# fraiseql-wire
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**Streaming JSON queries for Postgres 17, built for FraiseQL**
`fraiseql-wire` is a **minimal, async Rust query engine** that streams JSON data from Postgres with low latency and bounded memory usage.
It is **not a general-purpose Postgres driver**.
It is a focused, purpose-built transport for JSON queries of the form:
```sql
SELECT data
FROM {source}
[WHERE predicate]
[ORDER BY expression [COLLATE collation] [ASC|DESC]]
[LIMIT N] [OFFSET M]
```
Where `{source}` is a JSON-shaped relation (`v_{entity}` views or `tv_{entity}` tables).
The primary goal is to enable **efficient, backpressure-aware streaming of JSON** from Postgres into Rust, with support for hybrid filtering (SQL + Rust predicates), adaptive chunking, pause/resume flow control, and comprehensive metrics.
---
## Why fraiseql-wire?
Traditional database drivers are optimized for flexibility and completeness. FraiseQL-Wire is optimized for:
* 🚀 **Low latency** (process rows as soon as they arrive)
* 🧠 **Low memory usage** (no full result buffering)
* 🔁 **Streaming-first APIs** (`Stream<Item = Result<Value, _>>`)
* 🧩 **Hybrid filtering** (SQL + Rust predicates)
* 🔍 **JSON-native workloads**
If your application primarily:
* Reads JSON (`json` / `jsonb`)
* Uses views as an abstraction layer
* Needs to process large result sets incrementally
…then `fraiseql-wire` is a good fit.
---
## Non-goals
`fraiseql-wire` intentionally does **not** support:
* Writes (`INSERT`, `UPDATE`, `DELETE`)
* Transactions
* Prepared statements
* Arbitrary SQL
* Multi-column result sets
* Full Postgres type decoding
If you need those features, use `tokio-postgres` or `sqlx`.
---
## Supported Query Shape
All queries must conform to:
```sql
SELECT data
FROM {source}
[WHERE <predicate>]
[ORDER BY <expression> [COLLATE <collation>] [ASC|DESC]]
[LIMIT <count>]
[OFFSET <count>]
```
### Query Components
| **SELECT** | `SELECT data` only | Result column must be named `data` and type `json`/`jsonb` |
| **FROM** | `v_{entity}` / `tv_{entity}` | Views and tables with JSON column |
| **WHERE** | SQL predicates | Optional; use `where_sql()` in builder |
| **ORDER BY** | Server-side sorting | With optional COLLATE; server-executed, no client buffering |
| **LIMIT/OFFSET** | Pagination | For result set reduction |
| **Filtering** | SQL + Rust predicates | Hybrid: SQL reduces wire traffic, Rust refines streamed data |
### Hard Constraints
* Exactly **one column** in result set (named `data`)
* Column type must be `json` or `jsonb`
* Results streamed in-order (server-side ordering for ORDER BY)
* One active query per connection
* No client-side reordering or aggregation
---
## Example
### Streaming JSON results
```rust
use futures::StreamExt;
let client = FraiseClient::connect("postgres:///example").await?;
let mut stream = client
.query("user")
.where_sql("data->>'status' = 'active'")
.chunk_size(256)
.execute()
.await?;
while let Some(item) = stream.next().await {
let json = item?;
println!("{json}");
}
```
### Collecting (optional)
```rust
let users: Vec<serde_json::Value> =
stream.collect::<Result<_, _>>()?;
```
---
## Hybrid Predicates (SQL + Rust)
Not all predicates belong in SQL. FraiseQL-Wire supports **hybrid filtering**:
```rust
let stream = client
.query("user")
.where_sql("data->>'type' = 'customer'")
.where_rust(|json| expensive_check(json))
.execute()
.await?;
```
* SQL predicates reduce data sent over the wire
* Rust predicates allow expressive, application-level filtering
* Filtering happens **while streaming**
---
## Streaming Model
Under the hood:
* Results are read incrementally from the Postgres socket
* Rows are batched into small chunks
* Chunks are sent through a bounded async channel
* Consumers apply backpressure naturally via `.await`
This ensures:
* Bounded memory usage
* CPU and I/O overlap
* Fast time-to-first-row
---
## Cancellation & Drop Semantics
If the stream is dropped early:
* The in-flight query is cancelled
* The connection is closed
* Background tasks are terminated
This prevents runaway queries and resource leaks.
---
## Postgres 17 & Chunked Rows Mode
`fraiseql-wire` is designed to take advantage of **Postgres 17 streaming behavior**, and can optionally leverage **chunked rows mode** via a libpq-based backend.
The public API remains the same regardless of backend; chunking is an internal optimization.
---
## Quick Start
### Installation
Add to `Cargo.toml`:
```toml
[dependencies]
fraiseql-wire = "0.1"
tokio = { version = "1", features = ["full"] }
futures = "0.3"
serde_json = "1"
```
### Basic Usage
```rust
use fraiseql_wire::client::FraiseClient;
use futures::stream::StreamExt;
#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
// Connect to Postgres
let client = FraiseClient::connect("postgres://localhost/mydb").await?;
// Stream results
let mut stream = client.query("users").execute().await?;
while let Some(item) = stream.next().await {
let json = item?;
println!("{}", json);
}
Ok(())
}
```
### Running Examples
See `examples/` directory:
```bash
# Start Postgres with test data
docker-compose up -d
# Run examples
cargo run --example basic_query
cargo run --example filtering
cargo run --example ordering
cargo run --example streaming
cargo run --example error_handling
```
---
## Error Handling
Errors are surfaced as part of the stream:
```rust
Stream<Item = Result<serde_json::Value, FraiseError>>
```
Possible error sources include:
* Connection or authentication failures
* SQL execution errors
* Protocol violations
* Invalid result schema
* JSON decoding failures
* Query cancellation
Fatal errors terminate the stream.
For detailed error diagnosis, see [troubleshooting.md](troubleshooting.md).
---
## Performance Characteristics
* 📉 Memory usage scales with `chunk_size`, not result size
* ⏱ First rows are available immediately
* 🔄 Server I/O and client processing overlap
* 📦 JSON decoding is incremental
### Benchmarked Performance (v0.1.0)
**Memory Efficiency**: The key advantage
| 10K rows | 1.3 KB | 2.6 MB | **2000x** |
| 100K rows | 1.3 KB | 26 MB | **20,000x** |
| 1M rows | 1.3 KB | 260 MB | **200,000x** |
fraiseql-wire uses **O(chunk_size)** memory while traditional drivers use **O(result_size)**.
**Latency & Throughput**: Comparable to tokio-postgres
| Connection setup | ~250 ns (CPU) | ~250 ns (CPU) |
| Query parsing | ~5-30 µs | ~5-30 µs |
| Throughput | 100K-500K rows/sec | 100K-500K rows/sec |
| Time-to-first-row | 2-5 ms | 2-5 ms |
**For detailed performance analysis**, see [performance-tuning.md](performance-tuning.md) and [benches/comparison-guide.md](benches/comparison-guide.md).
---
## When to Use fraiseql-wire
Use this crate if you:
* Stream large JSON result sets
* Want predictable memory usage
* Use Postgres views as an API boundary
* Prefer async streams over materialized results
* Are building FraiseQL or similar query layers
---
## When *Not* to Use It
Avoid this crate if you need:
* Writes or transactions
* Arbitrary SQL
* Strong typing across many Postgres types
* Multi-query sessions
* Compatibility with existing ORMs
---
## Advanced Features
### Type-Safe Deserialization
Stream results as custom structs instead of raw JSON:
```rust
#[derive(Deserialize)]
struct Project {
id: String,
name: String,
status: String,
}
let stream = client.query::<Project>("projects").execute().await?;
while let Some(project) = stream.next().await {
let p: Project = project?;
println!("{}: {}", p.id, p.name);
}
```
Type `T` affects **only** deserialization; SQL, filtering, and ordering are identical regardless of `T`.
### Stream Control (Pause/Resume)
Pause and resume streams for advanced flow control:
```rust
let mut stream = client.query("entities").execute().await?;
// Process some rows
while let Some(item) = stream.next().await {
println!("{item?}");
break; // Stop after one
}
// Pause to do other work
stream.pause().await?;
// ... perform other operations ...
stream.resume().await?; // Continue from where we left off
```
### Adaptive Chunking
Automatic chunk size optimization based on channel occupancy:
```rust
let stream = client
.query("large_table")
.adaptive_chunking(true) // Enabled by default
.adaptive_min_size(16) // Don't go below 16
.adaptive_max_size(1024) // Don't exceed 1024
.execute()
.await?;
```
### SQL Field Projection
Reduce payload size via database-level field filtering:
```rust
let stream = client
.query("users")
.select_projection("jsonb_build_object('id', data->>'id', 'name', data->>'name')")
.execute()
.await?;
// Returns only id and name fields, reducing network overhead
```
### Metrics & Tracing
Built-in metrics via the `metrics` crate:
* `fraiseql_stream_rows_yielded` – Total rows yielded from streams
* `fraiseql_stream_rows_filtered` – Rows filtered by predicates
* `fraiseql_query_duration_ms` – Query execution time
* `fraiseql_memory_usage_bytes` – Estimated memory consumption
Enable tracing with:
```bash
RUST_LOG=fraiseql_wire=debug cargo run
```
---
## Project Status
✅ **Production Ready**
* API is stable and well-tested
* 166+ unit tests, comprehensive integration tests
* Zero clippy warnings (strict `-D warnings`)
* Fully optimized streaming engine with proven performance characteristics
* Ready for production use
All core features implemented with comprehensive CI validation:
* ✅ Async JSON streaming (integration tests across PostgreSQL 15-18)
* ✅ Hybrid SQL + Rust predicates (25+ WHERE operators with full test coverage)
* ✅ Type-safe deserialization (generic streaming API with custom struct support)
* ✅ Stream pause/resume (backpressure-aware flow control)
* ✅ Adaptive chunking (automatic memory-aware chunk optimization)
* ✅ SQL field projection (SELECT clause optimization for reduced payload)
* ✅ Server-side ordering (ORDER BY with COLLATE support, no client buffering)
* ✅ Pagination (LIMIT/OFFSET for result set reduction)
* ✅ Metrics & tracing (comprehensive observability via metrics crate)
* ✅ Error handling (detailed error types and recovery patterns)
* ✅ Connection pooling support (documented integration patterns)
* ✅ TLS/SCRAM authentication (PostgreSQL 17+ security features)
---
## Roadmap
* [x] Connection pooling integration guide
* [x] Advanced filtering patterns
* [x] PostgreSQL 15-18 compatibility
* [x] SCRAM/TLS end-to-end integration tests in CI
* [x] Comprehensive metrics and tracing
* [x] Server-side ordering (ORDER BY with COLLATE)
* [x] Pagination support (LIMIT/OFFSET)
* [x] SQL field projection for payload optimization
* [ ] Extended metric examples and dashboards
* [ ] PostgreSQL 19+ compatibility tracking
* [ ] Binary protocol optimization (extended query protocol)
---
## Documentation
| [testing-guide.md](testing-guide.md) | Running tests locally and in CI; release process |
| [troubleshooting.md](troubleshooting.md) | Error diagnosis and common issues |
| [performance-tuning.md](performance-tuning.md) | Tuning for production workloads |
| [benchmarking.md](benchmarking.md) | How to run and interpret benchmarks |
| [advanced-filtering.md](advanced-filtering.md) | Complex WHERE clause patterns |
| [typed-streaming-guide.md](typed-streaming-guide.md) | Type-safe streaming setup |
| [connection-pooling.md](connection-pooling.md) | Pool configuration and tuning |
| [metrics.md](metrics.md) | All exposed Prometheus metrics |
| [security-audit.md](security-audit.md) | Security assessment and findings |
| [postgres-compatibility.md](postgres-compatibility.md) | PostgreSQL version compatibility |
| [SECURITY.md](SECURITY.md) | Security best practices and deployment hardening |
| [docker-setup.md](docker-setup.md) | Docker development environment setup |
| [CONTRIBUTING.md](CONTRIBUTING.md) | Development workflows and contribution guidelines |
| [docs/operators.md](docs/operators.md) | WHERE clause operator reference |
| [docs/collation.md](docs/collation.md) | Sorting and collation reference |
| [benches/comparison-guide.md](benches/comparison-guide.md) | Benchmark comparison guide |
| [.github/publishing.md](.github/publishing.md) | crates.io publishing workflow |
### Examples
* **[examples/basic_query.rs](examples/basic_query.rs)** – Simple streaming usage
* **[examples/filtering.rs](examples/filtering.rs)** – SQL and Rust predicates
* **[examples/ordering.rs](examples/ordering.rs)** – ORDER BY with collation
* **[examples/streaming.rs](examples/streaming.rs)** – Large result handling and chunk tuning
* **[examples/error_handling.rs](examples/error_handling.rs)** – Error handling patterns
---
## Philosophy
> *This is not a Postgres driver.*
> *It is a JSON query pipe.*
By narrowing scope, `fraiseql-wire` delivers performance and clarity that general-purpose drivers cannot.
---
## Credits
**Author:**
* Lionel Hamayon (@evoludigit)
**Part of:** FraiseQL — Compiled GraphQL for deterministic Postgres execution
---
## License
MIT OR Apache-2.0