Using sql function generate_series() in redshift

Question

I'd like to use the generate series function in redshift, but have not been successful.

The redshift documentation says it's not supported. The following code does work:

select *
from generate_series(1,10,1)

outputs:

1
2
3
...
10

I'd like to do the same with dates. I've tried a number of variations, including:

select *
from generate_series(date('2008-10-01'),date('2008-10-10 00:00:00'),1)

kicks out:

 ERROR: function generate_series(date, date, integer) does not exist
 Hint: No function matches the given name and argument types.
 You may need to add explicit type casts. [SQL State=42883]

Also tried:

select *
from generate_series('2008-10-01 00:00:00'::timestamp,
'2008-10-10 00:00:00'::timestamp,'1 day')

And tried:

select *
from generate_series(cast('2008-10-01 00:00:00' as datetime),
cast('2008-10-10 00:00:00' as datetime),'1 day')

both kick out:

ERROR: function generate_series(timestamp without time zone, timestamp without time zone, "unknown") does not exist
Hint: No function matches the given name and argument types.
You may need to add explicit type casts. [SQL State=42883]

If not looks like I'll use this code from another post:

SELECT to_char(DATE '2008-01-01'
+ (interval '1 month' * generate_series(0,57)), 'YYYY-MM-DD') AS ym

PostgreSQL generate_series() with SQL function as arguments

Answer 1

Amazon Redshift seems to be based on PostgreSQL 8.0.2. The timestamp arguments to generate_series() were added in 8.4.

Something like this, which sidesteps that problem, might work in Redshift.

SELECT current_date + (n || ' days')::interval
from generate_series (1, 30) n

It works in PostgreSQL 8.3, which is the earliest version I can test. It's documented in 8.0.26.

Later . . .

It seems that generate_series() is unsupported in Redshift. But given that you've verified that select * from generate_series(1,10,1) does work, the syntax above at least gives you a fighting chance. (Although the interval data type is also documented as being unsupported on Redshift.)

Still later . . .

You could also create a table of integers.

create table integers (
  n integer primary key
);

Populate it however you like. You might be able to use generate_series() locally, dump the table, and load it on Redshift. (I don't know; I don't use Redshift.)

Anyway, you can do simple date arithmetic with that table without referring directly to generate_series() or to interval data types.

select (current_date + n)
from integers
where n < 31;

That works in 8.3, at least.