roachtest: update DSC mixed-version test for v25.3-v25.4

Updated the declarative schema changer job compatibility mixed-version
test to test statements added to the DSC in v25.3 and v25.4, replacing
the previous v24.2-v24.3 version range.

The test now validates backward and forward compatibility for:
- v25.3: ALTER TABLE ... DROP NOT NULL
- v25.4: TRUNCATE, RENAME TABLE, ALTER TABLE ... SET ON UPDATE,
  ALTER TABLE ... RENAME COLUMN

Added cluster version checks to conditionally execute DDLs based on
the active cluster version, ensuring the test runs correctly during
mixed-version upgrades.

Release note: None

Author: rafiss

pkg/cmd/roachtest/tests/mixed_version_job_compatibility_in_declarative_schema_changer.go

@@ -10,6 +10,7 @@ import (
 	gosql "database/sql"
 	"math/rand"
 
+	"github.com/cockroachdb/cockroach/pkg/clusterversion"
 	"github.com/cockroachdb/cockroach/pkg/cmd/roachtest/cluster"
 	"github.com/cockroachdb/cockroach/pkg/cmd/roachtest/option"
 	"github.com/cockroachdb/cockroach/pkg/cmd/roachtest/registry"
@@ -27,7 +28,7 @@ func registerDeclarativeSchemaChangerJobCompatibilityInMixedVersion(r registry.R
 	// This test requires us to come back and change the stmts in executeSupportedDDLs to be those
 	// supported in the "previous" major release.
 	r.Add(registry.TestSpec{
-		Name:    "declarative_schema_changer/job-compatibility-mixed-version-V242-V243",
+		Name:    "declarative_schema_changer/job-compatibility-mixed-version-V253-V254",
 		Owner:   registry.OwnerSQLFoundations,
 		Cluster: r.MakeClusterSpec(4),
 		// Disabled on IBM because s390x is only built on master and mixed-version
@@ -107,13 +108,19 @@ func executeSupportedDDLs(
 		return err
 	}
 
-	// DDLs supported in V24_2.
-	// TODO(sql-foundations): uncomment these when the final 24.2 cluster version
-	// is created.
-	v242DDLs := []string{
-		// `ALTER DATABASE testdb CONFIGURE ZONE USING gc.ttlseconds=1000`,
-		// `ALTER TABLE testdb.testsc.t CONFIGURE ZONE USING gc.ttlseconds=2000`,
-		// `COMMENT ON TYPE testdb.testsc.typ IS 'comment'`,
+	// DDLs supported in V25_3.
+	v253DDLs := []string{
+		`ALTER TABLE testdb.testsc.t2 ALTER COLUMN i DROP NOT NULL`,
+	}
+
+	// DDLs supported in V25_4.
+	v254DDLs := []string{
+		`TRUNCATE testdb.testsc.t3`,
+		`ALTER TABLE testdb.testsc.t RENAME TO t_renamed`,
+		`ALTER TABLE testdb.testsc.t_renamed RENAME TO t`,
+		`ALTER TABLE testdb.testsc.t2 ALTER COLUMN j SET ON UPDATE j + 1`,
+		`ALTER TABLE testdb.testsc.t2 RENAME COLUMN k TO k_renamed`,
+		`ALTER TABLE testdb.testsc.t2 RENAME COLUMN k_renamed TO k`,
 	}
 
 	// Used to clean up our CREATE-d elements after we are done with them.
@@ -130,9 +137,26 @@ func executeSupportedDDLs(
 		`DROP OWNED BY foo`,
 	}
 
-	ddls := append(v242DDLs, cleanup...)
+	clusterVersion, err := helper.ClusterVersion(r)
+	if err != nil {
+		return err
+	}
+	if clusterVersion.AtLeast(clusterversion.V25_3.Version()) {
+		for _, ddl := range v253DDLs {
+			if err := helper.ExecWithGateway(r, nodes, ddl); err != nil {
+				return err
+			}
+		}
+	}
+	if clusterVersion.AtLeast(clusterversion.V25_4.Version()) {
+		for _, ddl := range v254DDLs {
+			if err := helper.ExecWithGateway(r, nodes, ddl); err != nil {
+				return err
+			}
+		}
+	}
 
-	for _, ddl := range ddls {
+	for _, ddl := range cleanup {
 		if err := helper.ExecWithGateway(r, nodes, ddl); err != nil {
 			return err
 		}