[BUG] Empty value in indexed field throws exception

[utech626]

Version
5.05
Framework Version 4.8

Describe the bug
When inserting a record with a Empty String in a indexed field and exception is thrown.

Code to Reproduce
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

using LiteDB;

namespace LiteDBBug
{
public class MyRecord
{
[BsonId]
public int Id { get; set; }
public String Field11 { get; set; }
public String Field22 { get; set; }
public String Field33 { get; set; }
}

class Program
{
	static void Main(string[] args)
	{
		using (LiteDatabase _db = new LiteDatabase(@"MyData.db"))
		{
			var _col = _db.GetCollection<MyRecord>("records");

			_col.EnsureIndex(x => x.Field22, unique: false);

			var _rec1 = new MyRecord
			{
				Field11 = "value1",
				Field22 = "value2",
				Field33 = "value3"
			};
			//
			//	**Success** 
			//
			_col.Insert(_rec1);

			var _rec2 = new MyRecord
			{
				Field11 = "value1",
				Field22 = "",
				Field33 = "value3"
			};
			//
			//	**null reference exception**
			//
			_col.Insert(_rec2);
		}
	}
}

}

Expected behavior
Record should be stored into database

Screenshots/Stacktrace
System.NullReferenceException: Object reference not set to an instance of an object.
at LiteDB.BsonValue.GetHashCode()
at System.Collections.Generic.GenericEqualityComparer1.GetHashCode(T obj) at System.Linq.Set1.InternalGetHashCode(TElement value)
at System.Linq.Set1.Find(TElement value, Boolean add) at System.Linq.Enumerable.<DistinctIterator>d__641.MoveNext()
at LiteDB.Engine.LiteEngine.InsertDocument(Snapshot snapshot, BsonDocument doc, BsonAutoId autoId, IndexService indexer, DataService data)
at LiteDB.Engine.LiteEngine.<>c__DisplayClass7_0.b__0(TransactionService transaction)
at LiteDB.Engine.LiteEngine.AutoTransaction[T](Func2 fn) at LiteDB.Engine.LiteEngine.Insert(String collection, IEnumerable1 docs, BsonAutoId autoId)
at LiteDB.LiteCollection`1.Insert(T entity)
at LiteDBBug.Program.Main(String[] args) in C:\TFSSrc\Test\LiteDBBug\LiteDBBug\Program.cs:line 50

[seertenedos]

that was the cause of my issue and has been fixed but no release made yet.
#1592 (comment)

[riksking]

I got same error NRE.

My case

public static void WriteToExistDb(IEnumerable<object> chunk, string pathToDb, string tableName)
        {
            using (var testDb = new LiteDatabase(pathToDb))
            {
                var col = testDb.GetCollection<object>(tableName);
                foreach (var o in chunk)
                {
                    col.Insert(o);
                }
                //col.InsertBulk(chunk);
            }
        }

Call method like this

var words = new List<string>(chunk);

WriteToExistDb(words, _pathToDb, _wordsTableName);

end got error

System.NullReferenceException: 'Object reference not set to an instance of an object.'
at LiteDB.Engine.LiteEngine.InsertDocument(Snapshot snapshot, BsonDocument doc, BsonAutoId autoId, IndexService indexer, DataService data) in ~\LiteDB-master\LiteDB\Engine\Engine\Insert.cs:line 48
at LiteDB.Engine.LiteEngine.<>c__DisplayClass7_0.b__0(TransactionService transaction) in ~\LiteDB-master\LiteDB\Engine\Engine\Insert.cs:line 33
at LiteDB.Engine.LiteEngine.AutoTransaction[T](Func2 fn) in ~\LiteDB-master\LiteDB\Engine\Engine\Transaction.cs:line 101 at LiteDB.Engine.LiteEngine.Insert(String collection, IEnumerable1 docs, BsonAutoId autoId) in ~\LiteDB-master\LiteDB\Engine\Engine\Insert.cs:line 20
at LiteDB.LiteCollection1.Insert(T entity) in ~\LiteDB-master\LiteDB\Client\Database\Collections\Insert.cs:line 20 at Avtomat.Utils.LiteDbDataAccess.WriteToExistDb(IEnumerable1 chunk, String pathToDb, String tableName)

As you can see, I was build from master.

I was debug LiteDb and find that in this place

I get null in BsonDocument object.

next steps in debugger

[riksking]

With InsertBulk, I got similar error.

System.NullReferenceException: 'Object reference not set to an instance of an object.'
at LiteDB.Engine.LiteEngine.InsertDocument(Snapshot snapshot, BsonDocument doc, BsonAutoId autoId, IndexService indexer, DataService data) in ~\LiteDB-master\LiteDB\Engine\Engine\Insert.cs:line 48
at LiteDB.Engine.LiteEngine.<>c__DisplayClass7_0.b__0(TransactionService transaction) in ~\LiteDB-master\LiteDB\Engine\Engine\Insert.cs:line 33
at LiteDB.Engine.LiteEngine.AutoTransaction[T](Func2 fn) in ~\LiteDB-master\LiteDB\Engine\Engine\Transaction.cs:line 101 at LiteDB.Engine.LiteEngine.Insert(String collection, IEnumerable1 docs, BsonAutoId autoId) in ~\LiteDB-master\LiteDB\Engine\Engine\Insert.cs:line 20
at LiteDB.LiteCollection1.InsertBulk(IEnumerable1 entities, Int32 batchSize) in ~\LiteDB-master\LiteDB\Client\Database\Collections\Insert.cs:line 66
at Avtomat.Utils.LiteDbDataAccess.WriteToExistDb(IEnumerable`1 chunk, String pathToDb, String tableName)

[lbnascimento]

@riksking Your issue is very different.

First of all, you're opening your collection with GetCollection<object>. While this is technically supported, it is not recommended: the point of GetCollection<T> is that you set T to the C# class you're trying to store (Person, Customer, Account...) and the mapper converts your class to a BsonDocument upon insertion and converts it back to T upon retrieval.

The error is happening because you're trying to store strings in your LiteCollection<object>, and the mapper doesn't know how to map a string to a BsonDocument.

I'm going to close this issue, since the original problem is already fixed in the master. If you have any questions, please open another issue.