Github user kmanamcheri commented on a diff in the pull request:
https://github.com/apache/spark/pull/22614#discussion_r222348679
--- Diff:
sql/hive/src/main/scala/org/apache/spark/sql/hive/client/HiveShim.scala ---
@@ -746,34 +746,20 @@ private[client] class Shim_v0_13 extends Shim_v0_12 {
getAllPartitionsMethod.invoke(hive,
table).asInstanceOf[JSet[Partition]]
} else {
logDebug(s"Hive metastore filter is '$filter'.")
- val tryDirectSqlConfVar =
HiveConf.ConfVars.METASTORE_TRY_DIRECT_SQL
- // We should get this config value from the metaStore. otherwise
hit SPARK-18681.
- // To be compatible with hive-0.12 and hive-0.13, In the future we
can achieve this by:
- // val tryDirectSql =
hive.getMetaConf(tryDirectSqlConfVar.varname).toBoolean
- val tryDirectSql =
hive.getMSC.getConfigValue(tryDirectSqlConfVar.varname,
- tryDirectSqlConfVar.defaultBoolVal.toString).toBoolean
try {
// Hive may throw an exception when calling this method in some
circumstances, such as
- // when filtering on a non-string partition column when the hive
config key
- // hive.metastore.try.direct.sql is false
+ // when filtering on a non-string partition column.
getPartitionsByFilterMethod.invoke(hive, table, filter)
.asInstanceOf[JArrayList[Partition]]
} catch {
- case ex: InvocationTargetException if
ex.getCause.isInstanceOf[MetaException] &&
- !tryDirectSql =>
+ case ex: InvocationTargetException if
ex.getCause.isInstanceOf[MetaException] =>
logWarning("Caught Hive MetaException attempting to get
partition metadata by " +
"filter from Hive. Falling back to fetching all partition
metadata, which will " +
- "degrade performance. Modifying your Hive metastore
configuration to set " +
- s"${tryDirectSqlConfVar.varname} to true may resolve this
problem.", ex)
+ "degrade performance. Enable direct SQL mode in hive
metastore to attempt " +
+ "to improve performance. However, Hive's direct SQL mode is
an optimistic " +
+ "optimization and does not guarantee improved performance.")
--- End diff --
@mallman The key point to note here is that setting direct sql on HMS "may"
resolve the problem. It is not guaranteed. HMS only optimistically optimizes
this. If direct sql on HMS fails, it will fall back on ORM and then fail again.
Spark'ss behavior should not be inconsistent depending on HMS config value.
My suggested fix would still call getPartitionsByFilter and if that fails,
will call getAllPartitions. We won't be calling getAllPartitions in all cases.
It is a fallback mechanism.
@gatorsmile hmm.. why not? We know it might be slow and hence the warning.
Maybe the warning message should read that this could be slow depending on the
number of partitions since partition push-down to HMS failed.
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