litedb-org/LiteDB · error · LiteException

0

0

Error message

System collection '{name}' are not registered as system collection

What it means

Thrown by GetSystemCollection when a name starting with '$' is queried but is not found in the internal system-collection registry. LiteDB registers built-in system collections (like $cols, $sequences, etc.) at engine startup; any unregistered '$'-prefixed name triggers this. This is a LiteException (code 0) from an internal method.

Source

Thrown at LiteDB/Engine/Engine/SystemCollections.cs:19

using System;
using System.Collections.Generic;
using static LiteDB.Constants;

namespace LiteDB.Engine
{
    public partial class LiteEngine
    {
        /// <summary>
        /// Get registered system collection
        /// </summary>
        internal SystemCollection GetSystemCollection(string name)
        {
            if (_systemCollections.TryGetValue(name, out var sys))
            {
                return sys;
            }

            throw new LiteException(0, $"System collection '{name}' are not registered as system collection");
        }

        /// <summary>
        /// Register a new system collection that can be used in query for input/output data
        /// Collection name must starts with $
        /// </summary>
        internal void RegisterSystemCollection(SystemCollection systemCollection)
        {
            if (systemCollection == null) throw new ArgumentNullException(nameof(systemCollection));

            _systemCollections[systemCollection.Name] = systemCollection;
        }

        /// <summary>
        /// Register a new system collection that can be used in query for input data
        /// Collection name must starts with $
        /// </summary>
        internal void RegisterSystemCollection(string collectionName, Func<IEnumerable<BsonDocument>> factory)

View on GitHub (pinned to f906a5f850)

Solutions

1. Check the exact system collection name spelling against the LiteDB version's documentation (e.g., $cols, $sequences, $indexes).
2. If you intended a user collection, rename it to not start with '$'.
3. If you need a custom system collection, register it via RegisterSystemCollection before querying.

Example fix

// before
var result = db.GetCollection("$coll").Query().ToList(); // typo
// after
var result = db.GetCollection("$cols").Query().ToList();

// Validate system collection name before querying
var known = new[] { "$cols", "$sequences", "$indexes", "$database", "$transactions", "$snapshots" };
if (name.StartsWith("$") && !known.Contains(name))
    throw new InvalidOperationException($"'{name}' is not a registered system collection.");

static bool IsRegisteredSystemCollection(string name, ISet<string> registered) => registered.Contains(name);

When it happens

Trigger: Querying a collection whose name starts with '$' but is not a recognized system collection (e.g., a typo like `$coll` instead of `$cols`, or a custom name that was never registered via RegisterSystemCollection).

Common situations: Typo in a system collection name in a query string. Attempting to query a user-defined system collection that was never registered. Version differences where a system collection name changed or was removed. Code referencing '$'-prefixed collection names for user data by mistake.

Related errors

• 0
• 0
• 0
• 0
• 0

AI-assisted analysis of litedb-org/LiteDB@f906a5f850 (2026-08-13). Data as JSON: /api/errors/e51544afa3397e79. Report an issue: GitHub.