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https://issues.apache.org/jira/browse/SPARK-34993?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17319958#comment-17319958
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Kousuke Saruta edited comment on SPARK-34993 at 4/13/21, 7:14 AM:
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Hi [~laurikoobas].
 I think all of the results is correct.
 About the following two expressions,
{code:java}
 from_json('{"msg":"\\"}', schema_of_json(to_json(named_struct('msg', '\\'))))
 from_json('{"msg":"\\"}', 'msg string')
{code}
{"msg": "\\"}

is just a string literal.
So, if you need to give a json formed string which contains escaped characters 
like, 
{"msg": "\\"}
you should write
{"msg": "\\\\"}

 In this case, those expression should be:
{code:java}
 from_json('{"msg":"\\\\"}', schema_of_json(to_json(named_struct('msg', '\\'))))
 from_json('{"msg":"\\\\"}', 'msg string')
{code}
 

About thefollowing expression,
{code:java}
 from_json(to_json(named_struct('msg', '\\')), 
schema_of_json(to_json(named_struct('msg', '\\'))))
{code}
The evaluated result is

{"msg":"\"}

in my Spark 3.1.1 environment. It seems to be different from

{"msg":"\\"}

you get but it should be

{"msg": "\"}


was (Author: sarutak):
Hi [~laurikoobas].
 I think all of the results is correct.
 About the following two expressions,
{code:java}
 from_json('{"msg":"\\"}', schema_of_json(to_json(named_struct('msg', '\\'))))
 from_json('{"msg":"\\"}', 'msg string')
{code}
'\{"msg": "\\"}' is just a string literal and "\\" is regarded as "\".
 So, if you need to give an escaped character like "\\", you should write 
"\\\\".
 In this case, those expression should be:
{code:java}
 from_json('{"msg":"\\\\"}', schema_of_json(to_json(named_struct('msg', '\\'))))
 from_json('{"msg":"\\\\"}', 'msg string')
{code}
 

About thefollowing expression,
{code:java}
 from_json(to_json(named_struct('msg', '\\')), 
schema_of_json(to_json(named_struct('msg', '\\'))))
{code}
The evaluated result is \{"msg":"\"} in my Spark 3.1.1 environment. It seems to 
be different from the result you get (\{"msg":"\\"}) but it should be \{"msg": 
"\"}.

> from_json() acts differently on created and literal strings with backslashes
> ----------------------------------------------------------------------------
>
>                 Key: SPARK-34993
>                 URL: https://issues.apache.org/jira/browse/SPARK-34993
>             Project: Spark
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 3.1.1
>         Environment: Databricks DBR 8.1
>            Reporter: Lauri Koobas
>            Priority: Major
>         Attachments: image-2021-04-11-07-21-02-750.png
>
>
> JSON string with the value that contains backslashes fails to be recovered by 
> `from_json()`.
> I found that if the same string is created with `to_json(named_struct())` 
> then it actually does work.
>  
> The following code to reproduce. I would expect all of these methods to 
> return the same (correct) result:
> {code:java}
> select to_json(named_struct('msg', '\\'))
>  , schema_of_json(to_json(named_struct('msg', '\\')))
>  , from_json(to_json(named_struct('msg', '\\')), 
> schema_of_json(to_json(named_struct('msg', '\\'))))
>  , from_json('{"msg":"\\"}', schema_of_json(to_json(named_struct('msg', 
> '\\'))))
>  , from_json('{"msg":"\\"}', 'msg string')
>  
> {code}
>  
> !image-2021-04-11-07-21-02-750.png!



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