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# exposed
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Gustav Elmgren
02/08/2022, 4:24 PMHi everyone. I'm trying to add a custom function for postgres (the
nullifb
Bogdan
02/08/2022, 7:54 PMdo with generic
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Gustav Elmgren
02/09/2022, 4:57 PMI'm not sure how that would help me. A function requires a column type, but the
nullifb
Bogdan
02/10/2022, 3:41 PM Copy code
class NullIf<T>(expr: ExpressionWithColumnType<T>, default: Expression<T>) :
CustomFunction<T>("nullif", expr.columnType, expr, default)or
Copy code
class NullIf<T>(expr: Expression<T>, default: Expression<T>, columnType: IColumnType) :
CustomFunction<T>("nullif", columnType, expr, default)
fun <T> nullif(expr: ExpressionWithColumnType<T>, default: Expression<T>): NullIf<T> =
NullIf(expr, default, expr.columnType)
fun <T> nullif(expr: Expression<T>, default: ExpressionWithColumnType<T>): NullIf<T> =
NullIf(expr, default, default.columnType)
// optimistic: VarCharColumnType
fun <T> nullif(expr: Expression<T>, default: Expression<T>): NullIf<T> =
NullIf(expr, default, VarCharColumnType()) Copy code
fun <T> nullif(expr: ExpressionWithColumnType<T>, default: T): NullIf<T> =
NullIf(expr, QueryParameter(default, expr.columnType), expr.columnType)g
Gustav Elmgren
02/10/2022, 3:57 PMAh, I see. But in the cases where it returns null, it would still think it would be of type T, which cant be null?
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Bogdan
02/10/2022, 4:38 PMYes. Need a question mark
Copy code
fun <T> nullif(expr: ExpressionWithColumnType<T>, default: T): NullIf<T?> =+-
I showed an example. Experiment with generics to get the results you want
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Gustav Elmgren
02/11/2022, 11:11 AMI see. Thanks!!
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