graphql-engine/server/src-lib/Hasura/Backends/BigQuery/ToQuery.hs

{-# OPTIONS_GHC -fno-warn-orphans #-}

-- | Convert the simple BigQuery AST to an SQL query, ready to be passed
-- to the odbc package's query/exec functions.
module Hasura.Backends.BigQuery.ToQuery
  ( fromSelect,
    fromReselect,
    fromExpression,
    toBuilderFlat,
    toBuilderPretty,
    toTextFlat,
    toTextPretty,
    Printer (..),
    renderBuilderFlat,
    renderBuilderPretty,
    paramName,
  )
where

import Data.Aeson (ToJSON (..))
import Data.Bifunctor
import Data.Containers.ListUtils
import Data.HashMap.Strict.InsOrd qualified as OMap
import Data.List (intersperse)
import Data.List.NonEmpty qualified as NE
import Data.String
import Data.Text qualified as T
import Data.Text.Lazy qualified as LT
import Data.Text.Lazy.Builder (Builder)
import Data.Text.Lazy.Builder qualified as LT
import Data.Tuple
import Data.Vector qualified as V
import Hasura.Backends.BigQuery.Types
import Hasura.Prelude hiding (second)

--------------------------------------------------------------------------------
-- Types

data Printer
  = SeqPrinter [Printer]
  | SepByPrinter Printer [Printer]
  | NewlinePrinter
  | UnsafeTextPrinter Text
  | IndentPrinter Int Printer
  | ValuePrinter Value
  deriving (Show, Eq)

instance IsString Printer where
  fromString = UnsafeTextPrinter . fromString

(<+>) :: Printer -> Printer -> Printer
(<+>) x y = SeqPrinter [x, y]

--------------------------------------------------------------------------------
-- Instances

-- This is a debug instance, only here because it avoids a circular
-- dependency between this module and Types.hs.
instance ToJSON Expression where
  toJSON = toJSON . toTextPretty . fromExpression

--------------------------------------------------------------------------------
-- Printer generators

fromExpression :: Expression -> Printer
fromExpression =
  \case
    CastExpression e scalarType ->
      "CAST(" <+> fromExpression e <+> " AS " <+> fromScalarType scalarType <+> ")"
    InExpression e value ->
      "(" <+> fromExpression e <+> ") IN UNNEST(" <+> fromValue value <+> ")"
    JsonQueryExpression e -> "JSON_QUERY(" <+> fromExpression e <+> ")"
    JsonValueExpression e path ->
      "JSON_VALUE(" <+> fromExpression e <+> fromPath path <+> ")"
    ValueExpression value -> fromValue value
    AndExpression xs ->
      SepByPrinter
        (NewlinePrinter <+> "AND ")
        ( toList
            ( fmap
                (\x -> "(" <+> fromExpression x <+> ")")
                (fromMaybe (pure trueExpression) (NE.nonEmpty xs))
            )
        )
    OrExpression xs ->
      SepByPrinter
        (NewlinePrinter <+> " OR ")
        ( toList
            ( fmap
                (\x -> "(" <+> fromExpression x <+> ")")
                (fromMaybe (pure falseExpression) (NE.nonEmpty xs))
            )
        )
    NotExpression expression -> "NOT " <+> (fromExpression expression)
    ExistsExpression select ->
      "EXISTS (" <+> IndentPrinter 9 (fromSelect select) <+> ")"
    IsNullExpression expression ->
      "(" <+> fromExpression expression <+> ") IS NULL"
    IsNotNullExpression expression ->
      "(" <+> fromExpression expression <+> ") IS NOT NULL"
    ColumnExpression fieldName -> fromFieldName fieldName
    EqualExpression x y ->
      "(" <+> fromExpression x <+> ") = (" <+> fromExpression y <+> ")"
    NotEqualExpression x y ->
      "(" <+> fromExpression x <+> ") != (" <+> fromExpression y <+> ")"
    ToStringExpression e -> "CONCAT(" <+> fromExpression e <+> ", '')"
    SelectExpression s -> "(" <+> IndentPrinter 1 (fromSelect s) <+> ")"
    ListExpression xs -> " UNNEST ([" <+> SepByPrinter ", " (fromExpression <$> xs) <+> "])"
    OpExpression op x y ->
      "("
        <+> fromExpression x
        <+> ") "
        <+> fromOp op
        <+> fromExpression y
    FunctionExpression name args ->
      UnsafeTextPrinter name <+> "(" <+> SepByPrinter ", " (fromExpression <$> args) <+> ")"
    ConditionalProjection expression fieldName ->
      "(CASE WHEN(" <+> fromExpression expression
        <+> ") THEN "
        <+> fromFieldName fieldName
        <+> " ELSE NULL END)"

fromScalarType :: ScalarType -> Printer
fromScalarType =
  \case
    StringScalarType -> "STRING"
    BytesScalarType -> "BYTES"
    IntegerScalarType -> "INT64"
    FloatScalarType -> "FLOAT64"
    BoolScalarType -> "BOOL"
    TimestampScalarType -> "TIMESTAMP"
    DateScalarType -> "DATE"
    TimeScalarType -> "TIME"
    DatetimeScalarType -> "DATETIME"
    GeographyScalarType -> "GEOGRAPHY"
    StructScalarType -> "STRUCT"
    DecimalScalarType -> "DECIMAL"
    BigDecimalScalarType -> "BIGDECIMAL"

fromOp :: Op -> Printer
fromOp =
  \case
    LessOp -> "<"
    MoreOp -> ">"
    MoreOrEqualOp -> ">="
    LessOrEqualOp -> "<="
    InOp -> "IN"
    NotInOp -> "NOT IN"
    LikeOp -> "LIKE"
    NotLikeOp -> "NOT LIKE"

fromPath :: JsonPath -> Printer
fromPath path =
  ", " <+> string path
  where
    string =
      fromExpression
        . ValueExpression
        . StringValue
        . LT.toStrict
        . LT.toLazyText
        . go
    go =
      \case
        RootPath -> "$"
        IndexPath r i -> go r <> "[" <> LT.fromString (show i) <> "]"
        FieldPath r f -> go r <> "." <> LT.fromText f

fromFieldName :: FieldName -> Printer
fromFieldName (FieldName {..}) =
  fromNameText fieldNameEntity <+> "." <+> fromNameText fieldName

fromSelect :: Select -> Printer
fromSelect Select {..} = finalExpression
  where
    finalExpression = inner
    projections =
      SepByPrinter
        ("," <+> NewlinePrinter)
        (map fromProjection (toList (cleanProjections selectProjections)))
    inner =
      SepByPrinter
        NewlinePrinter
        [ "SELECT " <+> IndentPrinter 7 projections,
          "FROM " <+> IndentPrinter 5 (fromFrom selectFrom),
          SepByPrinter
            NewlinePrinter
            ( map
                ( \Join {..} ->
                    SeqPrinter
                      [ "LEFT OUTER JOIN "
                          <+> IndentPrinter 16 (fromJoinSource joinSource),
                        NewlinePrinter,
                        "AS " <+> fromJoinAlias joinAlias,
                        NewlinePrinter,
                        "ON ("
                          <+> IndentPrinter
                            4
                            ( SepByPrinter
                                (", " <+> NewlinePrinter)
                                (map fromOn joinOn)
                            )
                          <+> ")"
                      ]
                )
                selectJoins
            ),
          fromWhere selectWhere,
          fromOrderBys selectTop selectOffset selectOrderBy,
          case selectGroupBy of
            [] -> ""
            fieldNames ->
              "GROUP BY " <+> SepByPrinter ", " (map fromFieldName fieldNames)
        ]

fromOn :: (FieldName, FieldName) -> Printer
fromOn (x, y) = fromFieldName x <+> " = " <+> fromFieldName y

fromJoinSource :: JoinSource -> Printer
fromJoinSource =
  \case
    JoinSelect select -> "(" <+> IndentPrinter 1 (fromSelect select) <+> ")"

-- We're not using existingJoins at the moment, which was used to
-- avoid re-joining on the same table twice.
-- JoinReselect reselect -> "(" <+> fromReselect reselect <+> ")"

fromReselect :: Reselect -> Printer
fromReselect Reselect {..} =
  SepByPrinter
    NewlinePrinter
    [ "SELECT "
        <+> IndentPrinter 7 projections,
      fromWhere reselectWhere
    ]
  where
    projections =
      SepByPrinter
        ("," <+> NewlinePrinter)
        (map fromProjection (toList (cleanProjections reselectProjections)))

fromOrderBys ::
  Top -> Maybe Expression -> Maybe (NonEmpty OrderBy) -> Printer
fromOrderBys NoTop Nothing Nothing = "" -- An ORDER BY is wasteful if not needed.
fromOrderBys top moffset morderBys =
  SepByPrinter
    NewlinePrinter
    [ case morderBys of
        Nothing -> ""
        Just orderBys ->
          SeqPrinter
            [ "ORDER BY ",
              SepByPrinter
                ("," <+> NewlinePrinter)
                (map fromOrderBy (toList orderBys))
            ],
      case (top, moffset) of
        (NoTop, Nothing) -> ""
        (NoTop, Just offset) ->
          "LIMIT 9223372036854775807 /* Maximum */"
            -- Above: OFFSET is not supported without a LIMIT, therefore
            -- we set LIMIT to the maximum integer value. Such a large
            -- number of rows (9 quintillion) would not be possible to
            -- service: 9223 petabytes. No machine has such capacity at
            -- present.
            <+> " OFFSET "
            <+> fromExpression offset
        (Top n, Nothing) -> "LIMIT " <+> fromValue (IntegerValue (intToInt64 n))
        (Top n, Just offset) ->
          "LIMIT "
            <+> fromValue (IntegerValue (intToInt64 n))
            <+> " OFFSET "
            <+> fromExpression offset
    ]

fromOrderBy :: OrderBy -> Printer
fromOrderBy OrderBy {..} =
  "("
    <+> fromFieldName orderByFieldName
    <+> ") "
    <+> fromOrder orderByOrder
    <+> fromNullsOrder orderByNullsOrder

fromOrder :: Order -> Printer
fromOrder =
  \case
    AscOrder -> "ASC"
    DescOrder -> "DESC"

fromNullsOrder :: NullsOrder -> Printer
fromNullsOrder =
  \case
    NullsAnyOrder -> ""
    NullsFirst -> " NULLS FIRST"
    NullsLast -> " NULLS LAST"

fromJoinAlias :: EntityAlias -> Printer
fromJoinAlias EntityAlias {entityAliasText} =
  fromNameText entityAliasText

fromProjection :: Projection -> Printer
fromProjection =
  \case
    WindowProjection aliasedWindowFunction ->
      fromAliased (fmap fromWindowFunction aliasedWindowFunction)
    ExpressionProjection aliasedExpression ->
      fromAliased (fmap fromExpression aliasedExpression)
    FieldNameProjection aliasedFieldName ->
      fromAliased (fmap fromFieldName aliasedFieldName)
    AggregateProjection aliasedAggregate ->
      fromAliased (fmap fromAggregate aliasedAggregate)
    AggregateProjections aliasedAggregates ->
      fromAliased
        ( fmap
            ( \aggs ->
                "STRUCT("
                  <+> IndentPrinter
                    7
                    ( SepByPrinter
                        ", "
                        (fmap (fromAliased . fmap fromAggregate) (toList aggs))
                    )
                  <+> ")"
            )
            aliasedAggregates
        )
    StarProjection -> "*"
    ArrayAggProjection aliasedAgg -> fromAliased (fmap fromArrayAgg aliasedAgg)
    EntityProjection aliasedEntity ->
      fromAliased
        ( fmap
            ( \(fields :: [(FieldName, FieldOrigin)]) ->
                -- Example:
                --   STRUCT(
                --     IFNULL(
                --       `aa_articles1`.`aggregate`,
                --       STRUCT(0 as count, struct(null as id) as sum)
                --     ) as aggregate
                --   ) AS `articles_aggregate`
                --
                -- The (AS `articles_aggregate`) part at the end is rendered by 'fromAliased' evaluating
                -- at the root of this branch, and not by anything below
                "STRUCT("
                  <+> ( SepByPrinter
                          ", "
                          ( fields
                              <&> \(fName@FieldName {..}, fieldOrigin :: FieldOrigin) ->
                                "IFNULL(" <+> fromFieldName fName <+> ", " <+> fromFieldOrigin fieldOrigin
                                  <+> ") AS "
                                  <+> fromNameText fieldName
                          )
                      )
                  <+> ")"
            )
            aliasedEntity
        )
    ArrayEntityProjection entityAlias aliasedEntity ->
      fromAliased
        ( fmap
            ( \aggs ->
                "ARRAY(SELECT AS STRUCT "
                  <+> IndentPrinter
                    7
                    (SepByPrinter ", " (fmap fromFieldNameNaked (toList aggs)))
                  <+> " FROM "
                  <+> fromJoinAlias entityAlias
                  <+> ".agg)"
            )
            aliasedEntity
        )
      where
        fromFieldNameNaked :: FieldName -> Printer
        fromFieldNameNaked (FieldName {..}) =
          fromNameText fieldName

fromFieldOrigin :: FieldOrigin -> Printer
fromFieldOrigin = \case
  NoOrigin -> "NULL"
  AggregateOrigin aliasedAggregates ->
    "STRUCT("
      <+>
      -- Example: "0 AS count, STRUCT(NULL AS id) AS sum"
      SepByPrinter ", " (fromAliased . fmap fromNullAggregate <$> aliasedAggregates)
      <+> ")"

fromWindowFunction :: WindowFunction -> Printer
fromWindowFunction (RowNumberOverPartitionBy fieldNames morderBys) =
  "ROW_NUMBER() OVER(PARTITION BY "
    <+> SepByPrinter ", " (fmap fromFieldName (toList fieldNames))
    <+> ( case morderBys of
            Just {} -> " " <+> fromOrderBys NoTop Nothing morderBys
            Nothing -> ""
        )
    <+> ")"

fromArrayAgg :: ArrayAgg -> Printer
fromArrayAgg ArrayAgg {..} =
  SeqPrinter
    [ "ARRAY_AGG(",
      IndentPrinter 10 $
        SepByPrinter
          " "
          [ "STRUCT(" <+> IndentPrinter 7 projections <+> ")",
            fromOrderBys
              arrayAggTop
              Nothing
              ( fmap
                  ( fmap
                      ( \orderBy ->
                          orderBy
                            { orderByNullsOrder = NullsAnyOrder
                            -- Because BigQuery reports:
                            -- > NULLS FIRST not supported with descending sort order in aggregate functions
                            -- And the same error with 'ascending'.
                            }
                      )
                  )
                  arrayAggOrderBy
              )
          ],
      ")"
    ]
  where
    projections =
      SepByPrinter
        ("," <+> NewlinePrinter)
        (map fromProjection (toList (cleanProjections arrayAggProjections)))

fromNullAggregate :: Aggregate -> Printer
fromNullAggregate = \case
  CountAggregate _ -> "0"
  OpAggregate _text _exp -> "NULL"
  OpAggregates _text exps ->
    "STRUCT(" <+> SepByPrinter ", " (toList exps <&> \(alias, _exp) -> "NULL AS " <+> fromNameText alias) <+> ")"
  TextAggregate _text -> "NULL"

fromAggregate :: Aggregate -> Printer
fromAggregate =
  \case
    CountAggregate countable -> "COUNT(" <+> fromCountable countable <+> ")"
    OpAggregate text arg ->
      UnsafeTextPrinter text <+> "(" <+> fromExpression arg <+> ")"
    OpAggregates text args ->
      "STRUCT("
        <+> IndentPrinter
          7
          ( SepByPrinter
              ", "
              ( map
                  ( \(alias, arg) ->
                      UnsafeTextPrinter text
                        <+> "("
                        <+> fromExpression arg
                        <+> ") AS "
                        <+> fromNameText alias
                  )
                  (toList args)
              )
          )
        <+> ")"
    TextAggregate text -> fromExpression (ValueExpression (StringValue text))

fromCountable :: Countable FieldName -> Printer
fromCountable =
  \case
    StarCountable -> "*"
    NonNullFieldCountable fields ->
      SepByPrinter ", " (map fromFieldName (toList fields))
    DistinctCountable fields ->
      "DISTINCT "
        <+> SepByPrinter ", " (map fromFieldName (toList fields))

fromWhere :: Where -> Printer
fromWhere =
  \case
    Where expressions ->
      case (filter ((/= trueExpression) . collapse)) expressions of
        [] -> ""
        collapsedExpressions ->
          "WHERE "
            <+> IndentPrinter 6 (fromExpression (AndExpression collapsedExpressions))
      where
        collapse (AndExpression [x]) = collapse x
        collapse (AndExpression []) = trueExpression
        collapse (OrExpression [x]) = collapse x
        collapse x = x

fromSelectJson :: SelectJson -> Printer
fromSelectJson SelectJson {..} = finalExpression
  where
    finalExpression =
      SepByPrinter
        NewlinePrinter
        [ "SELECT " <+> IndentPrinter 7 fields,
          "FROM UNNEST(JSON_QUERY_ARRAY("
            <+> IndentPrinter 29 (fromExpression selectJsonBody)
            <+> "))",
          " AS " <+> jsonStringField
        ]
    jsonStringField = fromNameText "json"
    fields =
      SepByPrinter
        ("," <+> NewlinePrinter)
        (map extractJsonField selectJsonFields)
    extractJsonField (ColumnName name, scalarType) =
      "CAST(JSON_VALUE(" <+> jsonStringField <+> ", '$." <+> fromString (T.unpack name)
        <+> "') AS "
        <+> fromScalarType scalarType
        <+> ") AS "
        <+> fromNameText name

fromFrom :: From -> Printer
fromFrom =
  \case
    FromQualifiedTable aliasedQualifiedTableName ->
      fromAliased (fmap fromTableName aliasedQualifiedTableName)
    FromSelect select -> fromAliased (fmap (parens . fromSelect) select)
    FromSelectJson selectJson ->
      fromAliased (fmap (parens . fromSelectJson) selectJson)

fromTableName :: TableName -> Printer
fromTableName TableName {tableName, tableNameSchema} =
  fromNameText tableNameSchema <+> "." <+> fromNameText tableName

fromAliased :: Aliased Printer -> Printer
fromAliased Aliased {..} =
  aliasedThing
    <+> ((" AS " <+>) . fromNameText) aliasedAlias

fromNameText :: Text -> Printer
fromNameText t = UnsafeTextPrinter ("`" <> t <> "`")

trueExpression :: Expression
trueExpression = ValueExpression (BoolValue True)

falseExpression :: Expression
falseExpression = ValueExpression (BoolValue False)

fromValue :: Value -> Printer
fromValue = ValuePrinter

parens :: Printer -> Printer
parens x = "(" <+> IndentPrinter 1 x <+> ")"

--------------------------------------------------------------------------------
-- Quick and easy query printer

toBuilderFlat :: Printer -> Builder
toBuilderFlat = flip evalState mempty . runBuilderFlat

toBuilderPretty :: Printer -> Builder
toBuilderPretty = flip evalState mempty . runBuilderPretty

toTextPretty :: Printer -> Text
toTextPretty = LT.toStrict . LT.toLazyText . toBuilderPretty

toTextFlat :: Printer -> Text
toTextFlat = LT.toStrict . LT.toLazyText . toBuilderFlat

--------------------------------------------------------------------------------
-- Printer ready for consumption

-- | Produces a query with holes, and a mapping for each
renderBuilderFlat :: Printer -> (Builder, InsOrdHashMap Int Value)
renderBuilderFlat =
  second (OMap.fromList . map swap . OMap.toList) . flip runState mempty
    . runBuilderFlat

-- | Produces a query with holes, and a mapping for each
renderBuilderPretty :: Printer -> (Builder, InsOrdHashMap Int Value)
renderBuilderPretty =
  second (OMap.fromList . map swap . OMap.toList) . flip runState mempty
    . runBuilderPretty

--------------------------------------------------------------------------------
-- Real printer engines

paramName :: Int -> Builder
paramName next = "param" <> fromString (show next)

runBuilderFlat :: Printer -> State (InsOrdHashMap Value Int) Builder
runBuilderFlat = go 0
  where
    go level =
      \case
        UnsafeTextPrinter q -> pure (LT.fromText q)
        SeqPrinter xs -> fmap (mconcat . filter notEmpty) (mapM (go level) xs)
        SepByPrinter x xs -> do
          i <- go level x
          fmap (mconcat . intersperse i . filter notEmpty) (mapM (go level) xs)
        NewlinePrinter -> pure " "
        IndentPrinter n p -> go (level + n) p
        ValuePrinter (ArrayValue x) | V.null x -> pure "[]"
        ValuePrinter v -> do
          themap <- get
          next <-
            OMap.lookup v themap `onNothing` do
              next <- gets OMap.size
              modify (OMap.insert v next)
              pure next
          pure ("@" <> paramName next)
    notEmpty = (/= mempty)

runBuilderPretty :: Printer -> State (InsOrdHashMap Value Int) Builder
runBuilderPretty = go 0
  where
    go level =
      \case
        UnsafeTextPrinter q -> pure (LT.fromText q)
        SeqPrinter xs -> fmap (mconcat . filter notEmpty) (mapM (go level) xs)
        SepByPrinter x xs -> do
          i <- go level x
          fmap (mconcat . intersperse i . filter notEmpty) (mapM (go level) xs)
        NewlinePrinter -> pure ("\n" <> indentation level)
        IndentPrinter n p -> go (level + n) p
        ValuePrinter (ArrayValue x)
          | V.null x -> pure "[]"
        ValuePrinter v -> do
          themap <- get
          next <-
            OMap.lookup v themap `onNothing` do
              next <- gets OMap.size
              modify (OMap.insert v next)
              pure next
          pure ("@" <> paramName next)
    indentation n = LT.fromText (T.replicate n " ")
    notEmpty = (/= mempty)

--------------------------------------------------------------------------------
-- Projection cleanup

-- | TODO: For now, we're littering this around where projections are
-- built. I'd prefer to use ordered set, or else a newtype wrapper to
-- prove it's been sorted. But that would interrupt code
-- elsewhere. For now, this is an acceptable solution.
-- Plus, a warning issued about duplicates might be useful.
cleanProjections :: NonEmpty Projection -> NonEmpty Projection
cleanProjections = neOrdNub
  where
    neOrdNub :: NonEmpty Projection -> NonEmpty Projection
    neOrdNub = NE.fromList . nubOrdOn projectionAlias . NE.toList