RUNTIME_FILTER_MODE Query Option (CDH 5.7 or higher only)

The RUNTIME_FILTER_MODE query option adjusts the settings for the runtime filtering feature. It turns this feature on and off, and controls how extensively the filters are transmitted between hosts.

Type: numeric (0, 1, 2) or corresponding mnemonic strings (OFF, LOCAL, GLOBAL).

Default: 1 (equivalent to LOCAL; subject to change in future releases)

Added in: CDH 5.7.0 (Impala 2.5.0)

Usage notes:

The default setting of LOCAL does a similar level of optimization (such as partition pruning) as in earlier Impala releases. This setting is the default in CDH 5.7 / Impala 2.5, to allow for a period of post-upgrade testing for existing workloads. Typically, you should be able to change the setting to GLOBAL after ensuring the extra memory requirement does not cause performance regressions on your cluster. This setting is suitable for workloads with non-performance-critical queries, or if the coordinator node is under heavy CPU or memory pressure.

Consider changing this setting to GLOBAL after a period of testing to ensure that the slight additional memory requirement for global runtime filtering does not cause problems for your workload.

You might change the setting to OFF if your workload contains many queries involving partitioned tables or joins that do not experience a performance increase from the runtime filters feature. If the overhead of producing the runtime filters outweighs the performance benefit for queries, you can turn the feature off entirely.

Related information:

Partitioning for Impala Tables for details about runtime filtering. DISABLE_ROW_RUNTIME_FILTERING Query Option (CDH 5.7 or higher only), RUNTIME_BLOOM_FILTER_SIZE Query Option, RUNTIME_FILTER_WAIT_TIME_MS Query Option (CDH 5.7 or higher only), and MAX_NUM_RUNTIME_FILTERS Query Option (CDH 5.7 or higher only) for tuning options for runtime filtering.