Hash Indexes

[Centril]

[vovacooper]

would love to see hash indexes in the spacetimedb

[Centril]

Our most recent integration benchmarks trying out hash indices suggested that they did not actually gain any performance. However, microbenchmarks did suggest that there was a significant speedup.

For cases like entity_id: u32 and friends, we have another type of index already available: #[index(direct)].
It's substantially faster than btree and hash indices for monotonically increasing IDs but performs poorly for randomized data.
You may want to look at using direct for your use case.

[egormanga]

Please elaborate on “cases like entity_id: u32 and friends”, what is the particular case?

I don't see how entity_id would be monotonic without auto_inc, but that's already only useful on primary keys (thus an implicit index).

[Centril]

I don't see how entity_id would be monotonic without auto_inc, but that's already only useful on primary keys (thus an implicit index).

You can choose what the implicit index is backed by by doing e.g., #[primary_key] #[index(direct)] together.

[egormanga]

#[primary_key] #[index(direct)] together.

Great, thanks! I believe it might be a bit more intuitive to be able to write #[primary_key, index(direct)].