feat(database): use real COUNT(*) for small tables, fall back to estimate for large

row_estimate came from pg_class.reltuples, which is -1 for tables that
have never been ANALYZEd (the common case on a fresh/small DB), so the
admin table list showed -1 for every table — meaningless.

Replace row_estimate with row_count + row_count_estimated:
- total_size < 100MB: SELECT count(*) (real value, cost negligible on
  small tables; identifier quoted via PG escaping to stay injection-safe)
- total_size >= 100MB: fall back to reltuples estimate, flagged so the UI
  can prefix with ~

Frontend now shows real counts (1/2/14...) for small tables and ~N for
large ones; header copy updated to reflect the mixed source.

src/api/database/status.rs

@@ -43,8 +43,10 @@ pub struct DbStatus {
 #[derive(Serialize, Deserialize, Debug, Clone)]
 pub struct TableInfo {
     pub name: String,
-    /// 行数估算（`pg_class.reltuples`，非 COUNT(*)，UI 标注"~估算"）。
+    /// 行数：total_size 小于阈值时为真实 COUNT(*)，否则回退 reltuples 估算（见 row_count_estimated）。
-    pub row_estimate: i64,
+    pub row_count: i64,
+    /// true 表示 row_count 是 reltuples 估算值（大表回退，未 ANALYZE 时 reltuples=-1 会显示为估算）。
+    pub row_count_estimated: bool,
     pub table_size_bytes: i64,
     pub index_size_bytes: i64,
     pub total_size_bytes: i64,
@@ -118,7 +120,9 @@ pub async fn get_db_status() -> Result<DbStatus, ServerFnError> {
             None => (None, None),
         };
 
-        // 表清单：行数用 reltuples 估算，避免大表 COUNT(*) 拖垮库
+        // 表清单：大小/统计走 catalog；行数对小表用真实 COUNT(*)，大表回退 reltuples 估算。
+        // 阈值 100MB：超过则 COUNT(*) 成本过高（全表扫描），降级为估算值并标注。
+        const COUNT_SIZE_THRESHOLD: i64 = 100 * 1024 * 1024;
         let table_rows = client
             .query(
                 "SELECT c.relname, c.reltuples::bigint, pg_relation_size(c.oid), \
@@ -134,20 +138,40 @@ pub async fn get_db_status() -> Result<DbStatus, ServerFnError> {
             )
             .await
             .map_err(AppError::query)?;
-        let tables = table_rows
+        let tables = {
-            .into_iter()
+            let mut out = Vec::with_capacity(table_rows.len());
-            .map(|r| TableInfo {
+            for r in table_rows {
-                name: r.get(0),
+                let name: String = r.get(0);
-                row_estimate: r.get(1),
+                let reltuples: i64 = r.get(1);
-                table_size_bytes: r.get(2),
+                let total_size: i64 = r.get(4);
-                index_size_bytes: r.get(3),
+                // 小表：真实 COUNT(*)；大表：回退 reltuples 估算。
-                total_size_bytes: r.get(4),
+                // relname 来自 pg_class 可信，但表名可能含大写/特殊字符，需 PG 标识符转义（双引号包裹，内部双引号双写）。
-                last_vacuum: r.get(5),
+                let (row_count, estimated) = if total_size < COUNT_SIZE_THRESHOLD {
-                last_analyze: r.get(6),
+                    let ident = format!("\"{}\"", name.replace('"', "\"\""));
-                dead_tuples: r.get(7),
+                    let cnt: i64 = client
-                live_tuples: r.get(8),
+                        .query_one(&format!("SELECT count(*)::bigint FROM {}", ident), &[])
-            })
+                        .await
-            .collect();
+                        .map_err(AppError::query)?
+                        .get(0);
+                    (cnt, false)
+                } else {
+                    (reltuples, true)
+                };
+                out.push(TableInfo {
+                    name,
+                    row_count,
+                    row_count_estimated: estimated,
+                    table_size_bytes: r.get(2),
+                    index_size_bytes: r.get(3),
+                    total_size_bytes: total_size,
+                    last_vacuum: r.get(5),
+                    last_analyze: r.get(6),
+                    dead_tuples: r.get(7),
+                    live_tuples: r.get(8),
+                });
+            }
+            out
+        };
 
         // 索引占用 Top 10
         let index_rows = client

src/pages/admin/system.rs

@@ -273,17 +273,17 @@ fn DbStatusTab() -> Element {
                     }
                 }
 
-                // 表清单
+                // 表清单（小表显示真实行数；大表回退估算，行数前标 ~）
                 div { class: "{ADMIN_TABLE_CLASS}",
                     div { class: "px-4 py-3 border-b border-paper-border text-sm font-medium text-paper-primary",
-                        "表清单（~行数为估算）"
+                        "表清单（行数：小表为真实值，大表标 ~ 为估算）"
                     }
                     div { class: "overflow-x-auto",
                         table { class: "w-full text-sm",
                             thead {
                                 tr { class: "border-b border-paper-border text-left text-paper-secondary",
                                     th { class: "px-4 py-2 font-medium", "表名" }
-                                    th { class: "px-4 py-2 font-medium text-right", "~行数" }
+                                    th { class: "px-4 py-2 font-medium text-right", "行数" }
                                     th { class: "px-4 py-2 font-medium text-right", "表大小" }
                                     th { class: "px-4 py-2 font-medium text-right", "索引大小" }
                                     th { class: "px-4 py-2 font-medium text-right", "总大小" }
@@ -294,7 +294,9 @@ fn DbStatusTab() -> Element {
                                 for t in s.tables.iter() {
                                     tr { class: "border-b border-paper-border last:border-0 hover:bg-paper-entry transition-colors",
                                         td { class: "px-4 py-2 font-mono text-paper-primary", "{t.name}" }
-                                        td { class: "px-4 py-2 text-right text-paper-secondary", "{t.row_estimate}" }
+                                        td { class: "px-4 py-2 text-right text-paper-secondary",
+                                            if t.row_count_estimated { "~{t.row_count}" } else { "{t.row_count}" }
+                                        }
                                         td { class: "px-4 py-2 text-right text-paper-secondary", "{format_bytes(t.table_size_bytes)}" }
                                         td { class: "px-4 py-2 text-right text-paper-secondary", "{format_bytes(t.index_size_bytes)}" }
                                         td { class: "px-4 py-2 text-right text-paper-primary font-medium", "{format_bytes(t.total_size_bytes)}" }