sql/pgwire: support for decoding JSON[] OID by aliasing to JSONB[] OID

fixes cockroachdb#90839

Previously, with the parameter type oid (199) for JSON[], the pgwire parse message
will fail to be executed with a `unknown oid type: 199`. We now aliasing it
to the one for `JSONB[]`.

This commit follows the changes in cockroachdb#88379.

Release note (sql change): The pgwire protocol implementation can
now accept arguments of the JSON[] type (oid=199). Previously, it could
only accept JSONB[] (oid=3804). Internally, JSON[] and JSONB[] values are
still identical, so this change only affects how the values are received
over the wire protocol.

pkg/sql/conn_executor_prepare.go

@@ -417,11 +417,14 @@ func (ex *connExecutor) execBind(
 				} else {
 					typ, ok := types.OidToType[t]
 					if !ok {
+						// These special cases for json, json[] is here so we can
+						// support decoding parameters with oid=json/json[] without
+						// adding full support for these type.
+						// TODO(sql-exp): Remove this if we support JSON.
 						if t == oid.T_json {
-							// This special case is here so we can support decoding parameters
-							// with oid=json without adding full support for the JSON type.
-							// TODO(sql-exp): Remove this if we support JSON.
 							typ = types.Json
+						} else if t == oid.T__json {
+							typ = types.JSONArrayForDecodingOnly
 						} else {
 							var err error
 							typ, err = ex.planner.ResolveTypeByOID(ctx, t)

pkg/sql/pgwire/conn.go

@@ -969,13 +969,18 @@ func (c *conn) handleParse(
 				sqlTypeHints[i] = nil
 				continue
 			}
+			// This special case for json, json[] is here so we can support decoding
+			// parameters with oid=json/json[] without adding full support for these
+			// type.
+			// TODO(sql-exp): Remove this if we support JSON.
 			if t == oid.T_json {
-				// This special case is here so we can support decoding parameters
-				// with oid=json without adding full support for the JSON type.
-				// TODO(sql-exp): Remove this if we support JSON.
 				sqlTypeHints[i] = types.Json
 				continue
 			}
+			if t == oid.T__json {
+				sqlTypeHints[i] = types.JSONArrayForDecodingOnly
+				continue
+			}
 			v, ok := types.OidToType[t]
 			if !ok {
 				err := pgwirebase.NewProtocolViolationErrorf("unknown oid type: %v", t)

pkg/sql/pgwire/pgwirebase/encoding.go

@@ -503,6 +503,34 @@ func DecodeDatum(
 				return nil, err
 			}
 			return tree.ParseDJSON(string(b))
+		case oid.T__json, oid.T__jsonb:
+			var arr pgtype.JSONBArray
+			if err := arr.DecodeText(nil, b); err != nil {
+				return nil, tree.MakeParseError(string(b), typ, err)
+			}
+			if arr.Status != pgtype.Present {
+				return tree.DNull, nil
+			}
+			if err := validateArrayDimensions(len(arr.Dimensions), len(arr.Elements)); err != nil {
+				return nil, err
+			}
+			out := tree.NewDArray(types.Jsonb)
+			var d tree.Datum
+			var err error
+			for _, v := range arr.Elements {
+				if v.Status != pgtype.Present {
+					d = tree.DNull
+				} else {
+					d, err = tree.ParseDJSON(string(v.Bytes))
+					if err != nil {
+						return nil, err
+					}
+				}
+				if err := out.Append(d); err != nil {
+					return nil, err
+				}
+			}
+			return out, nil
 		case oid.T_tsquery:
 			ret, err := tsearch.ParseTSQuery(string(b))
 			if err != nil {