server: fix single char SQL generation (fixes hasura/graphql-engine#6814)

GitOrigin-RevId: cbbec459cf7b214d50a14e5ef09f2567356e6481

CHANGELOG.md

@@ -6,6 +6,7 @@
 
 (Add entries below in the order of: server, console, cli, docs, others)
 
+- server: fix parsing of values for Postgres char columns (fix #6814)
 - server: fix query execution of custom function containing a composite argument type
 - server: fix a bug in query validation that would cause some queries using default variable values to be rejected (fix #6867)
 - server: REST endpoint bugfix for UUID url params

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

@@ -217,7 +217,7 @@ txtEncodedVal = \case
   -- with 2 decimal places.
   PGValMoney m    -> TELit $ T.pack $ formatScientific Fixed (Just 2) m
   PGValBoolean b  -> TELit $ bool "false" "true" b
-  PGValChar t     -> TELit $ tshow t
+  PGValChar t     -> TELit $ T.singleton t
   PGValVarchar t  -> TELit t
   PGValText t     -> TELit t
   PGValCitext t   -> TELit t

server/tests-py/queries/graphql_mutation/insert/basic/insert_various_postgres_types.yaml

@@ -47,6 +47,7 @@
           c42_range_timestamp: '["2010-01-01 14:30:00","2010-01-01 15:30:02")'
           c43_range_timestamptz: '("2011-02-05 12:03:00+00","2012-03-04 16:40:04+00"]'
           c44_xml: '<foo>bar</foo>'
+          c45_char: '@'
   status: 200
   query:
     variables:
@@ -99,6 +100,7 @@
             , c42_range_timestamp: "[\"2010-01-01 14:30:00\",\"2010-01-01 15:30:02\")"
             , c43_range_timestamptz: "(\"2011-02-05 12:03:00+00\",\"2012-03-04 16:40:04+00\"]"
             , c44_xml: "<foo>bar</foo>"
+            , c45_char: "@"
             }
           ]
         ) {
@@ -143,6 +145,7 @@
             c42_range_timestamp
             c43_range_timestamptz
             c44_xml
+            c45_char
           }
         }
       }

server/tests-py/queries/graphql_mutation/insert/basic/schema_setup.yaml

@@ -83,7 +83,8 @@ args:
           c41_range_numeric numrange,
           c42_range_timestamp tsrange,
           c43_range_timestamptz tstzrange,
-          c44_xml xml
+          c44_xml xml,
+          c45_char char
       );
 
 - type: track_table