refactor: Move statements logic to own module

* Move gucHeader decoding to Statements
2019-09-11 12:01:41 -05:00
parent 620721dea7
commit 3c00f46e36
8 changed files with 239 additions and 256 deletions
@@ -36,13 +36,11 @@ library
                      PostgREST.OpenAPI
                      PostgREST.Parsers
                      PostgREST.QueryBuilder
+                      PostgREST.Statements
                      PostgREST.RangeQuery
                      PostgREST.Types
  other-modules:      Paths_postgrest
                      PostgREST.QueryBuilder.Private
-                      PostgREST.QueryBuilder.Procedure
-                      PostgREST.QueryBuilder.ReadStatement
-                      PostgREST.QueryBuilder.WriteStatement
  hs-source-dirs:     src
  build-depends:      base                      >= 4.9 && < 4.13
                    , HTTP                      >= 4000.3.7 && < 4000.4
@@ -26,7 +26,6 @@ import qualified Hasql.Transaction          as H
 import qualified Hasql.Transaction          as HT
 import qualified Hasql.Transaction.Sessions as HT

-import Data.Aeson                           as JSON
 import Data.Function                        (id)
 import Data.IORef                           (IORef, readIORef)
 import Data.Time.Clock                      (UTCTime)
@@ -56,12 +55,13 @@ import PostgREST.Error            (PgError (..), SimpleError (..),
 import PostgREST.Middleware
 import PostgREST.OpenAPI
 import PostgREST.Parsers          (pRequestColumns)
-import PostgREST.QueryBuilder     (callProc, createReadStatement,
-                                   createWriteStatement,
-                                   requestToCountQuery,
+import PostgREST.QueryBuilder     (requestToCountQuery,
                                   requestToQuery)
 import PostgREST.RangeQuery       (allRange, contentRangeH,
                                   rangeStatusHeader)
+import PostgREST.Statements       (callProcStatement,
+                                   createReadStatement,
+                                   createWriteStatement)
 import PostgREST.Types
 import Protolude                  hiding (Proxy, intercalate)

@@ -282,15 +282,14 @@ app dbStructure proc cols conf apiRequest =
            Right ((q, cq), bField) -> do
              let singular = contentType == CTSingularJSON
              row <- H.statement (toS $ pjRaw pJson) $
-                callProc qi (specifiedProcArgs cols proc) returnsScalar q cq shouldCount
+                callProcStatement qi (specifiedProcArgs cols proc) returnsScalar q cq shouldCount
                         singular (iPreferSingleObjectParameter apiRequest)
                         (contentType == CTTextCSV)
                         (contentType `elem` rawContentTypes) bField
                         (pgVersion dbStructure)
-              let (tableTotal, queryTotal, body, jsonHeaders) = row
+              let (tableTotal, queryTotal, body, gucHeaders) = row
                  (status, contentRange) = rangeStatusHeader topLevelRange queryTotal tableTotal
-                  decodedHeaders = first toS $ JSON.eitherDecode $ toS jsonHeaders :: Either Text [GucHeader]
-              case decodedHeaders of
+              case gucHeaders of
                Left _ -> return . errorResponseFor $ GucHeadersError
                Right hs ->
                  if singular && queryTotal /= 1
@@ -4,44 +4,35 @@
 {-# OPTIONS_GHC -fno-warn-orphans  #-}
 {-|
 Module      : PostgREST.QueryBuilder
-Description : PostgREST SQL generating functions.
+Description : PostgREST SQL fragments generating functions.

 This module provides functions to consume data types that
 represent database objects (e.g. Relation, Schema, SqlQuery)
-and produces SQL Statements.
+and produces SQL fragments.

 Any function that outputs a SQL fragment should be in this module.
 -}
 module PostgREST.QueryBuilder (
-    callProc
-  , createReadStatement
-  , createWriteStatement
-  , requestToQuery
+    requestToQuery
  , requestToCountQuery
  , unquoted
-  , ResultsWithCount
  , pgFmtSetLocal
  , pgFmtSetLocalSearchPath
  ) where

-import qualified Data.Aeson as JSON
-import qualified Data.Set   as S
+import qualified Data.Set as S

-import Data.Scientific (FPFormat (..), formatScientific, isInteger)
-import Data.Text       (intercalate, unwords)
-import Data.Tree       (Tree (..))
+import Data.Text (intercalate, unwords)
+import Data.Tree (Tree (..))

 import Data.Maybe

 import PostgREST.QueryBuilder.Private
-import PostgREST.QueryBuilder.Procedure
-import PostgREST.QueryBuilder.ReadStatement
-import PostgREST.QueryBuilder.WriteStatement
-import PostgREST.RangeQuery                  (allRange, rangeLimit,
-                                              rangeOffset)
+import PostgREST.RangeQuery           (allRange, rangeLimit,
+                                       rangeOffset)
 import PostgREST.Types
-import Protolude                             hiding (cast,
-                                              intercalate, replace)
+import Protolude                      hiding (cast, intercalate,
+                                       replace)

 requestToCountQuery :: Schema -> DbRequest -> SqlQuery
 requestToCountQuery _ (DbMutate _) = witness
@@ -144,10 +135,3 @@ requestToQuery schema _ (DbMutate (Delete mainTbl logicForest returnings)) =
    ]
  where
    qi = QualifiedIdentifier schema mainTbl
-
-unquoted :: JSON.Value -> Text
-unquoted (JSON.String t) = t
-unquoted (JSON.Number n) =
-  toS $ formatScientific Fixed (if isInteger n then Just 0 else Nothing) n
-unquoted (JSON.Bool b) = show b
-unquoted v = toS $ JSON.encode v
@@ -5,51 +5,22 @@ Description : Helper functions for PostgREST.QueryBuilder.
 -}
 module PostgREST.QueryBuilder.Private where

-import qualified Data.ByteString.Char8         as BS
+import qualified Data.Aeson                    as JSON
 import qualified Data.HashMap.Strict           as HM
 import           Data.Maybe
+import           Data.Scientific               (FPFormat (..),
+                                                formatScientific,
+                                                isInteger)
 import           Data.Text                     (intercalate,
                                                isInfixOf, replace,
                                                toLower, unwords)
 import qualified Data.Text                     as T (map, null,
                                                     takeWhile)
-import qualified Data.Text.Encoding            as T
-import qualified Hasql.Decoders                as HD
-import qualified Hasql.Encoders                as HE
-import qualified Hasql.Statement               as H
 import           PostgREST.Types
 import           Protolude                     hiding (cast,
                                                intercalate, replace)
 import           Text.InterpolatedString.Perl6 (qc)

-column :: HD.Value a -> HD.Row a
-column = HD.column . HD.nonNullable
-
-nullableColumn :: HD.Value a -> HD.Row (Maybe a)
-nullableColumn = HD.column . HD.nullable
-
-element :: HD.Value a -> HD.Array a
-element = HD.element . HD.nonNullable
-
-param :: HE.Value a -> HE.Params a
-param = HE.param . HE.nonNullable
-
-{-| The generic query result format used by API responses. The location header
-    is represented as a list of strings containing variable bindings like
-    @"k1=eq.42"@, or the empty list if there is no location header.
-}
-type ResultsWithCount = (Maybe Int64, Int64, [BS.ByteString], BS.ByteString)
-
-{-| Read and Write api requests use a similar response format which includes
-    various record counts and possible location header. This is the decoder
-    for that common type of query.
-}
-standardRow :: HD.Row ResultsWithCount
-standardRow = (,,,) <$> nullableColumn HD.int8 <*> column HD.int8
-                    <*> column header <*> column HD.bytea
-  where
-    header = HD.array $ HD.dimension replicateM $ element HD.bytea
-
 noLocationF :: Text
 noLocationF = "array[]::text[]"

@@ -131,9 +102,6 @@ fromQi t = (if s == "" then "" else pgFmtIdent s <> ".") <> pgFmtIdent n
    n = qiName t
    s = qiSchema t

-unicodeStatement :: Text -> HE.Params a -> HD.Result b -> Bool -> H.Statement a b
-unicodeStatement = H.Statement . T.encodeUtf8
-
 emptyOnFalse :: Text -> Bool -> Text
 emptyOnFalse val cond = if cond then "" else val

@@ -227,3 +195,10 @@ pgFmtSetLocalSearchPath vals =

 trimNullChars :: Text -> Text
 trimNullChars = T.takeWhile (/= '\x0')
+
+unquoted :: JSON.Value -> Text
+unquoted (JSON.String t) = t
+unquoted (JSON.Number n) =
+  toS $ formatScientific Fixed (if isInteger n then Just 0 else Nothing) n
+unquoted (JSON.Bool b) = show b
+unquoted v = toS $ JSON.encode v
@@ -1,88 +0,0 @@
-module PostgREST.QueryBuilder.Procedure where
-
-import           Data.Maybe
-import           Data.Text                      (intercalate, unwords)
-import qualified Hasql.Decoders                 as HD
-import qualified Hasql.Encoders                 as HE
-import qualified Hasql.Statement                as H
-import           PostgREST.QueryBuilder.Private
-import           PostgREST.Types
-import           Protolude                      hiding (cast,
-                                                 intercalate, replace)
-import           Text.InterpolatedString.Perl6  (qc)
-
-type ProcResults = (Maybe Int64, Int64, ByteString, ByteString)
-
-callProc :: QualifiedIdentifier -> [PgArg] -> Bool -> SqlQuery -> SqlQuery -> Bool ->
-            Bool -> Bool -> Bool -> Bool -> Maybe FieldName -> PgVersion ->
-            H.Statement ByteString ProcResults
-callProc qi pgArgs returnsScalar selectQuery countQuery countTotal isSingle paramsAsSingleObject asCsv asBinary binaryField pgVer =
-  unicodeStatement sql (param HE.unknown) decodeProc True
-  where
-    sql =[qc|
-      WITH
-      {argsRecord},
-      {sourceCTEName} AS (
-        {sourceBody}
-      )
-      SELECT
-        {countResultF} AS total_result_set,
-        pg_catalog.count(_postgrest_t) AS page_total,
-        {bodyF} AS body,
-        {responseHeaders} AS response_headers
-      FROM ({selectQuery}) _postgrest_t;|]
-
-    (argsRecord, args)
-      | paramsAsSingleObject = ("_args_record AS (SELECT NULL)", "$1::json")
-      | null pgArgs = (ignoredBody, "")
-      | otherwise = (
-          unwords [
-            normalizedBody <> ",",
-            "_args_record AS (",
-              "SELECT * FROM json_to_recordset(" <> selectBody <> ") AS _(" <>
-                intercalate ", " ((\a -> pgFmtIdent (pgaName a) <> " " <> pgaType a) <$> pgArgs) <> ")",
-            ")"]
-         , intercalate ", " ((\a -> pgFmtIdent (pgaName a) <> " := _args_record." <> pgFmtIdent (pgaName a)) <$> pgArgs))
-
-    sourceBody :: SqlFragment
-    sourceBody
-      | paramsAsSingleObject || null pgArgs =
-          if returnsScalar
-            then [qc| SELECT {fromQi qi}({args}) |]
-            else [qc| SELECT * FROM {fromQi qi}({args}) |]
-      | otherwise =
-          if returnsScalar
-            then [qc| SELECT {fromQi qi}({args}) FROM _args_record |]
-            else [qc| SELECT _.*
-                      FROM _args_record,
-                      LATERAL ( SELECT * FROM {fromQi qi}({args}) ) _ |]
-
-    bodyF
-     | returnsScalar = scalarBodyF
-     | isSingle = asJsonSingleF
-     | asCsv = asCsvF
-     | isJust binaryField = asBinaryF $ fromJust binaryField
-     | otherwise = asJsonF
-
-    scalarBodyF
-     | asBinary = asBinaryF _procName
-     | otherwise = unwords [
-        "CASE",
-          "WHEN pg_catalog.count(_postgrest_t) = 1",
-            "THEN (json_agg(_postgrest_t." <> pgFmtIdent _procName <> ")->0)::character varying",
-            "ELSE (json_agg(_postgrest_t." <> pgFmtIdent _procName <> "))::character varying",
-        "END"]
-
-    countResultF = if countTotal then "( "<> countQuery <> ")" else "null::bigint" :: Text
-    _procName = qiName qi
-    responseHeaders =
-      if pgVer >= pgVersion96
-        then "coalesce(nullif(current_setting('response.headers', true), ''), '[]')" :: Text -- nullif is used because of https://gist.github.com/steve-chavez/8d7033ea5655096903f3b52f8ed09a15
-        else "'[]'" :: Text
-
-decodeProc :: HD.Result ProcResults
-decodeProc =
-  fromMaybe (Just 0, 0, "[]", "[]") <$> HD.rowMaybe procRow
-  where
-    procRow = (,,,) <$> nullableColumn HD.int8 <*> column HD.int8
-                    <*> column HD.bytea <*> column HD.bytea
@@ -1,37 +0,0 @@
-module PostgREST.QueryBuilder.ReadStatement where
-
-import           Data.Maybe
-import           Data.Text                      (intercalate)
-import qualified Hasql.Decoders                 as HD
-import qualified Hasql.Encoders                 as HE
-import qualified Hasql.Statement                as H
-import           PostgREST.QueryBuilder.Private
-import           PostgREST.Types
-import           Protolude                      hiding (cast,
-                                                 intercalate, replace)
-import           Text.InterpolatedString.Perl6  (qc)
-
-createReadStatement :: SqlQuery -> SqlQuery -> Bool -> Bool -> Bool -> Maybe FieldName ->
-                       H.Statement () ResultsWithCount
-createReadStatement selectQuery countQuery isSingle countTotal asCsv binaryField =
-  unicodeStatement sql HE.noParams decodeStandard False
- where
-  sql = [qc|
-      WITH {sourceCTEName} AS ({selectQuery}) SELECT {cols}
-      FROM ( SELECT * FROM {sourceCTEName}) _postgrest_t |]
-  countResultF = if countTotal then "("<>countQuery<>")" else "null"
-  cols = intercalate ", " [
-      countResultF <> " AS total_result_set",
-      "pg_catalog.count(_postgrest_t) AS page_total",
-      noLocationF <> " AS header",
-      bodyF <> " AS body"
-    ]
-  bodyF
-    | asCsv = asCsvF
-    | isSingle = asJsonSingleF
-    | isJust binaryField = asBinaryF $ fromJust binaryField
-    | otherwise = asJsonF
-
-decodeStandard :: HD.Result ResultsWithCount
-decodeStandard =
-  HD.singleRow standardRow
@@ -1,58 +0,0 @@
-module PostgREST.QueryBuilder.WriteStatement where
-
-import           Data.Maybe
-import           Data.Text                      (intercalate, unwords)
-import qualified Hasql.Decoders                 as HD
-import qualified Hasql.Encoders                 as HE
-import qualified Hasql.Statement                as H
-import           PostgREST.ApiRequest           (PreferRepresentation (..))
-import           PostgREST.QueryBuilder.Private
-import           PostgREST.Types
-import           Protolude                      hiding (cast,
-                                                 intercalate, replace)
-import           Text.InterpolatedString.Perl6  (qc)
-
-createWriteStatement :: SqlQuery -> SqlQuery -> Bool -> Bool -> Bool ->
-                        PreferRepresentation -> [Text] ->
-                        H.Statement ByteString ResultsWithCount
-createWriteStatement selectQuery mutateQuery wantSingle isInsert asCsv rep pKeys =
-  unicodeStatement sql (param HE.unknown) decodeStandardMay True
-
- where
-  sql = case rep of
-    None -> [qc|
-      WITH {sourceCTEName} AS ({mutateQuery})
-      SELECT '', 0, {noLocationF}, '' |]
-    HeadersOnly -> [qc|
-      WITH {sourceCTEName} AS ({mutateQuery})
-      SELECT {cols}
-      FROM (SELECT 1 FROM {sourceCTEName}) _postgrest_t |]
-    Full -> [qc|
-      WITH {sourceCTEName} AS ({mutateQuery})
-      SELECT {cols}
-      FROM ({selectQuery}) _postgrest_t |]
-
-  cols = intercalate ", " [
-      "'' AS total_result_set", -- when updateing it does not make sense
-      "pg_catalog.count(_postgrest_t) AS page_total",
-      if isInsert
-        then unwords [
-          "CASE",
-            "WHEN pg_catalog.count(_postgrest_t) = 1 THEN",
-              "coalesce(" <> locationF pKeys <> ", " <> noLocationF <> ")",
-            "ELSE " <> noLocationF,
-          "END AS header"]
-        else noLocationF <> "AS header",
-      if rep == Full
-         then bodyF <> " AS body"
-         else "''"
-    ]
-
-  bodyF
-    | asCsv = asCsvF
-    | wantSingle = asJsonSingleF
-    | otherwise = asJsonF
-
-decodeStandardMay :: HD.Result ResultsWithCount
-decodeStandardMay =
- fromMaybe (Nothing, 0, [], "") <$> HD.rowMaybe standardRow
@@ -0,0 +1,210 @@
+{-|
+Module      : PostgREST.Statements
+Description : PostgREST single SQL statements.
+
+This module constructs single SQL statements that can be parametrized and prepared.
+
+- It consumes the SqlQuery types generated by the QueryBuilder module.
+- It generates the body format and some headers of the final HTTP response.
+
+TODO: Currently, createReadStatement is not using prepared statements, see https://github.com/PostgREST/postgrest/issues/718.
+-}
+module PostgREST.Statements (
+    createWriteStatement
+  , createReadStatement
+  , callProcStatement
+) where
+
+import           Data.Aeson                     as JSON
+import qualified Data.ByteString.Char8          as BS
+import           Data.Maybe
+import           Data.Text                      (intercalate, unwords)
+import           Data.Text.Encoding             (encodeUtf8)
+import qualified Hasql.Decoders                 as HD
+import qualified Hasql.Encoders                 as HE
+import qualified Hasql.Statement                as H
+import           PostgREST.ApiRequest           (PreferRepresentation (..))
+import           PostgREST.QueryBuilder.Private
+import           PostgREST.Types
+import           Protolude                      hiding (cast,
+                                                 intercalate, replace)
+import           Text.InterpolatedString.Perl6  (qc)
+
+{-| The generic query result format used by API responses. The location header
+    is represented as a list of strings containing variable bindings like
+    @"k1=eq.42"@, or the empty list if there is no location header.
+-}
+type ResultsWithCount = (Maybe Int64, Int64, [BS.ByteString], BS.ByteString)
+
+createWriteStatement :: SqlQuery -> SqlQuery -> Bool -> Bool -> Bool ->
+                        PreferRepresentation -> [Text] ->
+                        H.Statement ByteString ResultsWithCount
+createWriteStatement selectQuery mutateQuery wantSingle isInsert asCsv rep pKeys =
+  unicodeStatement sql (param HE.unknown) decodeStandard True
+ where
+  sql = case rep of
+    None -> [qc|
+      WITH {sourceCTEName} AS ({mutateQuery})
+      SELECT '', 0, {noLocationF}, '' |]
+    HeadersOnly -> [qc|
+      WITH {sourceCTEName} AS ({mutateQuery})
+      SELECT {cols}
+      FROM (SELECT 1 FROM {sourceCTEName}) _postgrest_t |]
+    Full -> [qc|
+      WITH {sourceCTEName} AS ({mutateQuery})
+      SELECT {cols}
+      FROM ({selectQuery}) _postgrest_t |]
+
+  cols = intercalate ", " [
+      "'' AS total_result_set", -- when updateing it does not make sense
+      "pg_catalog.count(_postgrest_t) AS page_total",
+      if isInsert
+        then unwords [
+          "CASE",
+            "WHEN pg_catalog.count(_postgrest_t) = 1 THEN",
+              "coalesce(" <> locationF pKeys <> ", " <> noLocationF <> ")",
+            "ELSE " <> noLocationF,
+          "END AS header"]
+        else noLocationF <> "AS header",
+      if rep == Full
+         then bodyF <> " AS body"
+         else "''"
+    ]
+
+  bodyF
+    | asCsv = asCsvF
+    | wantSingle = asJsonSingleF
+    | otherwise = asJsonF
+
+  decodeStandard :: HD.Result ResultsWithCount
+  decodeStandard =
+   fromMaybe (Nothing, 0, [], "") <$> HD.rowMaybe standardRow
+
+createReadStatement :: SqlQuery -> SqlQuery -> Bool -> Bool -> Bool -> Maybe FieldName ->
+                       H.Statement () ResultsWithCount
+createReadStatement selectQuery countQuery isSingle countTotal asCsv binaryField =
+  unicodeStatement sql HE.noParams decodeStandard False
+ where
+  sql = [qc|
+      WITH {sourceCTEName} AS ({selectQuery}) SELECT {cols}
+      FROM ( SELECT * FROM {sourceCTEName}) _postgrest_t |]
+  countResultF = if countTotal then "("<>countQuery<>")" else "null"
+  cols = intercalate ", " [
+      countResultF <> " AS total_result_set",
+      "pg_catalog.count(_postgrest_t) AS page_total",
+      noLocationF <> " AS header",
+      bodyF <> " AS body"
+    ]
+  bodyF
+    | asCsv = asCsvF
+    | isSingle = asJsonSingleF
+    | isJust binaryField = asBinaryF $ fromJust binaryField
+    | otherwise = asJsonF
+
+  decodeStandard :: HD.Result ResultsWithCount
+  decodeStandard =
+    HD.singleRow standardRow
+
+{-| Read and Write api requests use a similar response format which includes
+    various record counts and possible location header. This is the decoder
+    for that common type of query.
+-}
+standardRow :: HD.Row ResultsWithCount
+standardRow = (,,,) <$> nullableColumn HD.int8 <*> column HD.int8
+                    <*> column header <*> column HD.bytea
+  where
+    header = HD.array $ HD.dimension replicateM $ element HD.bytea
+
+type ProcResults = (Maybe Int64, Int64, ByteString, Either Text [GucHeader])
+
+callProcStatement :: QualifiedIdentifier -> [PgArg] -> Bool -> SqlQuery -> SqlQuery -> Bool ->
+                     Bool -> Bool -> Bool -> Bool -> Maybe FieldName -> PgVersion ->
+                     H.Statement ByteString ProcResults
+callProcStatement qi pgArgs returnsScalar selectQuery countQuery countTotal isSingle paramsAsSingleObject asCsv asBinary binaryField pgVer =
+  unicodeStatement sql (param HE.unknown) decodeProc True
+  where
+    sql =[qc|
+      WITH
+      {argsRecord},
+      {sourceCTEName} AS (
+        {sourceBody}
+      )
+      SELECT
+        {countResultF} AS total_result_set,
+        pg_catalog.count(_postgrest_t) AS page_total,
+        {bodyF} AS body,
+        {responseHeaders} AS response_headers
+      FROM ({selectQuery}) _postgrest_t;|]
+
+    (argsRecord, args)
+      | paramsAsSingleObject = ("_args_record AS (SELECT NULL)", "$1::json")
+      | null pgArgs = (ignoredBody, "")
+      | otherwise = (
+          unwords [
+            normalizedBody <> ",",
+            "_args_record AS (",
+              "SELECT * FROM json_to_recordset(" <> selectBody <> ") AS _(" <>
+                intercalate ", " ((\a -> pgFmtIdent (pgaName a) <> " " <> pgaType a) <$> pgArgs) <> ")",
+            ")"]
+         , intercalate ", " ((\a -> pgFmtIdent (pgaName a) <> " := _args_record." <> pgFmtIdent (pgaName a)) <$> pgArgs))
+
+    sourceBody :: SqlFragment
+    sourceBody
+      | paramsAsSingleObject || null pgArgs =
+          if returnsScalar
+            then [qc| SELECT {fromQi qi}({args}) |]
+            else [qc| SELECT * FROM {fromQi qi}({args}) |]
+      | otherwise =
+          if returnsScalar
+            then [qc| SELECT {fromQi qi}({args}) FROM _args_record |]
+            else [qc| SELECT _.*
+                      FROM _args_record,
+                      LATERAL ( SELECT * FROM {fromQi qi}({args}) ) _ |]
+
+    bodyF
+     | returnsScalar = scalarBodyF
+     | isSingle = asJsonSingleF
+     | asCsv = asCsvF
+     | isJust binaryField = asBinaryF $ fromJust binaryField
+     | otherwise = asJsonF
+
+    scalarBodyF
+     | asBinary = asBinaryF _procName
+     | otherwise = unwords [
+        "CASE",
+          "WHEN pg_catalog.count(_postgrest_t) = 1",
+            "THEN (json_agg(_postgrest_t." <> pgFmtIdent _procName <> ")->0)::character varying",
+            "ELSE (json_agg(_postgrest_t." <> pgFmtIdent _procName <> "))::character varying",
+        "END"]
+
+    countResultF = if countTotal then "( "<> countQuery <> ")" else "null::bigint" :: Text
+    _procName = qiName qi
+    responseHeaders =
+      if pgVer >= pgVersion96
+        then "coalesce(nullif(current_setting('response.headers', true), ''), '[]')" :: Text -- nullif is used because of https://gist.github.com/steve-chavez/8d7033ea5655096903f3b52f8ed09a15
+        else "'[]'" :: Text
+
+    decodeProc :: HD.Result ProcResults
+    decodeProc =
+      let row = fromMaybe (Just 0, 0, "[]", "[]") <$> HD.rowMaybe procRow in
+      (\(a, b, c, d) -> (a, b, c, first toS $ JSON.eitherDecode $ toS d)) <$> row
+      where
+        procRow = (,,,) <$> nullableColumn HD.int8 <*> column HD.int8
+                        <*> column HD.bytea <*> column HD.bytea
+
+unicodeStatement :: Text -> HE.Params a -> HD.Result b -> Bool -> H.Statement a b
+unicodeStatement = H.Statement . encodeUtf8
+
+-- Helper hasql functions
+
+column :: HD.Value a -> HD.Row a
+column = HD.column . HD.nonNullable
+
+nullableColumn :: HD.Value a -> HD.Row (Maybe a)
+nullableColumn = HD.column . HD.nullable
+
+element :: HD.Value a -> HD.Array a
+element = HD.element . HD.nonNullable
+
+param :: HE.Value a -> HE.Params a
+param = HE.param . HE.nonNullable