Crate Configuration¶

This section contains information on how to configure DataFusion in your Rust project. See the Configuration Settings section for a list of options that control DataFusion’s behavior.

Add latest non published DataFusion dependency¶

DataFusion changes are published to crates.io according to the release schedule

If you would like to test out DataFusion changes which are merged but not yet published, Cargo supports adding dependency directly to GitHub branch:

datafusion = { git = "https://github.com/apache/datafusion", branch = "main"}

Also it works on the package level

datafusion-common = { git = "https://github.com/apache/datafusion", branch = "main", package = "datafusion-common"}

And with features

datafusion = { git = "https://github.com/apache/datafusion", branch = "main", default-features = false, features = ["unicode_expressions"] }

Optimized Configuration¶

For an optimized build several steps are required. First, use the below in your Cargo.toml. It is worth noting that using the settings in the [profile.release] section will significantly increase the build time.

[dependencies]
datafusion = { version = "22.0" }
tokio = { version = "^1.0", features = ["rt-multi-thread"] }
snmalloc-rs = "0.3"

[profile.release]
lto = true
codegen-units = 1

Then, in main.rs. update the memory allocator with the below after your imports:

use datafusion::prelude::*;

#[global_allocator]
static ALLOC: snmalloc_rs::SnMalloc = snmalloc_rs::SnMalloc;

#[tokio::main]
async fn main() -> datafusion::error::Result<()> {
  Ok(())
}

Based on the instruction set architecture you are building on you will want to configure the target-cpu as well, ideally with native or at least avx2.

RUSTFLAGS='-C target-cpu=native' cargo run --release

Enable backtraces¶

By default Datafusion returns errors as a plain message. There is option to enable more verbose details about the error, like error backtrace. To enable a backtrace you need to add Datafusion backtrace feature to your Cargo.toml file:

datafusion = { version = "31.0.0", features = ["backtrace"]}

Set environment variables

RUST_BACKTRACE=1 ./target/debug/datafusion-cli
DataFusion CLI v31.0.0
> select row_numer() over (partition by a order by a) from (select 1 a);
Error during planning: Invalid function 'row_numer'.
Did you mean 'ROW_NUMBER'?

backtrace:    0: std::backtrace_rs::backtrace::libunwind::trace
             at /rustc/5680fa18feaa87f3ff04063800aec256c3d4b4be/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5
   1: std::backtrace_rs::backtrace::trace_unsynchronized
             at /rustc/5680fa18feaa87f3ff04063800aec256c3d4b4be/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2: std::backtrace::Backtrace::create
             at /rustc/5680fa18feaa87f3ff04063800aec256c3d4b4be/library/std/src/backtrace.rs:332:13
   3: std::backtrace::Backtrace::capture
             at /rustc/5680fa18feaa87f3ff04063800aec256c3d4b4be/library/std/src/backtrace.rs:298:9
   4: datafusion_common::error::DataFusionError::get_back_trace
             at /datafusion/datafusion/common/src/error.rs:436:30
   5: datafusion_sql::expr::function::<impl datafusion_sql::planner::SqlToRel<S>>::sql_function_to_expr
   ............

The backtraces are useful when debugging code. If there is a test in datafusion/core/src/physical_planner.rs

#[tokio::test]
async fn test_get_backtrace_for_failed_code() -> Result<()> {
    let ctx = SessionContext::new();

    let sql = "
    select row_numer() over (partition by a order by a) from (select 1 a);
    ";

    let _ = ctx.sql(sql).await?.collect().await?;

    Ok(())
}

To obtain a backtrace:

cargo build --features=backtrace
RUST_BACKTRACE=1 cargo test --features=backtrace --package datafusion --lib -- physical_planner::tests::test_get_backtrace_for_failed_code --exact --nocapture

running 1 test
Error: Plan("Invalid function 'row_numer'.\nDid you mean 'ROW_NUMBER'?\n\nbacktrace:    0: std::backtrace_rs::backtrace::libunwind::trace\n             at /rustc/129f3b9964af4d4a709d1383930ade12dfe7c081/library/std/src/../../backtrace/src/backtrace/libunwind.rs:105:5\n   1: std::backtrace_rs::backtrace::trace_unsynchronized\n...

Note: The backtrace wrapped into systems calls, so some steps on top of the backtrace can be ignored

To show the backtrace in a pretty-printed format use eprintln!("{e}");.

#[tokio::test]
async fn test_get_backtrace_for_failed_code() -> Result<()> {
    let ctx = SessionContext::new();

    let sql = "select row_numer() over (partition by a order by a) from (select 1 a);";

    let _ = match ctx.sql(sql).await {
        Ok(result) => result.show().await?,
        Err(e) => {
            eprintln!("{e}");
        }
    };

    Ok(())
}

Then run the test:

$ RUST_BACKTRACE=1 cargo test --features=backtrace --package datafusion --lib -- physical_planner::tests::test_get_backtrace_for_failed_code --exact --nocapture

running 1 test
Error during planning: Invalid function 'row_numer'.
Did you mean 'ROW_NUMBER'?

backtrace:    0: std::backtrace_rs::backtrace::libunwind::trace
             at /rustc/129f3b9964af4d4a709d1383930ade12dfe7c081/library/std/src/../../backtrace/src/backtrace/libunwind.rs:105:5
   1: std::backtrace_rs::backtrace::trace_unsynchronized
             at /rustc/129f3b9964af4d4a709d1383930ade12dfe7c081/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2: std::backtrace::Backtrace::create
             at /rustc/129f3b9964af4d4a709d1383930ade12dfe7c081/library/std/src/backtrace.rs:331:13
   3: std::backtrace::Backtrace::capture
   ...

Example Usage

DataFusion CLI