[jira] [Created] (HIVE-19700) Workaround for JLine issue with UnsupportedTerminal

["Naveen Gangam (JIRA)" <ji...@apache.org>]

Naveen Gangam created HIVE-19700:
------------------------------------

             Summary: Workaround for JLine issue with UnsupportedTerminal
                 Key: HIVE-19700
                 URL: https://issues.apache.org/jira/browse/HIVE-19700
             Project: Hive
          Issue Type: Bug
            Reporter: Naveen Gangam
            Assignee: Naveen Gangam
             Fix For: 2.2.1


From the JLine's ConsoleReader, readLine(prompt, mask) calls the following beforeReadLine() method.
{code}
        try {
            // System.out.println("is terminal supported " + terminal.isSupported());
            if (!terminal.isSupported()) {
                beforeReadLine(prompt, mask);
            }
{code}

So specifically when using UnsupportedTerminal {{-Djline.terminal}} and {{prompt=null}} and {{mask!=null}}, a "null" string gets printed to the console before and after the query result. {{UnsupportedTerminal}} is required to be used when running beeline as a background process, hangs otherwise.

{code}
    private void beforeReadLine(final String prompt, final Character mask) {
        if (mask != null && maskThread == null) {
            final String fullPrompt = "\r" + prompt
                + "                 "
                + "                 "
                + "                 "
                + "\r" + prompt;

            maskThread = new Thread()
            {
                public void run() {
                    while (!interrupted()) {
                        try {
                            Writer out = getOutput();
                            out.write(fullPrompt);
{code}

So the {{prompt}} is null and {{mask}} is NOT in atleast 2 scenarios in beeline. 
when beeline's silent=true, prompt is null
* https://github.com/apache/hive/blob/master/beeline/src/java/org/apache/hive/beeline/BeeLine.java#L1264
when running multiline queries
* https://github.com/apache/hive/blob/master/beeline/src/java/org/apache/hive/beeline/Commands.java#L1093

When executing beeline in script mode (commands in a file), there should not be any masking while reading lines from the script file. aka, entire line should be a beeline command or part of a multiline hive query.

So it should be safe to use a null mask instead of {{ConsoleReader.NULL_MASK}} when using UnsupportedTerminal as jline terminal.



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