What is the use of Hash tables in DI Studio

[SYN]

What is the use of Hash tables in DI Studio? Can any body explain with example. Thank you.

[RMP]

Hash tables are used in the Lookup transformation where lookups are performed against data in memory. This can have a significant impact on performance. Maybe you could be more specific with your question.

[shivas]

Hi,

See the definition from SAS DI documentation.

The optimizer considers a hash join when an index join is eliminated as a possibility. With

a hash join, the smaller table is reconfigured in memory as a hash table. SQL sequentially

scans the larger table and performs row-by-row hash lookup against the small table to form

the result set. A memory-sizing formula, which is not presented here, determines whether

a hash join is chosen.

Thanks,

Shiva