## Suggestion: Add fancier trace debugging functions to `Hasura.Prelude`
This PR adds two trace functions, `ltrace` and `ltraceM`, which use the `pretty-simple` package to `show` the input with nice formatting and colors for ease of reading (and comparing using diff tools such as `meld` or `vim-diff`).
I've also added warning pragmas to the functions, which means:
1. Traces will not be left in code, as CI builds with -Werror
2. Developers will have to change the `ghc-options` to `-Wwarn` in their `cabal.project.local` settings to use these functions
### Example
Usage:
```hs
selectFunctionAggregate ... = ... do
ltraceM "functionInfo" function
...
```
Output to terminal looks like this:
<img width="524" alt="Screen Shot 2021-08-12 at 10 33 24" src="https://user-images.githubusercontent.com/8547573/129158878-4a5e96ba-30a5-452c-8f33-9eb4b2cc5e2a.png">
### Dependencies
Requires adding the following dependencies:
- prettyprinter-ansi-terminal-1.1.2 (BSD2)
- pretty-simple-4.0.0.0 (BSD3)
Question: what is the process for adding new dependencies? How does decisions on this matter happen?
https://github.com/hasura/graphql-engine-mono/pull/2075
GitOrigin-RevId: 490b0f0ca595da319b43e92e190ba50c0b132cd5
### Description
A first PR, #1947, removed all the `Arbitrary` stuff from our codebase. But #1740, merged on the same day, added some tests relying on `Arbitrary`. In the merge process, some unneeded `Arbitrary` code got reintroduced.
This PR removes all `Arbitrary` stuff from `src-lib`, and cleans / refactor `Hasura.Generator` in `src-test` to only reduce it to the bare minimum amount of `Arbitrary` instances.
https://github.com/hasura/graphql-engine-mono/pull/1957
GitOrigin-RevId: 7e76009bb022205e3737fca45749411a266cc08c
Query plan caching was introduced by - I believe - hasura/graphql-engine#1934 in order to reduce the query response latency. During the development of PDV in hasura/graphql-engine#4111, it was found out that the new architecture (for which query plan caching wasn't implemented) performed comparably to the pre-PDV architecture with caching. Hence, it was decided to leave query plan caching until some day in the future when it was deemed necessary.
Well, we're in the future now, and there still isn't a convincing argument for query plan caching. So the time has come to remove some references to query plan caching from the codebase. For the most part, any code being removed would probably not be very well suited to the post-PDV architecture of query execution, so arguably not much is lost.
Apart from simplifying the code, this PR will contribute towards making the GraphQL schema generation more modular, testable, and easier to profile. I'd like to eventually work towards a situation in which it's easy to generate a GraphQL schema parser *in isolation*, without being connected to a database, and then parse a GraphQL query *in isolation*, without even listening any HTTP port. It is important that both of these operations can be examined in detail, and in isolation, since they are two major performance bottlenecks, as well as phases where many important upcoming features hook into.
Implementation
The following have been removed:
- The entirety of `server/src-lib/Hasura/GraphQL/Execute/Plan.hs`
- The core phases of query parsing and execution no longer have any references to query plan caching. Note that this is not to be confused with query *response* caching, which is not affected by this PR. This includes removal of the types:
- - `Opaque`, which is replaced by a tuple. Note that the old implementation was broken and did not adequately hide the constructors.
- - `QueryReusability` (and the `markNotReusable` method). Notably, the implementation of the `ParseT` monad now consists of two, rather than three, monad transformers.
- Cache-related tests (in `server/src-test/Hasura/CacheBoundedSpec.hs`) have been removed .
- References to query plan caching in the documentation.
- The `planCacheOptions` in the `TenantConfig` type class was removed. However, during parsing, unrecognized fields in the YAML config get ignored, so this does not cause a breaking change. (Confirmed manually, as well as in consultation with @sordina.)
- The metrics no longer send cache hit/miss messages.
There are a few places in which one can still find references to query plan caching:
- We still accept the `--query-plan-cache-size` command-line option for backwards compatibility. The `HASURA_QUERY_PLAN_CACHE_SIZE` environment variable is not read.
https://github.com/hasura/graphql-engine-mono/pull/1815
GitOrigin-RevId: 17d92b254ec093c62a7dfeec478658ede0813eb7
### 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
Remote relationships are now supported on SQL Server and BigQuery. The major change though is the re-architecture of remote join execution logic. Prior to this PR, each backend is responsible for processing the remote relationships that are part of their AST.
This is not ideal as there is nothing specific about a remote join's execution that ties it to a backend. The only backend specific part is whether or not the specification of the remote relationship is valid (i.e, we'll need to validate whether the scalars are compatible).
The approach now changes to this:
1. Before delegating the AST to the backend, we traverse the AST, collect all the remote joins while modifying the AST to add necessary join fields where needed.
1. Once the remote joins are collected from the AST, the database call is made to fetch the response. The necessary data for the remote join(s) is collected from the database's response and one or more remote schema calls are constructed as necessary.
1. The remote schema calls are then executed and the data from the database and from the remote schemas is joined to produce the final response.
### Known issues
1. Ideally the traversal of the IR to collect remote joins should return an AST which does not include remote join fields. This operation can be type safe but isn't taken up as part of the PR.
1. There is a lot of code duplication between `Transport/HTTP.hs` and `Transport/Websocket.hs` which needs to be fixed ASAP. This too hasn't been taken up by this PR.
1. The type which represents the execution plan is only modified to handle our current remote joins and as such it will have to be changed to accommodate general remote joins.
1. Use of lenses would have reduced the boilerplate code to collect remote joins from the base AST.
1. The current remote join logic assumes that the join columns of a remote relationship appear with their names in the database response. This however is incorrect as they could be aliased. This can be taken up by anyone, I've left a comment in the code.
### Notes to the reviewers
I think it is best reviewed commit by commit.
1. The first one is very straight forward.
1. The second one refactors the remote join execution logic but other than moving things around, it doesn't change the user facing functionality. This moves Postgres specific parts to `Backends/Postgres` module from `Execute`. Some IR related code to `Hasura.RQL.IR` module. Simplifies various type class function signatures as a backend doesn't have to handle remote joins anymore
1. The third one fixes partial case matches that for some weird reason weren't shown as warnings before this refactor
1. The fourth one generalizes the validation logic of remote relationships and implements `scalarTypeGraphQLName` function on SQL Server and BigQuery which is used by the validation logic. This enables remote relationships on BigQuery and SQL Server.
https://github.com/hasura/graphql-engine-mono/pull/1497
GitOrigin-RevId: 77dd8eed326602b16e9a8496f52f46d22b795598
This reverts the remote schema type customisation and namespacing feature temporarily as we test for certain conditions.
GitOrigin-RevId: f8ee97233da4597f703970c3998664c03582d8e7
This is a minor refactor (part of `Internal/Parser.hs` is moved into `Internal/Input.hs`) to remove `Collect.hs-boot` and `Directives.hs-boot` files. Without these changes:
1. Most changes would trigger recompilation from the modules with hs-boot files.
1. haskell-language-server fails for some reason in the presence of hs-boot files.
GitOrigin-RevId: 77a2e443417b449c5d7d9d418fc75fcdf076a9ae
This claws back ~7min from integration tests (run serially, as with `dev.sh test --integration`
Further improvements would do well to focus on optimizing metadata operations, as `setup` dominates
GitOrigin-RevId: 76637d6fa953c2404627c4391447a05bf09355fa
