sql/opt/norm: propagate kv errors from cast folding

Swallowing KV errors here leads to incorrect results. Writes can be missed
and serializability can be silently violated. This comes up in the context
of the randomized schema change testing.

Release note: None

pkg/sql/opt/norm/BUILD.bazel

@@ -32,6 +32,7 @@ go_library(
     importpath = "github.com/cockroachdb/cockroach/pkg/sql/opt/norm",
     visibility = ["//visibility:public"],
     deps = [
+        "//pkg/roachpb",
         "//pkg/sql/catalog/colinfo",
         "//pkg/sql/opt",
         "//pkg/sql/opt/cat",

pkg/sql/opt/norm/fold_constants_funcs.go

@@ -11,6 +11,7 @@
 package norm
 
 import (
+	"github.com/cockroachdb/cockroach/pkg/roachpb"
 	"github.com/cockroachdb/cockroach/pkg/sql/opt"
 	"github.com/cockroachdb/cockroach/pkg/sql/opt/cat"
 	"github.com/cockroachdb/cockroach/pkg/sql/opt/memo"
@@ -369,6 +370,15 @@ func (c *CustomFuncs) FoldCast(input opt.ScalarExpr, typ *types.T) (_ opt.Scalar
 
 	result, err := eval.Expr(c.f.evalCtx, texpr)
 	if err != nil {
+		// Casts can require KV operations. KV errors are not safe to swallow.
+		// Check if the error is a KV error, and, if so, propagate it rather
+		// than swallowing it. See #85677.
+		// TODO(mgartner): Ideally, casts that can error and cause adverse
+		// side-effects would be marked as volatile so that they are not folded.
+		// That would eliminate the need for this special error handling.
+		if errors.HasInterface(err, (*roachpb.ErrorDetailInterface)(nil)) {
+			panic(err)
+		}
 		return nil, false
 	}
 
@@ -395,6 +405,15 @@ func (c *CustomFuncs) FoldAssignmentCast(
 	datum := memo.ExtractConstDatum(input)
 	result, err := eval.PerformAssignmentCast(c.f.evalCtx, datum, typ)
 	if err != nil {
+		// Casts can require KV operations. KV errors are not safe to swallow.
+		// Check if the error is a KV error, and, if so, propagate it rather
+		// than swallowing it. See #85677.
+		// TODO(mgartner): Ideally, casts that can error and cause adverse
+		// side-effects would be marked as volatile so that they are not folded.
+		// That would eliminate the need for this special error handling.
+		if errors.HasInterface(err, (*roachpb.ErrorDetailInterface)(nil)) {
+			panic(err)
+		}
 		return nil, false
 	}