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release-21.2: opt: do not add invalid casts to match types in set operations #75276

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Jan 24, 2022
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release-21.2: opt: do not add invalid casts to match types in set operations #75276

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14 changes: 14 additions & 0 deletions pkg/sql/opt/optbuilder/testdata/union
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Original file line number Diff line number Diff line change
Expand Up @@ -1079,3 +1079,17 @@ sort
├── columns: t68702.a:7 b:8 c:9
└── scan t68702
└── columns: t68702.a:7 b:8 c:9 rowid:10!null crdb_internal_mvcc_timestamp:11 tableoid:12


# Regression test for #70831. Do not add non-existent casts to match types on
# either side of a set operation.
# NOTE: In Postgres this example successfully returns a result. Our tuple typing
# and casting logic doesn't match Postgres's semantics exactly, so we return a
# user error. See
# https://github.com/cockroachdb/cockroach/issues/70831#issuecomment-929547297.
build
SELECT * FROM (VALUES (ARRAY[(true, NULL)])) AS v1
EXCEPT ALL
SELECT * FROM (VALUES (ARRAY[]::RECORD[])) AS v2
----
error (42804): EXCEPT types tuple{bool, unknown}[] and tuple[] cannot be matched
25 changes: 16 additions & 9 deletions pkg/sql/opt/optbuilder/union.go
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Original file line number Diff line number Diff line change
Expand Up @@ -153,15 +153,20 @@ func determineUnionType(left, right *types.T, clauseTag string) *types.T {
}

if left.Equivalent(right) {
// Do a best-effort attempt to determine which type is "larger".
if left.Width() > right.Width() {
return left
}
// In the default case, use the left type.
src, tgt := right, left
if left.Width() < right.Width() {
return right
// If the right type is "larger", use it.
src, tgt = left, right
}
// In other cases, use the left type.
return left
if _, ok := tree.LookupCastVolatility(src, tgt, nil /* sessionData */); !ok {
// Error if no cast exists from src to tgt.
panic(pgerror.Newf(
pgcode.DatatypeMismatch,
"%v types %s and %s cannot be matched", clauseTag, left, right,
))
}
return tgt
}
leftFam, rightFam := left.Family(), right.Family()

Expand Down Expand Up @@ -189,7 +194,7 @@ func determineUnionType(left, right *types.T, clauseTag string) *types.T {
return right
}

// TODO(radu): Postgres has more encompassing rules:
// TODO(#75103): Postgres has more encompassing rules:
// http://www.postgresql.org/docs/12/static/typeconv-union-case.html
panic(pgerror.Newf(
pgcode.DatatypeMismatch,
Expand All @@ -198,7 +203,9 @@ func determineUnionType(left, right *types.T, clauseTag string) *types.T {
}

// addCasts adds a projection to a scope, adding casts as necessary so that the
// resulting columns have the given types.
// resulting columns have the given types. This function assumes that there is a
// valid cast from the column types in dst.cols to the corresponding types in
// outTypes.
func (b *Builder) addCasts(dst *scope, outTypes []*types.T) *scope {
expr := dst.expr.(memo.RelExpr)
dstCols := dst.cols
Expand Down
6 changes: 6 additions & 0 deletions pkg/sql/opt/optbuilder/union_test.go
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Expand Up @@ -72,6 +72,12 @@ func TestUnionType(t *testing.T) {
right: types.String,
expected: nil,
},
{
// Error.
left: types.MakeArray(types.MakeTuple([]*types.T{types.Bool})),
right: types.MakeArray(types.MakeTuple([]*types.T{types.Bool, types.Int})),
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i noticed that this test case differs from the one in #75219 - is that on purpose?

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Yes. In #75219 we're using the OID->OID castMap to determine which casts are valid. In the backports castMap does not yet exist, so we're using the family->family validCasts. They don't match up perfectly so the cast from types.Any -> types.Bool that is not allowed on master is allowed in these release branches, so the test had to change.

expected: nil,
},
}

for _, tc := range testCases {
Expand Down