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## Description We go through the module `Hasura.Backends.MSSQL.FromIr` and split it into separate self-contained units, which we document. Note that this PR has a slightly opinionated follow-up PR #3909 . ### Related Issues Fix #3666 ### Solution and Design The module `FromIr` has given rise to: * `FromIr.Expression` * `FromIr.Query` * `FromIr.Delete` * `FromIr.Insert` * `FromIr.Update` * `FromIr.SelectIntoTempTable` And `Execute.MutationResponse` has become `FromIr.MutationResponse` (after some slight adaptation of types). PR-URL: https://github.com/hasura/graphql-engine-mono/pull/3908 GitOrigin-RevId: 364acf1bcdf74f2e19464c31cdded12bd8e9aa59
86 lines
3.6 KiB
Haskell
86 lines
3.6 KiB
Haskell
{-# OPTIONS_HADDOCK ignore-exports #-}
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-- | Responsible for translating and building an MSSQL execution plan for
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-- delete mutations.
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--
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-- This module is used by "Hasura.Backends.MSSQL.Instances.Execute".
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module Hasura.Backends.MSSQL.Execute.Delete
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( executeDelete,
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)
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where
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import Database.MSSQL.Transaction qualified as Tx
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import Hasura.Backends.MSSQL.Connection
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import Hasura.Backends.MSSQL.FromIr as TSQL
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import Hasura.Backends.MSSQL.FromIr.Constants (tempTableNameDeleted)
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import Hasura.Backends.MSSQL.FromIr.Delete qualified as TSQL
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import Hasura.Backends.MSSQL.FromIr.MutationResponse
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import Hasura.Backends.MSSQL.FromIr.SelectIntoTempTable qualified as TSQL
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import Hasura.Backends.MSSQL.Plan
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import Hasura.Backends.MSSQL.SQL.Error
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import Hasura.Backends.MSSQL.ToQuery as TQ
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import Hasura.Backends.MSSQL.Types.Internal as TSQL
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import Hasura.Base.Error
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import Hasura.EncJSON
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import Hasura.GraphQL.Parser
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import Hasura.Prelude
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import Hasura.RQL.IR
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import Hasura.RQL.Types
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import Hasura.Session
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-- | Executes a Delete IR AST and return results as JSON.
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executeDelete ::
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MonadError QErr m =>
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UserInfo ->
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StringifyNumbers ->
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SourceConfig 'MSSQL ->
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AnnDelG 'MSSQL Void (UnpreparedValue 'MSSQL) ->
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m (ExceptT QErr IO EncJSON)
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executeDelete userInfo stringifyNum sourceConfig deleteOperation = do
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preparedDelete <- traverse (prepareValueQuery $ _uiSession userInfo) deleteOperation
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pure $ mssqlRunReadWrite (_mscExecCtx sourceConfig) (buildDeleteTx preparedDelete stringifyNum)
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-- | Converts a Delete IR AST to a transaction of three delete sql statements.
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--
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-- A GraphQL delete mutation does two things:
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--
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-- 1. Deletes rows in a table according to some predicate
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-- 2. (Potentially) returns the deleted rows (including relationships) as JSON
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--
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-- In order to complete these 2 things we need 3 SQL statements:
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--
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-- 1. @SELECT INTO <temp_table> WHERE <false>@ - creates a temporary table
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-- with the same schema as the original table in which we'll store the deleted rows
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-- from the table we are deleting
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-- 2. @DELETE FROM with OUTPUT@ - deletes the rows from the table and inserts the
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-- deleted rows to the temporary table from (1)
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-- 3. @SELECT@ - constructs the @returning@ query from the temporary table, including
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-- relationships with other tables.
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buildDeleteTx ::
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AnnDel 'MSSQL ->
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StringifyNumbers ->
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Tx.TxET QErr IO EncJSON
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buildDeleteTx deleteOperation stringifyNum = do
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let withAlias = "with_alias"
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createInsertedTempTableQuery =
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toQueryFlat $
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TQ.fromSelectIntoTempTable $
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TSQL.toSelectIntoTempTable tempTableNameDeleted (_adTable deleteOperation) (_adAllCols deleteOperation) RemoveConstraints
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-- Create a temp table
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Tx.unitQueryE defaultMSSQLTxErrorHandler createInsertedTempTableQuery
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let deleteQuery = TQ.fromDelete <$> TSQL.fromDelete deleteOperation
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deleteQueryValidated <- toQueryFlat <$> runFromIr deleteQuery
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-- Execute DELETE statement
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Tx.unitQueryE mutationMSSQLTxErrorHandler deleteQueryValidated
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mutationOutputSelect <- runFromIr $ mkMutationOutputSelect stringifyNum withAlias $ _adOutput deleteOperation
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let withSelect =
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emptySelect
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{ selectProjections = [StarProjection],
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selectFrom = Just $ FromTempTable $ Aliased tempTableNameDeleted "deleted_alias"
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}
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finalMutationOutputSelect = mutationOutputSelect {selectWith = Just $ With $ pure $ Aliased withSelect withAlias}
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mutationOutputSelectQuery = toQueryFlat $ TQ.fromSelect finalMutationOutputSelect
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-- Execute SELECT query and fetch mutation response
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encJFromText <$> Tx.singleRowQueryE defaultMSSQLTxErrorHandler mutationOutputSelectQuery
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