Configuration

better_duck_core::config::Config (re-exported as better_duck_core::Config) is a builder that collects DuckDB open-time settings. Pass the finished builder to a *_with_flags constructor. Every setter returns Result<Config>, because DuckDB validates each key/value as it is set — so chain with ?:

use better_duck_core::config::{AccessMode, Config, DefaultNullOrder, DefaultOrder};
use better_duck_core::connection::Connection;

let config = Config::default()
    .access_mode(AccessMode::ReadWrite)?
    .default_order(DefaultOrder::Desc)?
    .default_null_order(DefaultNullOrder::NullsLast)?
    .enable_external_access(true)?
    .enable_object_cache(true)?
    .max_memory("512MB")?
    .threads(2)?
    .custom_user_agent("better-duck-app")?
    .with("custom_setting", "value")?;      // arbitrary key/value escape hatch

let mut conn = Connection::open_in_memory_with_flags(config)?;

Config is Send. It is consumed by the constructor you pass it to.

Typed setters

Automatic, ReadOnly, or ReadWrite.

Default ORDER BY direction: Asc or Desc.

Where NULLs sort: NullsFirst or NullsLast.

Worker-thread count for query execution.

Memory limit, e.g. "512MB", "2GB".

Whether DuckDB may touch the filesystem/network (needed to install extensions, read files). On by default.

Cache parsed objects (e.g. Parquet metadata) between queries.

Autoload known extensions on first use.

Permit loading unsigned extension binaries. Takes no argument.

Appends to the user-agent DuckDB reports (telemetry/diagnostics).

The generic escape hatch

let config = Config::default().with("threads", "4")?.with("preserve_insertion_order", "false")?;

with(key, value) accepts any DuckDB setting name as strings. DuckDB errors on an unknown or invalid setting. An interior NUL in a key or value is rejected as Error::NulError.

open_with_flags internally sets duckdb_api = "rust" for you; you never need to set it.

Discovering available flags at runtime

DuckDB can enumerate its own settings, which Config surfaces as associated functions:

for flag in Config::flags().take(5) {
    println!("{}: {}", flag.name, flag.description);
}

Config::flag_count() -> usize — number of known flags.
Config::flag(index) -> Option<ConfigFlag> — the flag at index, as ConfigFlag { name: String, description: String }.
Config::flags() -> impl Iterator<Item = ConfigFlag> — iterate all of them.

Library version

let v: String = better_duck_core::config::library_version();   // e.g. "v1.5.5"
// also re-exported as better_duck_core::library_version

Returns the linked DuckDB version string — handy for logs and the min_duckdb_version of a loadable extension.

Connecting

Querying

Values & Types

Parameters & Statements

Writing Data

Columnar

Concurrency

Interop

Errors & Extensions

User-Defined Functions

Derives & Helpers

Typed setters

The generic escape hatch

Discovering available flags at runtime

Library version

See also

​Typed setters

​The generic escape hatch

​Discovering available flags at runtime

​Library version

​See also

Typed setters

The generic escape hatch

Discovering available flags at runtime

Library version

See also