Incorrect result returned by getFloat in JDBC.

[140378476]

Describe the bug
I got clearly incorrect results when retrieving data using method getFloat.

To Reproduce
Steps to reproduce the behavior:

1. Create timeseries: CREATE TIMESERIES root.t.d WITH DATATYPE=FLOAT, ENCODING=GORILLA
2. Insert data: INSERT INTO root.t(timestamp,d) VALUES(1,1.2345678)
3. Retrieve data using JDBC: (mostly copied from the user guide and converted to Kotlin)

    fun getConnection(): Connection? {
        // JDBC driver name and database URL
        val driver = "org.apache.iotdb.jdbc.IoTDBDriver"
        val url = "jdbc:iotdb://127.0.0.1:6667/"

        // Database credentials
        val username = "root"
        val password = "root"
        var connection: Connection? = null
        try {
            Class.forName(driver)
            connection = DriverManager.getConnection(url, username, password)
        } catch (e: ClassNotFoundException) {
            e.printStackTrace()
        } catch (e: SQLException) {
            e.printStackTrace()
        }
        return connection
    }

    fun select(){
        val connection = getConnection()
        if (connection == null) {
            println("get connection defeat")
            return
        }
        val statement: Statement = connection.createStatement()
        statement.execute("SELECT d from root.test")
        val rs = statement.resultSet
        rs.next()
        println("String:")
        println(rs.getString(2))
        println("Float:")
        println(rs.getFloat(2))
    }

4. The output is:

String:
1.2345678
Float:
1.0673209E9

I got incorrect result from getFloat().

Expected behavior
I should get a correct result from getFloat().

Desktop (please complete the following information):

• Version 0.10.1

Additional context
The inplementation in IoTDBRpcDataSet.java shows that it just converts
the bytes to float in the method, while the bytes are actually in the format of String.

A further dig into the source code shows that all data are in the format of String except the timestamp.
I presume that the raw data transferred from the database is in the format of String.
This may cause performance issue(extra parsing and formatting, more transfer cost).

[HTHou]

Hi, same reason of your last question. Try to use encoding type GORILLA ?

[140378476]

Using encoding type GORILLA did fix the precision loss issue, but the method getFloat still return
incorrect values.

I will try to make a simple fix for the latter problem.

[qiaojialin]

Hi, thanks for your detailed description, and welcome to contribute 👍

[Alima777]

Hi, I checked the code and found it's a typo mistake: It's in 326 line of AbstractIoTDBJDBCResultSet.

Thanks for your detailed description!! If you don't mind, welcome to pull a PR to fix it :D

[HTHou]

The bug is fixed. I'll close this issue.