perf: fix N+1 fetchAllForeignKeys with bulk queries (HIGH-6)

- fetchForeignKeys(forTables:) default now calls fetchAllForeignKeys()
  once and filters, leveraging existing bulk SQL in MySQL/PostgreSQL/MSSQL
- Add bulk fetchAllForeignKeys for SQLite using pragma_foreign_key_list
  joined with sqlite_master (single query instead of per-table pragma)
- Add performance guidance docs to PluginDatabaseDriver default impls

Author: datlechin

Plugins/SQLiteDriverPlugin/SQLitePlugin.swift

@@ -551,13 +551,44 @@ final class SQLitePluginDriver: PluginDatabaseDriver, @unchecked Sendable {
     }
 
     func fetchAllForeignKeys(schema: String?) async throws -> [String: [PluginForeignKeyInfo]] {
-        let tables = try await fetchTables(schema: schema)
-        var result: [String: [PluginForeignKeyInfo]] = [:]
-        for table in tables {
-            let fks = try await fetchForeignKeys(table: table.name, schema: schema)
-            if !fks.isEmpty { result[table.name] = fks }
+        let query = """
+            SELECT m.name AS table_name, p.id, p."table" AS referenced_table,
+                   p."from" AS column_name, p."to" AS referenced_column,
+                   p.on_update, p.on_delete
+            FROM sqlite_master m, pragma_foreign_key_list(m.name) p
+            WHERE m.type = 'table' AND m.name NOT LIKE 'sqlite_%'
+            ORDER BY m.name, p.id, p.seq
+            """
+        let result = try await execute(query: query)
+
+        var allForeignKeys: [String: [PluginForeignKeyInfo]] = [:]
+
+        for row in result.rows {
+            guard row.count >= 7,
+                  let tableName = row[0],
+                  let id = row[1],
+                  let refTable = row[2],
+                  let fromCol = row[3],
+                  let toCol = row[4] else {
+                continue
+            }
+
+            let onUpdate = row[5] ?? "NO ACTION"
+            let onDelete = row[6] ?? "NO ACTION"
+
+            let fk = PluginForeignKeyInfo(
+                name: "fk_\(tableName)_\(id)",
+                column: fromCol,
+                referencedTable: refTable,
+                referencedColumn: toCol,
+                onDelete: onDelete,
+                onUpdate: onUpdate
+            )
+
+            allForeignKeys[tableName, default: []].append(fk)
         }
-        return result
+
+        return allForeignKeys
     }
 
     func fetchIndexes(table: String, schema: String?) async throws -> [PluginIndexInfo] {

Plugins/TableProPluginKit/PluginDatabaseDriver.swift

@@ -165,6 +165,8 @@ public extension PluginDatabaseDriver {
 
     func fetchApproximateRowCount(table: String, schema: String?) async throws -> Int? { nil }
 
+    /// Default: fetches columns per-table sequentially (N+1 round-trips).
+    /// SQL drivers should override with a single bulk query (e.g. INFORMATION_SCHEMA.COLUMNS).
     func fetchAllColumns(schema: String?) async throws -> [String: [PluginColumnInfo]] {
         let tables = try await fetchTables(schema: schema)
         var result: [String: [PluginColumnInfo]] = [:]
@@ -174,6 +176,8 @@ public extension PluginDatabaseDriver {
         return result
     }
 
+    /// Default: fetches foreign keys per-table sequentially (N+1 round-trips).
+    /// SQL drivers should override with a single bulk query (e.g. INFORMATION_SCHEMA.KEY_COLUMN_USAGE).
     func fetchAllForeignKeys(schema: String?) async throws -> [String: [PluginForeignKeyInfo]] {
         let tables = try await fetchTables(schema: schema)
         var result: [String: [PluginForeignKeyInfo]] = [:]

TablePro/Core/Database/DatabaseDriver.swift

@@ -231,17 +231,9 @@ extension DatabaseDriver {
     }
 
     func fetchForeignKeys(forTables tableNames: [String]) async throws -> [String: [ForeignKeyInfo]] {
-        var result: [String: [ForeignKeyInfo]] = [:]
-        for name in tableNames {
-            do {
-                let fks = try await fetchForeignKeys(table: name)
-                if !fks.isEmpty { result[name] = fks }
-            } catch {
-                Logger(subsystem: "com.TablePro", category: "DatabaseDriver")
-                    .debug("Failed to fetch foreign keys for \(name): \(error.localizedDescription)")
-            }
-        }
-        return result
+        let all = try await fetchAllForeignKeys()
+        let nameSet = Set(tableNames)
+        return all.filter { nameSet.contains($0.key) }
     }
 
     /// Default fetchAllColumns: falls back to per-table fetchColumns (N+1).