rustyroad 1.8.0

Rusty Road is a framework written in Rust that is based on Ruby on Rails. It is designed to provide the familiar conventions and ease of use of Ruby on Rails, while also taking advantage of the performance and efficiency of Rust.
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//! Which operations require rewriting existing rows.

use crate::database::versions::ops::model::Migration;

#[test]
fn backfill_is_required_only_when_values_change() {
    let json = r#"{"operations":[
        {"add_column":{"table":"users","column":"a","type":"text"}},
        {"add_column":{"table":"users","column":"b","type":"text","up":"'x'"}},
        {"sql":{"up":"SELECT 1"}}]}"#;

    let migration: Migration = serde_json::from_str(json).expect("should parse");

    // A plain new column has no per-row value to compute.
    assert!(!migration.operations[0].needs_backfill());
    // An `up` expression must be evaluated for every existing row.
    assert!(migration.operations[1].needs_backfill());
    // Raw SQL is applied as written.
    assert!(!migration.operations[2].needs_backfill());
}

#[test]
fn altering_a_column_always_requires_backfill() {
    let json = r#"{"operations":[
        {"alter_column":{"table":"users","column":"email","type":"citext"}}]}"#;

    let migration: Migration = serde_json::from_str(json).expect("should parse");
    // The shadow column starts empty regardless of what changed.
    assert!(migration.operations[0].needs_backfill());
}

#[test]
fn dropping_a_column_backfills_only_to_keep_it_readable() {
    let without = r#"{"operations":[
        {"drop_column":{"table":"users","column":"legacy"}}]}"#;
    let with = r#"{"operations":[
        {"drop_column":{"table":"users","column":"legacy","down":"'unknown'"}}]}"#;

    let plain: Migration = serde_json::from_str(without).expect("should parse");
    let compensating: Migration = serde_json::from_str(with).expect("should parse");

    assert!(!plain.operations[0].needs_backfill());
    // A `down` expression keeps old readers supplied until completion.
    assert!(compensating.operations[0].needs_backfill());
}