# Memory

This driver implements read and write access layers of features contained entirely in memory. This is primarily useful as a high performance, and highly malleable working data store. All update options, geometry types, and field types are supported.

There is no way to open an existing Memory datastore. It must be created with CreateDataSource() and populated and used from that handle. When the datastore is closed all contents are freed and destroyed.

The driver does not implement spatial or attribute indexing, so spatial and attribute queries are still evaluated against all features. Fetching features by feature id should be very fast (just an array lookup and feature copy).

## Creation Issues

Any name may be used for a created datasource. There are no datasource or layer creation options supported. Layer names need to be unique, but are not otherwise constrained.

Before GDAL 2.1, feature ids passed to CreateFeature() are preserved unless they exceed 10000000 in which case they will be reset to avoid a requirement for an excessively large and sparse feature array. Starting with GDAL 2.1, sparse IDs can be handled.

New fields can be added or removed to a layer that already has features.