workload/schemachange: disable inserts when in 22.1 mixed version state

Previously, if we ran in a mixed version state with the schema changer
workload we could run into an optimizer bug (#80820). To address this,
this patch in a mixed version workload disables the insert portion of
the workload.

Release justification: improves test coverage by enabling the mixed
version test
Release note: None

pkg/cmd/roachtest/tests/mixed_version_schemachange.go

@@ -64,7 +64,7 @@ func runSchemaChangeWorkloadStep(loadNode, maxOps, concurrency int) versionStep
 			// crashes, deadlocks, etc.
 			// TODO(spaskob): remove when https://github.com/cockroachdb/cockroach/issues/47430
 			// is closed.
-			"--tolerate-errors=true",
+			//"--tolerate-errors=true",
 			fmt.Sprintf("--max-ops %d", maxOps),
 			fmt.Sprintf("--concurrency %d", concurrency),
 			fmt.Sprintf("{pgurl:1-%d}", u.c.Spec().NodeCount),

pkg/workload/schemachange/operation_generator.go

@@ -2373,6 +2373,16 @@ func (og *operationGenerator) insertRow(ctx context.Context, tx pgx.Tx) (stmt *o
 	if err != nil {
 		return nil, err
 	}
+	// If we aren't on 22.2 then disable the insert plugin, since 21.X
+	// can have queries fail due to an optimizer bug.
+	skipInserts, err := isClusterVersionLessThan(ctx, tx, clusterversion.ByKey(clusterversion.Start22_2))
+	if err != nil {
+		return nil, err
+	}
+	if skipInserts {
+		tableExists = false
+		tableName.SchemaName = "InvalidObjectName"
+	}
 	if !tableExists {
 		return makeOpStmtForSingleError(OpStmtDML,
 			fmt.Sprintf(
@@ -2488,7 +2498,6 @@ func (og *operationGenerator) insertRow(ctx context.Context, tx pgx.Tx) (stmt *o
 	for _, row := range rows {
 		formattedRows = append(formattedRows, fmt.Sprintf("(%s)", strings.Join(row, ",")))
 	}
-
 	stmt.sql = fmt.Sprintf(
 		`INSERT INTO %s (%s) VALUES %s`,
 		tableName,