SQL clause should persist adapted type

See https://github.com/cashapp/sqldelight/issues/2056#issuecomment-713866907.

Currently, if we union two tables with each column having the same java type, the generated query interface will use the underlying java type, as it is possible that each column has a different ColumnAdapter, so the query implementation wouldn’t be able to know which ColumnAdapter to use when creating the adapted type when constructing the query interface. Ideally, what we would want is the union to produce the adapted type, iff the ColumnAdapter for the column in each table are identical.

Example

Status Quo

People.sq

CREATE TABLE children(
  birthday TEXT AS java.time.LocalDate
);

CREATE TABLE adults(
  birthday TEXT AS java.time.LocalDate
);

birthdays:
SELECT birthday
FROM children
UNION
SELECT birthday
FROM adults;

Birthdays.kt

data class Birthdays(
  val birthday: String?
) {
  …
}

Database Initialization

test_database(
    driver,
    Adults.Adapter(birthdayAdapter = LocalDateColumnAdapter()),
    Children.Adapter(birthdayAdapter = LocalDateColumnAdapter())
)

Proposal

People.sq

typealias Date = java.time.LocalDate -- Or some other syntax

CREATE TABLE children(
  birthday TEXT AS Date
);

CREATE TABLE adults(
  birthday TEXT AS Date
);

birthdays:
SELECT birthday
FROM children
UNION
SELECT birthday
FROM adults;

Birthdays.kt

data class Birthdays(
  val birthday: java.time.LocalDate?
) {
  …
}

Database Initialization

test_database(
    driver,
    dateAdapter = LocalDateColumnAdapter()
)

[AlecStrong]

yea sounds good. agreed compile time safety is good, i usually err on the side of not making our own sql dialect

[veyndan]

Ah gotcha, thanks for the clarification! 😄