<!--
Licensed to the Apache Software Foundation (ASF) under one
or more contributor license agreements.  See the NOTICE file
distributed with this work for additional information
regarding copyright ownership.  The ASF licenses this file
to you under the Apache License, Version 2.0 (the
"License"); you may not use this file except in compliance
with the License.  You may obtain a copy of the License at

  http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing,
software distributed under the License is distributed on an
"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
KIND, either express or implied.  See the License for the
specific language governing permissions and limitations
under the License.
-->

# Getting Started

## Installation

Add `paimon` to your `Cargo.toml`:

```toml
[dependencies]
paimon = "0.2.0"
tokio = { version = "1", features = ["full"] }
```

By default, the `storage-fs` (local filesystem) and `storage-memory` (in-memory) backends are enabled. To use additional storage backends, enable the corresponding feature flags:

```toml
[dependencies]
paimon = { version = "0.2.0", features = ["storage-s3"] }
```

Available storage features:

| Feature          | Backend          |
|------------------|------------------|
| `storage-fs`     | Local filesystem |
| `storage-memory` | In-memory        |
| `storage-s3`     | Amazon S3        |
| `storage-oss`    | Alibaba Cloud OSS|
| `storage-cos`    | Tencent Cloud COS <sup>[1]</sup> |
| `storage-azdls`  | Azure Data Lake Storage Gen2 <sup>[1]</sup> |
| `storage-obs`    | Huawei Cloud OBS <sup>[1]</sup> |
| `storage-gcs`    | Google Cloud Storage <sup>[1]</sup> |
| `storage-hdfs`   | HDFS             |
| `storage-all`    | All of the above |

<sup>[1]</sup> Not in the latest release yet; available on the `main` branch. To use it now, depend on the git repository instead of a published version:

```toml
[dependencies]
paimon = { git = "https://github.com/apache/paimon-rust", features = ["storage-cos"] }
```

## Mosaic File Format

Mosaic data file reads are always available. The current Mosaic support is read-only: Paimon Rust can read existing `.mosaic` data files, including array and map columns, in a Paimon table, but it does not write Mosaic data files yet.

## Catalog Management

Paimon supports multiple catalog types. The `CatalogFactory` provides a unified way to create catalogs based on configuration options.

### Create a Catalog

The `CatalogFactory` automatically determines the catalog type based on the `metastore` option:

```rust
use paimon::{CatalogFactory, CatalogOptions, Options};

// Local filesystem (no credentials needed)
let mut options = Options::new();
options.set(CatalogOptions::WAREHOUSE, "/path/to/warehouse");
let catalog = CatalogFactory::create(options).await?;

// Amazon S3
let mut options = Options::new();
options.set(CatalogOptions::WAREHOUSE, "s3://bucket/warehouse");
options.set("s3.access-key-id", "your-access-key-id");
options.set("s3.secret-access-key", "your-secret-access-key");
options.set("s3.region", "us-east-1");
let catalog = CatalogFactory::create(options).await?;

// Alibaba Cloud OSS
let mut options = Options::new();
options.set(CatalogOptions::WAREHOUSE, "oss://bucket/warehouse");
options.set("fs.oss.accessKeyId", "your-access-key-id");
options.set("fs.oss.accessKeySecret", "your-access-key-secret");
options.set("fs.oss.endpoint", "oss-cn-hangzhou.aliyuncs.com");
let catalog = CatalogFactory::create(options).await?;

// Tencent Cloud COS
let mut options = Options::new();
options.set(CatalogOptions::WAREHOUSE, "cosn://bucket/warehouse");
options.set("fs.cosn.userinfo.secretId", "your-secret-id");
options.set("fs.cosn.userinfo.secretKey", "your-secret-key");
options.set("fs.cosn.endpoint", "https://cos.ap-shanghai.myqcloud.com");
let catalog = CatalogFactory::create(options).await?;

// Azure Data Lake Storage Gen2
let mut options = Options::new();
options.set(CatalogOptions::WAREHOUSE, "abfs://filesystem@account.dfs.core.windows.net/warehouse");
options.set("azure.account-key", "your-account-key");
let catalog = CatalogFactory::create(options).await?;

// If you use the short form "abfs://filesystem/warehouse", set the endpoint explicitly:
// options.set("azure.endpoint", "https://account.dfs.core.windows.net");

// Huawei Cloud OBS
let mut options = Options::new();
options.set(CatalogOptions::WAREHOUSE, "obs://bucket/warehouse");
options.set("fs.obs.access.key", "your-access-key-id");
options.set("fs.obs.secret.key", "your-secret-access-key");
options.set("fs.obs.endpoint", "https://obs.cn-north-4.myhuaweicloud.com");
let catalog = CatalogFactory::create(options).await?;

// Google Cloud Storage
let mut options = Options::new();
options.set(CatalogOptions::WAREHOUSE, "gs://bucket/warehouse");
options.set("gcs.credential-path", "/path/to/service-account.json");
let catalog = CatalogFactory::create(options).await?;

// REST catalog
let mut options = Options::new();
options.set(CatalogOptions::METASTORE, "rest");
options.set(CatalogOptions::URI, "http://localhost:8080");
options.set(CatalogOptions::WAREHOUSE, "my_warehouse");
let catalog = CatalogFactory::create(options).await?;
```

Supported metastore types:

| Metastore Type | Description                      |
|----------------|----------------------------------|
| `filesystem`   | Local or remote filesystem (default) |
| `rest`         | REST catalog server              |

### Local Disk Cache

Catalogs can cache immutable Paimon metadata and index file blocks on local
disk. The cache works with both filesystem and REST catalogs:

```rust
let mut options = Options::new();
options.set(CatalogOptions::WAREHOUSE, "s3://bucket/warehouse");
options.set(CatalogOptions::LOCAL_CACHE_ENABLED, "true");
options.set(CatalogOptions::LOCAL_CACHE_DIR, "/var/cache/paimon/worker-1");
options.set(CatalogOptions::LOCAL_CACHE_MAX_SIZE, "20 GiB");
options.set(CatalogOptions::LOCAL_CACHE_BLOCK_SIZE, "1 MiB");
options.set(
    CatalogOptions::LOCAL_CACHE_WHITELIST,
    "meta,global-index",
);
let catalog = CatalogFactory::create(options).await?;
```

| Option | Default | Description |
|--------|---------|-------------|
| `local-cache.enabled` | `false` | Enable catalog-scoped local block caching. |
| `local-cache.dir` | none | Base cache directory; required when caching is enabled. Paimon stores entries in a private versioned child directory. |
| `local-cache.max-size` | unlimited | Maximum encoded disk usage. Values accept byte units such as `512 MiB` or `20 GiB`. |
| `local-cache.block-size` | `1 MiB` | Block size used for cached range reads. |
| `local-cache.whitelist` | `meta,global-index` | Comma-separated eligible types: `meta`, `global-index`, `bucket-index`, `data`, and `file-index`. |

The cache is disk-only and is reused after process restarts. Cache keys include
a catalog-configuration fingerprint and the canonical storage object path, so
catalogs can safely use the same base directory without reading one another's
entries. Runtime cache read, write, validation, and eviction failures are
fail-open: the original storage remains the source of truth. Paimon mutable
markers and temporary files always bypass the cache; other eligible files rely
on Paimon's immutable-file convention. Cache managers using the same canonical
directory in one process share LRU and size accounting; if their configured
limits differ, the smallest `local-cache.max-size` is used. Restart recovery
runs on a blocking worker, reads only block headers and file metadata, and
validates payload CRC lazily on the first hit. Use a separate `local-cache.dir`
for each worker or process because processes do not share exact LRU or size
accounting.

### Manage Databases

```rust
use paimon::Catalog; // import the trait
use std::collections::HashMap;

// Create a database
catalog.create_database("my_db", false, HashMap::new()).await?;

// List databases
let databases = catalog.list_databases().await?;

// Drop a database (cascade = true to drop all tables inside)
catalog.drop_database("my_db", false, true).await?;
```

### Manage Tables

```rust
use paimon::catalog::Identifier;
use paimon::spec::{DataType, IntType, VarCharType, Schema};

// Define a schema
let schema = Schema::builder()
    .column("id", DataType::Int(IntType::new()))
    .column("name", DataType::VarChar(VarCharType::string_type()))
    .build()?;

// Create a table
let identifier = Identifier::new("my_db", "my_table");
catalog.create_table(&identifier, schema, false).await?;

// List tables in a database
let tables = catalog.list_tables("my_db").await?;

// Get a table handle
let table = catalog.get_table(&identifier).await?;
```

## Reading a Table

Paimon Rust uses a scan-then-read pattern: first scan the table to produce splits, then read data from those splits as Arrow `RecordBatch` streams.

```rust
use futures::StreamExt;

// Get a table from the catalog
let table = catalog.get_table(&Identifier::new("my_db", "my_table")).await?;

// Create a read builder
let read_builder = table.new_read_builder();

// Step 1: Scan — produces a Plan containing DataSplits
let plan = {
    let scan = read_builder.new_scan();
    scan.plan().await?
};

// Step 2: Read — consumes splits and returns Arrow RecordBatches
let reader = read_builder.new_read()?;
let mut stream = reader.to_arrow(plan.splits())?;

while let Some(batch) = stream.next().await {
    let batch = batch?;
    println!("RecordBatch: {batch:#?}");
}
```

## Building from Source

```bash
git clone https://github.com/apache/paimon-rust.git
cd paimon-rust
cargo build
```

## Running Tests

```bash
# Unit tests
cargo test

# Integration tests (requires Docker)
make docker-up
cargo test -p paimon-integration-tests
make docker-down
```
