Characters starting with backslash cannot be used in SQL about emqx HOT 8 CLOSED

The \\n seem to be added when the object is converted to JSON for submission. They should be converted back when executed on the backend. This appears to be a bug in the backend's JSON conversion.

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I created a ticket for the double quote string issue: https://emqx.atlassian.net/browse/EMQX-11971
@zmstone

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It's work as:

   rule_test {
      actions = []
      description = ""
      enable = true
      metadata {created_at = 1708919800638}
      name = ""
      sql = """~
                SELECT
                    tokens(payload, '
        	')
                FROM "x/3
        "~"""
    }

if we want to use \n as delimiter. just pass \n to http api. not \\n.

but as @wivwiv say:

<<"SELECT\n tokens(payload, '\\n\\t')\n FROM \"x/4\\n\"">>
<<"SELECT\n tokens(payload, '\n\t')\n FROM \"x/4\n\"">>

should has the same result.

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Expected results:

SELECT
  tokens('1
2
3
4', '\n') as c
FROM 't/#'

-- output
{ "c": ["1", "2", "3", "4"] }

SELECT
  tokens('1
2
3
4', '
') as c
FROM 't/#'

-- output
{ "c": ["1", "2", "3", "4"] }

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The issue seems to be the lack of escape sequence support.

which can be addressed in two ways:

• Add a unescape function

  SELECT
      tokens(payload, unescape('\n')) as val
  

• Add a new quote syntax like Python's b"..." quote.

  SELECT
      tokens(payload, b"\n") as val
  

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for internal ref: https://emqx.atlassian.net/browse/EMQX-11847

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@zmstone, you are right that the issue seems to be lack of escape sequence support in the strings in the SQL like language. Another interesting thing I found is that it looks like double quote strings are supported but they get evaluated to undefined! However, double quote strings seems to work fine in the FROM clause. I wonder if we could have single quote strings to mean literal strings and use double quote strings to mean strings with escape sequence support?

Anyway I think an unescape function seems like a good first step solution as it kind of solves the problem but still allows us to extend the syntax of the SQL like language if we want to.

SELECT
  '\n' as single_q,
  "\n" as double_q,
  '
  ' as newline
FROM
  "t/#"

RESULT:

{
  "double_q": "undefined",
  "newline": "\n  ",
  "single_q": "\\n"
}

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Thank you for the fix @kjellwinblad

I remember there is a issue or ticket about double quotes, but I cannot find it.
Anyways, double quotes handling is a separate matter, should create a new ticket to track it.

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