enhancementhelp wantedhole in api
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Description
I was looking to handle code that would generate INTERSECT clauses in a loop based on some input. For instance:
SELECT t.* FROM t WHERE t.foo = 'a'
INTERSECT
SELECT t.* FROM t WHERE t.foo = 'b'
INTERSECT
-- ...
(except more complicated to make the INTERSECT actually worth it)
Since https://github.com/diesel-rs/diesel/pull/2514 landed I tried this out but I think I'm running into the same issue one gets when adding filter clauses in a loop - the type of the fold accumulator changes each iteration. Specifically the two methods I tried were:
// This gets me "expected `BoxedSelectStatement`
// found `CombinationClause`"
let query_base = t.into_boxed();
let attempt_1 = (0..10).fold(query_base, |query, _| {
query.intersect(t.filter(t::foo.eq(1)))
});
// This gets me "expected `CombinationClause<one thing>`
// found `CombinationClause<other thing>`"
let query_base = t.intersect(t.filter(t::foo.eq(1)));
let attempt_2 = (0..10).fold(query_base, |query, _| {
query.intersect(t.filter(t::foo.eq(1)))
});
Would it be useful to have an into_boxed equivalent for intersect? Or is there already one and I just couldn't find it? Or is there another better way to achieve this functionality?