Controlling Segment Parallelism

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.

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.

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.