This commit provides the scaffolding for using the new sql stores.
The new interfaces, structs and methods are in sync with other projects
like Taproot Assets.
- Transactional Queries: the sqldb package defines the interfaces required
to execute transactional queries to our storage interface.
- Migration Files Embedded: the migration files are embedded into the binary.
- Database Migrations: I kept the use of 'golang-migrate' to ensure our
codebase remains in sync with the other projects, but can be changed.
- Build Flags for Conditional DB Target: flexibility to specify our database
target at compile-time based on the build flags in the same way we do
with our kv stores.
- Update modules: ran `go mod tidy`.
Schema for AMP invocies.
AMP invoices can be paid multiple times and each payment to an AMP invoice
is identified by a `set_id`.
The A in AMP stands for `Atomic`. All the htlcs belonging to the same
AMP payment (share the same set_id) will be resolved at the same time
with the same result: settled/canceled.
AMP invoices do not have an "invoice preimage". Instead, each htcl has
its own hash/preimage. When a new htlc is added the hash for that htlc
is attached to it. When all the htlcs of a set_id have been received we
are able to compute the preimage for each one of them.
Set of queries to deal with invoices. A couple of things to take into
account:
- Because the queries are not rewritten at runtime, we cannot have a
generic `INSERT` with different tuples.
- Because the queries are not rewritten at runtime, we cannot build
one query with only the filters that matter for that queries. The
two options are a combinatorial approach (a new query for every
permutation) or a generic query using the pattern
```
SELECT *
FROM table
WHERE (
-- Can be read as:
-- Match the filter 1 value if filter_1 != nil
column_1 >= sqlc.narg('filter_1') OR
sqlc.narg('filter_1') IS NULL
) AND (
column_2 >= sqlc.narg('filter_2') OR
sqlc.narg('filter_2') IS NULL
) ...
```
This is the schema for "ordinal" BOLT11 invoices.
The invoices table aims to keep an entry for each invoice, BOLT11 or not,
that will be supported.
Invoice related HTLCs will be stored in a separete table than forwarded
htlcs.
SQLite does not support `SEQUENCE`. We achieve atomic autoincrementals
using primary keys with autoincrement/serial. An invoice `AddIndex`
translates to `invoices(id)` while `SettleIndex` is `invoice_payments(id)`.
