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e8e4f30dd6
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
128 lines
5.3 KiB
Haskell
128 lines
5.3 KiB
Haskell
{-# OPTIONS_GHC -fno-warn-orphans #-}
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{-# LANGUAGE UndecidableInstances #-}
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module Hasura.Backends.Postgres.Instances.Metadata () where
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import Hasura.Prelude
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import qualified Data.HashMap.Strict as Map
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import Data.Text.Extended
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import qualified Hasura.Backends.Postgres.DDL as PG
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import Hasura.Backends.Postgres.SQL.Types (QualifiedTable)
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import Hasura.Backends.Postgres.Types.CitusExtraTableMetadata
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import Hasura.Base.Error
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import Hasura.RQL.Types.Backend (Backend)
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import Hasura.RQL.Types.Metadata.Backend
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import Hasura.RQL.Types.Relationship
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import Hasura.RQL.Types.Table
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import Hasura.SQL.Backend
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--------------------------------------------------------------------------------
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-- PostgresMetadata
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-- | We differentiate the handling of metadata between Citus and Vanilla
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-- Postgres because Citus imposes limitations on the types of joins that it
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-- permits, which then limits the types of relations that we can track.
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class PostgresMetadata (pgKind :: PostgresKind) where
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-- TODO: find a better name
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validateRel
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:: MonadError QErr m
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=> TableCache ('Postgres pgKind)
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-> QualifiedTable
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-> Either (ObjRelDef ('Postgres pgKind)) (ArrRelDef ('Postgres pgKind))
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-> m ()
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instance PostgresMetadata 'Vanilla where
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validateRel _ _ _ = pure ()
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instance PostgresMetadata 'Citus where
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validateRel
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:: forall m
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. MonadError QErr m
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=> TableCache ('Postgres 'Citus)
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-> QualifiedTable
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-> Either (ObjRelDef ('Postgres 'Citus)) (ArrRelDef ('Postgres 'Citus))
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-> m ()
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validateRel tableCache sourceTable relInfo = do
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sourceTableInfo <- lookupTableInfo sourceTable
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case relInfo of
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Left (RelDef _ obj _) ->
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case obj of
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RUFKeyOn (SameTable _) -> pure ()
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RUFKeyOn (RemoteTable targetTable _) -> checkObjectRelationship sourceTableInfo targetTable
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RUManual RelManualConfig { } -> pure ()
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Right (RelDef _ obj _) ->
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case obj of
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RUFKeyOn (ArrRelUsingFKeyOn targetTable _col) -> checkArrayRelationship sourceTableInfo targetTable
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RUManual RelManualConfig { } -> pure ()
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where
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lookupTableInfo tableName = Map.lookup tableName tableCache
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`onNothing` throw400 NotFound ("no such table " <>> tableName)
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checkObjectRelationship sourceTableInfo targetTable = do
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targetTableInfo <- lookupTableInfo targetTable
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let notSupported = throwNotSupportedError sourceTableInfo targetTableInfo "object"
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case ( _tciExtraTableMetadata $ _tiCoreInfo sourceTableInfo
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, _tciExtraTableMetadata $ _tiCoreInfo targetTableInfo
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) of
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(Distributed{}, Local) -> notSupported
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(Distributed{}, Reference) -> pure ()
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(Distributed{}, Distributed{}) -> pure ()
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(_, Distributed{}) -> notSupported
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(_, _) -> pure ()
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checkArrayRelationship sourceTableInfo targetTable = do
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targetTableInfo <- lookupTableInfo targetTable
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let notSupported = throwNotSupportedError sourceTableInfo targetTableInfo "array"
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case ( _tciExtraTableMetadata $ _tiCoreInfo sourceTableInfo
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, _tciExtraTableMetadata $ _tiCoreInfo targetTableInfo
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) of
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(Distributed{}, Distributed{}) -> pure ()
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(Distributed{}, _) -> notSupported
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(_, Distributed{}) -> notSupported
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(_, _) -> pure ()
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showDistributionType :: ExtraTableMetadata -> Text
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showDistributionType = \case
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Local -> "local"
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Distributed _ -> "distributed"
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Reference -> "reference"
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throwNotSupportedError :: TableInfo ('Postgres 'Citus) -> TableInfo ('Postgres 'Citus) -> Text -> m ()
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throwNotSupportedError sourceTableInfo targetTableInfo t =
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let tciSrc = _tiCoreInfo sourceTableInfo
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tciTgt = _tiCoreInfo targetTableInfo
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in
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throw400 NotSupported (
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showDistributionType (_tciExtraTableMetadata tciSrc) <>
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" tables (" <> toTxt (_tciName tciSrc) <> ") cannot have an " <> t <> " relationship against a " <>
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showDistributionType (_tciExtraTableMetadata $ _tiCoreInfo targetTableInfo) <>
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" table (" <> toTxt (_tciName tciTgt) <> ")")
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----------------------------------------------------------------
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-- BackendMetadata instance
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instance
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( Backend ('Postgres pgKind)
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, PostgresMetadata pgKind
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, PG.ToMetadataFetchQuery pgKind
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) => BackendMetadata ('Postgres pgKind) where
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buildComputedFieldInfo = PG.buildComputedFieldInfo
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fetchAndValidateEnumValues = PG.fetchAndValidateEnumValues
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resolveSourceConfig = PG.resolveSourceConfig
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resolveDatabaseMetadata = PG.resolveDatabaseMetadata
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createTableEventTrigger = PG.createTableEventTrigger
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buildEventTriggerInfo = PG.buildEventTriggerInfo @pgKind
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parseBoolExpOperations = PG.parseBoolExpOperations
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buildFunctionInfo = PG.buildFunctionInfo
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updateColumnInEventTrigger = PG.updateColumnInEventTrigger
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parseCollectableType = PG.parseCollectableType
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postDropSourceHook = PG.postDropSourceHook
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validateRelationship = validateRel @pgKind
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