diff --git a/plugin/task_manager/migration_api.go b/plugin/task_manager/migration_api.go
index f2898818..0c702365 100644
--- a/plugin/task_manager/migration_api.go
+++ b/plugin/task_manager/migration_api.go
@@ -76,7 +76,7 @@ func (h *APIHandler) getDataMigrationTaskInfo(w http.ResponseWriter, req *http.R
 	for i, index := range taskConfig.Indices {
 		indexName := index.Source.GetUniqueIndexName()
 		count := indexState[indexName].IndexDocs
-		sourceDocs := indexState[indexName].SourceDocs
+		sourceDocs := index.Source.Docs
 		var percent float64
 		if sourceDocs <= 0 {
 			percent = 100
@@ -86,7 +86,7 @@ func (h *APIHandler) getDataMigrationTaskInfo(w http.ResponseWriter, req *http.R
 				percent = 100
 			}
 		}
-		taskConfig.Indices[i].Source.Docs = sourceDocs
+		//taskConfig.Indices[i].Source.Docs = sourceDocs
 		taskConfig.Indices[i].Target.Docs = count
 		taskConfig.Indices[i].Percent = util.ToFixed(percent, 2)
 		taskConfig.Indices[i].ErrorPartitions = indexState[indexName].ErrorPartitions
@@ -257,114 +257,133 @@ We count data from two sources:
   - realtime bulk indexing info is only available for running index_migrations
 */
 func (h *APIHandler) getMigrationMajorTaskInfo(id string) (taskStats migration_model.ClusterMigrationTaskState, indexState map[string]MigrationIndexStateInfo, err error) {
-	taskQuery := util.MapStr{
-		"size": 500,
-		"query": util.MapStr{
-			"bool": util.MapStr{
-				"must": []util.MapStr{
-					{
-						"term": util.MapStr{
-							"parent_id": util.MapStr{
-								"value": id,
-							},
-						},
-					},
-					{
-						"term": util.MapStr{
-							"metadata.type": util.MapStr{
-								"value": "index_migration",
-							},
-						},
-					},
-				},
-			},
-		},
-	}
-	subTasks, err := migration_util.GetTasks(taskQuery)
-	if err != nil {
-		return taskStats, indexState, err
-	}
-
-	var indexMigrationTaskIDs []string
-	indexState = map[string]MigrationIndexStateInfo{}
-	for _, subTask := range subTasks {
-		taskLabels := util.MapStr(subTask.Metadata.Labels)
-		indexName := migration_util.GetMapStringValue(taskLabels, "unique_index_name")
-		if indexName == "" {
-			continue
-		}
-
-		cfg := migration_model.IndexMigrationTaskConfig{}
-		err = migration_util.GetTaskConfig(&subTask, &cfg)
-		if err != nil {
-			log.Errorf("failed to get task config, err: %v", err)
-			continue
-		}
-
-		taskStats.SourceDocs += cfg.Source.DocCount
-		st := indexState[indexName]
-		st.SourceDocs += cfg.Source.DocCount
-		indexState[indexName] = st
-
-		if subTask.Status == task.StatusRunning {
-			indexMigrationTaskIDs = append(indexMigrationTaskIDs, subTask.ID)
-			continue
-		}
-
-		indexDocs := migration_util.GetMapIntValue(taskLabels, "index_docs")
-		taskStats.IndexDocs += indexDocs
-		st.IndexDocs += indexDocs
-		if subTask.Status == task.StatusError {
-			st.ErrorPartitions += 1
-			taskStats.ErrorPartitions += 1
-		}
-		indexState[indexName] = st
-		indexMigrationTaskIDs = append(indexMigrationTaskIDs, subTask.ID)
-	}
-
-	if len(indexMigrationTaskIDs) == 0 {
-		return taskStats, indexState, nil
-	}
-
-	taskQuery = util.MapStr{
-		"size": 500,
-		"query": util.MapStr{
-			"bool": util.MapStr{
-				"must": []util.MapStr{
-					{
-						"terms": util.MapStr{
-							"parent_id": indexMigrationTaskIDs,
-						},
-					},
-					{
-						"term": util.MapStr{
-							"metadata.labels.pipeline_id": util.MapStr{
-								"value": "bulk_indexing",
-							},
-						},
-					},
-				},
-			},
-		},
-	}
-	subTasks, err = migration_util.GetTasks(taskQuery)
-	if err != nil {
-		return taskStats, indexState, err
-	}
-
 	var pipelineTaskIDs = map[string][]string{}
 	var pipelineIndexNames = map[string]string{}
-	for _, subTask := range subTasks {
-		taskLabels := util.MapStr(subTask.Metadata.Labels)
-		indexName := migration_util.GetMapStringValue(taskLabels, "unique_index_name")
-		if indexName == "" {
+	indexState = map[string]MigrationIndexStateInfo{}
+	const size = 500
+	var (
+		from = -size
+		hasMore = true
+	)
+	for hasMore {
+		from += size
+		taskQuery := util.MapStr{
+			"from": from,
+			"size": size,
+			"sort": []util.MapStr{
+				{
+					"created": util.MapStr{
+						"order": "asc",
+					},
+				},
+			},
+			"query": util.MapStr{
+				"bool": util.MapStr{
+					"must": []util.MapStr{
+						{
+							"term": util.MapStr{
+								"parent_id": util.MapStr{
+									"value": id,
+								},
+							},
+						},
+						{
+							"term": util.MapStr{
+								"metadata.type": util.MapStr{
+									"value": "index_migration",
+								},
+							},
+						},
+					},
+				},
+			},
+		}
+		subTasks, err := migration_util.GetTasks(taskQuery)
+		if err != nil {
+			return taskStats, indexState, err
+		}
+		if len(subTasks) < size {
+			hasMore = false
+		}
+
+		var indexMigrationTaskIDs []string
+		for _, subTask := range subTasks {
+			taskLabels := util.MapStr(subTask.Metadata.Labels)
+			indexName := migration_util.GetMapStringValue(taskLabels, "unique_index_name")
+			if indexName == "" {
+				continue
+			}
+
+			cfg := migration_model.IndexMigrationTaskConfig{}
+			err = migration_util.GetTaskConfig(&subTask, &cfg)
+			if err != nil {
+				log.Errorf("failed to get task config, err: %v", err)
+				continue
+			}
+
+			taskStats.SourceDocs += cfg.Source.DocCount
+			st := indexState[indexName]
+			st.SourceDocs += cfg.Source.DocCount
+			indexState[indexName] = st
+
+			if subTask.Status == task.StatusRunning {
+				indexMigrationTaskIDs = append(indexMigrationTaskIDs, subTask.ID)
+				continue
+			}
+
+			indexDocs := migration_util.GetMapIntValue(taskLabels, "index_docs")
+			taskStats.IndexDocs += indexDocs
+			st.IndexDocs += indexDocs
+			if subTask.Status == task.StatusError {
+				st.ErrorPartitions += 1
+				taskStats.ErrorPartitions += 1
+			}
+			indexState[indexName] = st
+			indexMigrationTaskIDs = append(indexMigrationTaskIDs, subTask.ID)
+		}
+
+		if len(indexMigrationTaskIDs) == 0 {
 			continue
 		}
 
-		pipelineIndexNames[subTask.ID] = indexName
+		taskQuery = util.MapStr{
+			"size": len(indexMigrationTaskIDs),
+			"query": util.MapStr{
+				"bool": util.MapStr{
+					"must": []util.MapStr{
+						{
+							"terms": util.MapStr{
+								"parent_id": indexMigrationTaskIDs,
+							},
+						},
+						{
+							"term": util.MapStr{
+								"metadata.labels.pipeline_id": util.MapStr{
+									"value": "bulk_indexing",
+								},
+							},
+						},
+					},
+				},
+			},
+		}
+		subTasks, err = migration_util.GetTasks(taskQuery)
+		if err != nil {
+			return taskStats, indexState, err
+		}
 
-		if instID := migration_util.GetMapStringValue(taskLabels, "execution_instance_id"); instID != "" {
-			pipelineTaskIDs[instID] = append(pipelineTaskIDs[instID], subTask.ID)
+		for _, subTask := range subTasks {
+			taskLabels := util.MapStr(subTask.Metadata.Labels)
+			indexName := migration_util.GetMapStringValue(taskLabels, "unique_index_name")
+			if indexName == "" {
+				continue
+			}
+
+			pipelineIndexNames[subTask.ID] = indexName
+
+			if instID := migration_util.GetMapStringValue(taskLabels, "execution_instance_id"); instID != "" {
+				pipelineTaskIDs[instID] = append(pipelineTaskIDs[instID], subTask.ID)
+			}
 		}
 	}