HashJoin#

public class HashJoin implements AutoCloseable #

This class represents a hash table built from the join keys of the right-side table for a join operation.

This hash table can then be reused across a series of left probe tables to compute gather maps for joins more efficiently when the right-side table is not changing. It can also be used to query the output row count of a join before manifesting the join gather maps. Passing that row count to the gather-map operation no longer avoids any work: the output size is always computed internally and a supplied count is only validated against it, so an incorrect count fails with a CudfException. Prefer the overloads without a row count; the row-count overloads will be deprecated in a future release.

Constructor Summary

HashJoin(Table buildKeys, boolean compareNullsEqual)

Construct a hash table for a join from a table representing the join key columns from the right-side table in the join.

Method Summary

`close()`
`getCompareNulls()`	Deprecated. Returns true if the hash table was built to match on nulls otherwise false.
`getCompareNullsEqual()`	Returns true if the hash table was built to match on nulls otherwise false.
`getNumberOfColumns()`	Get the number of join key columns for the table used to generate the hash table.

Constructors

public HashJoin(Table buildKeys, boolean compareNullsEqual)#

Construct a hash table for a join from a table representing the join key columns from the right-side table in the join.

The resulting instance must be closed to release the GPU resources associated with the instance.

Parameters:

buildKeys – table view containing the join keys for the right-side join table
compareNullsEqual – true if null key values should match otherwise false

Methods

public void close()#

public long getNumberOfColumns()#: Get the number of join key columns for the table used to generate the hash table.

public boolean getCompareNullsEqual()#: Returns true if the hash table was built to match on nulls otherwise false.

public boolean getCompareNulls() Deprecated#

Returns true if the hash table was built to match on nulls otherwise false.

Deprecated:: Use getCompareNullsEqual() instead.