Module migration 

Schema versioning and migration support for SqliteTaskStore.

This module provides a lightweight, forward-only migration runner that tracks applied schema versions in a schema_versions table. Migrations are defined as plain SQL strings and are executed inside transactions for atomicity.

Concurrency

Each migration runs inside a BEGIN EXCLUSIVE transaction, which acquires a database-level write lock before reading. This prevents concurrent migration runners from both seeing the same version as unapplied and attempting to apply it simultaneously.

Built-in migrations

Version	Description
1	Initial schema — tasks table with indexes on context_id and state
2	Add created_at column to tasks table
3	Add composite index on (context_id, state) for combined filter queries
4	Add (updated_at DESC, id DESC) index for list ordering
5	Add task_artifact_appends — the journal streaming appends are written to
6	Add idempotency_keys — the index client-supplied send keys are claimed in
7	Add task_events — the per-task log of what the agent emitted

This table listed 1 to 3 while seven existed — the failure mode of a list maintained by hand beside one maintained by the compiler. The test below fails if the two stop agreeing on how many there are.

SQLite’s ALTER TABLE has no ADD CONSTRAINT, so a CHECK in a table’s DDL reaches only databases built after it. task_events gained CHECK (seq > 0) in 0.13 and migration 7 carries it — that migration creates the table, sharing the constant with from_pool — but a database that already ran migration 7 keeps the unconstrained table. Correcting it means a full table rebuild for a constraint on values this crate does not write. pg_migration’s version 6 does it on PostgreSQL, which has ALTER TABLE ... ADD CONSTRAINT.

Example

use a2a_protocol_server::store::migration::MigrationRunner;
use sqlx::sqlite::SqlitePoolOptions;

let pool = SqlitePoolOptions::new()
    .connect("sqlite:tasks.db")
    .await?;

let runner = MigrationRunner::new(pool);
let applied = runner.run_pending().await?;
println!("Applied migrations: {applied:?}");

Structs

Migration

A single schema migration.

MigrationRunner

Runs schema migrations against a SQLite database.

Statics

BUILTIN_MIGRATIONS

Built-in migrations for the SqliteTaskStore schema.