DBMS_ASSERT.enquote_name() in Oracle - sql

Question

I have a sample code from http://phil-sqltips.blogspot.com/2015/07/beware-of-empty-partitions.html and I'd like to understand this xmlgen sql.
WITH t AS (
SELECT table_owner
, table_name
, partition_name
, TO_NUMBER (EXTRACTVALUE (XMLTYPE (DBMS_XMLGEN.getxml ('SELECT COUNT(*) AS rows_exist FROM '
|| DBMS_ASSERT.enquote_name (str => table_owner)
|| '.'
|| DBMS_ASSERT.enquote_name (str => table_name)
|| ' PARTITION ('
|| DBMS_ASSERT.enquote_name (str => partition_name)
|| ') WHERE ROWNUM <= 1'
)
)
, '/ROWSET/ROW/ROWS_EXIST'
)
) AS rows_exist
FROM all_tab_partitions
WHERE table_owner = 'WH'
AND table_name IN ('POINT_OF_SALE_FACTS')
ORDER BY table_owner
, table_name
, partition_position
)
SELECT 'ALTER TABLE '
|| DBMS_ASSERT.enquote_name (str => table_owner)
|| '.'
|| DBMS_ASSERT.enquote_name (str => table_name)
|| ' DROP PARTITION '
|| DBMS_ASSERT.enquote_name (str => partition_name)
|| ';' AS stmt
, t.*
FROM t
WHERE rows_exist = 0
;
I've found most of them except this,
DBMS_ASSERT.enquote_name (str => table_owner).
What is the syntax of arrow in (str => table_owner) inside of enquote_name?
I found this https://docs.oracle.com/cd/B28359_01/appdev.111/b28419/d_assert.htm#BABDEHBC but there is no such arrow syntax, and couldn't find web sites for this syntax.

Answer 1

That's the named parameter syntax. Here's the relevant documentation. So str => table_name says to set the str parameter to table_name.
In this case, it isn't necessary, since str is the first parameter for DBMS_ASSERT.ENQUOTE_NAME. So you could omit it and just call DBMS_ASSERT.enquote_name(table_owner).
But in some cases it can be very useful. For example, when there are multiple optional parameters (with defaults) and you only want to specify one of them. Or when you want to clarify the purpose of a parameter by displaying the parameter name next to the value.