What is the `Cacheable` type class about?
```haskell
class Eq a => Cacheable a where
unchanged :: Accesses -> a -> a -> Bool
default unchanged :: (Generic a, GCacheable (Rep a)) => Accesses -> a -> a -> Bool
unchanged accesses a b = gunchanged (from a) (from b) accesses
```
Its only method is an alternative to `(==)`. The added value of `unchanged` (and the additional `Accesses` argument) arises _only_ for one type, namely `Dependency`. Indeed, the `Cacheable (Dependency a)` instance is non-trivial, whereas every other `Cacheable` instance is completely boilerplate (and indeed either generated from `Generic`, or simply `unchanged _ = (==)`). The `Cacheable (Dependency a)` instance is the only one where the `Accesses` argument is not just passed onwards.
The only callsite of the `unchanged` method is in the `ArrowCache (Rule m)` method. That is to say that the `Cacheable` type class is used to decide when we can re-use parts of the schema cache between Metadata operations.
So what is the `Cacheable (Dependency a)` instance about? Normally, the output of a `Rule m a b` is re-used when the new input (of type `a`) is equal to the old one. But sometimes, that's too coarse: it might be that a certain `Rule m a b` only depends on a small part of its input of type `a`. A `Dependency` allows us to spell out what parts of `a` are being depended on, and these parts are recorded as values of types `Access a` in the state `Accesses`.
If the input `a` changes, but not in a way that touches the recorded `Accesses`, then the output `b` of that rule can be re-used without recomputing.
So now you understand _why_ we're passing `Accesses` to the `unchanged` method: `unchanged` is an equality check in disguise that just needs some additional context.
But we don't need to pass `Accesses` as a function argument. We can use the `reflection` package to pass it as type-level context. So the core of this PR is that we change the instance declaration from
```haskell
instance (Cacheable a) => Cacheable (Dependency a) where
```
to
```haskell
instance (Given Accesses, Eq a) => Eq (Dependency a) where
```
and use `(==)` instead of `unchanged`.
If you haven't seen `reflection` before: it's like a `MonadReader`, but it doesn't require a `Monad`.
In order to pass the current `Accesses` value, instead of simply passing the `Accesses` as a function argument, we need to instantiate the `Given Accesses` context. We use the `give` method from the `reflection` package for that.
```haskell
give :: forall r. Accesses -> (Given Accesses => r) -> r
unchanged :: (Given Accesses => Eq a) => Accesses -> a -> a -> Bool
unchanged accesses a b = give accesses (a == b)
```
With these three components in place, we can delete the `Cacheable` type class entirely.
The remainder of this PR is just to remove the `Cacheable` type class and its instances.
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/6877
GitOrigin-RevId: 7125f5e11d856e7672ab810a23d5bf5ad176e77f
- Remove `onJust` in favor of the more general `for_`
- Remove `withJust` which was used only once
- Remove `hashNub` in favor of `Ord`-based `uniques`
- Simplify some of the implementations in `Hasura.Prelude`
- Add `hlint` hint from `maybe True` to `all`, and `maybe False` to `any`
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/6173
GitOrigin-RevId: 2c6ebbe2d04f60071d2a53a2d43c6d62dbc4b84e
This PR expands the OpenAPI specification generated for metadata to include separate definitions for `SourceMetadata` for each native database type, and for DataConnector.
For the most part the changes add `HasCodec` implementations, and don't modify existing code otherwise.
The generated OpenAPI spec can be used to generate TypeScript definitions that distinguish different source metadata types based on the value of the `kind` properly. There is a problem: because the specified `kind` value for a data connector source is any string, when TypeScript gets a source with a `kind` value of, say, `"postgres"`, it cannot unambiguously determine whether the source is postgres, or a data connector. For example,
```ts
function consumeSourceMetadata(source: SourceMetadata) {
if (source.kind === "postgres" || source.kind === "pg") {
// At this point TypeScript infers that `source` is either an instance
// of `PostgresSourceMetadata`, or `DataconnectorSourceMetadata`. It
// can't narrow further.
source
}
if (source.kind === "something else") {
// TypeScript infers that this `source` must be an instance of
// `DataconnectorSourceMetadata` because `source.kind` does not match
// any of the other options.
source
}
}
```
The simplest way I can think of to fix this would be to add a boolean property to the `SourceMetadata` type along the lines of `isNative` or `isDataConnector`. This could be a field that only exists in serialized data, like the metadata version field. The combination of one of the native database names for `kind`, and a true value for `isNative` would be enough for TypeScript to unambiguously distinguish the source kinds.
But note that in the current state TypeScript is able to reference the short `"pg"` name correctly!
~~Tests are not passing yet due to some discrepancies in DTO serialization vs existing Metadata serialization. I'm working on that.~~
The placeholders that I used for table and function metadata are not compatible with the ordered JSON serialization in use. I think the best solution is to write compatible codecs for those types in another PR. For now I have disabled some DTO tests for this PR.
Here are the generated [OpenAPI spec](https://github.com/hasura/graphql-engine-mono/files/9397333/openapi.tar.gz) based on these changes, and the generated [TypeScript client code](https://github.com/hasura/graphql-engine-mono/files/9397339/client-typescript.tar.gz) based on that spec.
Ticket: [MM-66](https://hasurahq.atlassian.net/browse/MM-66)
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/5582
GitOrigin-RevId: e1446191c6c832879db04f129daa397a3be03f62
The module `Hasura.SQL.AnyBackend` was introduced (in #751) to centralize the logic for case-switching behavior that depends on the particular flavor of relational DB backend (Postgres vs MSSQL vs BigQuery vs MySQL vs DataConnectors). This allows us to write a bunch of code in a backend-agnostic way, even if runtime behavior does depend on the chosen backend. At the same time, it allows us to write backend-specific code without having to care (too much) about the existence of other backends.
In #851 this module was rewritten to use Template Haskell.
I've heard that one of the reasons for the use of TH was that this would make it easier to keep backends out of the compilation product entirely. This would allow customers, especially on OSS, to benefit from simpler software licensing.
However:
1. This conditional compilation never materialized.
2. It's not clear whether writing this particular module based on TH would be sufficient for conditional compilation. And in any case, it can be done using CPP pragmas as well.
3. The TH code is extraordinarily complex. Since its introduction, it has been documented extraordinarily well, but it's still very difficult to maintain and/or refactor, due to its non-idiomatic nature.
4. Hasura's company objectives are now Cloud-oriented, so that software licensing issues work differently, and in particular, do not depend on what's part of the compilation product.
So this PR reverts on #851 by spelling out the code generated by TH. This is a net-negative diff size. IOW we used to generate less code than the size of the code doing the generating. This makes the code readable and maintainable.
The generated code has been modified in one way, which I'll now describe.
In the scenario that support for a new backend is introduced, a constructor is added to the `BackendType` type. This would then cause `liftTag` to be partial, thus raising a compiler warning. Resolving this requires adding corresponding constructors to the `BackendTag` and `AnyBackend` types. This would then require amending **almost** all other methods.
The exceptions are `composeAnyBackend` and `unpackAnyBackend`. These methods test whether two values are compatible, i.e. belong to the same backend. Both have a default case that in one way or another ignores the input values. Using TH here ensures that all values that belong together are caught. But after spelling out the TH, the presence of the default case means that no compiler warning is thrown for a missing match of matching values. So in the default case, we now do an explicit check for equality. If there _is_ an equality, that means that there is a missing `case`. So this is reported as an `error` (which is very crude, but it should be).
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/5333
GitOrigin-RevId: 5aaf0a93394bd740aa7371526d3175c8142b3541
### Description
This PR rewrites OpenAPI to be more idiomatic. Some noteworthy changes:
- we accumulate all required information during the Analyze phase, to avoid having to do a single lookup in the schema cache during the OpenAPI generation phase (we now only need the schema cache as input to run the analysis)
- we no longer build intermediary endpoint information and aggregate it, we directly build the the `PathItem` for each endpoint; additionally, that means we no longer have to assume that different methods have the same metadata
- we no longer have to first declare types, then craft references: we do everything in one step
- we now properly deal with nullability by treating "typeName" and "typeName!" as different
- we add a bunch of additional fields in the generated "schema", such as title
- we do now support enum values in both input and output positions
- checking whether the request body is required is now performed on the fly rather than by introspecting the generated schema
- the methods in the file are sorted by topic
### Controversial point
However, this PR creates some additional complexity, that we might not want to keep. The main complexity is _knot-tying_: to avoid lookups when generating the OpenAPI, it builds an actual graph of input types, which means that we need something similar to (but simpler than) `MonadSchema`, to avoid infinite recursions when analyzing the input types of a query. To do this, this PR introduces `CircularT`, a lesser `SchemaT` that aims at avoiding ever having to reinvent this particular wheel ever again.
### Remaining work
- [x] fix existing tests (they are all failing due to some of the schema changes)
- [ ] add tests to cover the new features:
- [x] tests for `CircularT`
- [ ] tests for enums in output schemas
- [x] extract / document `CircularT` if we wish to keep it
- [x] add more comments to `OpenAPI`
- [x] have a second look at `buildVariableSchema`
- [x] fix all missing diagnostics in `Analyze`
- [x] add a Changelog entry?
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/4654
Co-authored-by: David Overton <7734777+dmoverton@users.noreply.github.com>
GitOrigin-RevId: f4a9191f22dfcc1dccefd6a52f5c586b6ad17172
## Description
Following on from #4572, this removes more dead code as identified by Weeder. Comments and thoughts similarly welcome!
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/4587
GitOrigin-RevId: 73aa6a5a2833ee41d29b71fcd0a72ed19822ca73
(Work here originally done by awjchen, rebased and fixed up for merge by
jberryman)
This is part of a merge train towards GHC 9.2 compatibility. The main
issue is the use of the new abstract `KeyMap` in 2.0. See:
https://hackage.haskell.org/package/aeson-2.0.3.0/changelog
Alex's original work is here:
#4305
BEHAVIOR CHANGE NOTE: This change causes a different arbitrary ordering
of serialized Json, for example during metadata export. CLI users care
about this in particular, and so we need to call it out as a _behavior
change_ as we did in v2.5.0. The good news though is that after this
change ordering should be more stable (alphabetical key order).
See: https://hasurahq.slack.com/archives/C01M20G1YRW/p1654012632634389
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/4611
Co-authored-by: awjchen <13142944+awjchen@users.noreply.github.com>
GitOrigin-RevId: 700265162c782739b2bb88300ee3cda3819b2e87
### Description
This PR is a first step in a series of cleanups of action relationships. This first step does not contain any behavioral change, and it simply reorganizes / prunes / rearranges / documents the code. Mainly:
- it divides some files in RQL.Types between metadata types, schema cache types, execution types;
- it renames some types for consistency;
- it minimizes exports and prunes unnecessary types;
- it moves some types in places where they make more sense;
- it replaces uses of `DMap BackendTag` with `BackendMap`.
Most of the "movement" within files re-organizes declarations in a "top-down" fashion, by moving all TH splices to the end of the file, which avoids order or declarations mattering.
### Optional list types
One main type change this PR makes is a replacement of variant list types in `CustomTypes.hs`; we had `Maybe [a]`, or sometimes `Maybe (NonEmpty a)`. This PR harmonizes all of them to `[a]`, as most of the code would use them as such, by doing `fromMaybe []` or `maybe [] toList`.
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/4613
GitOrigin-RevId: bc624e10df587eba862ff27a5e8021b32d0d78a2
## Description
This PR adds a config file for [`weeder`](https://github.com/ocharles/weeder) to the `-mono` repository. `weeder` checks for dead code by building a call graph from the given entry points (currently every module named `Main` with a `main` function) and then marking every function _not_ in that call graph as dead code.
To avoid very large PRs, I'm going to tackle this in a series. This first PR adds the basic configuration, plus removes as many weeds as it took for me to realise this was going to become a very big PR. The PRs after this will largely be removing dead code, until the final PR that will add Weeder to the CI pipeline.
### Related Issues
This closes#2973.
## Affected components
- Server
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/4572
GitOrigin-RevId: ac8eaa9473e5ac1f16babcb35388694392d0d7dc
No logic in this PR, just tidying things up (renaming the backend from `Experimental` to `DataWrapper`).
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/3779
GitOrigin-RevId: f11acf563ccd8b9f16bc23c5e92da392aa4cfb2c
This commit introduces an "experimental" backend adapter to the GraphQL Engine.
It defines a high-level interface which will eventually be used as the basis for implementing separate data source query generation & marshaling services that communicate with the GraphQL Engine Server via some protocol.
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/2684
Co-authored-by: awjchen <13142944+awjchen@users.noreply.github.com>
Co-authored-by: Chris Parks <592078+cdparks@users.noreply.github.com>
GitOrigin-RevId: 4463b682142ad6e069e223b88b14db511f634768
We'll see if this improves compile times at all, but I think it's worth
doing as at least the most minimal form of module documentation.
This was accomplished by first compiling everything with
-ddump-minimal-imports, and then a bunch of scripting (with help from
ormolu)
**EDIT** it doesn't seem to improve CI compile times but the noise floor is high as it looks like we're not caching library dependencies anymore
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/2730
GitOrigin-RevId: 667eb8de1e0f1af70420cbec90402922b8b84cb4
This commit applies ormolu to the whole Haskell code base by running `make format`.
For in-flight branches, simply merging changes from `main` will result in merge conflicts.
To avoid this, update your branch using the following instructions. Replace `<format-commit>`
by the hash of *this* commit.
$ git checkout my-feature-branch
$ git merge <format-commit>^ # and resolve conflicts normally
$ make format
$ git commit -a -m "reformat with ormolu"
$ git merge -s ours post-ormolu
https://github.com/hasura/graphql-engine-mono/pull/2404
GitOrigin-RevId: 75049f5c12f430c615eafb4c6b8e83e371e01c8e
### Description
This PR is the first of several PRs meant to introduce Generalized Joins. In this first PR, we add non-breaking changes to the Metadata types for DB-to-DB remote joins. Note that we are currently rejecting the new remote join format in order to keep folks from breaking their metadata (in case of a downgrade). These issues will be tackled (and JSON changes reverted) in subsequent PRs.
This PR also changes the way we construct the schema cache, and breaks the way we process sources in two steps: we first resolve each source and construct a cache of their tables' raw info, then in a second step we build the source output. This is so that we have access to the target source's tables when building db-to-db relationships.
### Notes
- this PR contains a few minor cleanups of the schema
- it also fixes a bug in how we do renames in remote schema relationships
- it introduces cross-source schema dependencies
https://github.com/hasura/graphql-engine-mono/pull/1727
Co-authored-by: Evie Ciobanu <1017953+eviefp@users.noreply.github.com>
GitOrigin-RevId: f625473077bc5fff5d941b70e9a116192bc1eb22
### Context
One of the ways we use the Backend type families is to use `Void` for all types for which a backend has no representation; this allows us to make some branches of our metadata and IR unrepresentable, making some functions total, where they would have to handle those unsupported cases otherwise.
However, one of the biggest features, functions, cannot be cut that way, due to one of the constraints on `FunctionName b`: the metadata generator requires it to have an `Arbitrary` instance, and `Arbitrary` does not have a recovery mechanism which would allow for a `Void` instance...
### Description
This PR solves this problem and removes the `Arbitrary` constraints in `Backend`. To do so, it introduces a new typeclass: `PartialArbitrary`, which is very similar to `Arbitrary`, except that it returns a `Maybe (Gen a)`, allowing for `Void` to have a well-formed instance. An `Arbitrary` instance for `Metadata` can easily be retrieved with `arbitrary = fromJust . partialArbitrary`.
Furthermore, `PartialArbitrary` has a generic implementation, inspired by the one in `generic-arbitrary`, which automatically prunes branches that return `Nothing`, allowing to automatically construct most types. Types that don't have a type parameter and therefore can't contain `Void` can easily get their `PartialArbitrary` instance from `Arbitrary` with `partialArbitrary = Just arbitrary`. This is what a default overlappable instance provides.
In conjunction with other cleanups in #1666, **this allows for Void function names**.
### Notes
While this solves the stated problem, there are other possible solutions we could explore, such as:
- switching from QuickCheck to a library that supports that kind of pruning natively
- removing the test altogether, and dropping all notion of Arbitrary from the code
There are also several things we could do with the Generator module:
- move it out of RQL.DDL.Metadata, to some place that makes more sense
- move ALL Arbitrary instances in the code to it, since nothing else uses Arbitrary
- or, to the contrary, move all those Arbitrary instances alongside their types, to avoid an orphan instance
https://github.com/hasura/graphql-engine-mono/pull/1667
GitOrigin-RevId: 88e304ea453840efb5c0d39294639b8b30eefb81
### Description
This PR fixes a major issue in the JSON instances of `AnyBackend`: they were not symmetrical! `FromJSON` always made the assumption that the value was an object, and that it contained a "kind" field if it happened to not be a Postgres value. `ToJSON` did NOT insert said field in the output, and did not enforce that the output was an object.
....however, it worked, because nowhere in the code did we yet rely on those being symmetrical. They are both used only once:
- `parseJSON` was used to decode a `Metadata` object, but the matching `toJSON` instance, which is heavily customized, does insert the "kind" field properly
- `toJSON` was only used on the `SchemaCache`, which has no corresponding `FromJSON` instance, since we only serialize it in debug endpoints
This PR makes no attempt at making the instances symmetrical. Instead, it implements simpler functions, and pushes the problem of identifying the proper backend (if any) to the call sites.
### Notes
Additionally, it cleans up some instances that were manually written where they could be auto-generated. In the process, this PR changes the semantics of `Show`, since the stock derived instance will include the constructor name, where before it was skipped. I think it is preferable.
https://github.com/hasura/graphql-engine-mono/pull/1672
GitOrigin-RevId: 0a1580a0e0f01c25b8c9fee7612dba6e7de055d5
### Description
This PR adds the required IR for DB to DB joins, based on @paf31 and @0x777 's `feature/db-to-db` branch.
To do so, it also refactors the IR to introduce a new type parameter, `r`, which is used to recursively constructs the `v` parameter of remote QueryDBs. When collecting remote joins, we replace `r` with `Const Void`, indicating at the type level that there cannot be any leftover remote join.
Furthermore, this PR refactors IR.Select for readability, moves some code from IR.Root to IR.Select to avoid having to deal with circular dependencies, and makes it compile by adding `error` in all new cases in the execution pipeline.
The diff doesn't make it clear, but most of Select.hs is actually unchanged. Declarations have just been reordered by topic, in the following order:
- type declarations
- instance declarations
- type aliases
- constructor functions
- traverse functions
https://github.com/hasura/graphql-engine-mono/pull/1580
Co-authored-by: Phil Freeman <630306+paf31@users.noreply.github.com>
GitOrigin-RevId: bbdcb4119cec8bb3fc32f1294f91b8dea0728721
event catalog:
- `hdb_catalog` is no longer automatically created
- catalog is initialised when the first event trigger is created
- catalog initialisation is done during the schema cache build, using `ArrowCache` so it is only run in response to a change to the set of event triggers
event queue:
- `processEventQueue` thread is prevented from starting when `HASURA_GRAPHQL_EVENTS_FETCH_INTERVAL=0`
- `processEventQueue` thread only processes sources for which at least one event trigger exists in some table in the source
Co-authored-by: Anon Ray <616387+ecthiender@users.noreply.github.com>
GitOrigin-RevId: 73f256465d62490cd2b59dcd074718679993d4fe
