use epoch for wf started column in MySQL backend (#72)

engine/storage/mysql/query.sql

@@ -155,7 +155,7 @@ WHERE
 
 -- name: GetWorkflowLastStarted :one
 SELECT
-  last_created_at
+  last_created_unix
 FROM
   wf_status
 WHERE

engine/storage/mysql/schema.00002.sql

@@ -0,0 +1,3 @@
+ALTER TABLE wf_status
+    DROP COLUMN last_created_at,
+    ADD COLUMN last_created_unix BIGINT NOT NULL DEFAULT (UNIX_TIMESTAMP());

engine/storage/mysql/schema.sql

@@ -84,7 +84,11 @@ CREATE TABLE wf_status (
     enrollment_id VARCHAR(255) NOT NULL,
     workflow_name VARCHAR(255) NOT NULL,
 
-    last_created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+    -- this was intended to be "DEFAULT (UNIX_TIMESTAMP() * 1000)"
+    -- which would complement the Golang `time.Time{}.UnixMilli()`.
+    -- however sqlc seems to not support that syntax, so we'll settle
+    -- for less precision.
+    last_created_unix BIGINT NOT NULL DEFAULT (UNIX_TIMESTAMP()),
 
     created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
     updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,

engine/storage/mysql/storage.go

@@ -245,17 +245,11 @@ func (s *MySQLStorage) CancelSteps(ctx context.Context, id, workflowName string)
 
 // RetrieveWorkflowStarted returns the last time a workflow was started for id.
 func (s *MySQLStorage) RetrieveWorkflowStarted(ctx context.Context, id, workflowName string) (time.Time, error) {
-	ret, err := s.q.GetWorkflowLastStarted(ctx, sqlc.GetWorkflowLastStartedParams{EnrollmentID: id, WorkflowName: workflowName})
+	epoch, err := s.q.GetWorkflowLastStarted(ctx, sqlc.GetWorkflowLastStartedParams{EnrollmentID: id, WorkflowName: workflowName})
 	if errors.Is(err, sql.ErrNoRows) {
 		return time.Time{}, nil
-	} else if err != nil {
-		return time.Time{}, err
 	}
-	parsedTime, err := time.Parse(mySQLTimestampFormat, ret)
-	if err != nil {
-		return time.Time{}, fmt.Errorf("parsing time: %w", err)
-	}
-	return parsedTime, err
+	return time.Unix(epoch, 0), err
 }
 
 // RecordWorkflowStarted stores the started time for workflowName for ids.
@@ -265,26 +259,25 @@ func (s *MySQLStorage) RecordWorkflowStarted(ctx context.Context, ids []string,
 	}
 	const numFields = 3
 	const subst = ", (?, ?, ?)"
-	fmt.Println(len(ids), len(ids)-1)
 	parms := make([]interface{}, len(ids)*numFields)
-	startedFormat := started.Format(mySQLTimestampFormat)
+	startedUnix := started.Unix()
 	for i, id := range ids {
 		// these must match the SQL query, below
 		parms[i*numFields] = id
 		parms[i*numFields+1] = workflowName
-		parms[i*numFields+2] = startedFormat
+		parms[i*numFields+2] = startedUnix
 	}
-	val := subst[2:] + strings.Repeat(subst, len(ids)-1)
+	values := strings.Repeat(subst, len(ids))[2:]
 	_, err := s.db.ExecContext(
 		ctx,
 		`
 INSERT INTO wf_status
-  (enrollment_id, workflow_name, last_created_at)
+  (enrollment_id, workflow_name, last_created_unix)
 VALUES
-  `+val+` AS new
+  `+values+` AS new
 ON DUPLICATE KEY
 UPDATE
-  last_created_at = new.last_created_at;`,
+  last_created_unix = new.last_created_unix;`,
 		parms...,
 	)
 	return err

engine/storage/test/test.go

@@ -273,11 +273,7 @@ func mainTest(t *testing.T, s storage.AllStorage) {
 			// 	t.Fatalf("invalid test data: step enqueueing with config: %v", err)
 			// }
 
-			// some backends may truncate the time and drop TZ
-			// so let's truncate ourselves and eliminate the TZ.
-			// since this value is used to compare the retrived value
-			// we'll stick with that.
-			storedAt := time.Now().UTC().Truncate(time.Second)
+			storedAt := time.Now()
 
 			err := s.StoreStep(ctx, tStep.step, storedAt)
 			if tStep.shouldError && err == nil {
@@ -301,8 +297,9 @@ func mainTest(t *testing.T, s storage.AllStorage) {
 					}
 					if ts.IsZero() {
 						t.Errorf("RetrieveWorkflowStarted: nil timestamp for id=%s, step=%s err=%v", id, tStep.step.WorkflowName, err)
-					} else if ts != storedAt {
-						t.Errorf("RetrieveWorkflowStarted: timestamp mismatch for id=%s, step=%s expected=%v got=%v", id, tStep.step.WorkflowName, storedAt, ts)
+					} else if t1, t2 := ts.Truncate(time.Second), storedAt.Truncate(time.Second); t1.Compare(t2) != 0 {
+						// truncate comparison in case backends don't persist precision less than 1s (e.g. SQL textual dates)
+						t.Errorf("RetrieveWorkflowStarted: timestamp mismatch for id=%s, step=%s expected=%v got=%v compare=%v", id, tStep.step.WorkflowName, t2, t1, t1.Compare(t2))
 					}
 				}
 			}