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
### Description
This monster of a PR took way too long. As the title suggests, it reduces the schema context carried in the readers to the very strict minimum. In practice, that means that to build a source, we only require:
- the global `SchemaContext`
- the global `SchemaOptions` (soon to be renamed `SchemaSourceOptions`)
- that source's `SourceInfo`
Furthermore, _we no longer carry "default" customization options throughout the schema_. All customization information is extracted from the `SourceInfo`, when required. This prevents an entire category of bugs we had previously encountered, such as parts of the code using uninitialized / unupdated customization info.
In turn, this meant that we could remove the explicit threading of the `SourceInfo` throughout the schema, since it is now always available through the reader context.
Finally, this meant making a few adjustments to relay and actions as well, such as the introduction of a new separate "context" for actions, and a change to how we create some of the action-specific postgres scalar parsers.
I'll highlight with review comments the areas of interest.
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/6709
GitOrigin-RevId: ea80fddcb24e2513779dd04b0b700a55f0028dd1
Just forcing some of the most numerous thunks (with -hi profiling), it
seems some of these were retaining significant amount of data
this can follow merge of, or supersede #6679
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/6710
GitOrigin-RevId: d0566ee288841e264637231a7f238946aa2e3564
This upgrades the version of Ormolu required by the HGE repository to v0.5.0.1, and reformats all code accordingly.
Ormolu v0.5 reformats code that uses infix operators. This is mostly useful, adding newlines and indentation to make it clear which operators are applied first, but in some cases, it's unpleasant. To make this easier on the eyes, I had to do the following:
* Add a few fixity declarations (search for `infix`)
* Add parentheses to make precedence clear, allowing Ormolu to keep everything on one line
* Rename `relevantEq` to `(==~)` in #6651 and set it to `infix 4`
* Add a few _.ormolu_ files (thanks to @hallettj for helping me get started), mostly for Autodocodec operators that don't have explicit fixity declarations
In general, I think these changes are quite reasonable. They mostly affect indentation.
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/6675
GitOrigin-RevId: cd47d87f1d089fb0bc9dcbbe7798dbceedcd7d83
>
## Description
->
This PR allows DC agents to define custom aggregate functions for their scalar types.
### Related Issues
->
GDC-189
### Solution and Design
>
We added a new property `aggregate_functions` to the scalar types capabilities. This allows the agent author to specify a set of aggregate functions supported by each scalar type, along with the function's result type.
During GraphQL schema generation, the custom aggregate functions are available via a new method `getCustomAggregateOperators` on the `Backend` type class.
Custom functions are merged with the builtin aggregate functions when building GraphQL schemas for table aggregate fields and for `order_by` operators on array relations.
### Steps to test and verify
>
• Codec tests for aggregate function capabilities have been added to the unit tests.
• Some custom aggregate operators have been added to the reference agent and are used in a new test in `api-tests`.
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/6199
GitOrigin-RevId: e9c0d1617af93847c1493671fdbb794f573bde0c
The main aim of the PR is:
1. To set up a module structure for 'remote-schemas' package.
2. Move parts by the remote schema codebase into the new module structure to validate it.
## Notes to the reviewer
Why a PR with large-ish diff?
1. We've been making progress on the MM project but we don't yet know long it is going to take us to get to the first milestone. To understand this better, we need to figure out the unknowns as soon as possible. Hence I've taken a stab at the first two items in the [end-state](https://gist.github.com/0x777/ca2bdc4284d21c3eec153b51dea255c9) document to figure out the unknowns. Unsurprisingly, there are a bunch of issues that we haven't discussed earlier. These are documented in the 'open questions' section.
1. The diff is large but that is only code moved around and I've added a section that documents how things are moved. In addition, there are fair number of PR comments to help with the review process.
## Changes in the PR
### Module structure
Sets up the module structure as follows:
```
Hasura/
RemoteSchema/
Metadata/
Types.hs
SchemaCache/
Types.hs
Permission.hs
RemoteRelationship.hs
Build.hs
MetadataAPI/
Types.hs
Execute.hs
```
### 1. Types representing metadata are moved
Types that capture metadata information (currently scattered across several RQL modules) are moved into `Hasura.RemoteSchema.Metadata.Types`.
- This new module only depends on very 'core' modules such as
`Hasura.Session` for the notion of roles and `Hasura.Incremental` for `Cacheable` typeclass.
- The requirement on database modules is avoided by generalizing the remote schemas metadata to accept an arbitrary 'r' for a remote relationship
definition.
### 2. SchemaCache related types and build logic have been moved
Types that represent remote schemas information in SchemaCache are moved into `Hasura.RemoteSchema.SchemaCache.Types`.
Similar to `H.RS.Metadata.Types`, this module depends on 'core' modules except for `Hasura.GraphQL.Parser.Variable`. It has something to do with remote relationships but I haven't spent time looking into it. The validation of 'remote relationships to remote schema' is also something that needs to be looked at.
Rips out the logic that builds remote schema's SchemaCache information from the monolithic `buildSchemaCacheRule` and moves it into `Hasura.RemoteSchema.SchemaCache.Build`. Further, the `.SchemaCache.Permission` and `.SchemaCache.RemoteRelationship` have been created from existing modules that capture schema cache building logic for those two components.
This was a fair amount of work. On main, currently remote schema's SchemaCache information is built in two phases - in the first phase, 'permissions' and 'remote relationships' are ignored and in the second phase they are filled in.
While remote relationships can only be resolved after partially resolving sources and other remote schemas, the same isn't true for permissions. Further, most of the work that is done to resolve remote relationships can be moved to the first phase so that the second phase can be a very simple traversal.
This is the approach that was taken - resolve permissions and as much as remote relationships information in the first phase.
### 3. Metadata APIs related types and build logic have been moved
The types that represent remote schema related metadata APIs and the execution logic have been moved to `Hasura.RemoteSchema.MetadataAPI.Types` and `.Execute` modules respectively.
## Open questions:
1. `Hasura.RemoteSchema.Metadata.Types` is so called because I was hoping that all of the metadata related APIs of remote schema can be brought in at `Hasura.RemoteSchema.Metadata.API`. However, as metadata APIs depended on functions from `SchemaCache` module (see [1](ceba6d6226/server/src-lib/Hasura/RQL/DDL/RemoteSchema.hs (L55)) and [2](ceba6d6226/server/src-lib/Hasura/RQL/DDL/RemoteSchema.hs (L91)), it made more sense to create a separate top-level module for `MetadataAPI`s.
Maybe we can just have `Hasura.RemoteSchema.Metadata` and get rid of the extra nesting or have `Hasura.RemoteSchema.Metadata.{Core,Permission,RemoteRelationship}` if we want to break them down further.
1. `buildRemoteSchemas` in `H.RS.SchemaCache.Build` has the following type:
```haskell
buildRemoteSchemas ::
( ArrowChoice arr,
Inc.ArrowDistribute arr,
ArrowWriter (Seq CollectedInfo) arr,
Inc.ArrowCache m arr,
MonadIO m,
HasHttpManagerM m,
Inc.Cacheable remoteRelationshipDefinition,
ToJSON remoteRelationshipDefinition,
MonadError QErr m
) =>
Env.Environment ->
( (Inc.Dependency (HashMap RemoteSchemaName Inc.InvalidationKey), OrderedRoles),
[RemoteSchemaMetadataG remoteRelationshipDefinition]
)
`arr` HashMap RemoteSchemaName (PartiallyResolvedRemoteSchemaCtxG remoteRelationshipDefinition, MetadataObject)
```
Note the dependence on `CollectedInfo` which is defined as
```haskell
data CollectedInfo
= CIInconsistency InconsistentMetadata
| CIDependency
MetadataObject
-- ^ for error reporting on missing dependencies
SchemaObjId
SchemaDependency
deriving (Eq)
```
this pretty much means that remote schemas is dependent on types from databases, actions, ....
How do we fix this? Maybe introduce a typeclass such as `ArrowCollectRemoteSchemaDependencies` which is defined in `Hasura.RemoteSchema` and then implemented in graphql-engine?
1. The dependency on `buildSchemaCacheFor` in `.MetadataAPI.Execute` which has the following signature:
```haskell
buildSchemaCacheFor ::
(QErrM m, CacheRWM m, MetadataM m) =>
MetadataObjId ->
MetadataModifier ->
```
This can be easily resolved if we restrict what the metadata APIs are allowed to do. Currently, they operate in an unfettered access to modify SchemaCache (the `CacheRWM` constraint):
```haskell
runAddRemoteSchema ::
( QErrM m,
CacheRWM m,
MonadIO m,
HasHttpManagerM m,
MetadataM m,
Tracing.MonadTrace m
) =>
Env.Environment ->
AddRemoteSchemaQuery ->
m EncJSON
```
This should instead be changed to restrict remote schema APIs to only modify remote schema metadata (but has access to the remote schemas part of the schema cache), this dependency is completely removed.
```haskell
runAddRemoteSchema ::
( QErrM m,
MonadIO m,
HasHttpManagerM m,
MonadReader RemoteSchemasSchemaCache m,
MonadState RemoteSchemaMetadata m,
Tracing.MonadTrace m
) =>
Env.Environment ->
AddRemoteSchemaQuery ->
m RemoteSchemeMetadataObjId
```
The idea is that the core graphql-engine would call these functions and then call
`buildSchemaCacheFor`.
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/6291
GitOrigin-RevId: 51357148c6404afe70219afa71bd1d59bdf4ffc6
This PR is the result of running the following commands:
```bash
$ git grep -l '".* : "' -- '*.hs' | xargs sed -i -E 's/(".*) : "/\1: "/'
$ scripts/dev.sh test --integration --accept
```
Also manually fixed a few tests and docs
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/6148
GitOrigin-RevId: cf8b87605d41d9ce86613a41ac5fd18691f5a641
The intent is to generalize `columnParser` to the point where it is the same across all backends, and then remove the interface in favor of a single implementation.
This extracts out `enumParser` and `possiblyNullable` as the two main areas that differ across backends. We may split `possiblyNullable` further so that we can extract some of that logic out into a common function too.
With these changes, the various `columnParser` implementations become semantically equivalent. They still do different things, and so reconciling them will require further changes.
Co-Authored-By: Antoine Leblanc <antoine@hasura.io>
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/5841
GitOrigin-RevId: eec1770931eed5d72da70c97d7d0f00e33fa15d2
### Description
This PR attempts to fix several issues with source customization as it relates to remote relationships. There were several issues regarding casing: at the relationship border, we didn't properly set the target source's case, we didn't have access to the list of supported features to decide whether the feature was allowed or not, and we didn't have access to the global default.
However, all of that information is available when we build the schema cache, as we do resolve the case of some elements such as function names: we can therefore resolve source information at the same time, and simplify both the root of the schema and the remote relationship border.
To do this, this PR introduces a new type, `ResolvedSourceCustomization`, to be used in the Schema Cache, as opposed to the metadata's `SourceCustomization`, following a pattern established by a lot of other types.
### Remaining work and open questions
One major point of confusion: it seems to me that we didn't set the case at all across remote relationships, which would suggest we would use the case of the LHS source across the subset of the RHS one that is accessible through the remote relationship, which would in turn "corrupt" the parser cache and might result in the wrong case being used for that source later on. Is that assesment correct, and was I right to fix it?
Another one is that we seem not to be using the local case of the RHS to name the field in an object relationship; unless I'm mistaken we only use it for array relationships? Is that intentional?
This PR is also missing tests that would show-case the difference, and a changelog entry. To my knowledge, all the tests of this feature are in the python test suite; this could be the opportunity to move them to the hspec suite, but this might be a considerable amount of work?
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/5619
GitOrigin-RevId: 51a81b713a74575e82d9f96b51633f158ce3a47b
### Description
This PR changes all the schema code to operate in a specific `SchemaT` monad, rather than in an arbitrary `m` monad. `SchemaT` is intended to be used opaquely with `runSourceSchema` and `runRemoteSchema`. The main goal of this is to allow a different reader context per part of the schema: this PR also minimizes the contexts. This means that we no longer require `SchemaOptions` when building remote schemas' schema, and this PR therefore removes a lot of dummy / placeholder values accordingly.
### Performance and stacking
This PR has been through several iterations. #5339 was the original version, that accomplished the same thing by stacking readers on top of the stack at every remote relationship boundary. This raised performance concerns, and @0x777 confirmed with an ad-hoc test that in some extreme cases we could see up to a 10% performance impact. This version, while more verbose, allows us to unstack / re-stack the readers, and avoid that problem. #5517 adds a new benchmark set to be able to automatically measure this on every PR.
### Remaining work
- [x] a comment (or perhaps even a Note?) should be added to `SchemaT`
- [x] we probably want for #5517 to be merged first so that we can confirm the lack of performance penalty
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/5458
GitOrigin-RevId: e06b83d90da475f745b838f1fd8f8b4d9d3f4b10
### Description
This PR is a first step towards having a dedicated reader context per schema block. It adds the required Reader instance, and switches from a `SchemaT ReaderT` stack to a `ReaderT SchemaT` stack. Furthermore, it cleans up / harmonizes some of the top-level schema building functions.
Sources and remotes are now built each within their own run of `runReaderT`: for now, the reader context is the same in both cases, meaning no special care is required at the boundary of remote relationships.
Actions are explicitly run with the source context for now; we could envision creating a third and distinct context for them.
This PR is expected to be a no-op.
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/5300
GitOrigin-RevId: a014e5b3504eb4ef740c820d305d6d2695f622f7
Followup to hasura/graphql-engine-mono#4713.
The `memoizeOn` method, part of `MonadSchema`, originally had the following type:
```haskell
memoizeOn
:: (HasCallStack, Ord a, Typeable a, Typeable b, Typeable k)
=> TH.Name
-> a
-> m (Parser k n b)
-> m (Parser k n b)
```
The reason for operating on `Parser`s specifically was that the `MonadSchema` effect would additionally initialize certain `Unique` values, which appear (nested in) the type of `Parser`.
hasura/graphql-engine-mono#518 changed the type of `memoizeOn`, to additionally allow memoizing `FieldParser`s. These also contained a `Unique` value, which was similarly initialized by the `MonadSchema` effect. The new type of `memoizeOn` was as follows:
```haskell
memoizeOn
:: forall p d a b
. (HasCallStack, HasDefinition (p n b) d, Ord a, Typeable p, Typeable a, Typeable b)
=> TH.Name
-> a
-> m (p n b)
-> m (p n b)
```
Note the type `p n b` of the value being memoized: by choosing `p` to be either `Parser k` or `FieldParser`, both can be memoized. Also note the new `HasDefinition (p n b) d` constraint, which provided a `Lens` for accessing the `Unique` value to be initialized.
A quick simplification is that the `HasCallStack` constraint has never been used by any code. This was realized in hasura/graphql-engine-mono#4713, by removing that constraint.
hasura/graphql-engine-mono#2980 removed the `Unique` value from our GraphQL-related types entirely, as their original purpose was never truly realized. One part of removing `Unique` consisted of dropping the `HasDefinition (p n b) d` constraint from `memoizeOn`.
What I didn't realize at the time was that this meant that the type of `memoizeOn` could be generalized and simplified much further. This PR finally implements that generalization. The new type is as follows:
```haskell
memoizeOn ::
forall a p.
(Ord a, Typeable a, Typeable p) =>
TH.Name ->
a ->
m p ->
m p
```
This change has a couple of consequences.
1. While constructing the schema, we often output `Maybe (Parser ...)`, to model that the existence of certain pieces of GraphQL schema sometimes depends on the permissions that a certain role has. The previous versions of `memoizeOn` were not able to handle this, as the only thing they could memoize was fully-defined (if not yet fully-evaluated) `(Field)Parser`s. This much more general API _would_ allow memoizing `Maybe (Parser ...)`s. However, we probably have to be continue being cautious with this: if we blindly memoize all `Maybe (Parser ...)`s, the resulting code may never be able to decide whether the value is `Just` or `Nothing` - i.e. it never commits to the existence-or-not of a GraphQL schema fragment. This would manifest as a non-well-founded knot tying, and this would get reported as an error by the implementation of `memoizeOn`.
tl;dr: This generalization _technically_ allows for memoizing `Maybe` values, but we probably still want to avoid doing so.
For this reason, the PR adds a specialized version of `memoizeOn` to `Hasura.GraphQL.Schema.Parser`.
2. There is no longer any need to connect the `MonadSchema` knot-tying effect with the `MonadParse` effect. In fact, after this PR, the `memoizeOn` method is completely GraphQL-agnostic, and so we implement hasura/graphql-engine-mono#4726, separating `memoizeOn` from `MonadParse` entirely - `memoizeOn` can be defined and implemented as a general Haskell typeclass method.
Since `MonadSchema` has been made into a single-type-parameter type class, it has been renamed to something more general, namely `MonadMemoize`. Its only task is to memoize arbitrary `Typeable p` objects under a combined key consisting of a `TH.Name` and a `Typeable a`.
Also for this reason, the new `MonadMemoize` has been moved to the more general `Control.Monad.Memoize`.
3. After this change, it's somewhat clearer what `memoizeOn` does: it memoizes an arbitrary value of a `Typeable` type. The only thing that needs to be understood in its implementation is how the manual blackholing works. There is no more semantic interaction with _any_ GraphQL code.
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/4725
Co-authored-by: Daniel Harvey <4729125+danieljharvey@users.noreply.github.com>
GitOrigin-RevId: 089fa2e82c2ce29da76850e994eabb1e261f9c92
### Description
By definition, root fields are at the root of the schema: only functions that craft root fields need to know about how to customize the name of root fields. However, the presence of `Has MkRootFieldName` in `MonadBuildSchemaBase` meant that the entirety of the schema building code was implicitly aware of / capable of altering root field names.
This PR removes this constraint, and moves it to the functions that do craft root fields. This has several upsides:
- it makes it more explicit where root fields are being crafted
- it prevents functions that should not use this from mistakenly applying it to non-root fields
- it simplifies the shared schema context
### Future work
- can we maybe pass this as an argument, instead of making it a required part of the context?
- ~~AFAICT, we only ever use `mempty` for it: is this actually dead code that we should actually just remove altogether?~~
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/5235
GitOrigin-RevId: 4268751f3ab87ae8e03b6fe9e1efa1b096200027
### Description
I am not 100% sure about this PR; while I think the code is better this way, I'm willing to be convinced otherwise.
In short, this PR moves the `RoleName` field into the `SchemaContext`, instead of being a nebulous `Has RoleName` constraint on the reader monad. The major upside of this is that it makes it an explicit named field, rather than something that must be given as part of a tuple of arguments when calling `runReader`.
However, the downside is that it breaks the helper permissions functions of `Schema.Table`, which relied on `Has RoleName r`. This PR makes the choice of passing the role name explicitly to all of those functions, which in turn means first explicitly fetching the role name in a lot of places. It makes it more explicit when a schema building block relies on the role name, but is a bit verbose...
### Alternatives
Some alternatives worth considering:
- attempting something like `Has context r, Has RoleName context`, which would allow them to be independent from the context but still fetch the role name from the reader, but might require type annotations to not be ambiguous
- keeping the permission functions the same, with `Has RoleName r`, and introducing a bunch of newtypes instead of using tuples to explicitly implement all the required `Has` instances
- changing the permission functions to `Has SchemaContext r`, since they are functions used only to build the schema, and therefore may be allowed to be tied to the context.
What do y'all think?
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/5073
GitOrigin-RevId: 8fd09fafb54905a4d115ef30842d35da0c3db5d2
In the process of decoupling the schema parsers from the GraphQL Engine, we need to remove dependencies on `Hasura.Base.Error`.
First of all, we have avoided using `QErr` in schema parsers code, instead returning a more appropriate data type which can be converted to a `Hasura.Base.Error.QErr` later.
Secondly, we create a new `ParseErrorCode` type to represent parse failure types, which are then converted to a `Hasura.Base.Error.Code` later.
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/5181
GitOrigin-RevId: 8655e26adb1e7d5e3d552c77a8a403f987b53467
