I've done some comparisons for inserts of various data sizes on mariadb, postgres, and sqlite without indexes.

I didn't have the patience of OP though to push it to 1B.

https://github.com/eatonphil/databases-intuition

looks like PGSQL 2x slower for uploading.

Looks like I'm not alone. But I don't, and don't think Mark does (he's a MySQL guy I believe), claim to be a Postgres expert.

http://smalldatum.blogspot.com/2023/09/trying-out-orioledb.h...

PostgreSQL supports heap tables, which should blow away SQLite's mandatory clustered index tables in an unindexed insert test.

In SQLite, would declaring the table without a rowid obviate the index? For example:

    CREATE TABLE IF NOT EXISTS integers
    (
       value INTEGER NOT NULL, 
    )
    WITHOUT ROWID;