Fix and test for postgres OID type decoding.

Co-authored-by: k.tokarev <[email protected]>

[#495]

Author: k-tokarev

src/main/java/io/r2dbc/postgresql/codec/NumericDecodeUtils.java

@@ -62,14 +62,14 @@ public static Number decodeNumber(ByteBuf buffer, PostgresqlObjectId dataType, @
                 return Short.parseShort(ByteBufUtils.decode(buffer));
             case INT4:
             case INT4_ARRAY:
-            case OID:
-            case OID_ARRAY:
                 if (FORMAT_BINARY == format) {
                     return buffer.readInt();
                 }
                 return Integer.parseInt(ByteBufUtils.decode(buffer));
             case INT8:
             case INT8_ARRAY:
+            case OID:
+            case OID_ARRAY:
                 if (FORMAT_BINARY == format) {
                     return buffer.readLong();
                 }

src/test/java/io/r2dbc/postgresql/codec/LongCodecUnitTests.java

@@ -21,8 +21,7 @@
 
 import static io.r2dbc.postgresql.client.EncodedParameter.NULL_VALUE;
 import static io.r2dbc.postgresql.client.ParameterAssert.assertThat;
-import static io.r2dbc.postgresql.codec.PostgresqlObjectId.INT8;
-import static io.r2dbc.postgresql.codec.PostgresqlObjectId.VARCHAR;
+import static io.r2dbc.postgresql.codec.PostgresqlObjectId.*;
 import static io.r2dbc.postgresql.message.Format.FORMAT_BINARY;
 import static io.r2dbc.postgresql.message.Format.FORMAT_TEXT;
 import static io.r2dbc.postgresql.util.ByteBufUtils.encode;
@@ -49,6 +48,14 @@ void decode() {
 
         assertThat(codec.decode(TEST.buffer(8).writeLong(100L), dataType, FORMAT_BINARY, Long.class)).isEqualTo(100L);
         assertThat(codec.decode(encode(TEST, "100"), dataType, FORMAT_TEXT, Long.class)).isEqualTo(100L);
+
+        /* According to documentation: "The oid type is currently implemented as an unsigned four-byte integer"
+         * (https://www.postgresql.org/docs/12/datatype-oid.html).
+         * There is no "unsigned four-byte integer" common type in java, so the closest type to hold all possible oid
+         * values is long. 2314556683 is a valid oid for example.
+         */
+        assertThat(codec.decode(encode(TEST, "2314556683"), OID.getObjectId(), FORMAT_TEXT, Long.class))
+            .isEqualTo(2314556683L);
     }
 
     @Test