Snapshot
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One exact retained read-only revision.
A snapshot has no mutation, transaction, connection, checkpoint, synchronization or conflict API. Reads fetch and authenticate pages on demand, as on a writable database. Concepts explains revisions and retention.
Operations
Section titled “Operations”Close the snapshot. Repeated calls have the same effect.
This never closes your Remote.
Run one statement with read execution intent against the pinned revision. Bounded by the snapshot connection’s maximum_rows.
status
Section titled “status”Return a typed SnapshotStatus of snapshot-owned state only.
Which engine answers a read
Section titled “Which engine answers a read”Use query_with_engine to choose the engine. Default reads use SQLite. Select DuckDB with QueryEngine::DuckDb. Only these two engines are supported. An invalid selection fails instead of selecting the default.
The native SDK loads DuckDB when you first request an analytical read. OpenOptions.analytical_engine selects the library for one database or snapshot. It takes priority over POTLUCKDB_DUCKDB_LIBRARY, package discovery where available, and the platform’s library search. An explicit selection, including an empty string, never uses a fallback.
See analytics engine installation for your platform. Without an implicit library, the read fails with analytical_engine_unavailable. If an explicit library cannot load, the read reports its loader error.
Enable the existing dependency’s analytics feature: potluckdb = { version = "...", features = ["analytics"] }. Its build script downloads this platform’s engine archive, verifies the archive against the pinned SHA-256 and embeds the extracted library path at build time. No environment setting is needed.
DuckDB rejects the named binding forms :name and @name. Both engines accept $name and positional ? bindings. Booleans bind as INTEGER 0/1 on both. IS therefore asks the same question on either engine, unlike a DuckDB BOOLEAN binding.
Bare table names read the database’s main schema. Qualifiers such as temp. are not seen. For table names ending in .csv, .parquet or .json, use potluckdb_scan('name'). DuckDB otherwise treats those names as files.
NUMERIC and DECIMAL columns read as doubles. A value that a double cannot hold exactly fails the query instead of arriving rounded.
A storage failure during an analytical read reports analytical_engine_error, with the failure named in its message. The same query succeeds when storage answers.
Either engine runs one read per query_with_engine. The analytical engine reads a snapshot of the same data through its own in-memory database. A statement sent to this engine therefore cannot change the stored data.
An engine can remain for the session’s lifetime. Changing its settings or catalog would change later queries on that session. Only SELECT and EXPLAIN are accepted. CREATE, SET, ATTACH, PREPARE and EXPLAIN ANALYZE are refused. EXPLAIN ANALYZE is refused because it executes the explained statement.
Use execute for writes to the stored data.
Specific to this language
Section titled “Specific to this language”query_with_engine
Section titled “query_with_engine”Rust has neither default arguments nor overloading, so the query engine is a second function.