Optionally Support SQLite instead of just Postgres

[brandonros]

Would it be possible?

[brandonros]

error: error returned from database: near "SET": syntax error
  --> database/transaction.rs:39:13
   |
39 |             sqlx::query!("SET TRANSACTION ISOLATION LEVEL SERIALIZABLE")
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: this error originates in the macro `$crate::sqlx_macros::expand_query` which comes from the expansion of the macro `sqlx::query` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0432]: unresolved imports `sqlx::PgConnection`, `sqlx::Postgres`
 --> database/transaction.rs:4:24
  |
4 | use sqlx::{Connection, PgConnection, Postgres};
  |                        ^^^^^^^^^^^^  ^^^^^^^^ no `Postgres` in the root
  |                        |
  |                        no `PgConnection` in the root
  |                        help: a similar name exists in the module: `Connection`

error[E0432]: unresolved import `sqlx::postgres`
 --> database/object_id.rs:2:12
  |
2 | use sqlx::{postgres::PgTypeInfo, Database};
  |            ^^^^^^^^ could not find `postgres` in `sqlx`

error[E0432]: unresolved imports `sqlx::postgres`, `sqlx::PgConnection`
 --> database/test.rs:8:12
  |
8 | use sqlx::{postgres::PgConnectOptions, ConnectOptions, Executor, PgConnection};
  |            ^^^^^^^^                                              ^^^^^^^^^^^^
  |            |                                                     |
  |            |                                                     no `PgConnection` in the root
  |            could not find `postgres` in `sqlx`                   help: a similar name exists in the module: `Connection`

error[E0433]: failed to resolve: could not find `postgres` in `sqlx`
  --> database/test.rs:15:21
   |
15 |     pub pool: sqlx::postgres::PgPool,
   |                     ^^^^^^^^ could not find `postgres` in `sqlx`

error[E0433]: failed to resolve: could not find `PgPool` in `sqlx`
   --> database/test.rs:129:22
    |
129 |     let pool = sqlx::PgPool::connect_with(pool_options).await?;
    |                      ^^^^^^ could not find `PgPool` in `sqlx`

error[E0412]: cannot find type `PgPool` in crate `sqlx`
   --> database/pool.rs:6:31
    |
6   | pub type PostgresPool = sqlx::PgPool;
    |                               ^^^^^^ help: a struct with a similar name exists: `Pool`
    |
   ::: /Users/brandonros/.cargo/git/checkouts/sqlx-16b768613d6d0f5a/263ae99/sqlx-core/src/pool/mod.rs:216:1
    |
216 | pub struct Pool<DB: Database>(pub(crate) Arc<SharedPool<DB>>);
    | ----------------------------- similarly named struct `Pool` defined here

error[E0412]: cannot find type `Postgres` in crate `sqlx`
   --> database/object_id.rs:209:44
    |
209 | impl<const PREFIX: usize> sqlx::Type<sqlx::Postgres> for ObjectId<PREFIX> {
    |                                            ^^^^^^^^ not found in `sqlx`

error[E0412]: cannot find type `Postgres` in crate `sqlx`
   --> database/object_id.rs:210:30
    |
210 |     fn type_info() -> <sqlx::Postgres as Database>::TypeInfo {
    |                              ^^^^^^^^ not found in `sqlx`

error[E0412]: cannot find type `Postgres` in crate `sqlx`
   --> database/object_id.rs:216:54
    |
216 | impl<'q, const PREFIX: usize> sqlx::Encode<'q, sqlx::Postgres> for ObjectId<PREFIX> {
    |                                                      ^^^^^^^^ not found in `sqlx`

error[E0412]: cannot find type `Postgres` in crate `sqlx`
   --> database/object_id.rs:219:26
    |
219 |         buf: &mut <sqlx::Postgres as sqlx::database::HasArguments<'q>>::ArgumentBuffer,
    |                          ^^^^^^^^ not found in `sqlx`

error[E0412]: cannot find type `Postgres` in crate `sqlx`
   --> database/object_id.rs:226:54
    |
226 | impl<'r, const PREFIX: usize> sqlx::Decode<'r, sqlx::Postgres> for ObjectId<PREFIX> {
    |                                                      ^^^^^^^^ not found in `sqlx`

error[E0412]: cannot find type `Postgres` in crate `sqlx`
   --> database/object_id.rs:228:23
    |
228 |         value: <sqlx::Postgres as sqlx::database::HasValueRef<'r>>::ValueRef,
    |                       ^^^^^^^^ not found in `sqlx`

warning: unused import: `Connection`
 --> database/transaction.rs:4:12
  |
4 | use sqlx::{Connection, PgConnection, Postgres};
  |            ^^^^^^^^^^
  |
  = note: `#[warn(unused_imports)]` on by default

warning: unused import: `ConnectOptions`
 --> database/test.rs:8:40
  |
8 | use sqlx::{postgres::PgConnectOptions, ConnectOptions, Executor, PgConnection};
  |                                        ^^^^^^^^^^^^^^

warning: unused import: `Executor`
 --> database/test.rs:8:56
  |
8 | use sqlx::{postgres::PgConnectOptions, ConnectOptions, Executor, PgConnection};

a list of errors when changing postgres feature to sqlite in Cargo.tomls

[dimfeld]

It would need a fair number of changes as there are a number of things that are either Postgres-specific or would need to be done completely differently for SQLite. Can't say it will never happen, but not in the plans for now.