MYSQL returns 当我尝试在一个事务中添加超过一百个条目时出现最大连接池错误

Question

我有股票数据库应用程序，因此用户将所有项目输入到稍后添加到数据库的数据网格中，但是只要项目超过 100 个项目，它就会 returns 错误：

Error connecting: Timeout expired. The timeout period elapsed prior to obtaining a connection from the pool. This may have occurred because all pooled connections were in use and max pool size was reached.

代码如下：

 For Each row As DataGridViewRow In DGV_ITEMS.Rows

        If row.IsNewRow = False Then

            Dim ITEM_CODE_VAL As Double = row.Cells(1).Value
            Dim ITEM_QUANTITY_VAL = row.Cells(2).Value
            Dim ITEM_NAME_VAL = row.Cells(3).Value
            Dim ITEM_PRICE_VAL = row.Cells(4).Value
            Dim ITEM_DATE_VAL = row.Cells(5).Value

            'FOR CHECK IF SUPPLIER ALL READY EXISTS
            Dim CON1 As New MySqlConnection("server=localhost; username=root; password=pwd; database=airtech_db;")
            Dim CMD1 As New MySqlCommand("SELECT * FROM `STOCK` where `ITEM_CODE`='" & row.Cells(1).Value & "';", con1)
            Dim dt1 As New DataTable
            Dim DR1 As MySqlDataReader
            CON1.Open()
            dt1.Clear()
            With dt1
                DR1 = CMD1.ExecuteReader
                DR1.Read()
                If DR1.HasRows = True Then
                    'MsgBox("Item already exists")
                    Call ADD_DATA_TO_EXISTING_RECORD(ITEM_CODE_VAL, ITEM_QUANTITY_VAL)
                    CON1.Close()
                Else
                    'Using con As New MySqlConnection(constring)
                    Using cmd As New MySqlCommand("Insert into `stock` values(null,@ITEM_CODE,@ITEM_NAME,@ITEM_PRICE,@ITEM_QUANTITY,@SALE_PRICE,@STOCK_DATE,'N/A');", con)
                        Try
                            Dim CON As New MySqlConnection("server=localhost; username=root; password=pwd; database=airtech_db;")
                            con.Open()
                            cmd.Parameters.AddWithValue("@ITEM_CODE", row.Cells(1).Value)
                            cmd.Parameters.AddWithValue("@ITEM_NAME", row.Cells(3).Value)
                            cmd.Parameters.AddWithValue("@ITEM_PRICE", row.Cells(4).Value)
                            cmd.Parameters.AddWithValue("@ITEM_QUANTITY", row.Cells(2).Value)
                            cmd.Parameters.AddWithValue("@SALE_PRICE", row.Cells(5).Value)
                            cmd.Parameters.AddWithValue("@STOCK_DATE", Date.Now.ToString("yyyy-MM-dd"))
                            cmd.ExecuteNonQuery()
                        Finally
                            con.Close()
                        End Try

                    End Using
                    'End Using

                End If
            End With
        End If
    Next

Answer 1

如果在循环中进行查询，将连接字符串移出循环，让命令和数据读取器在循环内完成工作

例如

Using con As New MySqlConnection(constring)
        con.Open()
        'any for Loop you want to run

        Using cmd As New MySqlCommand("Insert into `stock` values(null,@ITEM_CODE,@ITEM_NAME,@ITEM_PRICE,@ITEM_QUANTITY,@SALE_PRICE,@STOCK_DATE,'N/A');", con)
            cmd.Parameters.AddWithValue("@ITEM_CODE", row.Cells(1).Value)
            cmd.Parameters.AddWithValue("@ITEM_NAME", row.Cells(3).Value)
            cmd.Parameters.AddWithValue("@ITEM_PRICE", row.Cells(4).Value)
            cmd.Parameters.AddWithValue("@ITEM_QUANTITY", row.Cells(2).Value)
            cmd.Parameters.AddWithValue("@SALE_PRICE", row.Cells(5).Value)
            cmd.Parameters.AddWithValue("@STOCK_DATE", Date.Now.ToString("yyyy-MM-dd"))
            cmd.ExecuteNonQuery()
        End Using
    End Using
    Next
    con.Close()

MYSQL returns 当我尝试在一个事务中添加超过一百个条目时出现最大连接池错误

MYSQL returns MAXIMUM CONNECTION POOL error when I try to add more then hundred entries in one transaction

mysql

vb.net

visual-studio-2019