PREFETCH_MODE Query Option (CDH 5.8 or higher only)

Determines whether the prefetching optimization is applied during join query processing.

Type: numeric (0, 1) or corresponding mnemonic strings (NONE, HT_BUCKET).

Default: 1 (equivalent to HT_BUCKET)

Added in: CDH 5.8.0 (Impala 2.6.0)

Usage notes:

The default mode is 1, which means that hash table buckets are prefetched during join query processing.

Related information:

Joins in Impala SELECT Statements, Performance Considerations for Join Queries.