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#![doc(
html_logo_url = "https://raw.githubusercontent.com/apache/datafusion/19fe44cf2f30cbdd63d4a4f52c74055163c6cc38/docs/logos/standalone_logo/logo_original.svg",
html_favicon_url = "https://raw.githubusercontent.com/apache/datafusion/19fe44cf2f30cbdd63d4a4f52c74055163c6cc38/docs/logos/standalone_logo/logo_original.svg"
)]
#![cfg_attr(docsrs, feature(doc_cfg))]
// Make sure fast / cheap clones on Arc are explicit:
// https://github.com/apache/datafusion/issues/11143
//
// Eliminate unnecessary function calls(some may be not cheap) due to `xxx_or`
// for performance. Also avoid abusing `xxx_or_else` for readability:
// https://github.com/apache/datafusion/issues/15802
#![cfg_attr(
not(test),
deny(
clippy::clone_on_ref_ptr,
clippy::or_fun_call,
clippy::unnecessary_lazy_evaluations
)
)]
#![warn(missing_docs, clippy::needless_borrow)]
//! [DataFusion] is an extensible query engine written in Rust that
//! uses [Apache Arrow] as its in-memory format. DataFusion's target users are
//! developers building fast and feature rich database and analytic systems,
//! customized to particular workloads. Please see the [DataFusion website] for
//! additional documentation, [use cases] and examples.
//!
//! "Out of the box," DataFusion offers [SQL] and [`Dataframe`] APIs,
//! excellent [performance], built-in support for CSV, Parquet, JSON, and Avro,
//! extensive customization, and a great community.
//! [Python Bindings] are also available.
//!
//! DataFusion features a full query planner, a columnar, streaming, multi-threaded,
//! vectorized execution engine, and partitioned data sources. You can
//! customize DataFusion at almost all points including additional data sources,
//! query languages, functions, custom operators and more.
//! See the [Architecture] section below for more details.
//!
//! [DataFusion]: https://datafusion.apache.org/
//! [DataFusion website]: https://datafusion.apache.org
//! [Apache Arrow]: https://arrow.apache.org
//! [use cases]: https://datafusion.apache.org/user-guide/introduction.html#use-cases
//! [SQL]: https://datafusion.apache.org/user-guide/sql/index.html
//! [`DataFrame`]: dataframe::DataFrame
//! [performance]: https://benchmark.clickhouse.com/
//! [Python Bindings]: https://github.com/apache/datafusion-python
//! [Architecture]: #architecture
//!
//! # Examples
//!
//! The main entry point for interacting with DataFusion is the
//! [`SessionContext`]. [`Expr`]s represent expressions such as `a + b`.
//!
//! [`SessionContext`]: execution::context::SessionContext
//!
//! ## DataFrame
//!
//! To execute a query against data stored
//! in a CSV file using a [`DataFrame`]:
//!
//! ```rust
//! # use datafusion::prelude::*;
//! # use datafusion::error::Result;
//! # use datafusion::functions_aggregate::expr_fn::min;
//! # use datafusion::arrow::array::RecordBatch;
//!
//! # #[tokio::main]
//! # async fn main() -> Result<()> {
//! let ctx = SessionContext::new();
//!
//! // create the dataframe
//! let df = ctx
//! .read_csv("tests/data/example.csv", CsvReadOptions::new())
//! .await?;
//!
//! // create a plan
//! let df = df
//! .filter(col("a").lt_eq(col("b")))?
//! .aggregate(vec![col("a")], vec![min(col("b"))])?
//! .limit(0, Some(100))?;
//!
//! // execute the plan
//! let results: Vec<RecordBatch> = df.collect().await?;
//!
//! // format the results
//! let pretty_results =
//! arrow::util::pretty::pretty_format_batches(&results)?.to_string();
//!
//! let expected = vec![
//! "+---+----------------+",
//! "| a | min(?table?.b) |",
//! "+---+----------------+",
//! "| 1 | 2 |",
//! "+---+----------------+",
//! ];
//!
//! assert_eq!(pretty_results.trim().lines().collect::<Vec<_>>(), expected);
//! # Ok(())
//! # }
//! ```
//!
//! ## SQL
//!
//! To execute a query against a CSV file using [SQL]:
//!
//! ```
//! # use datafusion::prelude::*;
//! # use datafusion::error::Result;
//! # use datafusion::arrow::array::RecordBatch;
//!
//! # #[tokio::main]
//! # async fn main() -> Result<()> {
//! let ctx = SessionContext::new();
//!
//! ctx.register_csv("example", "tests/data/example.csv", CsvReadOptions::new())
//! .await?;
//!
//! // create a plan
//! let df = ctx
//! .sql("SELECT a, MIN(b) FROM example WHERE a <= b GROUP BY a LIMIT 100")
//! .await?;
//!
//! // execute the plan
//! let results: Vec<RecordBatch> = df.collect().await?;
//!
//! // format the results
//! let pretty_results =
//! arrow::util::pretty::pretty_format_batches(&results)?.to_string();
//!
//! let expected = vec![
//! "+---+----------------+",
//! "| a | min(example.b) |",
//! "+---+----------------+",
//! "| 1 | 2 |",
//! "+---+----------------+",
//! ];
//!
//! assert_eq!(pretty_results.trim().lines().collect::<Vec<_>>(), expected);
//! # Ok(())
//! # }
//! ```
//!
//! ## More Examples
//!
//! There are many additional annotated examples of using DataFusion in the [datafusion-examples] directory.
//!
//! [datafusion-examples]: https://github.com/apache/datafusion/tree/main/datafusion-examples
//!
//! # Architecture
//!
//! <!-- NOTE: The goal of this section is to provide a high level
//! overview of how DataFusion is organized and then link to other
//! sections of the docs with more details -->
//!
//! You can find a formal description of DataFusion's architecture in our
//! [SIGMOD 2024 Paper].
//!
//! [SIGMOD 2024 Paper]: https://dl.acm.org/doi/10.1145/3626246.3653368
//!
//! ## Design Goals
//! DataFusion's Architecture Goals are:
//!
//! 1. Work “out of the box”: Provide a very fast, world class query engine with
//! minimal setup or required configuration.
//!
//! 2. Customizable everything: All behavior should be customizable by
//! implementing traits.
//!
//! 3. Architecturally boring 🥱: Follow industrial best practice rather than
//! trying cutting edge, but unproven, techniques.
//!
//! With these principles, users start with a basic, high-performance engine
//! and specialize it over time to suit their needs and available engineering
//! capacity.
//!
//! ## Overview Presentations
//!
//! The following presentations offer high level overviews of the
//! different components and how they interact together.
//!
//! - [Apr 2023]: The Apache DataFusion Architecture talks
//! - _Query Engine_: [recording](https://youtu.be/NVKujPxwSBA) and [slides](https://docs.google.com/presentation/d/1D3GDVas-8y0sA4c8EOgdCvEjVND4s2E7I6zfs67Y4j8/edit#slide=id.p)
//! - _Logical Plan and Expressions_: [recording](https://youtu.be/EzZTLiSJnhY) and [slides](https://docs.google.com/presentation/d/1ypylM3-w60kVDW7Q6S99AHzvlBgciTdjsAfqNP85K30)
//! - _Physical Plan and Execution_: [recording](https://youtu.be/2jkWU3_w6z0) and [slides](https://docs.google.com/presentation/d/1cA2WQJ2qg6tx6y4Wf8FH2WVSm9JQ5UgmBWATHdik0hg)
//! - [July 2022]: DataFusion and Arrow: Supercharge Your Data Analytical Tool with a Rusty Query Engine: [recording](https://www.youtube.com/watch?v=Rii1VTn3seQ) and [slides](https://docs.google.com/presentation/d/1q1bPibvu64k2b7LPi7Yyb0k3gA1BiUYiUbEklqW1Ckc/view#slide=id.g11054eeab4c_0_1165)
//! - [March 2021]: The DataFusion architecture is described in _Query Engine Design and the Rust-Based DataFusion in Apache Arrow_: [recording](https://www.youtube.com/watch?v=K6eCAVEk4kU) (DataFusion content starts [~ 15 minutes in](https://www.youtube.com/watch?v=K6eCAVEk4kU&t=875s)) and [slides](https://www.slideshare.net/influxdata/influxdb-iox-tech-talks-query-engine-design-and-the-rustbased-datafusion-in-apache-arrow-244161934)
//! - [February 2021]: How DataFusion is used within the Ballista Project is described in _Ballista: Distributed Compute with Rust and Apache Arrow_: [recording](https://www.youtube.com/watch?v=ZZHQaOap9pQ)
//!
//! ## Customization and Extension
//!
//! DataFusion is designed to be highly extensible, so you can
//! start with a working, full featured engine, and then
//! specialize any behavior for your use case. For example,
//! some projects may add custom [`ExecutionPlan`] operators, or create their own
//! query language that directly creates [`LogicalPlan`] rather than using the
//! built in SQL planner, [`SqlToRel`].
//!
//! In order to achieve this, DataFusion supports extension at many points:
//!
//! * read from any datasource ([`TableProvider`])
//! * define your own catalogs, schemas, and table lists ([`catalog`] and [`CatalogProvider`])
//! * build your own query language or plans ([`LogicalPlanBuilder`])
//! * declare and use user-defined functions ([`ScalarUDF`], and [`AggregateUDF`], [`WindowUDF`])
//! * add custom plan rewrite passes ([`AnalyzerRule`], [`OptimizerRule`] and [`PhysicalOptimizerRule`])
//! * extend the planner to use user-defined logical and physical nodes ([`QueryPlanner`])
//!
//! You can find examples of each of them in the [datafusion-examples] directory.
//!
//! [`TableProvider`]: crate::datasource::TableProvider
//! [`CatalogProvider`]: crate::catalog::CatalogProvider
//! [`LogicalPlanBuilder`]: datafusion_expr::logical_plan::builder::LogicalPlanBuilder
//! [`ScalarUDF`]: crate::logical_expr::ScalarUDF
//! [`AggregateUDF`]: crate::logical_expr::AggregateUDF
//! [`WindowUDF`]: crate::logical_expr::WindowUDF
//! [`QueryPlanner`]: execution::context::QueryPlanner
//! [`OptimizerRule`]: datafusion_optimizer::optimizer::OptimizerRule
//! [`AnalyzerRule`]: datafusion_optimizer::analyzer::AnalyzerRule
//! [`PhysicalOptimizerRule`]: datafusion_physical_optimizer::PhysicalOptimizerRule
//!
//! ## Query Planning and Execution Overview
//!
//! ### SQL
//!
//! ```text
//! Parsed with SqlToRel creates
//! sqlparser initial plan
//! ┌───────────────┐ ┌─────────┐ ┌─────────────┐
//! │ SELECT * │ │Query { │ │Project │
//! │ FROM ... │──────────▶│.. │────────────▶│ TableScan │
//! │ │ │} │ │ ... │
//! └───────────────┘ └─────────┘ └─────────────┘
//!
//! SQL String sqlparser LogicalPlan
//! AST nodes
//! ```
//!
//! 1. The query string is parsed to an Abstract Syntax Tree (AST)
//! [`Statement`] using [sqlparser].
//!
//! 2. The AST is converted to a [`LogicalPlan`] and logical expressions
//! [`Expr`]s to compute the desired result by [`SqlToRel`]. This phase
//! also includes name and type resolution ("binding").
//!
//! [`Statement`]: https://docs.rs/sqlparser/latest/sqlparser/ast/enum.Statement.html
//!
//! ### DataFrame
//!
//! When executing plans using the [`DataFrame`] API, the process is
//! identical as with SQL, except the DataFrame API builds the
//! [`LogicalPlan`] directly using [`LogicalPlanBuilder`]. Systems
//! that have their own custom query languages typically also build
//! [`LogicalPlan`] directly.
//!
//! ### Planning
//!
//! ```text
//! AnalyzerRules and PhysicalPlanner PhysicalOptimizerRules
//! OptimizerRules creates ExecutionPlan improve performance
//! rewrite plan
//! ┌─────────────┐ ┌─────────────┐ ┌─────────────────┐ ┌─────────────────┐
//! │Project │ │Project(x, y)│ │ProjectExec │ │ProjectExec │
//! │ TableScan │──...──▶│ TableScan │─────▶│ ... │──...──▶│ ... │
//! │ ... │ │ ... │ │ DataSourceExec│ │ DataSourceExec│
//! └─────────────┘ └─────────────┘ └─────────────────┘ └─────────────────┘
//!
//! LogicalPlan LogicalPlan ExecutionPlan ExecutionPlan
//! ```
//!
//! To process large datasets with many rows as efficiently as
//! possible, significant effort is spent planning and
//! optimizing, in the following manner:
//!
//! 1. The [`LogicalPlan`] is checked and rewritten to enforce
//! semantic rules, such as type coercion, by [`AnalyzerRule`]s
//!
//! 2. The [`LogicalPlan`] is rewritten by [`OptimizerRule`]s, such as
//! projection and filter pushdown, to improve its efficiency.
//!
//! 3. The [`LogicalPlan`] is converted to an [`ExecutionPlan`] by a
//! [`PhysicalPlanner`]
//!
//! 4. The [`ExecutionPlan`] is rewritten by
//! [`PhysicalOptimizerRule`]s, such as sort and join selection, to
//! improve its efficiency.
//!
//! ## Data Sources
//!
//! ```text
//! Planning │
//! requests │ TableProvider::scan
//! information │ creates an
//! such as schema │ ExecutionPlan
//! │
//! ▼
//! ┌─────────────────────────┐ ┌───────────────┐
//! │ │ │ │
//! │impl TableProvider │────────▶│DataSourceExec │
//! │ │ │ │
//! └─────────────────────────┘ └───────────────┘
//! TableProvider
//! (built in or user provided) ExecutionPlan
//! ```
//!
//! A [`TableProvider`] provides information for planning and
//! an [`ExecutionPlan`] for execution. DataFusion includes two built-in
//! table providers that support common file formats and require no runtime services,
//! [`ListingTable`] and [`MemTable`]. You can add support for any other data
//! source and/or file formats by implementing the [`TableProvider`] trait.
//!
//! See also:
//!
//! 1. [`ListingTable`]: Reads data from one or more Parquet, JSON, CSV, or AVRO
//! files in one or more local or remote directories. Supports HIVE style
//! partitioning, optional compression, directly reading from remote
//! object store, file metadata caching, and more.
//!
//! 2. [`MemTable`]: Reads data from in memory [`RecordBatch`]es.
//!
//! 3. [`StreamingTable`]: Reads data from potentially unbounded inputs.
//!
//! [`ListingTable`]: crate::datasource::listing::ListingTable
//! [`MemTable`]: crate::datasource::memory::MemTable
//! [`StreamingTable`]: crate::catalog::streaming::StreamingTable
//!
//! ## Plan Representations
//!
//! ### Logical Plans
//! Logical planning yields [`LogicalPlan`] nodes and [`Expr`]
//! representing expressions which are [`Schema`] aware and represent statements
//! independent of how they are physically executed.
//! A [`LogicalPlan`] is a Directed Acyclic Graph (DAG) of other
//! [`LogicalPlan`]s, each potentially containing embedded [`Expr`]s.
//!
//! [`LogicalPlan`]s can be rewritten with [`TreeNode`] API, see the
//! [`tree_node module`] for more details.
//!
//! [`Expr`]s can also be rewritten with [`TreeNode`] API and simplified using
//! [`ExprSimplifier`]. Examples of working with and executing [`Expr`]s can be
//! found in the [`expr_api`.rs] example
//!
//! [`TreeNode`]: datafusion_common::tree_node::TreeNode
//! [`tree_node module`]: datafusion_expr::logical_plan::tree_node
//! [`ExprSimplifier`]: crate::optimizer::simplify_expressions::ExprSimplifier
//! [`expr_api`.rs]: https://github.com/apache/datafusion/blob/main/datafusion-examples/examples/expr_api.rs
//!
//! ### Physical Plans
//!
//! An [`ExecutionPlan`] (sometimes referred to as a "physical plan")
//! is a plan that can be executed against data. It a DAG of other
//! [`ExecutionPlan`]s each potentially containing expressions that implement the
//! [`PhysicalExpr`] trait.
//!
//! Compared to a [`LogicalPlan`], an [`ExecutionPlan`] has additional concrete
//! information about how to perform calculations (e.g. hash vs merge
//! join), and how data flows during execution (e.g. partitioning and
//! sortedness).
//!
//! [cp_solver] performs range propagation analysis on [`PhysicalExpr`]s and
//! [`PruningPredicate`] can prove certain boolean [`PhysicalExpr`]s used for
//! filtering can never be `true` using additional statistical information.
//!
//! [cp_solver]: crate::physical_expr::intervals::cp_solver
//! [`PruningPredicate`]: datafusion_physical_optimizer::pruning::PruningPredicate
//! [`PhysicalExpr`]: crate::physical_plan::PhysicalExpr
//!
//! ## Execution
//!
//! ```text
//! ExecutionPlan::execute Calling next() on the
//! produces a stream stream produces the data
//!
//! ┌────────────────┐ ┌─────────────────────────┐ ┌────────────┐
//! │ProjectExec │ │impl │ ┌───▶│RecordBatch │
//! │ ... │─────▶│SendableRecordBatchStream│────┤ └────────────┘
//! │ DataSourceExec│ │ │ │ ┌────────────┐
//! └────────────────┘ └─────────────────────────┘ ├───▶│RecordBatch │
//! ▲ │ └────────────┘
//! ExecutionPlan │ │ ...
//! │ │
//! │ │ ┌────────────┐
//! PhysicalOptimizerRules ├───▶│RecordBatch │
//! request information │ └────────────┘
//! such as partitioning │ ┌ ─ ─ ─ ─ ─ ─
//! └───▶ None │
//! └ ─ ─ ─ ─ ─ ─
//! ```
//!
//! [`ExecutionPlan`]s process data using the [Apache Arrow] memory
//! format, making heavy use of functions from the [arrow]
//! crate. Values are represented with [`ColumnarValue`], which are either
//! [`ScalarValue`] (single constant values) or [`ArrayRef`] (Arrow
//! Arrays).
//!
//! Calling [`execute`] produces 1 or more partitions of data,
//! as a [`SendableRecordBatchStream`], which implements a pull based execution
//! API. Calling [`next()`]`.await` will incrementally compute and return the next
//! [`RecordBatch`]. Balanced parallelism is achieved using [Volcano style]
//! "Exchange" operations implemented by [`RepartitionExec`].
//!
//! While some recent research such as [Morsel-Driven Parallelism] describes challenges
//! with the pull style Volcano execution model on NUMA architectures, in practice DataFusion achieves
//! similar scalability as systems that use push driven schedulers [such as DuckDB].
//! See the [DataFusion paper in SIGMOD 2024] for more details.
//!
//! [`execute`]: physical_plan::ExecutionPlan::execute
//! [`SendableRecordBatchStream`]: crate::physical_plan::SendableRecordBatchStream
//! [`ColumnarValue`]: datafusion_expr::ColumnarValue
//! [`ScalarValue`]: crate::scalar::ScalarValue
//! [`ArrayRef`]: arrow::array::ArrayRef
//! [`Stream`]: futures::stream::Stream
//!
//! See the [implementors of `ExecutionPlan`] for a list of physical operators available.
//!
//! [`RepartitionExec`]: https://docs.rs/datafusion/latest/datafusion/physical_plan/repartition/struct.RepartitionExec.html
//! [Volcano style]: https://doi.org/10.1145/93605.98720
//! [Morsel-Driven Parallelism]: https://db.in.tum.de/~leis/papers/morsels.pdf
//! [DataFusion paper in SIGMOD 2024]: https://github.com/apache/datafusion/files/15149988/DataFusion_Query_Engine___SIGMOD_2024-FINAL-mk4.pdf
//! [such as DuckDB]: https://github.com/duckdb/duckdb/issues/1583
//! [implementors of `ExecutionPlan`]: https://docs.rs/datafusion/latest/datafusion/physical_plan/trait.ExecutionPlan.html#implementors
//!
//! ## Streaming Execution
//!
//! DataFusion is a "streaming" query engine which means [`ExecutionPlan`]s incrementally
//! read from their input(s) and compute output one [`RecordBatch`] at a time
//! by continually polling [`SendableRecordBatchStream`]s. Output and
//! intermediate [`RecordBatch`]s each have approximately `batch_size` rows,
//! which amortizes per-batch overhead of execution.
//!
//! Note that certain operations, sometimes called "pipeline breakers",
//! (for example full sorts or hash aggregations) are fundamentally non streaming and
//! must read their input fully before producing **any** output. As much as possible,
//! other operators read a single [`RecordBatch`] from their input to produce a
//! single [`RecordBatch`] as output.
//!
//! For example, given this SQL:
//!
//! ```sql
//! SELECT name FROM 'data.parquet' WHERE id > 10
//! ```
//!
//! An simplified DataFusion execution plan is shown below. It first reads
//! data from the Parquet file, then applies the filter, then the projection,
//! and finally produces output. Each step processes one [`RecordBatch`] at a
//! time. Multiple batches are processed concurrently on different CPU cores
//! for plans with multiple partitions.
//!
//! ```text
//! ┌─────────────┐ ┌──────────────┐ ┌────────────────┐ ┌──────────────────┐ ┌──────────┐
//! │ Parquet │───▶│ DataSource │───▶│ FilterExec │───▶│ ProjectionExec │───▶│ Results │
//! │ File │ │ │ │ │ │ │ │ │
//! └─────────────┘ └──────────────┘ └────────────────┘ └──────────────────┘ └──────────┘
//! (reads data) (id > 10) (keeps "name" col)
//! RecordBatch ───▶ RecordBatch ────▶ RecordBatch ────▶ RecordBatch
//! ```
//!
//! DataFusion uses the classic "pull" based control flow (explained more in the
//! next section) to implement streaming execution. As an example,
//! consider the following SQL query:
//!
//! ```sql
//! SELECT date_trunc('month', time) FROM data WHERE id IN (10,20,30);
//! ```
//!
//! The diagram below shows the call sequence when a consumer calls [`next()`] to
//! get the next [`RecordBatch`] of output. While it is possible that some
//! steps run on different threads, typically tokio will use the same thread
//! that called [`next()`] to read from the input, apply the filter, and
//! return the results without interleaving any other operations. This results
//! in excellent cache locality as the same CPU core that produces the data often
//! consumes it immediately as well.
//!
//! ```text
//!
//! Step 3: FilterExec calls next() Step 2: ProjectionExec calls
//! on input Stream next() on input Stream
//! ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐
//! │ Step 1: Consumer
//! ▼ ▼ │ calls next()
//! ┏━━━━━━━━━━━━━━━━┓ ┏━━━━━┻━━━━━━━━━━━━━┓ ┏━━━━━━━━━━━━━━━━━━━━━━━━┓
//! ┃ ┃ ┃ ┃ ┃ ◀ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─
//! ┃ DataSource ┃ ┃ ┃ ┃ ┃
//! ┃ (e.g. ┃ ┃ FilterExec ┃ ┃ ProjectionExec ┃
//! ┃ ParquetSource) ┃ ┃id IN (10, 20, 30) ┃ ┃date_bin('month', time) ┃
//! ┃ ┃ ┃ ┃ ┃ ┣ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ▶
//! ┃ ┃ ┃ ┃ ┃ ┃
//! ┗━━━━━━━━━━━━━━━━┛ ┗━━━━━━━━━━━┳━━━━━━━┛ ┗━━━━━━━━━━━━━━━━━━━━━━━━┛
//! │ ▲ ▲ Step 6: ProjectionExec
//! │ │ │ computes date_trunc into a
//! └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ new RecordBatch returned
//! ┌─────────────────────┐ ┌─────────────┐ from client
//! │ RecordBatch │ │ RecordBatch │
//! └─────────────────────┘ └─────────────┘
//!
//! Step 4: DataSource returns a Step 5: FilterExec returns a new
//! single RecordBatch RecordBatch with only matching rows
//! ```
//!
//! [`next()`]: futures::StreamExt::next
//!
//! ## Thread Scheduling, CPU / IO Thread Pools, and [Tokio] [`Runtime`]s
//!
//! DataFusion automatically runs each plan with multiple CPU cores using
//! a [Tokio] [`Runtime`] as a thread pool. While tokio is most commonly used
//! for asynchronous network I/O, the combination of an efficient, work-stealing
//! scheduler, and first class compiler support for automatic continuation
//! generation (`async`) also makes it a compelling choice for CPU intensive
//! applications as explained in the [Using Rustlang’s Async Tokio
//! Runtime for CPU-Bound Tasks] blog.
//!
//! The number of cores used is determined by the `target_partitions`
//! configuration setting, which defaults to the number of CPU cores.
//! While preparing for execution, DataFusion tries to create this many distinct
//! `async` [`Stream`]s for each [`ExecutionPlan`].
//! The [`Stream`]s for certain [`ExecutionPlan`]s, such as [`RepartitionExec`]
//! and [`CoalescePartitionsExec`], spawn [Tokio] [`task`]s, that run on
//! threads managed by the [`Runtime`].
//! Many DataFusion [`Stream`]s perform CPU intensive processing.
//!
//! ### Cooperative Scheduling
//!
//! DataFusion uses cooperative scheduling, which means that each [`Stream`]
//! is responsible for yielding control back to the [`Runtime`] after
//! some amount of work is done. Please see the [`coop`] module documentation
//! for more details.
//!
//! [`coop`]: datafusion_physical_plan::coop
//!
//! ### Network I/O and CPU intensive tasks
//!
//! Using `async` for CPU intensive tasks makes it easy for [`TableProvider`]s
//! to perform network I/O using standard Rust `async` during execution.
//! However, this design also makes it very easy to mix CPU intensive and latency
//! sensitive I/O work on the same thread pool ([`Runtime`]).
//! Using the same (default) [`Runtime`] is convenient, and often works well for
//! initial development and processing local files, but it can lead to problems
//! under load and/or when reading from network sources such as AWS S3.
//!
//! ### Optimizing Latency: Throttled CPU / IO under Highly Concurrent Load
//!
//! If your system does not fully utilize either the CPU or network bandwidth
//! during execution, or you see significantly higher tail (e.g. p99) latencies
//! responding to network requests, **it is likely you need to use a different
//! [`Runtime`] for DataFusion plans**. The [thread_pools example]
//! has an example of how to do so.
//!
//! As shown below, using the same [`Runtime`] for both CPU intensive processing
//! and network requests can introduce significant delays in responding to
//! those network requests. Delays in processing network requests can and does
//! lead network flow control to throttle the available bandwidth in response.
//! This effect can be especially pronounced when running multiple queries
//! concurrently.
//!
//! ```text
//! Legend
//!
//! ┏━━━━━━┓
//! Processing network request ┃ ┃ CPU bound work
//! is delayed due to processing ┗━━━━━━┛
//! CPU bound work ┌─┐
//! │ │ Network request
//! ││ └─┘ processing
//!
//! ││
//! ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─
//! │ │
//!
//! ▼ ▼
//! ┌─────────────┐ ┌─┐┌─┐┏━━━━━━━━━━━━━━━━━━━┓┏━━━━━━━━━━━━━━━━━━━┓┌─┐
//! │ │thread 1 │ ││ │┃ Decoding ┃┃ Filtering ┃│ │
//! │ │ └─┘└─┘┗━━━━━━━━━━━━━━━━━━━┛┗━━━━━━━━━━━━━━━━━━━┛└─┘
//! │ │ ┏━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━┓
//! │Tokio Runtime│thread 2 ┃ Decoding ┃ Filtering ┃ Decoding ┃ ...
//! │(thread pool)│ ┗━━━━━━━━━━━━━━┻━━━━━━━━━━━━━━━━━━━┻━━━━━━━━━━━━━━┛
//! │ │ ... ...
//! │ │ ┏━━━━━━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━━━━┓┌─┐ ┏━━━━━━━━━━━━━━┓
//! │ │thread N ┃ Decoding ┃ Filtering ┃│ │ ┃ Decoding ┃
//! └─────────────┘ ┗━━━━━━━━━━━━━━━━━━━┻━━━━━━━━━━━━━━━━━━━┛└─┘ ┗━━━━━━━━━━━━━━┛
//! ─────────────────────────────────────────────────────────────▶
//! time
//! ```
//!
//! The bottleneck resulting from network throttling can be avoided
//! by using separate [`Runtime`]s for the different types of work, as shown
//! in the diagram below.
//!
//! ```text
//! A separate thread pool processes network Legend
//! requests, reducing the latency for
//! processing each request ┏━━━━━━┓
//! ┃ ┃ CPU bound work
//! │ ┗━━━━━━┛
//! │ ┌─┐
//! ┌ ─ ─ ─ ─ ┘ │ │ Network request
//! ┌ ─ ─ ─ ┘ └─┘ processing
//! │
//! ▼ ▼
//! ┌─────────────┐ ┌─┐┌─┐┌─┐
//! │ │thread 1 │ ││ ││ │
//! │ │ └─┘└─┘└─┘
//! │Tokio Runtime│ ...
//! │(thread pool)│thread 2
//! │ │
//! │"IO Runtime" │ ...
//! │ │ ┌─┐
//! │ │thread N │ │
//! └─────────────┘ └─┘
//! ─────────────────────────────────────────────────────────────▶
//! time
//!
//! ┌─────────────┐ ┏━━━━━━━━━━━━━━━━━━━┓┏━━━━━━━━━━━━━━━━━━━┓
//! │ │thread 1 ┃ Decoding ┃┃ Filtering ┃
//! │ │ ┗━━━━━━━━━━━━━━━━━━━┛┗━━━━━━━━━━━━━━━━━━━┛
//! │Tokio Runtime│ ┏━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━┓
//! │(thread pool)│thread 2 ┃ Decoding ┃ Filtering ┃ Decoding ┃ ...
//! │ │ ┗━━━━━━━━━━━━━━┻━━━━━━━━━━━━━━━━━━━┻━━━━━━━━━━━━━━┛
//! │ CPU Runtime │ ... ...
//! │ │ ┏━━━━━━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━┓
//! │ │thread N ┃ Decoding ┃ Filtering ┃ Decoding ┃
//! └─────────────┘ ┗━━━━━━━━━━━━━━━━━━━┻━━━━━━━━━━━━━━━━━━━┻━━━━━━━━━━━━━━┛
//! ─────────────────────────────────────────────────────────────▶
//! time
//! ```
//!
//! Note that DataFusion does not use [`tokio::task::spawn_blocking`] for
//! CPU-bounded work, because `spawn_blocking` is designed for blocking **IO**,
//! not designed CPU bound tasks. Among other challenges, spawned blocking
//! tasks can't yield waiting for input (can't call `await`) so they
//! can't be used to limit the number of concurrent CPU bound tasks or
//! keep the processing pipeline to the same core.
//!
//! [Tokio]: https://tokio.rs
//! [`Runtime`]: tokio::runtime::Runtime
//! [thread_pools example]: https://github.com/apache/datafusion/tree/main/datafusion-examples/examples/thread_pools.rs
//! [`task`]: tokio::task
//! [Using Rustlang’s Async Tokio Runtime for CPU-Bound Tasks]: https://thenewstack.io/using-rustlangs-async-tokio-runtime-for-cpu-bound-tasks/
//! [`RepartitionExec`]: physical_plan::repartition::RepartitionExec
//! [`CoalescePartitionsExec`]: physical_plan::coalesce_partitions::CoalescePartitionsExec
//!
//! ## State Management and Configuration
//!
//! [`ConfigOptions`] contain options to control DataFusion's
//! execution.
//!
//! [`ConfigOptions`]: datafusion_common::config::ConfigOptions
//!
//! The state required to execute queries is managed by the following
//! structures:
//!
//! 1. [`SessionContext`]: State needed to create [`LogicalPlan`]s such
//! as the table definitions and the function registries.
//!
//! 2. [`TaskContext`]: State needed for execution such as the
//! [`MemoryPool`], [`DiskManager`], and [`ObjectStoreRegistry`].
//!
//! 3. [`ExecutionProps`]: Per-execution properties and data (such as
//! starting timestamps, etc).
//!
//! [`SessionContext`]: crate::execution::context::SessionContext
//! [`TaskContext`]: crate::execution::context::TaskContext
//! [`ExecutionProps`]: crate::execution::context::ExecutionProps
//!
//! ### Resource Management
//!
//! The amount of memory and temporary local disk space used by
//! DataFusion when running a plan can be controlled using the
//! [`MemoryPool`] and [`DiskManager`]. Other runtime options can be
//! found on [`RuntimeEnv`].
//!
//! [`DiskManager`]: crate::execution::DiskManager
//! [`MemoryPool`]: crate::execution::memory_pool::MemoryPool
//! [`RuntimeEnv`]: crate::execution::runtime_env::RuntimeEnv
//! [`ObjectStoreRegistry`]: crate::datasource::object_store::ObjectStoreRegistry
//!
//! ## Crate Organization
//!
//! Most users interact with DataFusion via this crate (`datafusion`), which re-exports
//! all functionality needed to build and execute queries.
//!
//! There are three other crates that provide additional functionality that
//! must be used directly:
//! * [`datafusion_proto`]: Plan serialization and deserialization
//! * [`datafusion_substrait`]: Support for the substrait plan serialization format
//! * [`datafusion_sqllogictest`] : The DataFusion SQL logic test runner
//!
//! [`datafusion_proto`]: https://crates.io/crates/datafusion-proto
//! [`datafusion_substrait`]: https://crates.io/crates/datafusion-substrait
//! [`datafusion_sqllogictest`]: https://crates.io/crates/datafusion-sqllogictest
//!
//! DataFusion is internally split into multiple sub crates to
//! enforce modularity and improve compilation times. See the
//! [list of modules](#modules) for all available sub-crates. Major ones are
//!
//! * [datafusion_common]: Common traits and types
//! * [datafusion_catalog]: Catalog APIs such as [`SchemaProvider`] and [`CatalogProvider`]
//! * [datafusion_datasource]: File and Data IO such as [`FileSource`] and [`DataSink`]
//! * [datafusion_session]: [`Session`] and related structures
//! * [datafusion_execution]: State and structures needed for execution
//! * [datafusion_expr]: [`LogicalPlan`], [`Expr`] and related logical planning structure
//! * [datafusion_functions]: Scalar function packages
//! * [datafusion_functions_aggregate]: Aggregate functions such as `MIN`, `MAX`, `SUM`, etc
//! * [datafusion_functions_nested]: Scalar function packages for `ARRAY`s, `MAP`s and `STRUCT`s
//! * [datafusion_functions_table]: Table Functions such as `GENERATE_SERIES`
//! * [datafusion_functions_window]: Window functions such as `ROW_NUMBER`, `RANK`, etc
//! * [datafusion_optimizer]: [`OptimizerRule`]s and [`AnalyzerRule`]s
//! * [datafusion_physical_expr]: [`PhysicalExpr`] and related expressions
//! * [datafusion_physical_plan]: [`ExecutionPlan`] and related expressions
//! * [datafusion_physical_optimizer]: [`ExecutionPlan`] and related expressions
//! * [datafusion_sql]: SQL planner ([`SqlToRel`])
//!
//! [`SchemaProvider`]: datafusion_catalog::SchemaProvider
//! [`CatalogProvider`]: datafusion_catalog::CatalogProvider
//! [`Session`]: datafusion_session::Session
//! [`FileSource`]: datafusion_datasource::file::FileSource
//! [`DataSink`]: datafusion_datasource::sink::DataSink
//!
//! ## Citing DataFusion in Academic Papers
//!
//! You can use the following citation to reference DataFusion in academic papers:
//!
//! ```text
//! @inproceedings{lamb2024apache
//! title={Apache Arrow DataFusion: A Fast, Embeddable, Modular Analytic Query Engine},
//! author={Lamb, Andrew and Shen, Yijie and Heres, Dani{\"e}l and Chakraborty, Jayjeet and Kabak, Mehmet Ozan and Hsieh, Liang-Chi and Sun, Chao},
//! booktitle={Companion of the 2024 International Conference on Management of Data},
//! pages={5--17},
//! year={2024}
//! }
//! ```
//!
//! [sqlparser]: https://docs.rs/sqlparser/latest/sqlparser
//! [`SqlToRel`]: sql::planner::SqlToRel
//! [`Expr`]: datafusion_expr::Expr
//! [`LogicalPlan`]: datafusion_expr::LogicalPlan
//! [`AnalyzerRule`]: datafusion_optimizer::analyzer::AnalyzerRule
//! [`OptimizerRule`]: optimizer::optimizer::OptimizerRule
//! [`ExecutionPlan`]: physical_plan::ExecutionPlan
//! [`PhysicalPlanner`]: physical_planner::PhysicalPlanner
//! [`PhysicalOptimizerRule`]: datafusion_physical_optimizer::PhysicalOptimizerRule
//! [`Schema`]: arrow::datatypes::Schema
//! [`PhysicalExpr`]: physical_plan::PhysicalExpr
//! [`RecordBatch`]: arrow::array::RecordBatch
//! [`RecordBatchReader`]: arrow::record_batch::RecordBatchReader
//! [`Array`]: arrow::array::Array
/// DataFusion crate version
pub const DATAFUSION_VERSION: &str = env!("CARGO_PKG_VERSION");
extern crate core;
#[cfg(feature = "sql")]
extern crate sqlparser;
pub mod dataframe;
pub mod datasource;
pub mod error;
pub mod execution;
pub mod physical_planner;
pub mod prelude;
pub mod scalar;
// Re-export dependencies that are part of DataFusion public API (e.g. via DataFusionError)
pub use arrow;
pub use object_store;
#[cfg(feature = "parquet")]
pub use parquet;
#[cfg(feature = "avro")]
pub use datafusion_datasource_avro::apache_avro;
// re-export DataFusion sub-crates at the top level. Use `pub use *`
// so that the contents of the subcrates appears in rustdocs
// for details, see https://github.com/apache/datafusion/issues/6648
/// re-export of [`datafusion_common`] crate
pub mod common {
pub use datafusion_common::*;
/// re-export of [`datafusion_common_runtime`] crate
pub mod runtime {
pub use datafusion_common_runtime::*;
}
}
// Backwards compatibility
pub use common::config;
// NB datafusion execution is re-exported in the `execution` module
/// re-export of [`datafusion_catalog`] crate
pub mod catalog {
pub use datafusion_catalog::*;
}
/// re-export of [`datafusion_expr`] crate
pub mod logical_expr {
pub use datafusion_expr::*;
}
/// re-export of [`datafusion_expr_common`] crate
pub mod logical_expr_common {
pub use datafusion_expr_common::*;
}
/// re-export of [`datafusion_optimizer`] crate
pub mod optimizer {
pub use datafusion_optimizer::*;
}
/// re-export of [`datafusion_physical_optimizer`] crate
pub mod physical_optimizer {
pub use datafusion_physical_optimizer::*;
}
/// re-export of [`datafusion_physical_expr`] crate
pub mod physical_expr_common {
pub use datafusion_physical_expr_common::*;
}
/// re-export of [`datafusion_physical_expr`] crate
pub mod physical_expr {
pub use datafusion_physical_expr::*;
}
/// re-export of [`datafusion_physical_expr_adapter`] crate
pub mod physical_expr_adapter {
pub use datafusion_physical_expr_adapter::*;
}
/// re-export of [`datafusion_physical_plan`] crate
pub mod physical_plan {
pub use datafusion_physical_plan::*;
}
// Reexport testing macros for compatibility
pub use datafusion_common::assert_batches_eq;
pub use datafusion_common::assert_batches_sorted_eq;
/// re-export of [`datafusion_sql`] crate
#[cfg(feature = "sql")]
pub mod sql {
pub use datafusion_sql::*;
}
/// re-export of [`datafusion_functions`] crate
pub mod functions {
pub use datafusion_functions::*;
}
/// re-export of [`datafusion_functions_nested`] crate, if "nested_expressions" feature is enabled
pub mod functions_nested {
#[cfg(feature = "nested_expressions")]
pub use datafusion_functions_nested::*;
}
/// re-export of [`datafusion_functions_aggregate`] crate
pub mod functions_aggregate {
pub use datafusion_functions_aggregate::*;
}
/// re-export of [`datafusion_functions_window`] crate
pub mod functions_window {
pub use datafusion_functions_window::*;
}
/// re-export of [`datafusion_functions_table`] crate
pub mod functions_table {
pub use datafusion_functions_table::*;
}
/// re-export of variable provider for `@name` and `@@name` style runtime values.
pub mod variable {
pub use datafusion_expr::var_provider::{VarProvider, VarType};
}
#[cfg(not(target_arch = "wasm32"))]
pub mod test;
mod schema_equivalence;
pub mod test_util;
#[cfg(doctest)]
doc_comment::doctest!("../../../README.md", readme_example_test);
// Instructions for Documentation Examples
//
// The following commands test the examples from the user guide as part of
// `cargo test --doc`
//
// # Adding new tests:
//
// Simply add code like this to your .md file and ensure your md file is
// included in the lists below.
//
// ```rust
// <code here will be tested>
// ```
//
// Note that sometimes it helps to author the doctest as a standalone program
// first, and then copy it into the user guide.
//
// # Debugging Test Failures
//
// Unfortunately, the line numbers reported by doctest do not correspond to the
// line numbers of in the .md files. Thus, if a doctest fails, use the name of
// the test to find the relevant file in the list below, and then find the
// example in that file to fix.
//
// For example, if `user_guide_expressions(line 123)` fails,
// go to `docs/source/user-guide/expressions.md` to find the relevant problem.
//
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/user-guide/arrow-introduction.md",
user_guide_arrow_introduction
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/user-guide/concepts-readings-events.md",
user_guide_concepts_readings_events
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/user-guide/configs.md",
user_guide_configs
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/user-guide/crate-configuration.md",
user_guide_crate_configuration
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/user-guide/dataframe.md",
user_guide_dataframe
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/user-guide/example-usage.md",
user_guide_example_usage
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/user-guide/explain-usage.md",
user_guide_explain_usage
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/user-guide/expressions.md",
user_guide_expressions
);
#[cfg(doctest)]
doc_comment::doctest!("../../../docs/source/user-guide/faq.md", user_guide_faq);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/user-guide/introduction.md",
user_guide_introduction
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/user-guide/cli/datasources.md",
user_guide_cli_datasource
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/user-guide/cli/installation.md",
user_guide_cli_installation
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/user-guide/cli/overview.md",
user_guide_cli_overview
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/user-guide/cli/usage.md",
user_guide_cli_usage
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/user-guide/features.md",
user_guide_features
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/user-guide/sql/aggregate_functions.md",
user_guide_sql_aggregate_functions
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/user-guide/sql/data_types.md",
user_guide_sql_data_types
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/user-guide/sql/ddl.md",
user_guide_sql_ddl
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/user-guide/sql/dml.md",
user_guide_sql_dml
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/user-guide/sql/explain.md",
user_guide_sql_exmplain
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/user-guide/sql/information_schema.md",
user_guide_sql_information_schema
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/user-guide/sql/operators.md",
user_guide_sql_operators
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/user-guide/sql/prepared_statements.md",
user_guide_prepared_statements
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/user-guide/sql/scalar_functions.md",
user_guide_sql_scalar_functions
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/user-guide/sql/select.md",
user_guide_sql_select
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/user-guide/sql/special_functions.md",
user_guide_sql_special_functions
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/user-guide/sql/subqueries.md",
user_guide_sql_subqueries
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/user-guide/sql/window_functions.md",
user_guide_sql_window_functions
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/user-guide/sql/format_options.md",
user_guide_sql_format_options
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/library-user-guide/functions/adding-udfs.md",
library_user_guide_functions_adding_udfs
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/library-user-guide/functions/spark.md",
library_user_guide_functions_spark
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/library-user-guide/building-logical-plans.md",
library_user_guide_building_logical_plans
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/library-user-guide/catalogs.md",
library_user_guide_catalogs
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/library-user-guide/custom-table-providers.md",
library_user_guide_custom_table_providers
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/library-user-guide/extending-operators.md",
library_user_guide_extending_operators
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/library-user-guide/extensions.md",
library_user_guide_extensions
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/library-user-guide/index.md",
library_user_guide_index
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/library-user-guide/profiling.md",
library_user_guide_profiling
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/library-user-guide/query-optimizer.md",
library_user_guide_query_optimizer
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/library-user-guide/using-the-dataframe-api.md",
library_user_guide_dataframe_api
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/library-user-guide/using-the-sql-api.md",
library_user_guide_sql_api
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/library-user-guide/working-with-exprs.md",
library_user_guide_working_with_exprs
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/library-user-guide/upgrading.md",
library_user_guide_upgrading
);
#[cfg(doctest)]
doc_comment::doctest!(
"../../../docs/source/contributor-guide/api-health.md",
contributor_guide_api_health
);