257 lines
12 KiB
Haskell
257 lines
12 KiB
Haskell
{-# LANGUAGE LambdaCase #-}
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{-# LANGUAGE QuasiQuotes #-}
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{-|
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Module : PostgREST.Private.QueryFragment
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Description : Helper functions for PostgREST.QueryBuilder.
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Any function that outputs a SqlFragment should be in this module.
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-}
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module PostgREST.Private.QueryFragment where
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import qualified Data.ByteString.Char8 as BS (intercalate,
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pack, unwords)
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import qualified Data.ByteString.Lazy as BL
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import qualified Data.HashMap.Strict as HM
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import Data.Maybe
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import qualified Data.Text as T (intercalate,
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isInfixOf, map,
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null, replace,
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takeWhile,
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toLower)
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import qualified Hasql.DynamicStatements.Snippet as H
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import PostgREST.RangeQuery (NonnegRange,
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allRange,
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rangeLimit,
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rangeOffset)
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import PostgREST.Types
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import Protolude hiding (cast,
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intercalate,
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replace, toLower,
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toS)
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import Protolude.Conv (toS)
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import Text.InterpolatedString.Perl6 (qc)
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import qualified Hasql.Encoders as HE
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import PostgREST.Private.Common
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noLocationF :: SqlFragment
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noLocationF = "array[]::text[]"
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-- |
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-- These CTEs convert a json object into a json array, this way we can use json_populate_recordset for all json payloads
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-- Otherwise we'd have to use json_populate_record for json objects and json_populate_recordset for json arrays
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-- We do this in SQL to avoid processing the JSON in application code
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normalizedBody :: Maybe BL.ByteString -> H.Snippet
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normalizedBody body =
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"pgrst_payload AS (SELECT " <> jsonPlaceHolder body <> " AS json_data), " <>
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H.sql (BS.unwords [
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"pgrst_body AS (",
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"SELECT",
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"CASE WHEN json_typeof(json_data) = 'array'",
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"THEN json_data",
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"ELSE json_build_array(json_data)",
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"END AS val",
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"FROM pgrst_payload)"])
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-- | Equivalent to "$1::json"
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-- | TODO: At this stage there shouldn't be a Maybe since ApiRequest should ensure that an INSERT/UPDATE has a body
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jsonPlaceHolder :: Maybe BL.ByteString -> H.Snippet
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jsonPlaceHolder body =
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H.encoderAndParam (HE.nullable HE.unknown) (toS <$> body) <> "::json"
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selectBody :: SqlFragment
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selectBody = "(SELECT val FROM pgrst_body)"
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pgFmtLit :: Text -> SqlFragment
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pgFmtLit x =
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let trimmed = trimNullChars x
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escaped = "'" <> T.replace "'" "''" trimmed <> "'"
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slashed = T.replace "\\" "\\\\" escaped in
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encodeUtf8 $ if "\\" `T.isInfixOf` escaped
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then "E" <> slashed
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else slashed
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pgFmtIdent :: Text -> SqlFragment
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pgFmtIdent x = encodeUtf8 $ "\"" <> T.replace "\"" "\"\"" (trimNullChars x) <> "\""
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trimNullChars :: Text -> Text
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trimNullChars = T.takeWhile (/= '\x0')
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asCsvF :: SqlFragment
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asCsvF = asCsvHeaderF <> " || '\n' || " <> asCsvBodyF
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where
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asCsvHeaderF =
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"(SELECT coalesce(string_agg(a.k, ','), '')" <>
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" FROM (" <>
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" SELECT json_object_keys(r)::text as k" <>
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" FROM ( " <>
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" SELECT row_to_json(hh) as r from " <> sourceCTEName <> " as hh limit 1" <>
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" ) s" <>
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" ) a" <>
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")"
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asCsvBodyF = "coalesce(string_agg(substring(_postgrest_t::text, 2, length(_postgrest_t::text) - 2), '\n'), '')"
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asJsonF :: Bool -> SqlFragment
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asJsonF returnsScalar
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| returnsScalar = "coalesce(json_agg(_postgrest_t.pgrst_scalar), '[]')::character varying"
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| otherwise = "coalesce(json_agg(_postgrest_t), '[]')::character varying"
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asJsonSingleF :: Bool -> SqlFragment --TODO! unsafe when the query actually returns multiple rows, used only on inserting and returning single element
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asJsonSingleF returnsScalar
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| returnsScalar = "coalesce(string_agg(to_json(_postgrest_t.pgrst_scalar)::text, ','), '')::character varying"
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| otherwise = "coalesce(string_agg(to_json(_postgrest_t)::text, ','), '')::character varying"
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asBinaryF :: FieldName -> SqlFragment
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asBinaryF fieldName = "coalesce(string_agg(_postgrest_t." <> pgFmtIdent fieldName <> ", ''), '')"
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locationF :: [Text] -> SqlFragment
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locationF pKeys = [qc|(
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WITH data AS (SELECT row_to_json(_) AS row FROM {sourceCTEName} AS _ LIMIT 1)
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SELECT array_agg(json_data.key || '=eq.' || json_data.value)
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FROM data CROSS JOIN json_each_text(data.row) AS json_data
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WHERE json_data.key IN ('{fmtPKeys}')
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)|]
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where
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fmtPKeys = T.intercalate "','" pKeys
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fromQi :: QualifiedIdentifier -> SqlFragment
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fromQi t = (if T.null s then mempty else pgFmtIdent s <> ".") <> pgFmtIdent n
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where
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n = qiName t
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s = qiSchema t
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emptyOnFalse :: SqlFragment -> Bool -> SqlFragment
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emptyOnFalse val cond = if cond then mempty else val
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pgFmtColumn :: QualifiedIdentifier -> Text -> SqlFragment
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pgFmtColumn table "*" = fromQi table <> ".*"
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pgFmtColumn table c = fromQi table <> "." <> pgFmtIdent c
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pgFmtField :: QualifiedIdentifier -> Field -> H.Snippet
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pgFmtField table (c, jp) = H.sql (pgFmtColumn table c) <> pgFmtJsonPath jp
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pgFmtSelectItem :: QualifiedIdentifier -> SelectItem -> H.Snippet
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pgFmtSelectItem table (f@(fName, jp), Nothing, alias, _) = pgFmtField table f <> H.sql (pgFmtAs fName jp alias)
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-- Ideally we'd quote the cast with "pgFmtIdent cast". However, that would invalidate common casts such as "int", "bigint", etc.
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-- Try doing: `select 1::"bigint"` - it'll err, using "int8" will work though. There's some parser magic that pg does that's invalidated when quoting.
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-- Not quoting should be fine, we validate the input on Parsers.
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pgFmtSelectItem table (f@(fName, jp), Just cast, alias, _) = "CAST (" <> pgFmtField table f <> " AS " <> H.sql (encodeUtf8 cast) <> " )" <> H.sql (pgFmtAs fName jp alias)
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pgFmtOrderTerm :: QualifiedIdentifier -> OrderTerm -> H.Snippet
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pgFmtOrderTerm qi ot =
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pgFmtField qi (otTerm ot) <> " " <>
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H.sql (BS.unwords [
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BS.pack $ maybe mempty show $ otDirection ot,
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BS.pack $ maybe mempty show $ otNullOrder ot])
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pgFmtFilter :: QualifiedIdentifier -> Filter -> H.Snippet
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pgFmtFilter table (Filter fld (OpExpr hasNot oper)) = notOp <> " " <> case oper of
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Op op val -> pgFmtFieldOp op <> " " <> case op of
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"like" -> unknownLiteral (T.map star val)
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"ilike" -> unknownLiteral (T.map star val)
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"is" -> isAllowed val
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_ -> unknownLiteral val
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-- We don't use "IN", we use "= ANY". IN has the following disadvantages:
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-- + No way to use an empty value on IN: "col IN ()" is invalid syntax. With ANY we can do "= ANY('{}')"
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-- + Can invalidate prepared statements: multiple parameters on an IN($1, $2, $3) will lead to using different prepared statements and not take advantage of caching.
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In vals -> pgFmtField table fld <> " " <>
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case vals of
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[""] -> "= ANY('{}') "
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-- Here we build the pg array, e.g '{"Hebdon, John","Other","Another"}', manually. We quote the values to prevent the "," being treated as an element separator.
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-- TODO: Ideally this would be done on Hasql with an encoder, but the "array unknown" is not working(Hasql doesn't pass any value).
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_ -> "= ANY (" <> unknownLiteral ("{" <> T.intercalate "," ((\x -> "\"" <> x <> "\"") <$> vals) <> "}") <> ")"
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Fts op lang val ->
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pgFmtFieldOp op <> "(" <> ftsLang lang <> unknownLiteral val <> ") "
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where
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ftsLang = maybe mempty (\l -> unknownLiteral l <> ", ")
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pgFmtFieldOp op = pgFmtField table fld <> " " <> sqlOperator op
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sqlOperator o = H.sql $ HM.lookupDefault "=" o operators
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notOp = if hasNot then "NOT" else mempty
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star c = if c == '*' then '%' else c
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-- IS cannot be prepared. `PREPARE boolplan AS SELECT * FROM projects where id IS $1` will give a syntax error.
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-- The above can be fixed by using `PREPARE boolplan AS SELECT * FROM projects where id IS NOT DISTINCT FROM $1;`
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-- However that would not accept the TRUE/FALSE/NULL keywords. See: https://stackoverflow.com/questions/6133525/proper-way-to-set-preparedstatement-parameter-to-null-under-postgres.
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isAllowed :: Text -> H.Snippet
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isAllowed v = H.sql $ maybe
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(pgFmtLit v <> "::unknown") encodeUtf8
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(find ((==) . T.toLower $ v) ["null","true","false"])
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pgFmtJoinCondition :: JoinCondition -> H.Snippet
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pgFmtJoinCondition (JoinCondition (qi1, col1) (qi2, col2)) =
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H.sql $ pgFmtColumn qi1 col1 <> " = " <> pgFmtColumn qi2 col2
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pgFmtLogicTree :: QualifiedIdentifier -> LogicTree -> H.Snippet
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pgFmtLogicTree qi (Expr hasNot op forest) = H.sql notOp <> " (" <> intercalateSnippet (" " <> BS.pack (show op) <> " ") (pgFmtLogicTree qi <$> forest) <> ")"
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where notOp = if hasNot then "NOT" else mempty
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pgFmtLogicTree qi (Stmnt flt) = pgFmtFilter qi flt
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pgFmtJsonPath :: JsonPath -> H.Snippet
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pgFmtJsonPath = \case
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[] -> mempty
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(JArrow x:xs) -> "->" <> pgFmtJsonOperand x <> pgFmtJsonPath xs
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(J2Arrow x:xs) -> "->>" <> pgFmtJsonOperand x <> pgFmtJsonPath xs
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where
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pgFmtJsonOperand (JKey k) = unknownLiteral k
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pgFmtJsonOperand (JIdx i) = unknownLiteral i <> "::int"
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pgFmtAs :: FieldName -> JsonPath -> Maybe Alias -> SqlFragment
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pgFmtAs _ [] Nothing = mempty
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pgFmtAs fName jp Nothing = case jOp <$> lastMay jp of
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Just (JKey key) -> " AS " <> pgFmtIdent key
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Just (JIdx _) -> " AS " <> pgFmtIdent (fromMaybe fName lastKey)
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-- We get the lastKey because on:
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-- `select=data->1->mycol->>2`, we need to show the result as [ {"mycol": ..}, {"mycol": ..} ]
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-- `select=data->3`, we need to show the result as [ {"data": ..}, {"data": ..} ]
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where lastKey = jVal <$> find (\case JKey{} -> True; _ -> False) (jOp <$> reverse jp)
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Nothing -> mempty
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pgFmtAs _ _ (Just alias) = " AS " <> pgFmtIdent alias
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countF :: H.Snippet -> Bool -> (H.Snippet, SqlFragment)
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countF countQuery shouldCount =
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if shouldCount
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then (
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", pgrst_source_count AS (" <> countQuery <> ")"
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, "(SELECT pg_catalog.count(*) FROM pgrst_source_count)" )
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else (
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mempty
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, "null::bigint")
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returningF :: QualifiedIdentifier -> [FieldName] -> SqlFragment
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returningF qi returnings =
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if null returnings
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then "RETURNING 1" -- For mutation cases where there's no ?select, we return 1 to know how many rows were modified
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else "RETURNING " <> BS.intercalate ", " (pgFmtColumn qi <$> returnings)
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limitOffsetF :: NonnegRange -> H.Snippet
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limitOffsetF range =
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("LIMIT " <> limit <> " OFFSET " <> offset) `emptySnippetOnFalse` (range == allRange)
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where
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limit = maybe "ALL" (\l -> unknownEncoder (BS.pack $ show l)) $ rangeLimit range
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offset = unknownEncoder (BS.pack . show $ rangeOffset range)
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responseHeadersF :: PgVersion -> SqlFragment
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responseHeadersF pgVer =
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if pgVer >= pgVersion96
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then currentSettingF "response.headers"
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else "null"
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responseStatusF :: PgVersion -> SqlFragment
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responseStatusF pgVer =
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if pgVer >= pgVersion96
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then currentSettingF "response.status"
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else "null"
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currentSettingF :: Text -> SqlFragment
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currentSettingF setting =
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-- nullif is used because of https://gist.github.com/steve-chavez/8d7033ea5655096903f3b52f8ed09a15
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"nullif(current_setting(" <> pgFmtLit setting <> ", true), '')"
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-- Hasql Snippet utilitarians
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unknownEncoder :: ByteString -> H.Snippet
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unknownEncoder = H.encoderAndParam (HE.nonNullable HE.unknown)
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unknownLiteral :: Text -> H.Snippet
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unknownLiteral = unknownEncoder . encodeUtf8
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