ETS (Erlang Term Storage) storage backend for Zarr arrays.

Stores chunks and metadata in ETS tables, providing fast in-memory storage with multi-process access capabilities. Unlike the Memory backend which uses an Agent, ETS tables are shared memory accessible by multiple processes.

Configuration

Optional configuration:

• :table_name - ETS table name (optional, auto-generated if not provided)
• :named_table - Use named table (optional, default: true)
• :table_type - Table type (optional, default: :set)
• :access - Access level (optional, default: :public)
• :heir - Heir process for table (optional, default: :none)

Dependencies

No external dependencies - ETS is built into Erlang/OTP.

Example

# Register the ETS backend
:ok = ExZarr.Storage.Registry.register(ExZarr.Storage.Backend.ETS)

# Create array with ETS storage
{:ok, array} = ExZarr.create(
  shape: {1000, 1000},
  chunks: {100, 100},
  dtype: :float64,
  storage: :ets,
  table_name: :my_array_data
)

# Write and read data
ExZarr.Array.set_slice(array, data, start: {0, 0}, stop: {100, 100})
{:ok, result} = ExZarr.Array.get_slice(array, start: {0, 0}, stop: {100, 100})

Table Types

• :set - One value per unique key (default)
• :ordered_set - Sorted set (slower writes, faster ordered access)
• :bag - Multiple values per key allowed
• :duplicate_bag - Multiple identical values per key allowed

Access Levels

• :public - Any process can read/write (default)
• :protected - Any process can read, only owner can write
• :private - Only owner process can read/write

Named Tables

Named tables can be accessed by name from any process:

# Create with named table
{:ok, array} = ExZarr.create(
  storage: :ets,
  table_name: :shared_array,
  named_table: true,
  access: :public
)

# Access from different process
:ets.lookup(:shared_array, {:chunk, {0}})

Table Ownership

ETS tables are owned by the creating process by default. When that process dies, the table is deleted. Use the :heir option to transfer ownership:

{:ok, array} = ExZarr.create(
  storage: :ets,
  heir: self()
)

Performance Characteristics

• Very fast: Direct memory access, no message passing
• Concurrent: Multiple readers, single writer
• Scalable: Efficient for large datasets
• Non-persistent: Data lost on table deletion

Use Cases

• Multi-process data sharing
• High-performance caching
• Concurrent read workloads
• Inter-process communication
• When you need faster access than Agent/GenServer

Comparison with Memory Backend

Error Handling

ETS errors are returned as {:error, reason} tuples. Common errors:

• :table_not_found - Table doesn't exist
• :not_found - Key doesn't exist
• :access_denied - Permission error