Flutter postgres 和计算

Question

我目前正在开发一个桌面应用程序，可以直接与

postgres

数据库进行通信。由于插入需要数十分钟才能完成并冻结 UI，因此我在网上读到，通过使用隔离或计算，此过程可以变成“多线程”。不幸的是，我在使用计算时收到错误，指出连接无法在隔离中传递。
这是执行的完整代码。这是我得到的错误：

import 'package:excel/excel.dart';
import 'package:flutter/foundation.dart';
import 'package:postgres/postgres.dart';

import '../ConnectionRelated/PostgresConnectionHelper.dart';
import '../ConnectionRelated/RawQueryRunner.dart';

// A class to hold isolate parameters
class TaskParams {
  final Connection connection;
  final Sheet table;
  final int temperatureId;
  final String temperatureDataArray;

  TaskParams(this.connection, this.table, this.temperatureId,
      this.temperatureDataArray);
}

class TemperatureDataInserter2 {
  static void test_function(TaskParams taskParams) async {
    //
    // Connection connection, Sheet table,
    // int temperatureId, String temperatureDataArray
    Sheet? table= taskParams.table;
    Connection connection = taskParams.connection;
    int temperatureId = taskParams.temperatureId;
    String temperatureDataArray = taskParams.temperatureDataArray;

    // Fetch Fluoresence data from column 2 until 49, column indices 1 to 48
    for (int column = 1; column < table.rows[0].length; column++) {
      List<double> fluorescenceData = [];

      for (int i = 1; i < table.rows.length; i++) {
        var cellValue = table.rows[i][column]?.value;
        // Check the type of cell value and convert it to double
        if (cellValue is double) {
          fluorescenceData.add(cellValue);
        } else if (cellValue is int) {
          fluorescenceData.add(cellValue.toDouble());
        }
      }

      // Convert the Fluorescence data list to a PostgreSQL array format
      String fluorescenceDataArray = fluorescenceData.join(',');

      int temperatureIdOffset = temperatureId + column;

      String insertQuery = """
          INSERT INTO public.temperature_data (dna_test_id,
           temperature_celsius_array,
           fluorescence_array)
          VALUES ($temperatureIdOffset,
           ARRAY[$temperatureDataArray]::double precision[],
           ARRAY[$fluorescenceDataArray]::double precision[]);
          """;

      await new RawQueryRunner().run(connection, insertQuery);

      // final result = await compute(fibonacci, 40);
      // print('Fibonacci result: $result');
    }
  }

  Future<void> Execute(Excel excel) async {
    // if (!excel.tables.containsKey(sheetName)) {
    //   print('Sheet "$sheetName" does not exist');
    //   return;
    // }

    // final table = excel.tables[sheetName];
    final table = excel.tables["High Resolu…Melt Target Data"];
    if (table == null) {
      print('Table for sheet "$table" is null');
      return;
    } else {
      print('Table sheet name is: "$table"');
    }

    // // TableRowPrinter().run(table);
    // var table2 = excel.tables["Samples"]!;

    // SamplePrinter().run(table2);

    Connection? connection = await PostgresConnectionHelper().Connect();

    if (connection != null) {
      String sql = """
      INSERT INTO public.dna_test (id)
      SELECT nextval('test_results_id_seq')
      FROM generate_series(1, 48);
      """;

      // Adds 48 empty dna_tests with (the dna_test.id is auto incremental)
      await new RawQueryRunner().run(connection, sql);

      // Get the max id after inserting the new records
      String getMaxIdSql = "SELECT MAX(id) FROM public.dna_test";
      List<List<dynamic>> result = await connection.execute(getMaxIdSql);

      int maxId = result.first.first;
      int temperatureId = maxId - 48;

      // First column is temperatureData which is
      // second row first column (index 1,0)
      List<double> temperatureData = [];
      for (int i = 1; i < table.rows.length; i++) {
        var cellValue = table.rows[i][0]?.value;
        // Check the type of cell value and convert it to double
        if (cellValue is double) {
          temperatureData.add(cellValue);
        } else if (cellValue is int) {
          temperatureData.add(cellValue.toDouble());
        }
      }

      // Declaring and assigning the
      // maxTemperatureValue and minTemperatureValue
      var maxTemperatureValue = temperatureData[0];
      var minTemperatureValue = temperatureData[0];

      for (var i = 0; i < temperatureData.length; i++) {
        // Checking for largest value in the list
        if (temperatureData[i] > maxTemperatureValue) {
          maxTemperatureValue = temperatureData[i];
        }

        // Checking for smallest value in the list
        if (temperatureData[i] < minTemperatureValue) {
          minTemperatureValue = temperatureData[i];
        }
      }

      List<double> temperatureDataMinMaxRange = [];

      // Round the min and max Values on the 2 digits
      var roundedMinTemperatureValue =
          (minTemperatureValue * 100).roundToDouble() / 100;
      var roundedMaxTemperatureValue =
          (maxTemperatureValue * 100).roundToDouble() / 100;

      // Printing the values
      print("Smallest rounded value in the list : $roundedMinTemperatureValue");
      print("Largest rounded value in the list : $roundedMaxTemperatureValue");

      temperatureDataMinMaxRange.add(roundedMinTemperatureValue);
      temperatureDataMinMaxRange.add(roundedMaxTemperatureValue);

      // Convert the temperature data list to a PostgreSQL array format
      String temperatureDataArray = temperatureDataMinMaxRange.join(',');


      //The original code which must become multi threaded
      // Fetch Fluoresence data from column 2 until 49, column indices 1 to 48
      for (int column = 1; column < table.rows[0].length; column++) {
        List<double> fluorescenceData = [];

        for (int i = 1; i < table.rows.length; i++) {
          var cellValue = table.rows[i][column]?.value;
          // Check the type of cell value and convert it to double
          if (cellValue is double) {
            fluorescenceData.add(cellValue);
          } else if (cellValue is int) {
            fluorescenceData.add(cellValue.toDouble());
          }
        }

        // Convert the Fluorescence data list to a PostgreSQL array format
        String fluorescenceDataArray = fluorescenceData.join(',');

        int temperatureIdOffset = temperatureId + column;

        String insertQuery = """
          INSERT INTO public.temperature_data (dna_test_id,
           temperature_celsius_array,
           fluorescence_array)
          VALUES ($temperatureIdOffset,
           ARRAY[$temperatureDataArray]::double precision[],
           ARRAY[$fluorescenceDataArray]::double precision[]);
          """;

        await new RawQueryRunner().run(connection, insertQuery);
      }

      // The code where isolate crashes because it can't accept connection
      await compute(test_function,
          TaskParams(connection, table, temperatureId, temperatureDataArray));
    }
  }
}

Answer 1

设法通过在 test_function 内创建一个新连接来修复它，如下所示

Connection? connection = await PostgresConnectionHelper().Connect();

但是我有兴趣知道是否可能以及将连接作为参数传递的良好实践。