Remove connection from database provider

Content

This PR includes a refactor of the database API used to query entities from the database.

As of today we used the Provider trait to encapsulate a entity query, this trait come with a major issue: it needs to borrow a connection to the database, making it difficult to return a iterator to a query result. This PR replace this trait with a new one: Query. Basically a query is what was a provider but instead of owning a reference to a database connection it own a WhereCondition that will be applied when this query is run.

This means that a query implementation can't run itself like the provider could, instead you use an extension method directly on the sql connection: fetch. This method take a query as a parameter and nothing more since it own the where condition to apply

When we doesn't need the iterator returned by fetch there's two new other extension method on the db connection that are available:

fetch_one : return the first result of the iterator if any
fetch_and_collect : that collect the iterator into the desired container (like a iterator.collect do).

Query design philosophy

All implementation have been made using the following model

pub struct GetStakePoolQuery {
    condition: WhereCondition,
}

impl Query for GetStakePoolQuery {
    type Entity = StakePool;

    fn filters(&self) -> WhereCondition {
        self.condition.clone()
    }

    fn get_definition(&self, condition: &str) -> String { [...] }
}

This is at creation, and by the query itself, that the condition is defined:

impl GetStakePoolQuery {
    pub fn by_epoch(epoch: Epoch) -> StdResult<Self> {
        let condition = WhereCondition::new("epoch = ?*", vec![Value::Integer(epoch.try_into()?)]);

        Ok(Self { condition })
    }
}

Caveat: This system make it more difficult to chain conditions outside of the query (like in the repository). This is only visible in the changes to the OpenMessageRepository and its associated 'Get' queries but it may be cumbersome if we want to multiply such uses.

Usage

Before:

let provider = GetCardanoTransactionProvider::new(&self.connection);
let filters = provider.get_transaction_between_blocks_condition(range);
let transactions = provider.find(filters)?;

After:

let transactions = self
        .connection
        .fetch(GetCardanoTransactionQuery::between_blocks(range))?;

Pre-submit checklist

Branch
- [x] Tests are provided (if possible)
- [x] Crates versions are updated (if relevant)
- [ ] CHANGELOG file is updated (if relevant)
- [x] Commit sequence broadly makes sense
- [x] Key commits have useful messages
PR
- [x] No clippy warnings in the CI
- [x] Self-reviewed the diff
- [x] Useful pull request description
- [x] Reviewer requested

Comments

Caveat:

Before we could define helpers methods on the providers to execute the query and pre-process the result, this is no longer possible (that why some panic are pulled up from those, now suppressed, methods to the repositories).
The Query::get_definition method could lose its condition parameter and pull it up directly fromQuery::filter. But this would mean cloning the stored definition twice (one to get the filter sql expression needed and one to get the condition values in fetch). We may have to rethink the WhereCondition if we want to address that issue.

Issue(s)

Closes #1711

Test Results

3 files ±0 43 suites ±0 8m 35s :stopwatch: +10s 992 tests +1 992 :white_check_mark: +1 0 :zzz: ±0 0 :x: ±0 1 090 runs +1 1 090 :white_check_mark: +1 0 :zzz: ±0 0 :x: ±0

Results for commit c3a60e67. ± Comparison against base commit 8b66e454.

This pull request removes 28 and adds 29 tests. Note that renamed tests count towards both.

``` mithril-aggregator ‑ database::provider::certificate::get_certificate::tests::test_get_certificate_records mithril-aggregator ‑ database::provider::certificate::insert_certificate::tests::test_insert_certificate_record mithril-aggregator ‑ database::provider::certificate::insert_certificate::tests::test_insert_many_certificates_records mithril-aggregator ‑ database::provider::epoch_setting::delete_epoch_setting::tests::test_delete mithril-aggregator ‑ database::provider::epoch_setting::delete_epoch_setting::tests::test_prune mithril-aggregator ‑ database::provider::epoch_setting::get_epoch_setting::tests::test_get_epoch_settings mithril-aggregator ‑ database::provider::epoch_setting::update_epoch_setting::tests::test_update_epoch_setting mithril-aggregator ‑ database::provider::signed_entity::get_signed_entity::tests::test_get_signed_entity_records mithril-aggregator ‑ database::provider::signed_entity::insert_signed_entity::tests::test_insert_signed_entity_record mithril-aggregator ‑ database::provider::signer::get_signer::tests::test_get_signer_records … ``` ``` mithril-aggregator ‑ database::query::certificate::get_certificate::tests::test_get_all_certificate_records mithril-aggregator ‑ database::query::certificate::get_certificate::tests::test_get_certificate_records_by_epoch mithril-aggregator ‑ database::query::certificate::insert_certificate::tests::test_insert_certificate_record mithril-aggregator ‑ database::query::certificate::insert_certificate::tests::test_insert_many_certificates_records mithril-aggregator ‑ database::query::epoch_setting::delete_epoch_setting::tests::test_delete_below_threshold mithril-aggregator ‑ database::query::epoch_setting::delete_epoch_setting::tests::test_delete_by_epoch mithril-aggregator ‑ database::query::epoch_setting::get_epoch_setting::tests::test_get_epoch_settings mithril-aggregator ‑ database::query::epoch_setting::update_epoch_setting::tests::test_update_epoch_setting mithril-aggregator ‑ database::query::signed_entity::get_signed_entity::tests::test_get_signed_entity_records mithril-aggregator ‑ database::query::signed_entity::insert_signed_entity::tests::test_insert_signed_entity_record … ```

:recycle: This comment has been updated with latest results.

input-output-hk / mithril