MEM -- In Memory datasets

Added in version 3.11.

Driver short name

MEM

Driver built-in by default

This driver is built-in by default

GDAL supports the ability to hold datasets in a temporary in-memory format. This is primarily useful for temporary datasets in scripts or internal to applications. It is not generally of any use to application end-users.

This page documents its vector capabilities. Starting with GDAL 3.11, this driver has been unified with the long-time existing Memory driver to offer both raster and vector capabilities.

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 vector MEM dataset. It must be created with Create(name, 0, 0, 0, GDT_Unknown) and populated and used from that handle. When the dataset 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).

Driver capabilities

Supports Create()

This driver supports the GDALDriver::Create() operation

Supports Georeferencing

This driver supports georeferencing

Creation Issues

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

Sparse IDs can be handled when using CreateFeature().

New fields can be added or removed to a layer that already has features, although the user is responsible for making sure that no OGRFeature instance is accessible outside of the driver before changing the layer definition.

Layer creation options

Layer creation options can be specified in command-line tools using the syntax -lco <NAME>=<VALUE> or by providing the appropriate arguments to GDALDatasetCreateLayer() (C) or Dataset.CreateLayer (Python). The following layer creation options are available:

ADVERTIZE_UTF8=[YES/NO]: Defaults to NO. Whether the layer will contain UTF-8 strings.
FID=<string>: (GDAL >= 3.8) Defaults to empty string. Name of the FID column to create.