152 lines
4.4 KiB
Rust
152 lines
4.4 KiB
Rust
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use std::collections::BTreeMap;
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use std::io;
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use std::path::Path;
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use serde::{Deserialize, Serialize};
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use crate::protocol::{ColumnType, Row, SchemaColumn};
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// 数据字典：记每张表有哪些列、什么类型、多少行。
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#[derive(Debug, Clone, Default, Serialize, Deserialize)]
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/// 一张表的 schema
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pub struct TableSchema {
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pub columns: Vec<SchemaColumn>,
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#[serde(default)]
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pub row_count: u64,
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}
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#[derive(Debug, Default, Serialize, Deserialize)]
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/// 数据字典：表名到 schema
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pub struct Catalog {
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tables: BTreeMap<String, TableSchema>,
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}
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impl Catalog {
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// 读取与保存
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/// 从文件读；不存在给空字典
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pub fn load<P: AsRef<Path>>(path: P) -> io::Result<Self> {
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if !path.as_ref().exists() {
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return Ok(Catalog::default());
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}
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let bytes = std::fs::read(path)?;
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if bytes.is_empty() {
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return Ok(Catalog::default());
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}
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serde_json::from_slice(&bytes).map_err(io::Error::other)
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}
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/// 写回文件
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pub fn save<P: AsRef<Path>>(&self, path: P) -> io::Result<()> {
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let bytes = serde_json::to_vec_pretty(self).map_err(io::Error::other)?;
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std::fs::write(path, bytes)
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}
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// 查询
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/// 一张表的 schema
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pub fn describe(&self, table: &str) -> Option<&TableSchema> {
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self.tables.get(table)
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}
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/// 记录过的所有表名
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pub fn table_names(&self) -> Vec<String> {
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self.tables.keys().cloned().collect()
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}
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// 更新
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/// 按一行数据补列
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pub fn ensure_columns(&mut self, table: &str, row: &Row) {
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let entry = self.tables.entry(table.to_string()).or_default();
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for (k, v) in row {
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if entry.columns.iter().any(|c| &c.name == k) {
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continue;
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}
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if let Some(ty) = infer_type(v) {
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entry.columns.push(SchemaColumn {
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name: k.clone(),
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ty,
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});
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}
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}
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}
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/// 建表；已存在报错
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pub fn create_table(&mut self, table: &str, columns: Vec<SchemaColumn>) -> io::Result<()> {
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if self.tables.contains_key(table) {
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return Err(io::Error::new(
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io::ErrorKind::AlreadyExists,
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format!("table already exists: {}", table),
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));
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}
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self.tables.insert(
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table.to_string(),
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TableSchema {
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columns,
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row_count: 0,
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},
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);
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Ok(())
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}
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/// 按多行数据补列
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pub fn ensure_columns_from_rows(&mut self, table: &str, rows: &[Row]) {
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for r in rows {
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self.ensure_columns(table, r);
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}
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}
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/// 记一次插入：补列 + 行数 +1
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pub fn record_insert(&mut self, table: &str, row: &Row) {
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let entry = self.tables.entry(table.to_string()).or_default();
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for (k, v) in row {
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if entry.columns.iter().any(|c| &c.name == k) {
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continue;
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}
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if let Some(ty) = infer_type(v) {
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entry.columns.push(SchemaColumn { name: k.clone(), ty });
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}
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}
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entry.row_count += 1;
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}
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/// 记一次整表替换：列照补，行数重置
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pub fn record_replace_all(&mut self, table: &str, rows: &[Row]) {
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let entry = self.tables.entry(table.to_string()).or_default();
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for r in rows {
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for (k, v) in r {
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if entry.columns.iter().any(|c| &c.name == k) {
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continue;
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}
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if let Some(ty) = infer_type(v) {
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entry.columns.push(SchemaColumn { name: k.clone(), ty });
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}
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}
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}
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entry.row_count = rows.len() as u64;
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}
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/// 删表
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pub fn drop_table(&mut self, table: &str) -> io::Result<()> {
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if self.tables.remove(table).is_none() {
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return Err(io::Error::new(
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io::ErrorKind::NotFound,
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format!("unknown table: {}", table),
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));
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}
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Ok(())
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}
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}
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// 推断
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/// 由 JSON 值猜列类型
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fn infer_type(v: &serde_json::Value) -> Option<ColumnType> {
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match v {
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serde_json::Value::Number(_) => Some(ColumnType::Int),
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serde_json::Value::String(_) => Some(ColumnType::Str),
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serde_json::Value::Bool(_) => Some(ColumnType::Bool),
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_ => None,
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}
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}
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