jrgemignani commented on issue #1225:
URL: https://github.com/apache/age/issues/1225#issuecomment-1771498819
@cho2hhun When one outputs something from the `cypher()` function one needs
to specify what type it is, as you already know.
For the case of `agtype`, it generally has to be the type `agtype`. This is
because PG doesn't know how to generally cast `agtype` to certain other types.
Especially, since `agtype` is a composite and can be many different types -
```
psql-15.4-5432-pgsql=# SELECT * FROM cypher('graph_name', $$ WITH [1,2,3] as
lst RETURN lst[1] $$) AS (result agtype);
result
--------
2
(1 row)
psql-15.4-5432-pgsql=# SELECT * FROM cypher('graph_name', $$ WITH [1,2,3] as
lst RETURN lst[1] $$) AS (result integer);
result
--------
2
(1 row)
psql-15.4-5432-pgsql=# SELECT * FROM cypher('graph_name', $$ WITH [1,2,3] as
lst RETURN lst $$) AS (result agtype);
result
-----------
[1, 2, 3]
(1 row)
psql-15.4-5432-pgsql=# SELECT * FROM cypher('graph_name', $$ WITH [1,2,3] as
lst RETURN lst $$) AS (result _int4);
result
---------
{1,2,3}
(1 row)
```
However, if inside the cypher command you convert `agtype` to something
else, say a `cstring`, then you can utilize PG's casts to generate something
else -
```
psql-15.4-5432-pgsql=# SELECT to_json(result) FROM cypher('graph_name', $$
WITH [1,2,3] as lst RETURN ag_catalog.agtype_out(lst) $$) AS (result text);
to_json
-------------
"[1, 2, 3]"
(1 row)
psql-15.4-5432-pgsql=# SELECT pg_typeof(to_json(result)) FROM
cypher('graph_name', $$ WITH [1,2,3] as lst RETURN ag_catalog.agtype_out(lst)
$$) AS (result text);
pg_typeof
-----------
json
(1 row)
psql-15.4-5432-pgsql=#
```
It would probably be a good idea for our team to add in some additional
casts to make this easier for others.
Hope this is helpful.
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