distsql: improve columnar operator test harness for decimals

We recently merged a change to add decimals with different numbers of
trailing zeroes in the "interesting datums" set, and it made some
existing tests fail because they used direct string comparison for
equality. This commit adjusts the test harness to be smarter for
decimals.

Release note: None

pkg/sql/distsql/columnar_utils_test.go

@@ -35,6 +35,7 @@ import (
 	"github.com/cockroachdb/cockroach/pkg/sql/rowenc"
 	"github.com/cockroachdb/cockroach/pkg/sql/rowexec"
 	"github.com/cockroachdb/cockroach/pkg/sql/sem/eval"
+	"github.com/cockroachdb/cockroach/pkg/sql/sem/tree"
 	"github.com/cockroachdb/cockroach/pkg/sql/types"
 	"github.com/cockroachdb/cockroach/pkg/storage"
 	"github.com/cockroachdb/cockroach/pkg/util/randutil"
@@ -271,6 +272,26 @@ func verifyColOperator(t *testing.T, args verifyColOperatorArgs) error {
 				return false, err
 			}
 			return math.Abs(expFloat-actualFloat) < floatPrecision, nil
+		case types.DecimalFamily:
+			// Decimals might have a different number of trailing zeroes, so
+			// they too require special handling.
+
+			// We first try direct string matching. If that succeeds, then
+			// great!
+			if expected == actual {
+				return true, nil
+			}
+			// Now parse both strings as decimals and use decimal-specific
+			// comparison.
+			expDecimal, err := tree.ParseDDecimal(expected)
+			if err != nil {
+				return false, err
+			}
+			actualDecimal, err := tree.ParseDDecimal(actual)
+			if err != nil {
+				return false, err
+			}
+			return tree.CompareDecimals(&expDecimal.Decimal, &actualDecimal.Decimal) == 0, nil
 		default:
 			return expected == actual, nil
 		}