EventQL Parser

A complete lexer and parser for EventQL (EQL), a query language designed for event sourcing systems.

Features

• Complete EventQL Support: Parse queries with FROM, WHERE, GROUP BY, ORDER BY, LIMIT, and PROJECT clauses
• Rich Expression Language: Supports arithmetic, comparison, logical operators, and field access
• Detailed Error Reporting: Position-aware error messages with line and column numbers
• Type-Safe AST: Strongly-typed abstract syntax tree for query analysis and execution

Quick Start

use eventql_parser::parse_query;

fn main() {
    let query = parse_query(
        "FROM e IN events WHERE e.id == 1 PROJECT INTO e"
    ).unwrap();

    println!("Parsed query: {:?}", query);
}

EventQL Language

EventQL supports querying event streams with a SQL-like syntax:

FROM e IN events
WHERE e.price > 100 AND e.category == "electronics"
ORDER BY e.timestamp DESC
LIMIT 10
PROJECT INTO { id: e.id, price: e.price }

Supported Clauses

• FROM: Define event sources (streams, subqueries)
• WHERE: Filter events with expressions
• GROUP BY: Group events by field or expression
• ORDER BY: Sort results (ASC/DESC)
• LIMIT: Limit number of results
• PROJECT: Define output shape

Operators

• Arithmetic: +, -, *, /
• Comparison: ==, !=, <, <=, >, >=
• Logical: AND, OR, XOR, NOT
• Field Access: e.field, e.nested.field

Acknowledgements

This parser is based on the EventQL language specification from EventSourcingDB by The Native Web. EventSourcingDB is an event store database that provides a powerful query language (EventQL) for querying and analyzing event streams in event-sourced systems.

The EventQL Reference

License

MIT