add jsonb to string cast support for postgres (fix #6577, #2602)

GITHUB_PR_NUMBER: 7818
GITHUB_PR_URL: https://github.com/hasura/graphql-engine/pull/7818

PR-URL: https://github.com/hasura/graphql-engine-mono/pull/2898
Co-authored-by: Teo Stocco <9053709+zifeo@users.noreply.github.com>
Co-authored-by: Rikin Kachhia <54616969+rikinsk@users.noreply.github.com>
Co-authored-by: Rakesh Emmadi <12475069+rakeshkky@users.noreply.github.com>
GitOrigin-RevId: 1100f3ce44ea07867a2d7de5b6bb059510f100e1

CHANGELOG.md

@@ -7,6 +7,7 @@
 
 ### Bug fixes and improvements
 
+- server: add jsonb to string cast support - postgres 
 - server: improve performance of fetching postgres catalog metadata for tables and functions
 - server: Queries present in query collections, such as allow-list, and rest-endpoints are now validated (against the schema)
 - server: Redesigns internal implementation of webhook transforms.

docs/graphql/core/api-reference/graphql-api/query.rst

@@ -814,7 +814,10 @@ CastExp
 
 .. note::
 
-   Currently, only casting between ``geometry`` and ``geography`` types is allowed.
+   Currently, only the following type casts are supported:
+
+   - between PostGIS ``geometry`` and ``geography`` types
+   - from Postgres ``jsonb`` type to ``string`` type.
 
 .. _OrderByExp:
 

docs/graphql/core/databases/ms-sql-server/queries/query-filters.rst

@@ -558,7 +558,7 @@ Fetch a list of articles whose titles contain the word “amet”:
                 "city": "Bengaluru",
                 "state": "Karnataka",
                 "pincode": 560095,
-                "phone": "9090909090",
+                "phone": "9090909090"
               }
             }
           ]

docs/graphql/core/databases/postgres/queries/query-filters.rst

@@ -644,7 +644,7 @@ Fetch all authors living within a particular pincode (present in ``address`` JSO
               "city": "Bengaluru",
               "state": "Karnataka",
               "pincode": 560095,
-              "phone": "9090909090",
+              "phone": "9090909090"
             }
           }
         ]
@@ -2026,13 +2026,55 @@ Cast a field to a different type before filtering (_cast)
 ---------------------------------------------------------
 
 The ``_cast`` operator can be used to cast a field to a different type, which allows type-specific
-operators to be used on fields that otherwise would not support them. Currently, only casting
-between PostGIS ``geometry`` and ``geography`` types is supported.
+operators to be used on fields that otherwise would not support them.
+
+Currently, only the following type casts are supported:
+
+- between PostGIS ``geometry`` and ``geography`` types
+- from Postgres ``jsonb`` type to ``string`` type.
 
 Casting using ``_cast`` corresponds directly to
 `SQL type casts <https://www.postgresql.org/docs/current/sql-expressions.html#SQL-SYNTAX-TYPE-CASTS>`__.
 
-**Example: cast ``geometry`` to ``geography``**
+**Example: cast jsonb to string**
+
+Columns of type ``jsonb`` can be cast to ``String`` to use :ref:`text operators <text_operators>` on a
+``jsonb`` field:
+
+.. graphiql::
+  :view_only:
+  :query:
+    query get_authors_in_bengaluru {
+      authors(
+        where: {
+          address: {_cast: {String: {_ilike: "%bengaluru%"}}}
+        }
+      ) {
+        id
+        name
+        address
+      }
+    }
+  :response:
+    {
+      "data": {
+        "authors": [
+          {
+            "id": 1,
+            "name": "Ash",
+            "address": {
+              "street_address": "161, 19th Main Road, Koramangala 6th Block",
+              "city": "Bengaluru",
+              "state": "Karnataka",
+              "pincode": 560095,
+              "phone": "9090909090"
+            }
+          }
+        ]
+      }
+    }
+
+**Example: cast geometry to geography**
 
 Filtering using ``_st_d_within`` over large distances can be inaccurate for location data stored in
 ``geometry`` columns. For accurate queries, cast the field to ``geography`` before comparing:
@@ -2073,7 +2115,7 @@ Filtering using ``_st_d_within`` over large distances can be inaccurate for loca
       "distance": 1000000
     }
 
-**Example: cast ``geography`` to ``geometry``**
+**Example: cast geography to geometry**
 
 Columns of type ``geography`` are more accurate, but they don’t support as many operations as
 ``geometry``. Cast to ``geometry`` to use those operations in a filter:

server/src-lib/Hasura/Backends/Postgres/DDL/BoolExp.hs

@@ -208,6 +208,7 @@ parseBoolExpOperations rhsParser rootTable fim columnRef value = do
         checkValidCast targetType = case (colTy, targetType) of
           (ColumnScalar PGGeometry, PGGeography) -> return ()
           (ColumnScalar PGGeography, PGGeometry) -> return ()
+          (ColumnScalar PGJSONB, PGText) -> return ()
           _ ->
             throw400 UnexpectedPayload $
               "cannot cast column of type " <> colTy <<> " to type " <>> targetType

server/src-lib/Hasura/Backends/Postgres/Instances/Schema.hs

@@ -599,6 +599,7 @@ comparisonExps = P.memoize 'comparisonExps \columnType -> do
       let maybeScalars = case sourceType of
             ColumnScalar PGGeography -> Just (PGGeography, PGGeometry)
             ColumnScalar PGGeometry -> Just (PGGeometry, PGGeography)
+            ColumnScalar PGJSONB -> Just (PGJSONB, PGText)
             _ -> Nothing
 
       forM maybeScalars $ \(sourceScalar, targetScalar) -> do

server/tests-py/queries/graphql_query/boolexp/jsonb/query_cast_jsonb_to_string.yaml

@@ -0,0 +1,18 @@
+description: Test casting from jsonb to string
+url: /v1/graphql
+status: 200
+query:
+  query: |
+    query {
+      article(where: {tags: {_cast: {String: {_like: "%bestseller%"}}}}){
+        id
+        tags
+      }
+    }
+response:
+  data:
+    article:
+    - id: 2
+      tags:
+      - bestseller
+      - latest

server/tests-py/test_graphql_queries.py

@@ -934,6 +934,9 @@ class TestGraphQLQueryBoolExpSearchMSSQL:
 @usefixtures('per_class_tests_db_state')
 class TestGraphQLQueryBoolExpJsonB:
 
+    def test_query_cast_geometry_to_geography(self, hge_ctx, transport):
+        check_query_f(hge_ctx, self.dir() + '/query_cast_jsonb_to_string.yaml', transport)
+
     def test_jsonb_contains_article_latest(self, hge_ctx, transport):
         check_query_f(hge_ctx, self.dir() + '/select_article_author_jsonb_contains_latest.yaml', transport)