OnlineLDAOptimizer does not handle persistance correctly

scala> import org.apache.spark.ml.clustering.LDA
import org.apache.spark.ml.clustering.LDA

scala> val dataset = spark.read.format("libsvm").load("data/mllib/sample_lda_libsvm_data.txt")
20/01/13 20:00:30 WARN LibSVMFileFormat: 'numFeatures' option not specified, determining the number of features by going though the input. If you know the number in advance, please specify it via 'numFeatures' option to avoid the extra scan. dataset: org.apache.spark.sql.DataFrame = [label: double, features: vector]

scala> val lda = new LDA().setK(10).setMaxIter(100).setOptimizer("em")
lda: org.apache.spark.ml.clustering.LDA = lda_0e9a6cf09801

scala> sc.getPersistentRDDs
res0: scala.collection.Map[Int,org.apache.spark.rdd.RDD[_]] = Map()

scala> val model = lda.fit(dataset)
model: org.apache.spark.ml.clustering.LDAModel = DistributedLDAModel: uid=lda_0e9a6cf09801, k=10, numFeatures=11

scala> sc.getPersistentRDDs
res1: scala.collection.Map[Int,org.apache.spark.rdd.RDD[_]] = Map(809 -> EdgeRDD MapPartitionsRDD[809] at mapPartitions at EdgeRDDImpl.scala:119, 1337 -> EdgeRDD MapPartitionsRDD[1337] at mapPartitions at EdgeRDDImpl.scala:119, 977 -> EdgeRDD MapPartitionsRDD[977] at mapPartitions at EdgeRDDImpl.scala:119, 1073 -> EdgeRDD MapPartitionsRDD[1073] at mapPartitions at EdgeRDDImpl.scala:119, 449 -> EdgeRDD MapPartitionsRDD[449] at mapPartitions at EdgeRDDImpl.scala:119, 1793 -> EdgeRDD MapPartitionsRDD[1793] at mapPartitions at EdgeRDDImpl.scala:119, 185 -> EdgeRDD MapPartitionsRDD[185] at mapPartitions at EdgeRDDImpl.scala:119, 1001 -> EdgeRDD MapPartitionsRDD[1001] at mapPartitions at EdgeRDDImpl.scala:119, 1601 -> EdgeRDD MapPartitionsRDD[1601] at mapPartitions a...

scala> sc.getPersistentRDDs.size
res2: Int = 106

scala> sc.getPersistentRDDs.foreach(println)
(809,EdgeRDD MapPartitionsRDD[809] at mapPartitions at EdgeRDDImpl.scala:119)
(1337,EdgeRDD MapPartitionsRDD[1337] at mapPartitions at EdgeRDDImpl.scala:119)
(977,EdgeRDD MapPartitionsRDD[977] at mapPartitions at EdgeRDDImpl.scala:119)
(1073,EdgeRDD MapPartitionsRDD[1073] at mapPartitions at EdgeRDDImpl.scala:119)
(449,EdgeRDD MapPartitionsRDD[449] at mapPartitions at EdgeRDDImpl.scala:119)
(1793,EdgeRDD MapPartitionsRDD[1793] at mapPartitions at EdgeRDDImpl.scala:119)
(185,EdgeRDD MapPartitionsRDD[185] at mapPartitions at EdgeRDDImpl.scala:119)
(1001,EdgeRDD MapPartitionsRDD[1001] at mapPartitions at EdgeRDDImpl.scala:119)
(1601,EdgeRDD MapPartitionsRDD[1601] at mapPartitions at EdgeRDDImpl.scala:119)
(1529,EdgeRDD MapPartitionsRDD[1529] at mapPartitions at EdgeRDDImpl.scala:119)
(1265,EdgeRDD MapPartitionsRDD[1265] at mapPartitions at EdgeRDDImpl.scala:119)
(257,EdgeRDD MapPartitionsRDD[257] at mapPartitions at EdgeRDDImpl.scala:119)
(1409,EdgeRDD MapPartitionsRDD[1409] at mapPartitions at EdgeRDDImpl.scala:119)
(1985,EdgeRDD MapPartitionsRDD[1985] at mapPartitions at EdgeRDDImpl.scala:119)
(785,EdgeRDD MapPartitionsRDD[785] at mapPartitions at EdgeRDDImpl.scala:119)
(1313,EdgeRDD MapPartitionsRDD[1313] at mapPartitions at EdgeRDDImpl.scala:119)
(1577,EdgeRDD MapPartitionsRDD[1577] at mapPartitions at EdgeRDDImpl.scala:119)
(881,EdgeRDD MapPartitionsRDD[881] at mapPartitions at EdgeRDDImpl.scala:119)
(29,VertexRDD, VertexRDD ZippedPartitionsRDD2[29] at zipPartitions at VertexRDD.scala:322)
(2105,EdgeRDD MapPartitionsRDD[2105] at mapPartitions at EdgeRDDImpl.scala:119)
(353,EdgeRDD MapPartitionsRDD[353] at mapPartitions at EdgeRDDImpl.scala:119)
(905,EdgeRDD MapPartitionsRDD[905] at mapPartitions at EdgeRDDImpl.scala:119)
(1169,EdgeRDD MapPartitionsRDD[1169] at mapPartitions at EdgeRDDImpl.scala:119)
(89,EdgeRDD MapPartitionsRDD[89] at mapPartitions at EdgeRDDImpl.scala:119)
(1433,EdgeRDD MapPartitionsRDD[1433] at mapPartitions at EdgeRDDImpl.scala:119)
(1697,EdgeRDD MapPartitionsRDD[1697] at mapPartitions at EdgeRDDImpl.scala:119)
(233,EdgeRDD MapPartitionsRDD[233] at mapPartitions at EdgeRDDImpl.scala:119)
(761,EdgeRDD MapPartitionsRDD[761] at mapPartitions at EdgeRDDImpl.scala:119)
(2441,EdgeRDD MapPartitionsRDD[2441] at mapPartitions at EdgeRDDImpl.scala:119)
(2249,EdgeRDD MapPartitionsRDD[2249] at mapPartitions at EdgeRDDImpl.scala:119)
(1217,EdgeRDD MapPartitionsRDD[1217] at mapPartitions at EdgeRDDImpl.scala:119)
(137,EdgeRDD MapPartitionsRDD[137] at mapPartitions at EdgeRDDImpl.scala:119)
(2414,VertexRDD, VertexRDD ZippedPartitionsRDD2[2414] at zipPartitions at VertexRDD.scala:322)
(65,EdgeRDD MapPartitionsRDD[65] at mapPartitions at EdgeRDDImpl.scala:119)
(329,EdgeRDD MapPartitionsRDD[329] at mapPartitions at EdgeRDDImpl.scala:119)
(665,EdgeRDD MapPartitionsRDD[665] at mapPartitions at EdgeRDDImpl.scala:119)
(1457,EdgeRDD MapPartitionsRDD[1457] at mapPartitions at EdgeRDDImpl.scala:119)
(2345,EdgeRDD MapPartitionsRDD[2345] at mapPartitions at EdgeRDDImpl.scala:119)
(1121,EdgeRDD MapPartitionsRDD[1121] at mapPartitions at EdgeRDDImpl.scala:119)
(593,EdgeRDD MapPartitionsRDD[593] at mapPartitions at EdgeRDDImpl.scala:119)
(857,EdgeRDD MapPartitionsRDD[857] at mapPartitions at EdgeRDDImpl.scala:119)
(1361,EdgeRDD MapPartitionsRDD[1361] at mapPartitions at EdgeRDDImpl.scala:119)
(1937,EdgeRDD MapPartitionsRDD[1937] at mapPartitions at EdgeRDDImpl.scala:119)
(1889,EdgeRDD MapPartitionsRDD[1889] at mapPartitions at EdgeRDDImpl.scala:119)
(2153,EdgeRDD MapPartitionsRDD[2153] at mapPartitions at EdgeRDDImpl.scala:119)
(569,EdgeRDD MapPartitionsRDD[569] at mapPartitions at EdgeRDDImpl.scala:119)
(1241,EdgeRDD MapPartitionsRDD[1241] at mapPartitions at EdgeRDDImpl.scala:119)
(2057,EdgeRDD MapPartitionsRDD[2057] at mapPartitions at EdgeRDDImpl.scala:119)
(953,EdgeRDD MapPartitionsRDD[953] at mapPartitions at EdgeRDDImpl.scala:119)
(425,EdgeRDD MapPartitionsRDD[425] at mapPartitions at EdgeRDDImpl.scala:119)
(2033,EdgeRDD MapPartitionsRDD[2033] at mapPartitions at EdgeRDDImpl.scala:119)
(32,EdgeRDD MapPartitionsRDD[32] at mapPartitions at EdgeRDDImpl.scala:119)
(161,EdgeRDD MapPartitionsRDD[161] at mapPartitions at EdgeRDDImpl.scala:119)
(689,EdgeRDD MapPartitionsRDD[689] at mapPartitions at EdgeRDDImpl.scala:119)
(2225,EdgeRDD MapPartitionsRDD[2225] at mapPartitions at EdgeRDDImpl.scala:119)
(2393,EdgeRDD MapPartitionsRDD[2393] at mapPartitions at EdgeRDDImpl.scala:119)
(281,EdgeRDD MapPartitionsRDD[281] at mapPartitions at EdgeRDDImpl.scala:119)
(545,EdgeRDD MapPartitionsRDD[545] at mapPartitions at EdgeRDDImpl.scala:119)
(641,EdgeRDD MapPartitionsRDD[641] at mapPartitions at EdgeRDDImpl.scala:119)
(713,EdgeRDD MapPartitionsRDD[713] at mapPartitions at EdgeRDDImpl.scala:119)
(1865,EdgeRDD MapPartitionsRDD[1865] at mapPartitions at EdgeRDDImpl.scala:119)
(113,EdgeRDD MapPartitionsRDD[113] at mapPartitions at EdgeRDDImpl.scala:119)
(377,EdgeRDD MapPartitionsRDD[377] at mapPartitions at EdgeRDDImpl.scala:119)
(737,EdgeRDD MapPartitionsRDD[737] at mapPartitions at EdgeRDDImpl.scala:119)
(2129,EdgeRDD MapPartitionsRDD[2129] at mapPartitions at EdgeRDDImpl.scala:119)
(521,EdgeRDD MapPartitionsRDD[521] at mapPartitions at EdgeRDDImpl.scala:119)
(1841,EdgeRDD MapPartitionsRDD[1841] at mapPartitions at EdgeRDDImpl.scala:119)
(2369,EdgeRDD MapPartitionsRDD[2369] at mapPartitions at EdgeRDDImpl.scala:119)
(2390,VertexRDD, VertexRDD ZippedPartitionsRDD2[2390] at zipPartitions at VertexRDD.scala:322)
(473,EdgeRDD MapPartitionsRDD[473] at mapPartitions at EdgeRDDImpl.scala:119)
(209,EdgeRDD MapPartitionsRDD[209] at mapPartitions at EdgeRDDImpl.scala:119)
(617,EdgeRDD MapPartitionsRDD[617] at mapPartitions at EdgeRDDImpl.scala:119)
(1145,EdgeRDD MapPartitionsRDD[1145] at mapPartitions at EdgeRDDImpl.scala:119)
(1049,EdgeRDD MapPartitionsRDD[1049] at mapPartitions at EdgeRDDImpl.scala:119)
(1961,EdgeRDD MapPartitionsRDD[1961] at mapPartitions at EdgeRDDImpl.scala:119)
(1025,EdgeRDD MapPartitionsRDD[1025] at mapPartitions at EdgeRDDImpl.scala:119)
(497,EdgeRDD MapPartitionsRDD[497] at mapPartitions at EdgeRDDImpl.scala:119)
(1649,EdgeRDD MapPartitionsRDD[1649] at mapPartitions at EdgeRDDImpl.scala:119)
(1553,EdgeRDD MapPartitionsRDD[1553] at mapPartitions at EdgeRDDImpl.scala:119)
(1817,EdgeRDD MapPartitionsRDD[1817] at mapPartitions at EdgeRDDImpl.scala:119)
(1913,EdgeRDD MapPartitionsRDD[1913] at mapPartitions at EdgeRDDImpl.scala:119)
(1289,EdgeRDD MapPartitionsRDD[1289] at mapPartitions at EdgeRDDImpl.scala:119)
(1385,EdgeRDD MapPartitionsRDD[1385] at mapPartitions at EdgeRDDImpl.scala:119)
(1721,EdgeRDD MapPartitionsRDD[1721] at mapPartitions at EdgeRDDImpl.scala:119)
(2273,EdgeRDD MapPartitionsRDD[2273] at mapPartitions at EdgeRDDImpl.scala:119)
(1481,EdgeRDD MapPartitionsRDD[1481] at mapPartitions at EdgeRDDImpl.scala:119)
(1745,EdgeRDD MapPartitionsRDD[1745] at mapPartitions at EdgeRDDImpl.scala:119)
(401,EdgeRDD MapPartitionsRDD[401] at mapPartitions at EdgeRDDImpl.scala:119)
(2009,EdgeRDD MapPartitionsRDD[2009] at mapPartitions at EdgeRDDImpl.scala:119)
(2081,EdgeRDD MapPartitionsRDD[2081] at mapPartitions at EdgeRDDImpl.scala:119)
(929,EdgeRDD MapPartitionsRDD[929] at mapPartitions at EdgeRDDImpl.scala:119)
(1193,EdgeRDD MapPartitionsRDD[1193] at mapPartitions at EdgeRDDImpl.scala:119)
(833,EdgeRDD MapPartitionsRDD[833] at mapPartitions at EdgeRDDImpl.scala:119)
(36,EdgeRDD MapPartitionsRDD[36] at mapPartitionsWithIndex at GraphImpl.scala:106)
(1097,EdgeRDD MapPartitionsRDD[1097] at mapPartitions at EdgeRDDImpl.scala:119)
(1625,EdgeRDD MapPartitionsRDD[1625] at mapPartitions at EdgeRDDImpl.scala:119)
(1673,EdgeRDD MapPartitionsRDD[1673] at mapPartitions at EdgeRDDImpl.scala:119)
(305,EdgeRDD MapPartitionsRDD[305] at mapPartitions at EdgeRDDImpl.scala:119)
(2201,EdgeRDD MapPartitionsRDD[2201] at mapPartitions at EdgeRDDImpl.scala:119)
(2417,EdgeRDD MapPartitionsRDD[2417] at mapPartitions at EdgeRDDImpl.scala:119)
(1505,EdgeRDD MapPartitionsRDD[1505] at mapPartitions at EdgeRDDImpl.scala:119)
(2321,EdgeRDD MapPartitionsRDD[2321] at mapPartitions at EdgeRDDImpl.scala:119)
(2438,VertexRDD, VertexRDD ZippedPartitionsRDD2[2438] at zipPartitions at VertexRDD.scala:322)
(2297,EdgeRDD MapPartitionsRDD[2297] at mapPartitions at EdgeRDDImpl.scala:119)
(1769,EdgeRDD MapPartitionsRDD[1769] at mapPartitions at EdgeRDDImpl.scala:119)
(2177,EdgeRDD MapPartitionsRDD[2177] at mapPartitions at EdgeRDDImpl.scala:119)