clockworklabs/SpacetimeDB · error · syn::Error

invalid combination: auto_inc, unique index or primary key c

Error message

invalid combination: auto_inc, unique index or primary key cannot have a default value

What it means

A column cannot combine `#[default(...)]` with any of `#[auto_inc]`, `#[primary_key]`, or `#[unique]`: auto-inc and primary-key values are generated by the database, and unique values must be supplied deliberately, so a client-side default would be meaningless or ambiguous. After attribute collection, the macro checks for this combination and errors at the default expression's span.

Source

Thrown at crates/bindings-macro/src/table.rs:907

                    check_duplicate(&auto_inc, span)?;
                    auto_inc = Some(span);
                }
                ColumnAttr::PrimaryKey(span) => {
                    check_duplicate(&primary_key, span)?;
                    primary_key = Some(span);
                }
                ColumnAttr::Index(index_arg) => args.indices.push(index_arg),
                ColumnAttr::Default(expr, span) => {
                    check_duplicate(&default_value, span)?;
                    default_value = Some(expr);
                }
            }
        }

        if let Some(default_value) = &default_value
            && (auto_inc.is_some() || primary_key.is_some() || unique.is_some())
        {
            return Err(syn::Error::new(
                default_value.span(),
                "invalid combination: auto_inc, unique index or primary key cannot have a default value",
            ));
        };

        let column = Column {
            index: col_num,
            ident: field_ident,
            vis: field.vis,
            ty: field.ty,
            default_value,
        };

        if unique.is_some() || primary_key.is_some() {
            unique_columns.push(column.clone());
        }
        if auto_inc.is_some() {
            sequenced_columns.push(column.clone());

View on GitHub (pinned to 524b4487d9)

Solutions

1. Remove `#[default(...)]` from the auto_inc / primary_key / unique column
2. Or remove the conflicting attribute if the default is what you actually need
3. Move the defaulting logic into the reducer that inserts the row

Example fix

// before
#[spacetimedb::table(accessor = user)]
struct User {
    #[primary_key]
    #[auto_inc]
    #[default(0)]
    id: u64,
}

// after
#[spacetimedb::table(accessor = user)]
struct User {
    #[primary_key]
    #[auto_inc]
    id: u64,
}

# flag columns that combine default with auto_inc/primary_key/unique
grep -rn -A3 'default(' src/ | grep -E 'auto_inc|primary_key|unique' || echo OK

When it happens

Trigger: A single column carrying `#[default(expr)]` together with `#[auto_inc]`, `#[primary_key]`, or `#[unique]` (any one of them triggers the check).

Common situations: Adding `#[default(...)]` broadly to all columns during schema design; migrating older schemas where id columns happened to carry defaults.

Related errors

• unions not supported
• must specify table accessor, e.g. `#[spacetimedb::table(acce
• a direct index must be paired with a `#[unique] constraint
• not a column of the table
• spacetimedb table must be a struct

AI-assisted analysis of clockworklabs/SpacetimeDB@524b4487d9 (2026-08-16). Data as JSON: /api/errors/12382d5c21f67008. Report an issue: GitHub.