadata = %(param_5)s AND prices.name = %(param_6)s'] [parameters: {'param_1': 1067, 'param_3': True, 'param_6': 'Grandmaster', 'param_5': 0, 'param_4': True, 'param_2': 1}]

I tried adding all the typecasts in creation of new_item, but it was of no use, the error persisted. What should I do to fix it?

@SergeyGornostaev no, it's an integer. I'll update the code and show that I forced all python type conversions. — RomaValcer
@SergeyGornostaev if you put this as an answer, I'll gladly mark it as correct. — RomaValcer

Sergey Gornostaev Sergey Gornostaev · Accepted Answer · 2017-02-26T11:59:35

Column item_metadata defined as a string, so it must be a string. With SQLite it worked because SQLite uses dynamic typing. It does not enforce data type constraints. Data of any type can (usually) be inserted into any column.

SQLAlchemy + Postgres: "You might need to add explicit type casts" on merge

1 Answers