Set limit to array_agg() - sql

Question

I have the following Postgres query:
SELECT array_agg("Esns".id )
FROM public."Esns",
public."PurchaseOrderItems"
WHERE
"Esns"."PurchaseOrderItemId" = "PurchaseOrderItems".id
AND "PurchaseOrderItems"."GradeId"=2
LIMIT 2;
The limit will affect the rows. I want it to limit the array_agg() to 2 items. The following query works but I get my output with each entry in quotes:
SELECT array_agg ("temp")
FROM (
SELECT "Esns".id
FROM public."Esns",
public."PurchaseOrderItems"
WHERE
"Esns"."PurchaseOrderItemId" = "PurchaseOrderItems".id
AND "PurchaseOrderItems"."GradeId"=2
LIMIT 4
) as "temp" ;
This give me the following output
{(13),(14),(15),(12)}
Any ideas?

Answer 1

select id[1], id[2]
from (
SELECT array_agg("Esns".id ) as id
FROM public."Esns",
public."PurchaseOrderItems"
WHERE
"Esns"."PurchaseOrderItemId" = "PurchaseOrderItems".id
AND "PurchaseOrderItems"."GradeId"=2
) s
or if you want the output as array you can slice it:
SELECT (array_agg("Esns".id ))[1:2] as id_array
FROM public."Esns",
public."PurchaseOrderItems"
WHERE
"Esns"."PurchaseOrderItemId" = "PurchaseOrderItems".id
AND "PurchaseOrderItems"."GradeId"=2

Answer 2

The parentheses (not "quotes") in the result are decorators for the row literals. You are building an array of whole rows (which happen to contain only a single column). Instead, aggregate only the column.
Also, direct array construction from a query result is typically simpler and faster:
SELECT ARRAY (
SELECT e.id
FROM public."Esns" e
JOIN public."PurchaseOrderItems" p ON p.id = e."PurchaseOrderItemId"
WHERE p."GradeId" = 2
-- ORDER BY ???
LIMIT 4 -- or 2?
)
You need to ORDER BY something if you want a stable result and / or pick certain rows. Otherwise the result is arbitrary and can change with every next call.
While being at it I rewrote the query with explicit JOIN syntax, which is generally preferable, and used table aliases to simplify.