Maximum number of scanner threads (on each node) used for each query. By default, Impala uses as many cores as are available (one thread per core). You might lower this value if queries are using excessive resources on a busy cluster. Impala imposes a maximum value automatically, so a high value has no practical effect.
Has no effect if multi-threaded query execution is enabled, i.e.
MT_DOP is greater than 0.
Type: numeric
Default: 0