Spark HiveContext does not retrieve newly inserted records from Hive Table - apache-spark-sql

Question

I am using Spark 1.4. HiveContext is used to connect Hive. I did the following
val hx = new HiveContext(sc)
import hx.implicits._
hx.sql("select * from tab").show
// it is fine, result was shown as expected
then, I inserted a few records into tab from beeline console
hx.refreshTable("tab")
hx.sql("select * from tab").show
// still old records, no newly inserted records
My question is: why the HiveContext didn't retrieve the newly inserted records?

Answer 1

hiveContext.refreshTable(tableName: String) - this will refresh only metadata of the table (not the actual data)
Notes from official documentaition : (credits: https://spark.apache.org)
refreshTable(tableName: String): Unit
Invalidate and refresh all the cached the metadata of the given table. For performance reasons, Spark SQL or the external data source library it uses might cache certain metadata about a table, such as the location of blocks. When those change outside of Spark SQL, users should call this function to invalidate the cache
To retrive newly inserted records:- uncache first and cache again using , uncacheTable(String tableName) and cacheTable(String tableName)

Answer 2

If the target table is partitioned, You need to insert with 'partition' option. If you miss out the partition, data will not be visible.
INSERT OVERWRITE TABLE tablename1 PARTITION (partcol1=val1, partcol2=val2...) SELECT col1,col2,.... FROM tablename2

Answer 3

On a differently slight case, I have an RDD coming from a Spark SQL statement via HiveContext. The solution which worked for me after some experiments was to actually regenerate the RDD itself.
It does not matter whether you are using the DDL by Spark SQL or sending SQL statements directly via hiveContext.sql.
I have seen around people using a "count trick" in order to force the recomputation of a dataset but at least in my attempts I couldn't get to see the new data this way.
Anyway trying caching, refreshing and friends did not work for me, if somebody has some proper pattern here please share.