Crate substrait_explain

Substrait-Explain

Transform complex Substrait protobuf plans into readable, SQL EXPLAIN-like text

A Rust library that converts Substrait query plans between protobuf format and a human-readable text format. It transforms verbose, nested protobuf structures into concise, SQL-like text that’s easy to read and debug.

Key Features

• Human-readable output: Convert complex Substrait plans into simple, readable text
• Bidirectional conversion: Parse text format back into Substrait plans
• Extension support: Full support for Substrait extensions and custom functions
• Error handling: Graceful error handling that doesn’t prevent output generation
• Flexible formatting: Configurable output options for different use cases
• Complete grammar: Full specification of the text format in the grammar module

For installation instructions, see the README.

Quick Start

Parse and Format Plans

The main workflow is parsing text format and formatting plans. This example demonstrates both basic usage and extension handling:

use substrait_explain::{parse, format};

// Parse a plan from text format (includes extensions for custom functions)
let plan_text = r#"
=== Extensions
URIs:
  @  1: https://github.com/substrait-io/substrait/blob/main/extensions/functions_arithmetic.yaml
Functions:
  # 10 @  1: add

=== Plan
Project[$0, $1, add($0, $1)]
  Read[table1 => col1:i32?, col2:i32?]
"#;

let plan = parse(plan_text).unwrap();
let (output, errors) = format(&plan);
println!("{}", output);

// Check for any formatting warnings
if !errors.is_empty() {
    println!("Warnings: {:?}", errors);
}

Custom Formatting

Control output detail with formatting options:

use substrait_explain::{parse, format_with_options, OutputOptions, Visibility};

let plan = parse(r#"
=== Plan
Project[$0, 42, 54:i16]
  Read[data => name:string?, num:i64]
"#).unwrap();

// Verbose output with all details
let verbose = OutputOptions::verbose();
let (text, _) = format_with_options(&plan, &verbose);

// Custom options
let custom = OutputOptions {
    literal_types: Visibility::Always,
    indent: "    ".to_string(),
    ..OutputOptions::default()
};
let (text, _) = format_with_options(&plan, &custom);

Error Handling

The library provides graceful error handling for formatting, producing best-effort output even if there are errors:

use substrait_explain::{parse, format};

match parse("=== Plan\nInvalidRelation[invalid]") {
    Ok(plan) => {
        let (text, errors) = format(&plan);
        println!("Formatted: {}", text);
        if !errors.is_empty() {
            println!("Warnings: {:?}", errors);
        }
    }
    Err(e) => println!("Parse error: {}", e),
}

Output Format

The library produces a structured text format that’s easy to read and parse. For a complete specification of the text format grammar, see the grammar module.

Basic Plan Structure

=== Extensions
URIs:
  @  1: https://github.com/substrait-io/substrait/blob/main/extensions/functions_arithmetic.yaml
  @  2: https://github.com/substrait-io/substrait/blob/main/extensions/functions_aggregate.yaml
Functions:
  # 10 @  1: add
  # 11 @  2: sum
  # 12 @  2: count
=== Plan
Root[result]
  Aggregate[$0 => $0, sum($1), count($1)]
    Project[$0, add($1, $2)]
      Read[table1 => category:string, col1:i32?, col2:i32?]

Relation Format

Each relation is displayed on a single line with the format: RelationName[arguments => columns]

• arguments: Input expressions, field references, or function calls
• columns: Output column names and types
• indentation: Shows the relationship hierarchy

Expression Format

• Field references: $0, $1, etc.
• Literals: 42, "hello", true
• Function calls: add($0, $1), sum($2) (scalar and aggregate functions)
• Types: i32, string?, list<i64>

Configuration Options

Control output formatting with OutputOptions:

use substrait_explain::{OutputOptions, Visibility};

// Default - concise output
let default = OutputOptions::default();

// Verbose - show all details
let verbose = OutputOptions::verbose();

// Custom - show literal types and use 4-space indentation
let custom = OutputOptions {
    literal_types: Visibility::Always,
    indent: "    ".to_string(),
    ..OutputOptions::default()
};

Re-exports

pub use parser::ParseError;

pub use textify::foundation::FormatError;

pub use textify::foundation::OutputOptions;

pub use textify::foundation::Visibility;

Modules

extensions

Classes for handling extensions, including the simple extensions that represent functions, types, and type variations that can appear in Substrait simple extension YAML files.

fixtures

grammar

Substrait Text Format Grammar

parser

textify

Output a plan in text format.

Functions

format

Format a Substrait plan as human-readable text.

format_with_options

Format a Substrait plan with custom options.

parse

Parse a Substrait plan from text format.