datafusion-arrowmetal 0.4.1

//! ArrowMetal inside Apache DataFusion: a physical optimizer rule and a custom `ExecutionPlan`.
//!
//! [`ArrowMetalRule`] walks DataFusion's optimized physical plan and replaces the nodes ArrowMetal
//! can run with the same answer by a [`MetalExec`]: `SortExec` (with or without `fetch`), a hash
//! `AggregateExec` over column keys with `sum`/`min`/`max`/`count`/`avg` or none (DISTINCT),
//! a `FilterExec` whose predicate translates, and a `HashJoinExec` (inner, left, right) on equal
//! int32, int64 or Utf8 keys. `MetalExec` collects its input's partitions, runs the operation
//! through ArrowMetal's plan runner on the GPU, and emits `RecordBatch`es with the schema
//! DataFusion expects. Anything it does not support is left unchanged, and the reason is recorded
//! in the rule's [`Report`].
//!
//! The default config ([`ArrowMetalConfig::default`]) takes full sorts from 250,000 input rows,
//! aggregates where the measured table (`src/agg_table.rs`) takes their shape (a replaced
//! aggregate estimates its group count from a sample of its keys when it runs and either runs on
//! ArrowMetal or hands the node back to DataFusion's own operators, [`AggregateChoice`]), and
//! joins where the measured join table (`src/join_table.rs`) takes them ([`JoinChoice`]). Top-k
//! and filters are left.
//!
//! ```no_run
//! # async fn f() -> datafusion::error::Result<()> {
//! use datafusion::prelude::*;
//! use datafusion_arrowmetal::{session_context, ArrowMetalConfig, ArrowMetalRule};
//!
//! // The measured take-list; `ArrowMetalConfig::all()` takes every shape the rule can translate.
//! let rule = ArrowMetalRule::new(ArrowMetalConfig::default());
//! let ctx = session_context(SessionConfig::new(), rule.clone());
//! // register tables, run SQL ...
//! for d in rule.report().decisions() { println!("{d}"); }
//! # Ok(()) }
//! ```

#![warn(missing_docs)]

mod agg_table;
mod choice;
mod exec;
mod gpu;
mod join_table;
mod probe;
mod rule;
mod translate;

pub use exec::{AggKind, AggSpec, JoinHow, MetalExec, MetalOp, SortKey};
pub use probe::GroupEstimate;
pub use rule::{AggregateChoice, ArrowMetalConfig, ArrowMetalRule, Decision, GroupChoice, JoinChoice, Report};

use std::sync::Arc;

use datafusion::execution::session_state::SessionStateBuilder;
use datafusion::physical_optimizer::optimizer::PhysicalOptimizer;
use datafusion::physical_optimizer::PhysicalOptimizerRule;
use datafusion::prelude::{SessionConfig, SessionContext};

/// DataFusion's default physical optimizer rules with `rule` inserted before the last two:
/// the post-optimization `FilterPushdown` (which wires dynamic filters to the operators that own
/// them, so a node replaced after it would leave a dynamic filter nobody updates) and
/// `SanityCheckPlan` (so the rewritten plan is still checked for distribution and ordering).
pub fn physical_optimizer_rules(
    rule: ArrowMetalRule,
) -> Vec<Arc<dyn PhysicalOptimizerRule + Send + Sync>> {
    let mut rules = PhysicalOptimizer::new().rules;
    let at = rules
        .iter()
        .rposition(|r| r.name() == "SanityCheckPlan")
        .unwrap_or(rules.len());
    // The post-optimization FilterPushdown sits just before SanityCheckPlan in 55.1.0.
    let at = if at > 0 && rules[at - 1].name().starts_with("FilterPushdown") { at - 1 } else { at };
    rules.insert(at, Arc::new(rule));
    rules
}

/// Registers `rule` on a `SessionStateBuilder` (see [`physical_optimizer_rules`] for where).
pub fn with_arrowmetal(builder: SessionStateBuilder, rule: ArrowMetalRule) -> SessionStateBuilder {
    builder.with_physical_optimizer_rules(physical_optimizer_rules(rule))
}

/// A `SessionContext` with DataFusion's defaults plus `rule`.
pub fn session_context(config: SessionConfig, rule: ArrowMetalRule) -> SessionContext {
    let state = with_arrowmetal(
        SessionStateBuilder::new().with_config(config).with_default_features(),
        rule,
    )
    .build();
    SessionContext::new_with_state(state)
}