Known Issues Iceberg

Learn about the known issues in Iceberg, the impact or changes to the functionality, and the workaround.

CDPD-57551: Performance issue can occur on reads after writes of Iceberg tables

Hive might generate too many small files, which causes performance degradation.

Maintain a relatively small number of data files under the iceberg table/partition directory to have efficient reads. To alleviate poor performance caused by too many small files, run the following queries:

TRUNCATE TABLE target;
INSERT OVERWRITE TABLE target select * from target FOR SYSTEM_VERSION AS OF <preTruncateSnapshotId>;

CDPD-66305: Do not turn on the optimized Iceberg V2 operator in 7.2.18.0

In this release, the optimized Iceberg V2 operator is disabled by default due to a correctness issue. The correct setting for the property that turns off the operator is DISABLE_OPTIMIZED_ICEBERG_V2_READ=true.

Accept the default setting of the V2 operator. Do not change the setting from true to false.

CDPD-64629: Performance degradation of Iceberg tables compared to Hive tables

Cloudera testing of Iceberg and Hive tables using the Hive TPC-DS 1 Tb dataset (Parquet) revealed a slower performance executing a few of the queries in TPCDS. Overall performance of Iceberg executing queries on Hive external tables of Iceberg is faster than Hive.