JAVA-1171: Allowing query documents to exceed the maximum document size by 16K, so that, for example, the findAndModify command can be used to upsert a 16M document. Without this headroom, the additional space taken by the surrounding command document would push it over 16M, and the driver would through an exception. 16K was chosen as the value because it matches the constant used in the server code base.

Author: jyemin

src/main/com/mongodb/DBCollectionImpl.java

@@ -46,6 +46,11 @@
 
 @SuppressWarnings("deprecation")
 class DBCollectionImpl extends DBCollection {
+
+    // Add an extra 16K to the maximum allowed size of a query document, so that, for example,
+    // a 16M document can be upserted via findAndModify
+    private static final int QUERY_DOCUMENT_HEADROOM = 16 * 1024;
+
     private final DBApiLayer db;
     private final String namespace;
 
@@ -73,7 +78,8 @@ QueryResultIterator find(DBObject ref, DBObject fields, int numToSkip, int batch
             trace("find: " + namespace + " " + JSON.serialize(ref));
         }
 
-        OutMessage query = OutMessage.query(this, options, numToSkip, chooseBatchSize(batchSize, limit, 0), ref, fields, readPref, encoder);
+        OutMessage query = OutMessage.query(this, options, numToSkip, chooseBatchSize(batchSize, limit, 0), ref, fields, readPref,
+                                            encoder, db.getMongo().getMaxBsonObjectSize() + QUERY_DOCUMENT_HEADROOM);
 
         Response res = db.getConnector().call(_db, this, query, null, 2, readPref, decoder);
 

src/test/com/mongodb/DBCollectionTest.java

@@ -506,6 +506,15 @@ public void testFindAndRemoveTimeout() {
         }
     }
 
+    @Test
+    public void testFindAndReplaceA16MDocument() {
+        BasicDBObject documentWithJustId = new BasicDBObject("_id", 42);
+        DBObject foundDocument = collection.findAndModify(documentWithJustId, new BasicDBObject("_id", 1), null, false,
+                                                          new BasicDBObject("_id", 42).append("b", new byte[16 * 1024 * 1024 - 30]), true,
+                                                          true);
+        assertEquals(documentWithJustId, foundDocument);
+    }
+
     @Test
     public void testWriteConcernExceptionOnInsert() throws UnknownHostException {
         assumeTrue(isReplicaSet(getMongoClient()));