changefeedccl: update nemeses test to use the declarative schema changer

This change updates the nemeses test, which asserts the behavior of changefeeds
under a randomized DML/DDL workload. Previously, the test would only run
with the legacy schema changer. This is not ideal because, by default, the
declarative schema changer is used in production. This change makes it so that
the declarative schema changer is used 90% of the time instead.

Informs: cockroachdb#106906
Epic: none

Release note: None

pkg/ccl/changefeedccl/cdctest/BUILD.bazel

@@ -31,7 +31,6 @@ go_library(
         "//pkg/util/fsm",
         "//pkg/util/hlc",
         "//pkg/util/log",
-        "//pkg/util/randutil",
         "//pkg/util/syncutil",
         "//pkg/util/timeutil",
         "@com_github_cockroachdb_errors//:errors",

pkg/ccl/changefeedccl/cdctest/nemeses.go

@@ -18,7 +18,6 @@ import (
 
 	"github.com/cockroachdb/cockroach/pkg/util/fsm"
 	"github.com/cockroachdb/cockroach/pkg/util/log"
-	"github.com/cockroachdb/cockroach/pkg/util/randutil"
 	"github.com/cockroachdb/errors"
 )
 
@@ -30,7 +29,9 @@ import (
 // duplicates, which the two cdctest.Validator implementations verify for the
 // real output of a changefeed. The output rows and resolved timestamps of the
 // tested feed are fed into them to check for anomalies.
-func RunNemesis(f TestFeedFactory, db *gosql.DB, isSinkless bool) (Validator, error) {
+func RunNemesis(
+	f TestFeedFactory, db *gosql.DB, isSinkless bool, rng *rand.Rand,
+) (Validator, error) {
 	// possible additional nemeses:
 	// - schema changes
 	// - merges
@@ -42,7 +43,6 @@ func RunNemesis(f TestFeedFactory, db *gosql.DB, isSinkless bool) (Validator, er
 	// - sink chaos
 
 	ctx := context.Background()
-	rng, _ := randutil.NewPseudoRand()
 
 	eventPauseCount := 10
 	if isSinkless {

pkg/ccl/changefeedccl/helpers_test.go

@@ -73,13 +73,6 @@ func maybeDisableDeclarativeSchemaChangesForTest(
 	return disable
 }
 
-// disableDeclarativeSchemaChangesForTest tests that are disabled due to differences
-// in changefeed behaviour and are tracked by issue #80545.
-func disableDeclarativeSchemaChangesForTest(t testing.TB, sqlDB *sqlutils.SQLRunner) {
-	sqlDB.Exec(t, "SET use_declarative_schema_changer='off'")
-	sqlDB.Exec(t, "SET CLUSTER SETTING  sql.defaults.use_declarative_schema_changer='off'")
-}
-
 func waitForSchemaChange(
 	t testing.TB, sqlDB *sqlutils.SQLRunner, stmt string, arguments ...interface{},
 ) {

pkg/ccl/changefeedccl/nemeses_test.go

@@ -19,6 +19,7 @@ import (
 	"github.com/cockroachdb/cockroach/pkg/testutils/sqlutils"
 	"github.com/cockroachdb/cockroach/pkg/util/leaktest"
 	"github.com/cockroachdb/cockroach/pkg/util/log"
+	"github.com/cockroachdb/cockroach/pkg/util/randutil"
 )
 
 func TestChangefeedNemeses(t *testing.T) {
@@ -27,12 +28,15 @@ func TestChangefeedNemeses(t *testing.T) {
 	skip.UnderRace(t, "takes >1 min under race")
 
 	testFn := func(t *testing.T, s TestServer, f cdctest.TestFeedFactory) {
+		rng, seed := randutil.NewPseudoRand()
+		t.Logf("random seed: %d", seed)
+
 		sqlDB := sqlutils.MakeSQLRunner(s.DB)
-		disableDeclarativeSchemaChangesForTest(t, sqlDB)
+		_ = maybeDisableDeclarativeSchemaChangesForTest(t, sqlDB, rng)
 		// TODO(dan): Ugly hack to disable `eventPause` in sinkless feeds. See comment in
 		// `RunNemesis` for details.
 		isSinkless := strings.Contains(t.Name(), "sinkless")
-		v, err := cdctest.RunNemesis(f, s.DB, isSinkless)
+		v, err := cdctest.RunNemesis(f, s.DB, isSinkless, rng)
 		if err != nil {
 			t.Fatalf("%+v", err)
 		}