hash join
Short Description
The hash join node builds a hash table in memory based on the smaller table and then scans the larger one looking for matches
Detailed Description​
The hash join node builds a hash table in memory based on the smaller table and then scans the larger one looking for matches. Hash joins are computationally expensive and require additional memory for the hash table to be built in, which is why a merge join is preferred if possible.
If the hash table is too big for memory, it will spill to disk which will impact performance.
Additional Links​
- CockroachDB Docs - Hash Joins
- CockroachDB Docs - Supported Join Algorithms
- CockroachDB Docs - Cost Based Optimizer
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