roachtest: fix schema change cancel test

Speed up the test by reducing the fraction of data that is processed
by the backfill before issuing a cancel.

Make the test easier to understand.

Wait enough time for the rollback to complete processing.

fixes cockroachdb#33335

Release note: None

pkg/cmd/roachtest/schemachange.go

@@ -19,6 +19,7 @@ import (
 	"context"
 	gosql "database/sql"
 	"fmt"
+	"github.com/cockroachdb/cockroach/pkg/base"
 	"time"
 
 	"github.com/cockroachdb/cockroach/pkg/jobs"
@@ -324,45 +325,44 @@ func makeIndexAddTpccTest(numNodes, warehouses int, length time.Duration) testSp
 }
 
 func registerSchemaChangeCancelIndexTPCC1000(r *registry) {
-	r.Add(makeIndexAddRollbackTpccTest(5, 1000, time.Hour*2))
+	r.Add(makeIndexAddRollbackTpccTest(5, 1000, time.Minute * 30))
 }
 
 // Creates an index and job, returning the job ID and a notify channel for
 // when the schema change completes or rolls back.
 func createIndexAddJob(
 	ctx context.Context, c *cluster, prefix string,
 ) (int64, <-chan error, error) {
-	setup := func(db *gosql.DB) (txn *gosql.Tx, jobID int64, err error) {
-		txn, err = db.Begin()
-		if err != nil {
-			return nil, 0, err
-		}
-		if _, err = txn.Exec(`CREATE INDEX foo ON tpcc.order (o_carrier_id);`); err != nil {
-			return nil, 0, err
-		}
-		if err = txn.QueryRow(`SELECT job_id FROM [SHOW JOBS] ORDER BY created DESC LIMIT 1`).Scan(&jobID); err != nil {
-			return nil, 0, err
-		}
-
-		return txn, jobID, nil
-	}
-
 	conn := c.Conn(ctx, 1)
-
-	txn, jobID, err := setup(conn)
+	defer conn.Close()
+	oldJobID, err := jobutils.QueryRecentJobID(conn, 0)
 	if err != nil {
-		conn.Close()
 		return 0, nil, err
 	}
 
-	c.l.Printf("%s: created index add job %d\n", prefix, jobID)
-
+	// CREATE INDEX in a separate goroutine because it takes a lot of time.
 	notifyCommit := make(chan error)
 	go func() {
+		conn := c.Conn(ctx, 1)
 		defer conn.Close()
-		notifyCommit <- txn.Commit()
+		_, err := conn.Exec(`CREATE INDEX foo ON tpcc.order (o_carrier_id);`)
+		notifyCommit <- err
 	}()
 
+	// Find the job id for the CREATE INDEX.
+	var jobID int64
+	for r := retry.Start(base.DefaultRetryOptions()); r.Next(); {
+		jobID, err = jobutils.QueryRecentJobID(conn, 0)
+		if err != nil {
+			return 0, nil, err
+		}
+		if jobID != oldJobID {
+			break
+		}
+	}
+
+	c.l.Printf("%s: created index add job %d\n", prefix, jobID)
+
 	return jobID, notifyCommit, nil
 }
 
@@ -396,7 +396,7 @@ func makeIndexAddRollbackTpccTest(numNodes, warehouses int, length time.Duration
 						ctx,
 						conn,
 						createID,
-						0.25,
+						0.12,
 						retryOpts,
 					); err != nil {
 						return err
@@ -407,20 +407,22 @@ func makeIndexAddRollbackTpccTest(numNodes, warehouses int, length time.Duration
 					}
 					c.l.Printf("%s: canceled job %d\n", prefix, createID)
 
-					if schemaChangeErr := <-notifyCommit; !testutils.IsError(schemaChangeErr, "job canceled") {
-						return errors.Errorf("expected 'job canceled' error, but got %+v", schemaChangeErr)
+					if err := <-notifyCommit; !testutils.IsError(err, "job canceled") {
+						c.l.Printf("%s: canceled job %d, got: %+v\n", prefix, createID, err)
+						return errors.Errorf("expected 'job canceled' error, but got %+v", err)
 					}
 
-					c.l.Printf("%s: rollback began %d\n", prefix, createID)
 					rollbackID, err := jobutils.QueryRecentJobID(conn, 0)
 					if err != nil {
 						return err
 					} else if rollbackID == createID {
 						return errors.Errorf("no rollback job created")
 					}
 
-					rollbackTimeoutSecs := int((gcTTL + (15 * time.Minute)).Seconds())
-					retryOpts = retry.Options{InitialBackoff: 5 * time.Second, Multiplier: 1, MaxRetries: rollbackTimeoutSecs / 5}
+					c.l.Printf("%s: rollback for %d began: %d\n", prefix, createID, rollbackID)
+
+					backoff := 30 * time.Second
+					retryOpts = retry.Options{InitialBackoff: backoff, MaxBackoff: backoff, Multiplier: 1, MaxRetries: int(length/backoff)}
 					return jobutils.WaitForStatus(ctx, conn, rollbackID, jobs.StatusSucceeded, retryOpts)
 				},
 				Duration: length,