[MM-29951] searchengine/bleve/indexing: use oldest entity creation time instead (#17203)

* searchengine/bleve/indexing: use oldest entity creation time instead

* add test

* fix feature flag

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

services/searchengine/bleveengine/indexer/indexing_job.go

@@ -162,17 +162,18 @@ func (worker *BleveIndexerWorker) DoJob(job *model.Job) {
 		progress.StartAtTime = startInt
 		progress.LastEntityTime = progress.StartAtTime
 	} else {
-		// Set start time to oldest post in the database.
-		oldestPost, err := worker.jobServer.Store.Post().GetOldest()
+		// Set start time to oldest entity in the database.
+		// A user or a channel may be created before any post.
+		oldestEntityCreationTime, err := worker.jobServer.Store.Post().GetOldestEntityCreationTime()
 		if err != nil {
-			mlog.Error("Worker: Failed to fetch oldest post for job.", mlog.String("workername", worker.name), mlog.String("job_id", job.Id), mlog.String("start_time", startString), mlog.Err(err))
-			appError := model.NewAppError("BleveIndexerWorker", "bleveengine.indexer.do_job.get_oldest_post.error", nil, err.Error(), http.StatusInternalServerError)
+			mlog.Error("Worker: Failed to fetch oldest entity for job.", mlog.String("workername", worker.name), mlog.String("job_id", job.Id), mlog.String("start_time", startString), mlog.Err(err))
+			appError := model.NewAppError("BleveIndexerWorker", "bleveengine.indexer.do_job.get_oldest_entity.error", nil, err.Error(), http.StatusInternalServerError)
 			if err := worker.jobServer.SetJobError(job, appError); err != nil {
 				mlog.Error("Worker: Failed to set job error", mlog.String("workername", worker.name), mlog.String("job_id", job.Id), mlog.Err(err), mlog.NamedErr("set_error", appError))
 			}
 			return
 		}
-		progress.StartAtTime = oldestPost.CreateAt
+		progress.StartAtTime = oldestEntityCreationTime
 		progress.LastEntityTime = progress.StartAtTime
 	}
 

services/searchengine/bleveengine/indexer/indexing_job_test.go

@@ -0,0 +1,68 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package ebleveengine
+
+import (
+	"errors"
+	"io/ioutil"
+	"os"
+	"testing"
+
+	"github.com/mattermost/mattermost-server/v5/jobs"
+	"github.com/mattermost/mattermost-server/v5/model"
+	"github.com/mattermost/mattermost-server/v5/services/searchengine/bleveengine"
+	"github.com/mattermost/mattermost-server/v5/store/storetest"
+	"github.com/mattermost/mattermost-server/v5/utils/testutils"
+	"github.com/stretchr/testify/require"
+)
+
+func TestBleveIndexer(t *testing.T) {
+	mockStore := &storetest.Store{}
+	defer mockStore.AssertExpectations(t)
+
+	t.Run("Call GetOldestEntityCreationTime for the first indexing call", func(t *testing.T) {
+		job := &model.Job{
+			Id:       model.NewId(),
+			CreateAt: model.GetMillis(),
+			Status:   model.JOB_STATUS_PENDING,
+			Type:     model.JOB_TYPE_BLEVE_POST_INDEXING,
+		}
+
+		mockStore.JobStore.On("UpdateStatusOptimistically", job.Id, model.JOB_STATUS_PENDING, model.JOB_STATUS_IN_PROGRESS).Return(true, nil)
+		mockStore.JobStore.On("UpdateOptimistically", job, model.JOB_STATUS_IN_PROGRESS).Return(true, nil)
+		mockStore.PostStore.On("GetOldestEntityCreationTime").Return(int64(1), errors.New("")) // intentionally return error to return from function
+
+		tempDir, err := ioutil.TempDir("", "setupConfigFile")
+		require.NoError(t, err)
+
+		t.Cleanup(func() {
+			os.RemoveAll(tempDir)
+		})
+
+		cfg := &model.Config{
+			BleveSettings: model.BleveSettings{
+				EnableIndexing: model.NewBool(true),
+				IndexDir:       model.NewString(tempDir),
+			},
+		}
+
+		jobServer := &jobs.JobServer{
+			Store: mockStore,
+			ConfigService: &testutils.StaticConfigService{
+				Cfg: cfg,
+			},
+		}
+
+		bleveEngine := bleveengine.NewBleveEngine(cfg, jobServer)
+		aErr := bleveEngine.Start()
+		require.Nil(t, aErr)
+
+		worker := &BleveIndexerWorker{
+			jobServer: jobServer,
+			engine:    bleveEngine,
+		}
+
+		worker.DoJob(job)
+	})
+}