Snapshot

Java and Kotlin: also in Python · Node · Go · Rust · Swift · Dart · .NET · C++ · Objective-C

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.

At a glance

Read

• query(): Run one statement with read execution intent against the pinned revision.
• status(): Return a typed SnapshotStatus of snapshot-owned state only.

Close

• close(): Close the snapshot.

Read

query

Run one statement with read execution intent against the pinned revision. Bounded by the snapshot connection’s maximumRows.

status

Return a typed SnapshotStatus of snapshot-owned state only.

Close

close

Close the snapshot. Repeated calls have the same effect.

This never closes your Remote.

Which engine answers a read

Use query 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.Builder.analyticalEngine 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.

The analytics engine page lists each platform’s library URL and SHA-256 digest.

1. Download the library for your platform.
2. Verify its digest.
3. Name the library in this language’s open option.

OpenOptions options = OpenOptions.builder().analyticalEngine("/opt/potluckdb/lib/libduckdb.so").build();

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. 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.