Question

目前，我已在每个图表的开头调用数据库连接以获取数据集，并在加载数据集后关闭连接。

有没有办法全局调用数据库连接，所以我们不必每次都调用它。我认为这会提高速度，同时代码也很容易维护。

示例代码：

    output$moveyear1 <- renderPlot({
    #DB connection
    con = dbConnect(MySQL(), user='', password='', db='', host='')
    # query to fetch data.
    query = paste("select * from table1 ",sep="")
    result = dbGetQuery(con, query)
    dbDisconnect(con)
    # draw the graph
    ggplot(result, aes(gameYear,DEPARTMENT_NAME)) + 
      geom_tile(color="white", size=0.1,aes(fill=MoveCount))+
      facet_wrap(~TEAM_ID) + labs(x="GameYear") + ggtitle("Total Move made in a Year")
  }})

  output$avgtt <- renderPlot({
    #DB connection
    con = dbConnect(MySQL(), user='', password='', db='', host='')
    # query to fetch data.
    query = paste("select * from table2",sep="")
    result = dbGetQuery(con, query)
    dbDisconnect(con)
    # draw the graph
    ggplot(result, aes(gameYear,DEPARTMENT_NAME)) + 
      geom_tile(color="white", size=0.1,aes(fill=AvgTT))+
      facet_wrap(~TEAM_ID) + labs(x="GameYear") + ggtitle("Average Time taken for Move")
  }})

Answer 1

将其放在名为global.R的文件中，或者将其放在服务器和ui函数之外：

library(DBI) ##or whichever one you're using
#DB connection
con = dbConnect(MySQL(), user='', password='', db='', host='')
# query to fetch data.
query = paste("select * from table1 ",sep="")
result1 = dbGetQuery(con, query)
dbDisconnect(con)
   #leave the connection open if they're from the same place
#DB connection
con = dbConnect(MySQL(), user='', password='', db='', host='')
# query to fetch data.
query = paste("select * from table2",sep="")
result2 = dbGetQuery(con, query)
dbDisconnect(con)

ui <- fluidPage(

# Application title
titlePanel("Your App"),

# Sidebar with a slider input for number of bins 
sidebarLayout(),

  # Show a plot of the generated distribution
  mainPanel(
     plotOutput("moveyear1"),
     plotOutput("avgtt")
    )
   )
  )

server <-  shinyServer(function(input, output, session) {

output$moveyear1 <- renderPlot({
ggplot(result1, aes(gameYear,DEPARTMENT_NAME)) + 
      geom_tile(color="white", size=0.1,aes(fill=MoveCount))+
      facet_wrap(~TEAM_ID) + labs(x="GameYear") + ggtitle("Total Move made in a Year")
  })

output$avgtt <- renderPlot({
ggplot(result2, aes(gameYear,DEPARTMENT_NAME)) + 
      geom_tile(color="white", size=0.1,aes(fill=AvgTT))+
      facet_wrap(~TEAM_ID) + labs(x="GameYear") + ggtitle("Average Time taken for Move")
  })

shinyApp(ui = ui , server = server)

有没有办法全局调用数据库连接，所以我们不必每次都调用它

1 个答案: