ALTER TABLE .. DROP PARTITION doesn't invalidate the cache

scala> sql("CREATE TABLE tbl2 (id int, part int) USING parquet PARTITIONED BY (part)")
res31: org.apache.spark.sql.DataFrame = []

scala> sql("INSERT INTO tbl2 PARTITION (part=0) SELECT 0")
res32: org.apache.spark.sql.DataFrame = []

scala> sql("INSERT INTO tbl2 PARTITION (part=1) SELECT 1")
res33: org.apache.spark.sql.DataFrame = []

scala> val df1 = spark.table("tbl2")
df1: org.apache.spark.sql.DataFrame = [id: int, part: int]

scala> val df2 = spark.table("tbl2")
df2: org.apache.spark.sql.DataFrame = [id: int, part: int]

scala> df2.cache
res34: df2.type = [id: int, part: int]

scala> df1.show(false)
+---+----+
|id |part|
+---+----+
|0  |0   |
|1  |1   |
+---+----+


scala> df2.show(false)
+---+----+
|id |part|
+---+----+
|0  |0   |
|1  |1   |
+---+----+

scala> sql("ALTER TABLE tbl2 DROP PARTITION(part=0)")
res37: org.apache.spark.sql.DataFrame = []

scala> df1.show(false)
+---+----+
|id |part|
+---+----+
|0  |0   |
|1  |1   |
+---+----+


scala> df2.show(false)
+---+----+
|id |part|
+---+----+
|0  |0   |
|1  |1   |
+---+----+

scala> sql("CREATE TABLE tbl3 (id int, part int) USING parquet PARTITIONED BY (part)")
res40: org.apache.spark.sql.DataFrame = []

scala> sql("INSERT INTO tbl3 PARTITION (part=0) SELECT 0")
res41: org.apache.spark.sql.DataFrame = []

scala> sql("INSERT INTO tbl3 PARTITION (part=1) SELECT 1")
res42: org.apache.spark.sql.DataFrame = []

scala> val df3 = spark.table("tbl3")
df3: org.apache.spark.sql.DataFrame = [id: int, part: int]

scala> df3.show(false)
+---+----+
|id |part|
+---+----+
|0  |0   |
|1  |1   |
+---+----+


scala> sql("ALTER TABLE tbl3 DROP PARTITION(part=0)")
res44: org.apache.spark.sql.DataFrame = []

scala> df3.show(false)
+---+----+
|id |part|
+---+----+
|1  |1   |
+---+----+