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: 2 (equivalent to GLOBAL); formerly was 1 / LOCAL, in CDH 5.7 / Impala 2.5
Added in: CDH 5.7.0 (Impala 2.5.0)
In CDH 5.8 / Impala 2.6 and higher, the default is GLOBAL. This setting is recommended for a wide variety of workloads, to provide best performance with "out of the box" settings.
The lowest setting of LOCAL does a similar level of optimization (such as partition pruning) as in earlier Impala releases. This setting was the default in CDH 5.7 / Impala 2.5, to allow for a period of post-upgrade testing for existing workloads. This setting is suitable for workloads with non-performance-critical queries, or if the coordinator node is under heavy CPU or memory pressure.
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.
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 (CDH 5.7 or higher only), 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.