Auke Booij caf9957aca Remove Unique from Definition ... GraphQL types can refer to each other in a circular way. The PDV framework used to use values of type `Unique` to recognize two fragments of GraphQL schema as being the same instance. Internally, this is based on `Data.Unique` from the `base` package, which simply increases a counter on every creation of a `Unique` object. **NB**: The `Unique` values are _not_ used for knot tying the schema combinators themselves (i.e. `Parser`s). The knot tying for `Parser`s is purely based on keys provided to `memoizeOn`. The `Unique` values are _only_ used to recognize two pieces of GraphQL _schema_ as being identical. Originally, the idea was that this would help us with a perfectly correct identification of GraphQL types. But this fully correct equality checking of GraphQL types was never implemented, and does not seem to be necessary to prevent bugs. Specifically, these `Unique` values are stored as part of `data Definition a`, which specifies a part of our internal abstract syntax tree for the GraphQL types that we expose. The `Unique` values get initialized by the `SchemaT` effect. In #2894 and #2895, we are experimenting with how (parts of) the GraphQL types can be hidden behind certain permission predicates. This would allow a single GraphQL schema in memory to serve all roles, implementing #2711. The permission predicates get evaluated at query parsing time when we know what role is doing a certain request, thus outputting the correct GraphQL types for that role. If the approach of #2895 is followed, then the `Definition` objects, and thus the `Unique` values, would be hidden behind the permission predicates. Since the permission predicates are evaluated only after the schema is already supposed to be built, this means that the permission predicates would prevent us from initializing the `Unique` values, rendering them useless. The simplest remedy to this is to remove our usage of `Unique` altogether from the GraphQL schema and schema combinators. It doesn't serve a functional purpose, doesn't prevent bugs, and requires extra bookkeeping. PR-URL: https://github.com/hasura/graphql-engine-mono/pull/2980 GitOrigin-RevId: 50d3f9e0b9fbf578ac49c8fc773ba64a94b1f43d		2021-12-01 16:21:35 +00:00
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migration-guidelines.md	server: relocate some of the pre metadata separation source catalog migrations	2021-11-03 14:21:40 +00:00
overview.md	Add new documentation folder and two documentation files	2021-09-15 10:04:24 +00:00
schema.md	Remove Unique from Definition	2021-12-01 16:21:35 +00:00
tips.md	pass MSSQL_SA_PASSWORD to mssql container, and add MSSQL_HOST	2021-11-25 10:23:53 +00:00