Compound operations

[Edvinas01]

I have a list of operations (they get generated dynamically based on user input and table columns) which need to be joined into a single operation using OR operator:

val ops : List<Op<Boolean>> = ...

In order to do so, I've created a helper utility:

abstract class CompoundOp<T>(
    private val exp: List<Expression<T>>,
    private val op: String
) : Op<T>() {

    override fun toSQL(queryBuilder: QueryBuilder) = exp
        .joinToString(separator = op) { exp ->
            "(${exp.toSQL(queryBuilder)})"
        }
}

class CompoundOrOp<T>(exp: List<Expression<T>>) : CompoundOp<T>(exp, " OR ")

then I can use it in the following way:

val ops : List<Op<Boolean>> = ...

val op: Op<Boolean> = CompoundOrOp(ops)

which results in:

(COLUMN_A = TRUE) OR (COLUMN_B = FALSE) OR (COLUMN_C = 'foo')

However I think I'm missing something. Is there a way to achieve this with current functions and classes present in the library? If not, could this be added as a new feature?

[Tapac]

No, Exposed doesn't have such operations and I don't face a need of them in my practice, could you share use-cases where such compounds could be useful?

Also, you can replace a code above with simple:

fun List<Op<Boolean>>.compoundOr() = reduce { op, nextOp -> op or nextOp }

[Edvinas01]

My use case is that I have quite a lot of "data tables" which depend on flat data structures (that is my entities do not contain joins).

In order to reduce the need of manually having to type out all specific filtering queries, I've created an utility class which takes dependsOnColumns and creates the filter query dynamically. The result of this is List<Op<Boolean>> which I need to pass to searchQuery method.

Previously I was using Spring Data, it had something similar where you can pass an array of Predicate to QueryBuilder.or. That is why I'm looking for similar functionality in Exposed.

[Edvinas01]

Also the reduce operation which you've shown doesn't quite cut it, it will create such result:

(exp OR (exp OR))

while I'm looking for:

exp OR exp OR exp

[Tapac]

Fixed in master: added compondAnd/compoundOr functions and optimized or operator to generate (exp) or (exp) or (exp)