laminar-derive 0.18.4

Derive macros for LaminarDB Record and FromRecordBatch traits
Documentation

laminar-derive

Derive macros for LaminarDB -- Record, FromRecordBatch, FromRow, and ConnectorConfig.

Overview

Procedural macros for Arrow RecordBatch conversion and connector config parsing. Eliminates the boilerplate of writing to_record_batch() / from_batch() by hand.

Macros

#[derive(Record)]

Generates Record::schema(), Record::to_record_batch(), and Record::event_time() for typed data ingestion.

use laminar_derive::Record;

#[derive(Record)]
struct Trade {
    symbol: String,
    price: f64,
    volume: i64,
    #[event_time]
    ts: i64,
}

Attributes:

  • #[event_time] -- marks a field as the event time column
  • #[column("name")] -- overrides the Arrow column name
  • #[nullable] -- marks a non-Option field as nullable in the schema

Supported types: bool, i8-i64, u8-u64, f32, f64, String, Vec<u8>, Option<T>

#[derive(FromRecordBatch)]

Generates from_batch() and from_batch_all() for deserializing Arrow RecordBatches into typed structs. Fields are matched by name.

use laminar_derive::FromRecordBatch;

#[derive(FromRecordBatch)]
struct OhlcBar {
    symbol: String,
    open: f64,
    high: f64,
    low: f64,
    close: f64,
}

#[derive(FromRow)]

Like FromRecordBatch, but also implements laminar_db::FromBatch. Fields are matched by position (column order in SELECT), not by name.

use laminar_derive::FromRow;

#[derive(FromRow)]
struct Result {
    symbol: String,    // 1st SELECT column
    total: i64,        // 2nd SELECT column
    avg_price: f64,    // 3rd SELECT column
}

#[derive(ConnectorConfig)]

Generates from_config(), validate(), and config_keys() for connector configuration parsing.

use laminar_derive::ConnectorConfig;

#[derive(ConnectorConfig)]
struct MySourceConfig {
    #[config(key = "bootstrap.servers", required, description = "Kafka brokers")]
    bootstrap_servers: String,

    #[config(key = "batch.size", default = "1000")]
    batch_size: usize,

    #[config(key = "timeout.ms", default = "30000", duration_ms)]
    timeout: std::time::Duration,

    #[config(key = "api.key", env = "MY_API_KEY")]
    api_key: Option<String>,
}

Attributes:

  • #[config(key = "...")] -- config key name
  • #[config(required)] -- field is required
  • #[config(default = "...")] -- default value
  • #[config(env = "...")] -- environment variable fallback
  • #[config(description = "...")] -- documentation for the key
  • #[config(duration_ms)] -- parse as Duration from milliseconds

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