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https://issues.apache.org/jira/browse/SPARK-28036?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16877765#comment-16877765
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ShuMing Li edited comment on SPARK-28036 at 7/28/19 2:28 PM:
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[[email protected]] It's not the same with `Postgres`:
* In Postgres:
** left({{str}} {{text}}, {{n}} {{int}}): Return first {{n}} characters in the
string. When {{n is negative, return all but last |n}}| characters;
** right({{str}} {{text}}, {{n}} {{int}}): Return last {{n}} characters in the
string. When {{n}} is negative, return all but first |{{n}}| characters;
* In Spark:
** left(str, len) - Returns the leftmost `len`(`len` can be string type)
characters from the string `str`,if `len` is less or equal than 0 the result is
an empty string;
** right(str, len) - Returns the rightmost `len`(`len` can be string type)
characters from the string `str`,if `len` is less or equal than 0 the result is
an empty string.
They are different when `n`/`len` is negative. So maybe need to change Spark to
adapt to Postgres's meaning.
was (Author: lishuming):
[[email protected]] It's not the same with `Postgres`:
* In Postgres:
** left({{str}} {{text}}, {{n}} {{int}}): Return first {{n}} characters in the
string. When {{n }}is negative, return all but last |{{n}}| characters;
** right({{str}} {{text}}, {{n}} {{int}}): Return last {{n}} characters in the
string. When {{n}} is negative, return all but first |{{n}}| characters;
* In Spark:
** left(str, len) - Returns the leftmost `len`(`len` can be string type)
characters from the string `str`,if `len` is less or equal than 0 the result is
an empty string;
** right(str, len) - Returns the rightmost `len`(`len` can be string type)
characters from the string `str`,if `len` is less or equal than 0 the result is
an empty string.
They are different when `n`/`len` is negative. So maybe need to change Spark to
adapt to Postgres's meaning.
> Built-in udf left/right has inconsistent behavior
> -------------------------------------------------
>
> Key: SPARK-28036
> URL: https://issues.apache.org/jira/browse/SPARK-28036
> Project: Spark
> Issue Type: Sub-task
> Components: SQL
> Affects Versions: 3.0.0
> Reporter: Yuming Wang
> Priority: Major
>
> PostgreSQL:
> {code:sql}
> postgres=# select left('ahoj', -2), right('ahoj', -2);
> left | right
> ------+-------
> ah | oj
> (1 row)
> {code}
> Spark SQL:
> {code:sql}
> spark-sql> select left('ahoj', -2), right('ahoj', -2);
> spark-sql>
> {code}
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