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| title: Controlling Segment Parallelism |
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| The `gp_external_max_segs` server configuration parameter controls the number of virtual segments that can simultaneously access a single `gpfdist` instance. The default is 64. You can set the number of segments such that some segments process external data files and some perform other database processing. Set this parameter in the `hawq-site.xml` file of your master instance. |
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| The number of segments in the `gpfdist` location list specify the minimum number of virtual segments required to serve data to a `gpfdist` external table. |
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| The `hawq_rm_nvseg_perquery_perseg_limit` and `hawq_rm_nvseg_perquery_limit` parameters also control segment parallelism by specifying the maximum number of segments used in running queries on a `gpfdist` external table on the cluster. |
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