Module expr

rusty_promql_parser::parser

Module expr 

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Main expression parser for PromQL.

This module provides the top-level expr function that parses any valid PromQL expression into an AST. It uses a Pratt parser (precedence climbing) algorithm for correct handling of binary operator precedence and associativity.

§Expression Grammar (Simplified)

expr          = unary_expr | binary_expr
binary_expr   = expr binary_op expr
unary_expr    = unary_op? postfix_expr
postfix_expr  = primary_expr postfix*
postfix       = subquery_range | matrix_range
primary_expr  = number | string | selector | paren_expr | function_call | aggregation
paren_expr    = "(" expr ")"

§Operator Precedence (Lowest to Highest)

  1. or - Set union
  2. and, unless - Set intersection/difference
  3. ==, !=, <, <=, >, >= - Comparison
  4. +, - - Addition/subtraction
  5. *, /, %, atan2 - Multiplication/division
  6. ^ - Power (right-associative)

§Examples

use rusty_promql_parser::parser::expr::expr;

// Simple metric
let (rest, e) = expr("http_requests_total").unwrap();
assert!(rest.is_empty());

// Binary expression with correct precedence
let (rest, e) = expr("1 + 2 * 3").unwrap(); // Parses as: 1 + (2 * 3)
assert!(rest.is_empty());

// Complex aggregation
let (rest, e) = expr("sum(rate(http_requests[5m])) by (job)").unwrap();
assert!(rest.is_empty());

Functions§

expr
Parse a PromQL expression