Overview

A3S ORM is a type-safe Rust SQL query builder inspired by Kysely. Table declarations constrain columns, values, assignments, and decoded results while the actual SQL, bound parameters, and execution point remain visible.

It is not an Active Record framework. Records do not own persistence methods, field access does not execute queries, and runtime values never enter SQL text.

Core data flow

typed tables and expressions
            |
     immutable query AST
            |
       dialect compiler
            |
     SQL + bound parameters
            |
    async Executor and driver

Each layer owns one category of responsibility:

Layer	Owns	Does not own
Schema and Expression	Table identity, column ownership, value families, legal comparisons	SQL dialects and connections
Query	SELECT, INSERT, UPDATE, DELETE, and their structure	Opening database connections
Dialect	Identifier quoting, placeholders, capability checks	Transactions and row decoding
Executor	Async execution, transactions, connections, and driver rows	Builder type state
Decode	Checked conversion from driver-neutral values	Implicit correction of incompatible types

Guarantees you can rely on

A column can only be used with its owning table or an explicit alias.
Comparisons, assignments, and inserted values must use compatible Rust and SQL value families.
Dynamic values can only enter compiled output as bound parameters.
Unsupported dialect capabilities return errors instead of approximate syntax.
CTEs, subqueries, windows, and outer queries share one parameter sequence.
Database separates build, execution, decoding, no-row, and too-many-row failures.

v0.2.0 does not include typed UPDATE CTEs, UPDATE FROM, or set_expression. Use reviewed static sql_query statements for atomic worker claims, or upgrade to v0.3.0.

Dialects and runtimes

Capability	PostgreSQL	SQLite	MySQL
SQL compilation	Yes	Yes	Yes
Bundled async driver	Yes	Yes	No
`RETURNING`	Yes	Yes	Rejected
`ON CONFLICT`	Yes	Yes	Rejected
Row and table locks	Yes	Rejected	Rejected
Transactions	Yes	Yes	No
Locked migrations	Advisory lock	`BEGIN IMMEDIATE`	No

SQLite is the default feature. PostgreSQL uses a bounded Deadpool pool and adds transaction policy, TLS, health snapshots, and retry classification. MySQL currently provides compilation only.

Next steps

Read installation and features, then complete the quick start. Review architecture and production boundaries before deployment.

#Overview

#Core data flow

#Guarantees you can rely on

#Dialects and runtimes

#Next steps

Overview

Core data flow

Guarantees you can rely on

Dialects and runtimes

Next steps