Fix Postgres not padding timestamps correctly (fix hasura/graphql-engine#8096)

## Description

As identified in hasura/graphql-engine#8096, the format string we used for timestamps was incorrect; we were using `%F`, which expands to `%Y-%m-%d`; but that meant that the year was not padded to four digits: `0001` would be represented simply as `1`. However, Postgres inteprets that `1` as `2001`, probably due to interpretation rules about two-digit years (in `25/12/01`, `01` is indeed `2001`).

```
# create table timestamp_test ( test timestamptz );
CREATE TABLE
# insert into timestamp_test values ('1-01-01T00:00:57Z');
INSERT 0 1
# select * from timestamp_test;
          test
------------------------
 2001-01-01 00:00:57+00
(1 row)
```

To fix this, this PR changes the format string to use `%0Y`, which always pads the year number with zeroes.

## Remaining work

- [x] write Changelog entry
- [ ] copy timestamp tests from the python suite into the hspec tests

PR-URL: https://github.com/hasura/graphql-engine-mono/pull/3536
GitOrigin-RevId: fa144111358339fd4a35b32d888c1d2c5b418ea6

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ### Bug fixes and improvements
 
+- server: fixed a bug where timestamp values sent to postgres would erroneously trim leading zeroes (#8096)
 - server: fix bug when event triggers where defined on tables that contained non lower-case alphabet characters
 - server: avoid encoding 'varchar' values to UTF8 in MSSQL backends
 - server: add support for MSSQL event triggers (#7228)

server/graphql-engine.cabal

@@ -1091,9 +1091,9 @@ test-suite tests-hspec
     Harness.Backend.Sqlserver
 
  -- Harness.Test
+    Harness.Test.BackendType
     Harness.Test.Context
     Harness.Test.Schema
-    Harness.Test.BackendType
 
  -- Harness.Quoter
     Harness.Quoter.Graphql
@@ -1107,30 +1107,31 @@ test-suite tests-hspec
     Test.CustomFieldNamesSpec
     Test.DirectivesSpec
     Test.HelloWorldSpec
+    Test.InsertCheckPermissionSpec
+    Test.InsertEnumColumnSpec
     Test.LimitOffsetSpec
     Test.NestedRelationshipsSpec
     Test.ObjectRelationshipsLimitSpec
     Test.ObjectRelationshipsSpec
     Test.OrderingSpec
+    Test.PostgresTypesSpec
     Test.PrimaryKeySpec
-    Test.RemoteRelationship.MetadataAPI.Common
+    Test.RemoteRelationship.FromRemoteSchemaSpec
     Test.RemoteRelationship.MetadataAPI.ClearMetadataSpec
+    Test.RemoteRelationship.MetadataAPI.Common
     Test.RemoteRelationship.MetadataAPI.DropSource.DBtoDBRelationshipSpec
     Test.RemoteRelationship.MetadataAPI.DropSource.RSToDBRelationshipSpec
-    Test.RemoteRelationship.FromRemoteSchemaSpec
     Test.RemoteRelationship.XToDBArrayRelationshipSpec
     Test.RemoteRelationship.XToDBObjectRelationshipSpec
     Test.RemoteRelationship.XToRemoteSchemaRelationshipSpec
     Test.RequestHeadersSpec
-    Test.SerializationSpec
+    Test.RunSQLSpec
+    Test.SQLServer.InsertVarcharColumnSpec
     Test.SelectSpec
+    Test.SerializationSpec
     Test.ServiceLivenessSpec
     Test.ViewsSpec
     Test.WhereSpec
-    Test.RunSQLSpec
-    Test.InsertCheckPermissionSpec
-    Test.InsertEnumColumnSpec
-    Test.SQLServer.InsertVarcharColumnSpec
 
 test-suite tests-dc-api
   import: common-all, common-exe

server/src-lib/Hasura/Backends/Postgres/SQL/Value.hs

@@ -120,10 +120,8 @@ pgScalarValueToJson = \case
   PGValText t -> toJSON t
   PGValCitext t -> toJSON t
   PGValDate d -> toJSON d
-  PGValTimeStamp u ->
-    toJSON $ formatTime defaultTimeLocale "%FT%T%QZ" u
-  PGValTimeStampTZ u ->
-    toJSON $ formatTime defaultTimeLocale "%FT%T%QZ" u
+  PGValTimeStamp u -> String $ formatTimestamp u
+  PGValTimeStampTZ u -> String $ formatTimestamp u
   PGValTimeTZ (ZonedTimeOfDay tod tz) ->
     toJSON (show tod ++ timeZoneOffsetString tz)
   PGNull _ -> Null
@@ -243,10 +241,8 @@ txtEncodedVal = \case
   PGValText t -> TELit t
   PGValCitext t -> TELit t
   PGValDate d -> TELit $ T.pack $ showGregorian d
-  PGValTimeStamp u ->
-    TELit $ T.pack $ formatTime defaultTimeLocale "%FT%T%QZ" u
-  PGValTimeStampTZ u ->
-    TELit $ T.pack $ formatTime defaultTimeLocale "%FT%T%QZ" u
+  PGValTimeStamp u -> TELit $ formatTimestamp u
+  PGValTimeStampTZ u -> TELit $ formatTimestamp u
   PGValTimeTZ (ZonedTimeOfDay tod tz) ->
     TELit $ T.pack (show tod ++ timeZoneOffsetString tz)
   PGNull _ ->
@@ -332,6 +328,9 @@ binEncoder = \case
   PGValLtxtquery t -> Q.toPrepVal t
   PGValUnknown t -> (PTI.auto, Just (TE.encodeUtf8 t, PQ.Text))
 
+formatTimestamp :: FormatTime t => t -> Text
+formatTimestamp = T.pack . formatTime defaultTimeLocale "%0Y-%m-%dT%T%QZ"
+
 txtEncoder :: PGScalarValue -> S.SQLExp
 txtEncoder colVal = case txtEncodedVal colVal of
   TENull -> S.SENull

server/tests-hspec/Test/PostgresTypesSpec.hs

@@ -0,0 +1,97 @@
+{-# LANGUAGE QuasiQuotes #-}
+{-# LANGUAGE RecordWildCards #-}
+
+-- | Tests around Postgres-specific database types
+module Test.PostgresTypesSpec (spec) where
+
+import Harness.Backend.Postgres as Postgres
+import Harness.GraphqlEngine qualified as GraphqlEngine
+import Harness.Quoter.Graphql
+import Harness.Quoter.Sql
+import Harness.Quoter.Yaml
+import Harness.Test.Context qualified as Context
+import Harness.TestEnvironment (TestEnvironment)
+import Test.Hspec
+import Prelude
+
+--------------------------------------------------------------------------------
+-- Preamble
+
+spec :: SpecWith TestEnvironment
+spec =
+  Context.run
+    [ Context.Context
+        { name = Context.Backend Context.Postgres,
+          mkLocalTestEnvironment = Context.noLocalTestEnvironment,
+          setup = postgresSetup,
+          teardown = postgresTeardown,
+          customOptions = Nothing
+        }
+    ]
+    tests
+
+--------------------------------------------------------------------------------
+-- Postgres
+
+postgresSetup :: (TestEnvironment, ()) -> IO ()
+postgresSetup (testEnvironment, _) = do
+  -- Clear and reconfigure the metadata
+  GraphqlEngine.setSource testEnvironment Postgres.defaultSourceMetadata
+
+  -- Setup tables
+  Postgres.run_
+    [sql|
+create table timestamp_test (
+  id   serial primary key,
+  time timestamptz
+);
+|]
+
+  -- Track the tables
+  GraphqlEngine.post_
+    testEnvironment
+    "/v1/metadata"
+    [yaml|
+type: postgres_track_table
+args:
+  source: postgres
+  table:
+    schema: hasura
+    name: timestamp_test
+|]
+
+postgresTeardown :: (TestEnvironment, ()) -> IO ()
+postgresTeardown _ = do
+  Postgres.run_
+    [sql|
+DROP TABLE hasura.timestamp_test;
+|]
+
+--------------------------------------------------------------------------------
+-- Tests
+
+tests :: Context.Options -> SpecWith TestEnvironment
+tests opts = do
+  it "doesn't mess up timestamps on insertion" $ \testEnvironment ->
+    shouldReturnYaml
+      opts
+      ( GraphqlEngine.postGraphql
+          testEnvironment
+          [graphql|
+mutation {
+  insert_hasura_timestamp_test(objects:[{
+    time: "0001-01-01T00:00:57Z"
+  }]) {
+    returning {
+      time
+    }
+  }
+}
+|]
+      )
+      [yaml|
+data:
+  insert_hasura_timestamp_test:
+    returning:
+      - time: "0001-01-01T00:00:57+00:00"
+|]