Relation field ordering vs performance

[ydewit]

Does the order of relation fields affect indexing/performance like it does in relation databases?

I am assuming yes, but since I am new to Souffle and to Datalog it seemed worth asking.

[psubotic]

In souffle based on the access patterns we derive a minimal set of indexes (b-trees with unique ordering). So the way you declare a relation does not have any effect, but the accesses to a relation will be used to compute b-tree orders. This generally has a price in terms of memory (due to replication). For more details see: http://www.vldb.org/pvldb/vol12/p141-subotic.pdf Note: that the indexing and literal ordering problems cannot be fully decoupled and the literal orders in a rule affect the indexing problem. We have some work for offline literal orders that take into account indexing. For more details see: https://psubotic.github.io/papers/lopstr2022.pdf

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[ydewit]

Thank you!