[SOLVED] Normalize array subscripts so they start with 1


PostgreSQL can work with array subscripts starting anywhere.
Consider this example that creates an array with 3 elements with subscripts from 5 to 7:

SELECT '[5:7]={1,2,3}'::int[];



We get the first element at subscript 5:

SELECT ('[5:7]={1,2,3}'::int[])[5];

I want to normalize 1-dimensional arrays to start with array subscript 1.
The best I could come up with:

SELECT ('[5:7]={1,2,3}'::int[])[array_lower('[5:7]={1,2,3}'::int[], 1):array_upper('[5:7]={1,2,3}'::int[], 1)]

The same, easier the read:

WITH   cte(a) AS (SELECT '[5:7]={1,2,3}'::int[])
SELECT a[array_lower(a, 1):array_upper(a, 1)]
FROM   cte;

Do you know a simpler / faster or at least more elegant way?

Benchmark with old solutions on Postgres 9.5

db<>fiddle here

Benchmark including new solution on Postgres 14

db<>fiddle here


There is a simpler method that is ugly, but I believe technically correct: extract the largest possible slice out of the array, as opposed to the exact slice with computed bounds.
It avoids the two function calls.


select ('[5:7]={1,2,3}'::int[])[-2147483648:2147483647];

results in:


Answered By – Daniel Vérité

Answer Checked By – Robin (BugsFixing Admin)

Leave a Reply

Your email address will not be published. Required fields are marked *