Internals of Hash-Semi-Join (Multi-Process-Unit Version) - 2023.2 English

Vitis Libraries
Release Date
2023-12-20
Version
2023.2 English

This document describes the structure and execution of Hash-Semi-Join, implemented as hashSemiJoin function. Its implementation is based on Hash-Join-MPU.

Hash-Semi-Join returns rows from the outer table where a field of outer table matches with the one of inner table. Even if a record of outer table matches with many rows in inner table, the one of outer table is output only once.

the operation of hash semi join
Hash-Semi-Join is written using the EXISTS or IN constructs. For example:
select * from S where S.key in ( select key from T )