v2.2.0 Unnecessary suggestions for indexes that already exist as leftmost term in another index.

[Epigene]

Hi,

Say there's a UniqueEvent model with a belongs_to :cause association.
unique_events table already has a multi-column uniqueness index like [:cause_id, :some_type, :uuid], unique: true, name: "very_unique_index".

lol_dba will still suggest to add a [:cause_id] index, even though there already is an index where :cause_id is the leftmost term (and no partial indexing is going on).

[plentz]

@Epigene do you know if having an index com a column on the leftmost term has the same behavior in all databases?

[Epigene]

Who can say about all. MySQL and PSQL definitely have the same behavior. Which ones do we seek to support?

[luisdavim]

This is not the case for all MySQL versions....

[Epigene]

@luisdavim It was the case for MySQL at the moment of writing back in 2020 and I doubt anything's changed. Here's the relevant part from MySQL v8 docs.

Are you referring to some older versions, have any specific ones in mind?