Substrait-Explain

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

A Rust library for parsing and formatting Substrait query plans in a human-readable text format.

What does it do?

Substrait query plans are complex protobuf structures that are difficult to read and debug. This library transforms them into human-readable text that looks similar to SQL EXPLAIN output.

Before - Raw Substrait protobuf (72 lines of nested YAML):

extensionUris:
  - extensionUriAnchor: 1
    uri: https://github.com/substrait-io/substrait/blob/main/extensions/functions_arithmetic.yaml
extensions:
  - extensionFunction:
      extensionUriReference: 1
      functionAnchor: 10
      name: gt
  - extensionFunction:
      extensionUriReference: 1
      functionAnchor: 11
      name: multiply
relations:
  - root:
      input:
        filter:
          common:
            emit:
              outputMapping:
                - 0
                - 1
          input:
            project:
              common:
                emit:
                  outputMapping:
                    - 0
                    - 1
                    - 2
              input:
                read:
                  baseSchema:
                    names:
                      - quantity
                      - price
                    struct:
                      types:
                        - i32:
                            nullability: NULLABILITY_NULLABLE
                        - fp64:
                            nullability: NULLABILITY_NULLABLE
                      nullability: NULLABILITY_REQUIRED
                  namedTable:
                    names:
                      - orders
              expressions:
                - scalarFunction:
                    functionReference: 11
                    arguments:
                      - value:
                          selection:
                            directReference:
                              structField: {}
                      - value:
                          selection:
                            directReference:
                              structField:
                                field: 1
          condition:
            scalarFunction:
              functionReference: 10
              arguments:
                - value:
                    selection:
                      directReference:
                        structField:
                          field: 2
                - value:
                    literal:
                      i64: "100"
      names:
        - revenue

After - Human-readable text (13 lines):

=== Extensions
URIs:
  @  1: https://github.com/substrait-io/substrait/blob/main/extensions/functions_arithmetic.yaml
Functions:
  # 10 @  1: gt
  # 11 @  1: multiply

=== Plan
Root[revenue]
  Filter[gt($2, 100) => $0, $1]
    Project[$0, $1, multiply($0, $1)]
      Read[orders => quantity:i32?, price:fp64?]

Now you can easily see what the query does: it reads from an orders table, multiplies quantity and price, filters for orders where the result is greater than 100, and outputs the revenue.

Supported Relations

The following Substrait relations are currently supported in the text format:

• Read
• Project
• Filter
• Aggregate
• Root

Support for additional relations (e.g., Join, Sort, Set, etc.) is planned for future releases. If you need a specific relation, please open an issue or contribute!

Quick Start

use substrait_explain::{parse, format};

// Parse a plan from text format
let plan_text = r#"
=== 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: multiply
  ## 11 @  2: sum
  ## 12 @  2: count
=== Plan
Root[result]
  Aggregate[$0 => $0, sum($1), count($1)]
    Project[$0, multiply($1, $2)]
      Read[orders => category:string, quantity:i32?, price:i64]
"#;

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

For more detailed examples and API documentation, see the API documentation.

Installation

Add to your Cargo.toml:

[dependencies]
substrait-explain = "0.1.0"
substrait = "0.57.0"  # For protobuf types

Documentation

• API Documentation - Complete API reference with examples and configuration options
• Grammar Specification - Detailed specification of the text format grammar
• Full Documentation - Generated API docs using GitHub Pages, including grammar and API docs.

Examples

# Basic usage - demonstrates parsing and formatting simple plans
cargo run --example basic_usage

# Advanced usage - shows different output options and protobuf comparison
cargo run --example advanced_usage --features serde

License

This project is licensed under the Apache License, Version 2.0 - see the LICENSE file for details.

Contributing

We welcome contributions! Please see CONTRIBUTING.md for details on how to get started.