alamb opened a new issue #935:
URL: https://github.com/apache/arrow-datafusion/issues/935
**Is your feature request related to a problem or challenge? Please describe
what you are trying to do.**
The more standard SQL datafusion supports, the easier it will be to
integrate it into the rest of the analytics ecosystem
**Describe the solution you'd like**
I would like to be able to run the following queries without error:
```shell
cargo run --bin datafusion-cli
```
```sql
-- works
SELECT TRIM(' bar ');
-- does not work (examples from mysql)
SELECT TRIM(LEADING 'x' FROM 'xxxbarxxx');
SELECT TRIM(BOTH 'x' FROM 'xxxbarxxx');
SELECT TRIM(TRAILING 'xyz' FROM 'barxxyz');
```
Actual output:
```sql
> SELECT TRIM(' bar ');
+------------------------+
| trim(Utf8(" bar ")) |
+------------------------+
| bar |
+------------------------+
1 row in set. Query took 0.003 seconds.
> SELECT TRIM(LEADING 'x' FROM 'xxxbarxxx');
Plan("TRIM LEADING is not yet supported ")
> SELECT TRIM(BOTH 'x' FROM 'xxxbarxxx');
Plan("TRIM BOTH is not yet supported ")
> SELECT TRIM(TRAILING 'xyz' FROM 'barxxyz');
Plan("TRIM TRAILING is not yet supported ")
```
**Describe alternatives you've considered**
A clear and concise description of any alternative solutions or features
you've considered.
**Additional context**
SQL (postgres and mysql) offer support for extended `TRIM` syntax, and with
https://github.com/apache/arrow-datafusion/pull/934 DataFusion's SQL parser can
parse this syntax.
Here are links to the references:
* https://dev.mysql.com/doc/refman/8.0/en/string-functions.html#function_trim
* https://www.postgresql.org/docs/current/functions-string.html
Here is a copy of the syntax from the mysql manual:
```
TRIM([{BOTH | LEADING | TRAILING} [remstr] FROM] str), TRIM([remstr FROM]
str)
Returns the string str with all remstr prefixes or suffixes removed. If none
of the specifiers BOTH, LEADING, or TRAILING is given, BOTH is assumed. remstr
is optional and, if not specified, spaces are removed.
mysql> SELECT TRIM(' bar ');
-> 'bar'
mysql> SELECT TRIM(LEADING 'x' FROM 'xxxbarxxx');
-> 'barxxx'
mysql> SELECT TRIM(BOTH 'x' FROM 'xxxbarxxx');
-> 'bar'
mysql> SELECT TRIM(TRAILING 'xyz' FROM 'barxxyz');
-> 'barx'
```
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