Positional information in zone layout aggregations

[brancz]

We'd like to create a tri-gram index over string arrays (eg. trigrams to postings lists that represent the segments/splits that contain a trigram) to narrow a search down to only those segments that could possibly match eg. a LIKE or ILIKE expression, and only run those through an OnPair pushed-down filter. We could of course build our own layout and do whatever we want, but zone layouts seem so close, because I think we could build what we want, if only we had positional information in the aggregation functions. I don't know, nor have I explored much about that infrastructure so maybe what I'm asking is impossible, but based on the current function signature it feels like we might not be terribly far off today already, and then we could maybe even make trigram indexes a first-class feature in vortex (maybe hierarchical bloomfilters as well).

@connortsui20 @AdamGS @joseph-isaacs @a10y