---
<a id="en"></a>
# tosql_meta : Metadata Definition for SQL Structs
Defines the `Meta` struct used to store type and field information for SQL serialization.
## Table of Contents
- [Introduction](#introduction)
- [Features](#features)
- [Usage](#usage)
- [API Reference](#api-reference)
- [Tech Stack](#tech-stack)
- [Directory Structure](#directory-structure)
- [Related Crates](#related-crates)
- [History](#history)
## Introduction
`tosql_meta` is a lightweight crate that provides the `Meta` struct. This struct is essential for the `tosql` ecosystem, as it holds the schema definition (field names and types) of a Rust struct. It is used by `tosql_derive` to generate metadata and by `to_mysql` to construct SQL statements.
## Features
- **Simple Data Structure**: Defines a clean `Meta` struct to hold schema information.
- **Serialization Support**: Implements `bitcode` encoding and decoding for efficient metadata transfer.
- **Interoperability**: Acts as the common schema definition shared across the `tosql` ecosystem.
## Usage
This crate is primarily used internally by `tosql` and `tosql_derive`, but it can be used directly if you are building custom SQL generation tools.
Add it to your `Cargo.toml`:
```toml
[dependencies]
tosql_meta = "0.1"
```
Use it in your code:
```rust
use tosql_meta::Meta;
use kind2sql::Kind;
let meta = Meta {
kind_li: vec![Kind::U64, Kind::String],
field_li: vec!["id".to_string(), "name".to_string()],
};
println!("Fields: {:?}", meta.field_li);
```
## API Reference
### `pub struct Meta`
The core struct of this crate.
```rust
#[derive(bitcode::Encode, bitcode::Decode, PartialEq, Debug)]
pub struct Meta {
pub kind_li: Vec<Kind>,
pub field_li: Vec<String>,
}
```
- **`kind_li`**: A vector of `Kind` enums representing the data types of the fields.
- **`field_li`**: A vector of strings representing the names of the fields.
## Tech Stack
- **Rust**: The core programming language.
- **bitcode**: Used for extremely fast binary serialization of the `Meta` struct.
- **kind2sql**: Provides the `Kind` enum for type definitions.
## Directory Structure
```
tosql_meta/
├── Cargo.toml # Project configuration
├── readme/ # Documentation
│ ├── en.md # English README
│ └── zh.md # Chinese README
└── src/
└── lib.rs # Meta struct definition
```
## Related Crates
- [tosql](https://docs.rs/crate/tosql): The core trait definition.
- [tosql_derive](https://docs.rs/crate/tosql_derive): Macro to derive `ToSqlTrait`.
- [to_mysql](https://docs.rs/crate/to_mysql): MySQL SQL generation logic.
## History
**The Origin of Metadata**
The term "metadata" was coined in 1968 by Philip Baggett, but it wasn't until the 1990s that it became widely used in the tech industry. In the context of databases, metadata is "data about data"—it describes the structure, constraints, and types of the actual data stored in tables. Just as a library card catalog tells you where to find a book without being the book itself, `tosql_meta` tells the SQL generator how to interpret the binary data of your structs.
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---
<a id="zh"></a>
# tosql_meta : SQL 结构体元数据定义
定义了用于存储 SQL 序列化所需的类型和字段信息的 `Meta` 结构体。
## 目录
- [简介](#简介)
- [特性](#特性)
- [使用方法](#使用方法)
- [API 参考](#api-参考)
- [技术栈](#技术栈)
- [目录结构](#目录结构)
- [相关库](#相关库)
- [历史](#历史)
## 简介
`tosql_meta` 是一个轻量级库，提供了 `Meta` 结构体。该结构体在 `tosql` 生态系统中至关重要，因为它保存了 Rust 结构体的模式定义（字段名称和类型）。`tosql_derive` 使用它来生成元数据，`to_mysql` 使用它来构建 SQL 语句。
## 特性
- **简洁的数据结构**：定义了清晰的 `Meta` 结构体来保存模式信息。
- **序列化支持**：实现了 `bitcode` 编码和解码，以支持高效的元数据传输。
- **互操作性**：作为 `tosql` 生态系统中共享的通用模式定义。
## 使用方法
此库主要由 `tosql` 和 `tosql_derive` 内部使用，但如果您正在构建自定义 SQL 生成工具，也可以直接使用它。
将其添加到您的 `Cargo.toml`：
```toml
[dependencies]
tosql_meta = "0.1"
```
在代码中使用：
```rust
use tosql_meta::Meta;
use kind2sql::Kind;
let meta = Meta {
kind_li: vec![Kind::U64, Kind::String],
field_li: vec!["id".to_string(), "name".to_string()],
};
println!("字段: {:?}", meta.field_li);
```
## API 参考
### `pub struct Meta`
本库的核心结构体。
```rust
#[derive(bitcode::Encode, bitcode::Decode, PartialEq, Debug)]
pub struct Meta {
pub kind_li: Vec<Kind>,
pub field_li: Vec<String>,
}
```
- **`kind_li`**：表示字段数据类型的 `Kind` 枚举向量。
- **`field_li`**：表示字段名称的字符串向量。
## 技术栈
- **Rust**：核心编程语言。
- **bitcode**：用于 `Meta` 结构体的极速二进制序列化。
- **kind2sql**：提供用于类型定义的 `Kind` 枚举。
## 目录结构
```
tosql_meta/
├── Cargo.toml # 项目配置
├── readme/ # 文档
│ ├── en.md # 英文 README
│ └── zh.md # 中文 README
└── src/
└── lib.rs # Meta 结构体定义
```
## 相关库
- [tosql](https://docs.rs/crate/tosql)：核心 trait 定义。
- [tosql_derive](https://docs.rs/crate/tosql_derive)：用于派生 `ToSqlTrait` 的宏。
- [to_mysql](https://docs.rs/crate/to_mysql)：MySQL SQL 生成逻辑。
## 历史
**元数据的起源**
“元数据”（Metadata）一词由 Philip Baggett 于 1968 年创造，但直到 20 世纪 90 年代才在科技行业广泛使用。在数据库语境下，元数据是“关于数据的数据”——它描述了存储在表中的实际数据的结构、约束和类型。就像图书馆的卡片目录告诉你去哪里找书但本身不是书一样，`tosql_meta` 告诉 SQL 生成器如何解释结构体的二进制数据。
---
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