Module Granary_columnar.PersistSource

Persistence for columnar stores via the Store B-tree.

Each columnar table has an allocated Granary_store.Store.tree_id (stored in the catalog's Granary_catalog.Catalog.storage variant). The entire in-memory Col_store.t is serialised via Col_store.encode and stored as a single value under a well-known key within that tree. The B-tree overflow chain transparently handles values up to 1 GiB.

Sourceval save : S.rw S.txn -> S.tree_id -> Col_store.t -> unit Lwt.t

save tx tree_id store serialises store and writes it to the B-tree at tree_id under a reserved key. Must be called within a write transaction.

Sourceval load : _ S.txn -> S.tree_id -> Row.column list -> Col_store.t option Lwt.t

load tx tree_id schema reads a previously persisted columnar store from the B-tree at tree_id. Returns None if no data has been persisted yet (fresh table). Raises Failure on corrupt data. Works with both RO and RW transactions.