Row Format

Apache Fory™ provides a high-performance row format for zero-copy deserialization.

Overview

Unlike traditional object serialization that reconstructs entire objects in memory, row format enables random access to fields directly from binary data without full deserialization.

Key benefits:

• Zero-copy access: Read fields without allocating or copying data
• Partial deserialization: Access only the fields you need
• Memory-mapped files: Work with data larger than RAM
• Cache-friendly: Sequential memory layout for better CPU cache utilization
• Lazy evaluation: Defer expensive operations until field access

When to Use Row Format

• Analytics workloads with selective field access
• Large datasets where only a subset of fields is needed
• Memory-constrained environments
• High-throughput data pipelines
• Reading from memory-mapped files or shared memory

Basic Usage

use fory::{to_row, from_row};
use fory::ForyRow;
use std::collections::BTreeMap;

#[derive(ForyRow)]
struct UserProfile {
    id: i64,
    username: String,
    email: String,
    scores: Vec<i32>,
    preferences: BTreeMap<String, String>,
    is_active: bool,
}

let profile = UserProfile {
    id: 12345,
    username: "alice".to_string(),
    email: "alice@example.com".to_string(),
    scores: vec![95, 87, 92, 88],
    preferences: BTreeMap::from([
        ("theme".to_string(), "dark".to_string()),
        ("language".to_string(), "en".to_string()),
    ]),
    is_active: true,
};

// Serialize to row format
let row_data = to_row(&profile);

// Zero-copy deserialization - no object allocation!
let row = from_row::<UserProfile>(&row_data);

// Access fields directly from binary data
assert_eq!(row.id(), 12345);
assert_eq!(row.username(), "alice");
assert_eq!(row.email(), "alice@example.com");
assert_eq!(row.is_active(), true);

// Access collections efficiently
let scores = row.scores();
assert_eq!(scores.size(), 4);
assert_eq!(scores.get(0), 95);
assert_eq!(scores.get(1), 87);

let prefs = row.preferences();
assert_eq!(prefs.keys().size(), 2);
assert_eq!(prefs.keys().get(0), "language");
assert_eq!(prefs.values().get(0), "en");

How It Works

• Fields are encoded in a binary row with fixed offsets for primitives
• Variable-length data (strings, collections) stored with offset pointers
• Null bitmap tracks which fields are present
• Nested structures supported through recursive row encoding

Performance Comparison

Operation	Object Format	Row Format
Full deserialization	Allocates all objects	Zero allocation
Single field access	Full deserialization required	Direct offset read
Memory usage	Full object graph in memory	Only accessed fields in memory
Suitable for	Small objects, full access	Large objects, selective access

ForyRow vs ForyObject

Feature	#[derive(ForyRow)]	#[derive(ForyObject)]
Deserialization	Zero-copy, lazy	Full object reconstruction
Field access	Direct from binary	Normal struct access
Memory usage	Minimal	Full object
Best for	Analytics, large data	General serialization

Related Topics

• Basic Serialization - Object graph serialization
• Cross-Language - Row format across languages
• Row Format Specification - Protocol details