Serialization error when incrementing a counter

[prk3]

I'm trying to increment a counter column with a query like this:

UPDATE monthly_counters SET action_counter = action_counter + ? WHERE ...;

My code is proving a value of type i64:

session.execute_unpaged(&increment_by_statement, (100i64,)).await?;

Execution fails at serialization of parameters:

Serializing values failed: SerializationError: Failed to serialize query arguments (i64,): failed to serialize column sent_activations: SerializationError: Failed to type check Rust type i64 against CQL type Counter: expected one of the CQL types: [BigInt]

It seems that i64 can't be used to increment a counter. I tried providing CqlValue::BigInt(100) and num_bingint::BigInt, none of those worked. How would I provide a value to that query?

[Lorak-mmk]

We have a section of documentation about Counter type: https://rust-driver.docs.scylladb.com/stable/data-types/counter.html

It sadly doesn't have an update example, but it does show what type to use: use scylla::frame::value::Counter;

So you example would be:

use scylla::frame::value::Counter;
session.execute_unpaged(&increment_by_statement, (Counter(100i64),)).await?;

[Lorak-mmk]

@wprzytula possible minor issue: I see there is i64 deserialization for Counter: impl_fixed_numeric_type!(i64, [BigInt | Counter]);. For the sake of type safety and consistency with serialization shouldn't only the Counter type be able to deserialize Counter column?

[prk3]

We have a section of documentation about Counter type: https://rust-driver.docs.scylladb.com/stable/data-types/counter.html

It sadly doesn't have an update example, but it does show what type to use: use scylla::frame::value::Counter;

So you example would be:

use scylla::frame::value::Counter;
session.execute_unpaged(&increment_by_statement, (Counter(100i64),)).await?;

I missed that doc. Your solution works like a charm. Thank you! Fell free to close this issue one you figure out what to do with serialization vs deserialization type discrepancy.

[Lorak-mmk]

For completeness, I opened a PR that adds an example snippet that updates the counter value: #1100

[wprzytula]

@wprzytula possible minor issue: I see there is i64 deserialization for Counter: impl_fixed_numeric_type!(i64, [BigInt | Counter]);. For the sake of type safety and consistency with serialization shouldn't only the Counter type be able to deserialize Counter column?

Agreed. I encourage you to fix that.

[Lorak-mmk]

@wprzytula possible minor issue: I see there is i64 deserialization for Counter: impl_fixed_numeric_type!(i64, [BigInt | Counter]);. For the sake of type safety and consistency with serialization shouldn't only the Counter type be able to deserialize Counter column?

Agreed. I encourage you to fix that.

#1106