表结构改动进 WAL

chusql-core/storage/src/runtime.rs

@@ -280,6 +280,35 @@ impl Server {
                 let _ = std::fs::remove_file(self.index_path(table, column));
                 Ok(())
             }
+            WalOp::CreateTable { table, columns } => {
+                self.with_table(table, |_t| Ok(()))?;
+                let mut c = self.catalog.lock().map_err(|_| std::io::Error::other("catalog lock poisoned"))?;
+                c.create_table(table, columns.clone())?;
+                c.save(self.catalog_path())
+            }
+            WalOp::DropTable { table } => {
+                let dropped_indexes: Vec<String> = {
+                    let mut c = self.catalog.lock().map_err(|_| std::io::Error::other("catalog lock poisoned"))?;
+                    let idx = c
+                        .describe(table)
+                        .map(|s| s.indexes.iter().map(|i| i.column.clone()).collect())
+                        .unwrap_or_default();
+                    if c.describe(table).is_some() {
+                        c.drop_table(table)?;
+                        c.save(self.catalog_path())?;
+                    }
+                    idx
+                };
+                self.tables.lock().map_err(|_| std::io::Error::other("table lock poisoned"))?.remove(table);
+                let _ = std::fs::remove_file(self.table_path(table));
+                let _ = std::fs::remove_file(self.index_path(table, "id"));
+                for col in dropped_indexes {
+                    let _ = std::fs::remove_file(self.index_path(table, &col));
+                }
+                Ok(())
+            }
+            WalOp::CreateIndex { table, column } => self.apply_create_index(table, column),
+            WalOp::DropIndex { table, column } => self.apply_drop_index(table, column),
             WalOp::ReplaceSchema { table, columns, rows } => {
                 let old_indexes: Vec<String> = {
                     let c = self.catalog.lock().map_err(|_| std::io::Error::other("catalog lock poisoned"))?;
@@ -426,6 +455,8 @@ impl Server {
         let table = match op {
             WalOp::HideColumn { .. } => return Ok(()),
             WalOp::Commit => return Ok(()),
+            // 删表后不需要写回
+            WalOp::DropTable { .. } => return Ok(()),
             WalOp::Accounts { .. } => USERS_TABLE,
             WalOp::Insert { table, .. }
             | WalOp::InsertBatch { table, .. }
@@ -433,6 +464,9 @@ impl Server {
             | WalOp::ReplaceAll { table, .. }
             | WalOp::DropColumn { table, .. }
             | WalOp::Compact { table, .. }
+            | WalOp::CreateTable { table, .. }
+            | WalOp::CreateIndex { table, .. }
+            | WalOp::DropIndex { table, .. }
             | WalOp::ReplaceSchema { table, .. } => table,
         };
         self.with_table(table, |t| t.flush())
@@ -515,10 +549,27 @@ impl Server {
                 let c = self.catalog.lock().unwrap();
                 Ok(c.describe(table).is_some_and(|s| !s.columns.iter().any(|col| &col.name == column)))
             }
+            WalOp::CreateTable { table, .. } => self.table_exists(table),
+            WalOp::DropTable { table } => Ok(!self.table_exists(table)?
+                && !self.table_path(table).exists()
+                && !self.index_path(table, "id").exists()),
+            WalOp::CreateIndex { table, column } => Ok(self.index_exists(table, column)),
+            WalOp::DropIndex { table, column } => {
+                Ok(!self.index_exists(table, column) && !self.index_path(table, column).exists())
+            }
             _ => Ok(false),
         }
     }
 
+    /// 这个列有索引吗
+    fn index_exists(&self, table: &str, column: &str) -> bool {
+        self.catalog
+            .lock()
+            .unwrap()
+            .describe(table)
+            .is_some_and(|s| s.indexes.iter().any(|i| i.column == column))
+    }
+
     /// 这些行是不是都已经在表里
     fn applied_rows(&self, table: &str, rows: &[Row]) -> std::io::Result<bool> {
         if rows.is_empty() {
@@ -598,35 +649,38 @@ impl Server {
         Ok(())
     }
 
-    /// 给一列建索引
+    /// 建索引前的检查：内置列、未知表列、重复索引
-    fn create_index(&self, table: &str, column: &str) -> std::io::Result<()> {        if column == "id" {
+    fn check_create_index(&self, table: &str, column: &str) -> std::io::Result<()> {
+        if column == "id" {
             return Err(std::io::Error::new(
                 std::io::ErrorKind::AlreadyExists,
                 "id is the built-in index and cannot be created twice",
             ));
         }
-        {
+        let c = self.catalog.lock().map_err(|_| std::io::Error::other("catalog lock poisoned"))?;
-            let c = self.catalog.lock().unwrap();
+        let Some(schema) = c.describe(table) else {
-            let Some(schema) = c.describe(table) else {
+            return Err(std::io::Error::new(
-                return Err(std::io::Error::new(
+                std::io::ErrorKind::NotFound,
-                    std::io::ErrorKind::NotFound,
+                format!("unknown table: {}", table),
-                    format!("unknown table: {}", table),
+            ));
-                ));
+        };
-            };
+        if !schema.columns.iter().any(|c| c.name == column) {
-            if !schema.columns.iter().any(|c| c.name == column) {
+            return Err(std::io::Error::new(
-                return Err(std::io::Error::new(
+                std::io::ErrorKind::NotFound,
-                    std::io::ErrorKind::NotFound,
+                format!("unknown column: {}", column),
-                    format!("unknown column: {}", column),
+            ));
-                ));
-            }
-            if schema.indexes.iter().any(|i| i.column == column) {
-                return Err(std::io::Error::new(
-                    std::io::ErrorKind::AlreadyExists,
-                    format!("index on column \"{}\" already exists", column),
-                ));
-            }
         }
+        if schema.indexes.iter().any(|i| i.column == column) {
+            return Err(std::io::Error::new(
+                std::io::ErrorKind::AlreadyExists,
+                format!("index on column \"{}\" already exists", column),
+            ));
+        }
+        Ok(())
+    }
 
+    /// 建索引文件并登记到 catalog
+    fn apply_create_index(&self, table: &str, column: &str) -> std::io::Result<()> {
         let path = self.index_path(table, column);
         let (page_size, order, pool) = (self.cfg.page_size, self.cfg.btree_order, self.cfg.pool_size);
         self.with_table(table, |t| {
@@ -639,33 +693,43 @@ impl Server {
         c.save(self.catalog_path())
     }
 
-    /// 去掉一列的索引（连文件一起删）
+    /// 去索引前的检查：内置列、未知表、索引不存在
-    fn drop_index(&self, table: &str, column: &str) -> std::io::Result<()> {
+    fn check_drop_index(&self, table: &str, column: &str) -> std::io::Result<()> {
         if column == "id" {
             return Err(std::io::Error::new(
                 std::io::ErrorKind::InvalidInput,
                 "id is the built-in index and cannot be dropped",
             ));
         }
-        {
+        let c = self.catalog.lock().map_err(|_| std::io::Error::other("catalog lock poisoned"))?;
-            let c = self.catalog.lock().unwrap();
+        let Some(schema) = c.describe(table) else {
-            if c.describe(table).is_none() {
+            return Err(std::io::Error::new(
-                return Err(std::io::Error::new(
+                std::io::ErrorKind::NotFound,
-                    std::io::ErrorKind::NotFound,
+                format!("unknown table: {}", table),
-                    format!("unknown table: {}", table),
+            ));
-                ));
+        };
+        if !schema.indexes.iter().any(|i| i.column == column) {
+            return Err(std::io::Error::new(
+                std::io::ErrorKind::NotFound,
+                format!("no index on column \"{}\"", column),
+            ));
+        }
+        Ok(())
+    }
+
+    /// 摘掉索引定义并删文件；重放时容忍 catalog 里已没有它
+    fn apply_drop_index(&self, table: &str, column: &str) -> std::io::Result<()> {
+        if self.table_exists(table)? {
+            self.with_table(table, |t| {
+                t.detach_index(column);
+                Ok(())
+            })?;
+            let mut c = self.catalog.lock().map_err(|_| std::io::Error::other("catalog lock poisoned"))?;
+            if c.describe(table).is_some_and(|s| s.indexes.iter().any(|i| i.column == column)) {
+                c.remove_index(table, column)?;
+                c.save(self.catalog_path())?;
             }
         }
-        self.with_table(table, |t| {
-            t.detach_index(column);
-            Ok(())
-        })?;
-
-        let mut c = self.catalog.lock().unwrap();
-        c.remove_index(table, column)?;
-        c.save(self.catalog_path())?;
-        drop(c);
-
         let _ = std::fs::remove_file(self.index_path(table, column));
         Ok(())
     }
@@ -892,13 +956,6 @@ impl Server {
 
     /// 持门后分发一条请求
     fn dispatch(&self, req: Request) -> Response {
-        let _ddl_guard = if matches!(req, Request::CreateTable { .. } | Request::DropTable { .. }
-            | Request::CreateIndex { .. } | Request::DropIndex { .. }) {
-            match self.write_lock.lock() {
-                Ok(guard) => Some(guard),
-                Err(_) => return Response::Error { message: "write lock poisoned".into() },
-            }
-        } else { None };
         if self.recovery_required.load(Ordering::Acquire) && !matches!(req, Request::Ping) {
             return Response::Error { message: "storage recovery required".into() };
         }
@@ -1168,76 +1225,76 @@ impl Server {
 
             Request::CreateTable { table, columns } => {
                 log_debug!(request, "create_table table={} cols={}", table, columns.len());
-
+                let exists = match self.table_exists(&table) {
-                {
+                    Ok(exists) => exists,
-                    let c = self.catalog.lock().unwrap();
+                    Err(e) => {
-                    if c.describe(&table).is_some() {
                         return Response::Error {
-                            message: format!("create_table {}: table already exists", table),
+                            message: format!("create_table {}: {}", table, e),
-                        };
+                        }
+                    }
+                };
+                if exists {
+                    return Response::Error {
+                        message: format!("create_table {}: table already exists", table),
+                    };
+                }
+                let tname = table.clone();
+                let op = WalOp::CreateTable { table, columns };
+                match self.write_via_wal(&op) {
+                    Ok(()) => Response::Ok,
+                    Err(e) => {
+                        log_warn!(request, "create_table {}: {}", tname, e);
+                        Response::Error {
+                            message: format!("create_table {}: {}", tname, e),
+                        }
                     }
                 }
-
-                if let Err(e) = self.with_table(&table, |_t| Ok(())) {
-                    return Response::Error {
-                        message: format!("create_table {}: {}", table, e),
-                    };
-                }
-
-                let mut c = self.catalog.lock().unwrap();
-                if let Err(e) = c.create_table(&table, columns) {
-                    return Response::Error {
-                        message: format!("create_table {}: {}", table, e),
-                    };
-                }
-                if let Err(e) = c.save(self.catalog_path()) {
-                    return Response::Error {
-                        message: format!("create_table {}: catalog save: {}", table, e),
-                    };
-                }
-                Response::Ok
             }
 
             Request::DropTable { table } => {
                 log_debug!(request, "drop_table table={}", table);
-
+                let exists = match self.table_exists(&table) {
-                let dropped_indexes: Vec<String> = {
+                    Ok(exists) => exists,
-                    let mut c = self.catalog.lock().unwrap();
+                    Err(e) => {
-                    let idx = c
-                        .describe(&table)
-                        .map(|s| s.indexes.iter().map(|i| i.column.clone()).collect())
-                        .unwrap_or_default();
-                    if let Err(e) = c.drop_table(&table) {
                         return Response::Error {
                             message: format!("drop_table {}: {}", table, e),
-                        };
+                        }
                     }
-                    if let Err(e) = c.save(self.catalog_path()) {
-                        return Response::Error {
-                            message: format!("drop_table {}: catalog save: {}", table, e),
-                        };
-                    }
-                    idx
                 };
-
+                if !exists {
-                self.tables.lock().unwrap().remove(&table);
+                    return Response::Error {
-                let _ = std::fs::remove_file(self.table_path(&table));
+                        message: format!("drop_table {}: unknown table: {}", table, table),
-                let _ = std::fs::remove_file(self.index_path(&table, "id"));
+                    };
-                for col in dropped_indexes {
+                }
-                    let _ = std::fs::remove_file(self.index_path(&table, &col));
+                let tname = table.clone();
+                let op = WalOp::DropTable { table };
+                match self.write_via_wal(&op) {
+                    Ok(()) => Response::Ok,
+                    Err(e) => {
+                        log_warn!(request, "drop_table {}: {}", tname, e);
+                        Response::Error {
+                            message: format!("drop_table {}: {}", tname, e),
+                        }
+                    }
                 }
-
-                Response::Ok
             }
 
             Request::CreateIndex { table, column } => {
                 log_debug!(request, "create_index table={} column={}", table, column);
-                match self.create_index(&table, &column) {
+                if let Err(e) = self.check_create_index(&table, &column) {
+                    log_warn!(request, "create_index {}({}): {}", table, column, e);
+                    return Response::Error {
+                        message: format!("create_index {}({}): {}", table, column, e),
+                    };
+                }
+                let tname = table.clone();
+                let op = WalOp::CreateIndex { table, column };
+                match self.write_via_wal(&op) {
                     Ok(()) => Response::Ok,
                     Err(e) => {
-                        log_warn!(request, "create_index {}({}): {}", table, column, e);
+                        log_warn!(request, "create_index {}: {}", tname, e);
                         Response::Error {
-                            message: format!("create_index {}({}): {}", table, column, e),
+                            message: format!("create_index {}: {}", tname, e),
                         }
                     }
                 }
@@ -1245,12 +1302,20 @@ impl Server {
 
             Request::DropIndex { table, column } => {
                 log_debug!(request, "drop_index table={} column={}", table, column);
-                match self.drop_index(&table, &column) {
+                if let Err(e) = self.check_drop_index(&table, &column) {
+                    log_warn!(request, "drop_index {}({}): {}", table, column, e);
+                    return Response::Error {
+                        message: format!("drop_index {}({}): {}", table, column, e),
+                    };
+                }
+                let tname = table.clone();
+                let op = WalOp::DropIndex { table, column };
+                match self.write_via_wal(&op) {
                     Ok(()) => Response::Ok,
                     Err(e) => {
-                        log_warn!(request, "drop_index {}({}): {}", table, column, e);
+                        log_warn!(request, "drop_index {}: {}", tname, e);
                         Response::Error {
-                            message: format!("drop_index {}({}): {}", table, column, e),
+                            message: format!("drop_index {}: {}", tname, e),
                         }
                     }
                 }

chusql-core/storage/src/wal.rs

@@ -19,6 +19,10 @@ const OP_REPLACE_SCHEMA: u8 = 7;
 const OP_HIDE_COLUMN: u8 = 8;
 const OP_COMPACT: u8 = 9;
 const OP_COMMIT: u8 = 10;
+const OP_CREATE_TABLE: u8 = 11;
+const OP_DROP_TABLE: u8 = 12;
+const OP_CREATE_INDEX: u8 = 13;
+const OP_DROP_INDEX: u8 = 14;
 
 #[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
 pub enum WalOp {
@@ -51,6 +55,21 @@ pub enum WalOp {
         columns: Vec<SchemaColumn>,
         rows: Vec<Row>,
     },
+    CreateTable {
+        table: String,
+        columns: Vec<SchemaColumn>,
+    },
+    DropTable {
+        table: String,
+    },
+    CreateIndex {
+        table: String,
+        column: String,
+    },
+    DropIndex {
+        table: String,
+        column: String,
+    },
     /// 一组写操作的提交标记；没有标记的组算未提交
     Commit,
 }
@@ -67,6 +86,11 @@ struct ReplaceSchemaPayload {
     rows: Vec<Row>,
 }
 
+#[derive(Debug, Serialize, Deserialize)]
+struct CreateTablePayload {
+    columns: Vec<SchemaColumn>,
+}
+
 pub struct Wal {
     path: PathBuf,
     handle: Mutex<Option<File>>,
@@ -319,6 +343,23 @@ fn encode(op: &WalOp, lsn: u64) -> io::Result<Vec<u8>> {
             .map_err(io::Error::other)?;
             (OP_REPLACE_SCHEMA, table.clone(), p)
         }
+        WalOp::CreateTable { table, columns } => (
+            OP_CREATE_TABLE,
+            table.clone(),
+            serde_json::to_vec(&CreateTablePayload { columns: columns.clone() })
+                .map_err(io::Error::other)?,
+        ),
+        WalOp::DropTable { table } => (OP_DROP_TABLE, table.clone(), Vec::new()),
+        WalOp::CreateIndex { table, column } => (
+            OP_CREATE_INDEX,
+            table.clone(),
+            serde_json::to_vec(column).map_err(io::Error::other)?,
+        ),
+        WalOp::DropIndex { table, column } => (
+            OP_DROP_INDEX,
+            table.clone(),
+            serde_json::to_vec(column).map_err(io::Error::other)?,
+        ),
         WalOp::Commit => (OP_COMMIT, String::new(), Vec::new()),
     };
 
@@ -410,6 +451,25 @@ fn decode_body(body: &[u8]) -> Result<(u64, WalOp), String> {
                 rows: p.rows,
             }
         }
+        OP_CREATE_TABLE => {
+            let p: CreateTablePayload = serde_json::from_slice(payload)
+                .map_err(|e| format!("bad create_table payload: {e}"))?;
+            WalOp::CreateTable {
+                table,
+                columns: p.columns,
+            }
+        }
+        OP_DROP_TABLE => WalOp::DropTable { table },
+        OP_CREATE_INDEX => {
+            let column: String = serde_json::from_slice(payload)
+                .map_err(|e| format!("bad create_index payload: {e}"))?;
+            WalOp::CreateIndex { table, column }
+        }
+        OP_DROP_INDEX => {
+            let column: String = serde_json::from_slice(payload)
+                .map_err(|e| format!("bad drop_index payload: {e}"))?;
+            WalOp::DropIndex { table, column }
+        }
         other => return Err(format!("unknown op type: {}", other)),
     };
     Ok((lsn, op))

chusql-core/storage/tests/runtime_test.rs

@@ -1201,6 +1201,199 @@ fn uncommitted_group_is_discarded_on_restart() -> Result<(), Box<dyn std::error:
     Ok(())
 }
 
+/// 直接删表后文件不留，重建同名表是空表
+#[test]
+fn drop_table_removes_files() -> Result<(), Box<dyn std::error::Error>> {
+    let (_srv, data) = start_server();
+    let mut c = connect()?;
+    request_ok(&mut c, serde_json::json!({"method":"create_table","table":"m4_gone","columns":[{"name":"id","ty":"int"},{"name":"note","ty":"text"}]}))?;
+    request_ok(&mut c, serde_json::json!({"method":"create_index","table":"m4_gone","column":"note"}))?;
+    request_ok(&mut c, serde_json::json!({"method":"insert","table":"m4_gone","row":{"id":1,"note":"a"}}))?;
+    assert!(data.path().join("databases/main/m4_gone.db").exists(), "建表要落数据文件");
+
+    request_ok(&mut c, serde_json::json!({"method":"drop_table","table":"m4_gone"}))?;
+    assert!(!data.path().join("databases/main/m4_gone.db").exists(), "数据文件要删掉");
+    assert!(!data.path().join("databases/main/m4_gone.idx").exists(), "id 索引要删掉");
+    assert!(!data.path().join("databases/main/m4_gone.note.idx").exists(), "二级索引要删掉");
+
+    request_ok(&mut c, serde_json::json!({"method":"create_table","table":"m4_gone","columns":[{"name":"id","ty":"int"},{"name":"note","ty":"text"}]}))?;
+    let rows: serde_json::Value =
+        serde_json::from_str(&send(&mut c, r#"{"method":"scan","table":"m4_gone"}"#))?;
+    assert_eq!(rows["rows"], serde_json::json!([]), "旧数据不能复活");
+    Ok(())
+}
+
+/// 建表操作进了 WAL 后，重启按提交组把表重建出来
+#[test]
+fn create_table_replays_after_restart() -> Result<(), Box<dyn std::error::Error>> {
+    use chusql_core_storage::protocol::SchemaColumn;
+    use chusql_core_storage::wal::{Wal, WalOp};
+    let (server, data) = start_server();
+    drop(server);
+
+    let group = vec![WalOp::CreateTable {
+        table: "m4_create".into(),
+        columns: vec![
+            SchemaColumn {
+                name: "id".into(),
+                ty: "int".into(),
+                ..Default::default()
+            },
+            SchemaColumn {
+                name: "note".into(),
+                ty: "text".into(),
+                ..Default::default()
+            },
+        ],
+    }];
+    let wal = Wal::new(data.path().join("databases/main/wal.log"));
+    let commit_lsn = wal.append_group(&group)?;
+    drop(wal);
+
+    let _server = start_server_in(data.path());
+    let mut c = connect()?;
+    let schema: serde_json::Value =
+        serde_json::from_str(&send(&mut c, r#"{"method":"describe_table","table":"m4_create"}"#))?;
+    assert_eq!(schema["status"], "schema", "{schema}");
+    assert_eq!(schema["columns"][1]["name"], "note", "{schema}");
+    assert!(data.path().join("databases/main/m4_create.db").exists(), "建表要落数据文件");
+    let checkpoint = std::fs::read(data.path().join("databases/main/wal.checkpoint"))?;
+    assert_eq!(u64::from_le_bytes(checkpoint[..8].try_into()?), commit_lsn);
+    Ok(())
+}
+
+/// 删表操作进了 WAL 后，重启把表和数据文件一起清掉
+#[test]
+fn drop_table_replays_after_restart() -> Result<(), Box<dyn std::error::Error>> {
+    use chusql_core_storage::wal::{Wal, WalOp};
+    let (server, data) = start_server();
+    let mut c = connect()?;
+    request_ok(&mut c, serde_json::json!({"method":"create_table","table":"m4_drop","columns":[{"name":"id","ty":"int"}]}))?;
+    request_ok(&mut c, serde_json::json!({"method":"insert","table":"m4_drop","row":{"id":1}}))?;
+    drop(c);
+    drop(server);
+
+    let wal = Wal::new(data.path().join("databases/main/wal.log"));
+    wal.append_group(&[WalOp::DropTable {
+        table: "m4_drop".into(),
+    }])?;
+    drop(wal);
+
+    let _server = start_server_in(data.path());
+    let mut c = connect()?;
+    let schema: serde_json::Value =
+        serde_json::from_str(&send(&mut c, r#"{"method":"describe_table","table":"m4_drop"}"#))?;
+    assert_eq!(schema["status"], "error", "{schema}");
+    let left: Vec<String> = std::fs::read_dir(data.path().join("databases/main"))?
+        .map(|e| e.unwrap().file_name().to_string_lossy().into_owned())
+        .collect();
+    assert!(!data.path().join("databases/main/m4_drop.db").exists(), "数据文件要删掉，现存 {left:?}");
+    assert!(!data.path().join("databases/main/m4_drop.idx").exists(), "id 索引要删掉，现存 {left:?}");
+    Ok(())
+}
+
+/// 建索引操作进了 WAL 后，重启补建索引文件
+#[test]
+fn create_index_replays_after_restart() -> Result<(), Box<dyn std::error::Error>> {
+    use chusql_core_storage::wal::{Wal, WalOp};
+    let (server, data) = start_server();
+    let mut c = connect()?;
+    request_ok(&mut c, serde_json::json!({"method":"create_table","table":"m4_idx","columns":[{"name":"id","ty":"int"},{"name":"note","ty":"text"}]}))?;
+    request_ok(&mut c, serde_json::json!({"method":"insert","table":"m4_idx","row":{"id":1,"note":"a"}}))?;
+    drop(c);
+    drop(server);
+
+    let wal = Wal::new(data.path().join("databases/main/wal.log"));
+    wal.append_group(&[WalOp::CreateIndex {
+        table: "m4_idx".into(),
+        column: "note".into(),
+    }])?;
+    drop(wal);
+
+    let _server = start_server_in(data.path());
+    let mut c = connect()?;
+    let schema: serde_json::Value =
+        serde_json::from_str(&send(&mut c, r#"{"method":"describe_table","table":"m4_idx"}"#))?;
+    assert_eq!(schema["status"], "schema", "{schema}");
+    let indexed = |schema: &serde_json::Value, column: &str| {
+        schema["indexes"]
+            .as_array()
+            .map(|list| list.iter().any(|i| i["column"] == column))
+            .unwrap_or(false)
+    };
+    assert!(indexed(&schema, "note"), "{schema}");
+    assert!(data.path().join("databases/main/m4_idx.note.idx").exists(), "索引文件要建出来");
+    let found: serde_json::Value = serde_json::from_str(&send(
+        &mut c,
+        r#"{"method":"lookup_by_index","table":"m4_idx","column":"note","key":"a"}"#,
+    ))?;
+    assert_eq!(found["rows"], serde_json::json!([{"id":1,"note":"a"}]), "{found}");
+    Ok(())
+}
+
+/// 删索引操作进了 WAL 后，重启清掉索引定义和文件
+#[test]
+fn drop_index_replays_after_restart() -> Result<(), Box<dyn std::error::Error>> {
+    use chusql_core_storage::wal::{Wal, WalOp};
+    let (server, data) = start_server();
+    let mut c = connect()?;
+    request_ok(&mut c, serde_json::json!({"method":"create_table","table":"m4_didx","columns":[{"name":"id","ty":"int"},{"name":"note","ty":"text"}]}))?;
+    request_ok(&mut c, serde_json::json!({"method":"create_index","table":"m4_didx","column":"note"}))?;
+    drop(c);
+    drop(server);
+
+    let wal = Wal::new(data.path().join("databases/main/wal.log"));
+    wal.append_group(&[WalOp::DropIndex {
+        table: "m4_didx".into(),
+        column: "note".into(),
+    }])?;
+    drop(wal);
+
+    let _server = start_server_in(data.path());
+    let mut c = connect()?;
+    let schema: serde_json::Value =
+        serde_json::from_str(&send(&mut c, r#"{"method":"describe_table","table":"m4_didx"}"#))?;
+    assert_eq!(schema["status"], "schema", "{schema}");
+    let columns: Vec<&str> = schema["indexes"]
+        .as_array()
+        .map(|list| list.iter().filter_map(|i| i["column"].as_str()).collect())
+        .unwrap_or_default();
+    assert_eq!(columns, vec!["id"], "{schema}");
+    assert!(!data.path().join("databases/main/m4_didx.note.idx").exists(), "索引文件要删掉");
+    Ok(())
+}
+
+/// 已生效的建表记录重启时被跳过，不报恢复失败
+#[test]
+fn already_applied_create_table_is_skipped_on_restart() -> Result<(), Box<dyn std::error::Error>> {
+    use chusql_core_storage::protocol::SchemaColumn;
+    use chusql_core_storage::wal::{Wal, WalOp};
+    let (server, data) = start_server();
+    let mut c = connect()?;
+    request_ok(&mut c, serde_json::json!({"method":"create_table","table":"m4_done","columns":[{"name":"id","ty":"int"}]}))?;
+    drop(c);
+    drop(server);
+
+    let wal = Wal::new(data.path().join("databases/main/wal.log"));
+    wal.append_group(&[WalOp::CreateTable {
+        table: "m4_done".into(),
+        columns: vec![SchemaColumn {
+            name: "id".into(),
+            ty: "int".into(),
+            ..Default::default()
+        }],
+    }])?;
+    drop(wal);
+
+    let _server = start_server_in(data.path());
+    let mut c = connect()?;
+    let schema: serde_json::Value =
+        serde_json::from_str(&send(&mut c, r#"{"method":"describe_table","table":"m4_done"}"#))?;
+    assert_eq!(schema["status"], "schema", "{schema}");
+    assert_eq!(std::fs::metadata(data.path().join("databases/main/wal.log"))?.len(), 0);
+    Ok(())
+}
+
 /// 给第二列建索引后能按那一列查
 #[test]
 fn create_index_on_secondary_column() {

docs/architecture.md

@@ -51,7 +51,7 @@ chusql-server
 
 显式事务在会话层实现：`BEGIN` 把当前数据库整库读成内存快照，事务内的语句都在快照上执行；`COMMIT` 计算快照与库的差分，用一条 `apply_transaction` 请求交给存储层应用；`ROLLBACK` 直接丢弃快照。因此隔离级别是快照读加原子提交：事务里看不到别的事务未提交或后来提交的改动，提交对外一次性可见。
 
-WAL 负责崩溃恢复：每条记录带自增 LSN，一组写操作与一条提交标记一次落盘；进程重启时按标记分组重放已提交的记录、丢弃没有标记的整组，重放前逐条做幂等检查，恢复结束把最大 LSN 写进 `wal.checkpoint` 并清空 WAL。`SystemStatus` 应答里的 `last_lsn` 报告该检查点 LSN。
+WAL 负责崩溃恢复：每条记录带自增 LSN，一组写操作与一条提交标记一次落盘；进程重启时按标记分组重放已提交的记录、丢弃没有标记的整组，重放前逐条做幂等检查，恢复结束把最大 LSN 写进 `wal.checkpoint` 并清空 WAL。`SystemStatus` 应答里的 `last_lsn` 报告该检查点 LSN。建表、删表、建索引、删索引与数据改动走同一条 WAL，恢复时一并重放。
 
 系统数据库及部分管理操作仅允许管理员访问。