Postgres documentation says that |"now()| is a traditional PostgreSQL
equivalent to |transaction_timestamp()|".
Also both use the same implementation.
But them have different parallel safety property:
postgres=# \df+ now
List of functions
Schema | Name | Result data type | Argument data types |
Type | Volatility | Parallel | Owner | Security | Access privileges
| Language |
Source code | Description
------------+------+--------------------------+---------------------+------+------------+------------+----------+----------+-------------------+----------+
-------------+--------------------------
pg_catalog | now | timestamp with time zone | | func | stable |
restricted | knizhnik | invoker | | internal |
now | current transaction time
(1 row)
postgres=# \df+ transaction_timestamp
List of functions
Schema | Name | Result data type |
Argument data types | Type | Volatility | Parallel | Owner | Security
| Access privileg
es | Language | Source code | Description
------------+-----------------------+--------------------------+---------------------+------+------------+----------+----------+----------+----------------
---+----------+-------------+--------------------------
pg_catalog | transaction_timestamp | timestamp with time zone
| | func | stable | safe | knizhnik |
invoker |
| internal | now | current transaction time
(1 row)
As a result using now() in query disable parallel execution while
transaction_timestamp allows it.
Was it done intentionally or it is just a bug?
--
Konstantin Knizhnik
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company
