types: add a .Canonical method to types

This adds a `.Canonical` method to types. This will be used by LDR to
determine which type should be used as the parameter type when creating
prepared statements to replicate arbitrary types.

Canonical is needed because decoding a KV from the source cluster and
querying a local row will return datums that match the canonical type.
So we need a generic way to know the decoded Canonical type of all
types.

Release note: none
Part of: cockroachdb#148310

Author: jeffswenson

pkg/sql/randgen/datum.go

@@ -239,19 +239,16 @@ func RandDatumWithNullChance(
 		}
 		return tree.NewDJsonpath(*jp.AST)
 	case types.TupleFamily:
-		tuple := tree.DTuple{D: make(tree.Datums, len(typ.TupleContents()))}
 		if nullChance == 0 {
 			nullChance = 10
 		}
+		datums := make([]tree.Datum, len(typ.TupleContents()))
 		for i := range typ.TupleContents() {
-			tuple.D[i] = RandDatumWithNullChance(
+			datums[i] = RandDatumWithNullChance(
 				rng, typ.TupleContents()[i], nullChance, favorCommonData, targetColumnIsUnique,
 			)
 		}
-		// Calling ResolvedType causes the internal TupleContents types to be
-		// populated.
-		tuple.ResolvedType()
-		return &tuple
+		return tree.NewDTuple(typ, datums...)
 	case types.BitFamily:
 		width := typ.Width()
 		if width == 0 {
@@ -381,6 +378,9 @@ func RandArrayWithCommonDataChance(
 		contents = RandArrayContentsType(rng)
 	}
 	arr := tree.NewDArray(contents)
+	if err := arr.MaybeSetCustomOid(typ); err != nil {
+		panic(err)
+	}
 	for i := 0; i < rng.Intn(10); i++ {
 		if err :=
 			arr.Append(
@@ -451,6 +451,8 @@ func adjustDatum(datum tree.Datum, typ *types.T) tree.Datum {
 		}
 		return datum
 
+	case types.OidFamily:
+		return tree.NewDOidWithType(datum.(*tree.DOid).Oid, typ)
 	default:
 		return datum
 	}

pkg/sql/randgen/types_test.go

@@ -11,6 +11,7 @@ import (
 
 	"github.com/cockroachdb/cockroach/pkg/sql/types"
 	"github.com/cockroachdb/cockroach/pkg/util/leaktest"
+	"github.com/cockroachdb/cockroach/pkg/util/randutil"
 	"github.com/cockroachdb/errors"
 )
 
@@ -50,3 +51,27 @@ loop:
 		t.Fatal(errors.Errorf("%s", s))
 	}
 }
+
+func TestCanonical(t *testing.T) {
+	defer leaktest.AfterTest(t)()
+
+	rng, _ := randutil.NewTestRand()
+	for range 1000 {
+		typ := RandType(rng)
+
+		if !typ.Canonical().Equivalent(typ.WithoutTypeModifiers()) {
+			t.Errorf("fail: canonical type of %+v should be equivalent to the type without modifiers", typ)
+		}
+
+		datum := RandDatum(rng, typ, false)
+		datumTyp := datum.ResolvedType()
+		if !datumTyp.Equivalent(typ.Canonical()) {
+			t.Errorf("fail: canonical type of %+v is %+v and the datum's type is %+v", typ, typ.Canonical(), datumTyp)
+		}
+
+		if datumTyp.Oid() != typ.Canonical().Oid() {
+			t.Errorf("fail type %+v: canonical type oid %d does not match the datum's (%+v) oid %+v",
+				typ, typ.Canonical().Oid(), datum, datumTyp.Oid())
+		}
+	}
+}

pkg/sql/types/BUILD.bazel

@@ -38,6 +38,7 @@ go_test(
     name = "types_test",
     size = "small",
     srcs = [
+        "canonical_test.go",
         "types_test.go",
         "types_text_marshal_test.go",
     ],