Re^7: Documentation of REGEXP support in DBD::SQLite?

[LanX]

Thanks :)

> Because, of course, if there are too many hits (here: 897633), the system switches to SeqScan

This doesn't decisively answer the question if trigrams are indexed by bigrams... 🤔

What if you search a bigram which is - by design- only in few rows?

Or an and combination of multiple bigrams?

And to be sure, please use the like '%ab%' form again.

[erix]

(For decisive answers, read the postgres code ;))

And to be sure, please use like '%ab%' again.

I can't get bigrams to respond quickly; also not when there is only one matching value; with this data it will always Seq scan (sometimes with parallel workers: just under 1 second).

In postgres, 'LIKE' doesn't allow regex (although its simple pattern search can sometimes use the trigram or btree index). Postgres uses the tilde for regex search (~ case sensitive, ~* case insensitive).

[LanX]

> I can't get bigrams to respond quickly

Hence they are not indexed.

> although its simple pattern search can sometimes use the trigram or btree index

That's why I wanted LIKE, to be sure the trigram optimization can be chosen