litedb-org/LiteDB · error · LiteException

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Error message

This collection has no more space for new indexes

What it means

Thrown by CollectionPage.InsertCollectionIndex when a collection cannot accept another standard index. Two conditions trigger it: the collection already has 255 indexes (the byte slot limit), or the serialized length of the new index entry plus existing entries exceeds P_INDEXES_COUNT — the fixed byte region reserved for index metadata inside the single collection header page. Each CollectionIndex occupies space proportional to its name and expression string.

Solutions

1. Drop unused indexes before creating new ones (db.GetCollection(name).DropIndex(...)).
2. Shorten index names and/or expression strings to fit in the reserved header region.
3. If you genuinely need more than 255 indexes, reconsider the data model — LiteDB collections are capped by design.
4. Audit existing indexes with GetIndexes() before adding more.

Example fix

// before — too many indexes
col.EnsureIndex("idx_256", "$ field256"); // throws

// after — drop unused, then add
col.CreateIndex("idx_256", "$ field256");
// or remove a stale one first:
col.DropIndex("idx_old");

const int MAX_INDEXES = 255;

public void CreateIndexSafely(ILiteCollection<BsonDocument> col, string name, string expr, bool unique)
{
    var existing = col.GetIndexes().Count();
    if (existing >= MAX_INDEXES)
        throw new InvalidOperationException($"Collection '{col.Name}' already has {existing} indexes (max {MAX_INDEXES}). Drop one first.");
    col.CreateIndex(name, BsonExpression.Create(expr), unique);
}

static bool CanAddIndex(ILiteCollection<BsonDocument> col) =>
    col.GetIndexes().Count() < 255;

try
{
    col.EnsureIndex(name, expr);
}
catch (LiteException ex) when (ex.Message.Contains("no more space for new indexes"))
{
    // Drop a stale index or report to the user that the collection is at capacity.
    throw new InvalidOperationException("Collection has reached its index limit (255) or header space is full.", ex);
}

When it happens

Trigger: Calling EnsureIndex / CreateIndex (or db.Execute with CREATE INDEX) on a collection that is at the 255-index hard cap, or whose header page has insufficient free bytes for the new index metadata due to long index names/expressions.

Common situations: Programmatically generating many indexes (e.g. one per dynamic field); using very long index names or complex expression strings that consume the reserved byte budget; accumulating indexes over time without cleanup.

Related errors

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AI-assisted analysis of litedb-org/LiteDB@f906a5f850 (2026-08-13). Data as JSON: /api/errors/3982142c16874766. Report an issue: GitHub.

Appendix: source

Thrown at LiteDB/Engine/Pages/CollectionPage.cs:203

        public VectorIndexMetadata GetVectorIndexMetadata(string name)
        {
            return _vectorIndexes.TryGetValue(name, out var metadata) ? metadata : null;
        }

        /// <summary>
        /// Insert new index inside this collection page
        /// </summary>
        public CollectionIndex InsertCollectionIndex(string name, string expr, bool unique)
        {
            if (_indexes.ContainsKey(name) || _vectorIndexes.ContainsKey(name))
            {
                throw LiteException.IndexAlreadyExist(name);
            }

            var totalLength = this.GetSerializedLength(CollectionIndex.GetLength(name, expr), 0);

            if (_indexes.Count == 255 || totalLength >= P_INDEXES_COUNT) throw new LiteException(0, $"This collection has no more space for new indexes");

            var slot = (byte)(_indexes.Count == 0 ? 0 : (_indexes.Max(x => x.Value.Slot) + 1));

            var index = new CollectionIndex(slot, 0, name, expr, unique);

            _indexes[name] = index;

            this.IsDirty = true;

            return index;
        }

        public (CollectionIndex Index, VectorIndexMetadata Metadata) InsertVectorIndex(string name, string expr, ushort dimensions, VectorDistanceMetric metric)
        {
            if (_indexes.ContainsKey(name) || _vectorIndexes.ContainsKey(name))
            {
                throw LiteException.IndexAlreadyExist(name);
            }

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