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| <!DOCTYPE concept PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd"> |
| <concept id="max_num_runtime_filters" rev="2.5.0"> |
| |
| <title>MAX_NUM_RUNTIME_FILTERS Query Option (<keyword keyref="impala25"/> or higher only)</title> |
| <titlealts audience="PDF"><navtitle>MAX_NUM_RUNTIME_FILTERS</navtitle></titlealts> |
| <prolog> |
| <metadata> |
| <data name="Category" value="Impala"/> |
| <data name="Category" value="Impala Query Options"/> |
| <data name="Category" value="Performance"/> |
| <data name="Category" value="Developers"/> |
| <data name="Category" value="Data Analysts"/> |
| </metadata> |
| </prolog> |
| |
| <conbody> |
| |
| <p rev="2.5.0"> |
| <indexterm audience="hidden">MAX_NUM_RUNTIME_FILTERS query option</indexterm> |
| The <codeph>MAX_NUM_RUNTIME_FILTERS</codeph> query option |
| sets an upper limit on the number of runtime filters that can be produced for each query. |
| </p> |
| |
| <p conref="../shared/impala_common.xml#common/type_integer"/> |
| |
| <p> |
| <b>Default:</b> 10 |
| </p> |
| |
| <p conref="../shared/impala_common.xml#common/added_in_250"/> |
| |
| <p conref="../shared/impala_common.xml#common/usage_notes_blurb"/> |
| |
| <p> |
| Each runtime filter imposes some memory overhead on the query. |
| Depending on the setting of the <codeph>RUNTIME_BLOOM_FILTER_SIZE</codeph> |
| query option, each filter might consume between 1 and 16 megabytes |
| per plan fragment. There are typically 5 or fewer filters per plan fragment. |
| </p> |
| |
| <p> |
| Impala evaluates the effectiveness of each filter, and keeps the |
| ones that eliminate the largest number of partitions or rows. |
| Therefore, this setting can protect against |
| potential problems due to excessive memory overhead for filter production, |
| while still allowing a high level of optimization for suitable queries. |
| </p> |
| |
| <p conref="../shared/impala_common.xml#common/runtime_filtering_option_caveat"/> |
| |
| <p conref="../shared/impala_common.xml#common/kudu_blurb"/> |
| |
| <p rev="2.11.0 IMPALA-4252" conref="../shared/impala_common.xml#common/filter_option_bloom_only"/> |
| |
| <p conref="../shared/impala_common.xml#common/related_info"/> |
| <p> |
| <xref href="impala_runtime_filtering.xml"/>, |
| <!-- <xref href="impala_partitioning.xml#dynamic_partition_pruning"/>, --> |
| <xref href="impala_runtime_bloom_filter_size.xml#runtime_bloom_filter_size"/>, |
| <xref href="impala_runtime_filter_mode.xml#runtime_filter_mode"/> |
| </p> |
| |
| </conbody> |
| </concept> |