Crate substrait_explain

Expand description

§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()
};

§Command Line Interface

The library includes a command line interface for converting between different Substrait plan formats and validating plans. The CLI is available behind the cli feature flag.

§Installation

Install the CLI with:

cargo install substrait-explain --features cli

Or build from source:

cargo build --release --features cli

§Commands

§Convert Command

The convert command transforms plans between different formats:

# Convert text format to JSON
substrait-explain convert -f text -t json -i plan.substrait -o plan.json

# Convert JSON back to text
substrait-explain convert -f json -t text -i plan.json -o plan.substrait

# Convert to binary protobuf format
substrait-explain convert -f text -t protobuf -i plan.substrait -o plan.pb

# Use stdin/stdout (default)
cat plan.substrait | substrait-explain convert -f text -t json > plan.json

Supported formats:

text - Human-readable Substrait text format
json - JSON serialized protobuf
yaml - YAML serialized protobuf
protobuf/proto/pb - Binary protobuf format

Options:

-f, --from <FORMAT> - Input format (default: text)
-t, --to <FORMAT> - Output format (default: text)
-i, --input <FILE> - Input file (default: stdin)
-o, --output <FILE> - Output file (default: stdout)
--show-literal-types - Show type annotations on literals
--show-expression-types - Show type annotations on expressions
--verbose - Show detailed progress information

§Validate Command

The validate command performs a roundtrip test on text format plans:

# Validate a plan file
substrait-explain validate -i plan.substrait

# Validate from stdin
cat plan.substrait | substrait-explain validate

# Validate with verbose output
substrait-explain validate -i plan.substrait --verbose