Parsing PG Tuples

Has a way been explored to parse Postgres Tuples into JavaScript objects?

I have a query that must select a tuple (i.e. it can’t be flattened), say in the form of a composite type:

create type custom_type as (
  a int,
  b text
);

When you do something like:

select x::custom_type as x from y;

You get an object in pg that looks like:

{
  "x": "(2,'Hello, world!')"
}

Has a library been developed to parse this format? Is there a way to get this information in a better format from postgres? In my scenario I’ve queried pg_catalog for all the database type information, so I know the type OIDs of the tuple attributes.

Another option to explore is calling to_json or a similar function in the select statement, so:

select to_json(x::custom_type) as x from y;

…but if I do that I’m afraid that what I get back will be incompatible with what pg-types parses. Is there any guarantee that I’ll only get back, say strings, so I can run the pg-types parsers anyway on the returned JSON object?

Thanks!

---

In case I’m falling victim to the XY problem for a more complete picture I’m the author of PostGraphQL and I’m trying to add support for Postgres compound types in general.

[vitaly-t]

I had another look at it within pg-types. The library is definitely getting it as text. However, the type Id i’m getting is 73804, which is a very high number:

Field {
       name: 'data',
       tableID: 73807,
       columnID: 2,
       dataTypeID: 73804,
       dataTypeSize: -1,
       dataTypeModifier: -1,
       format: 'text' }

@brianc my guess is that high type Id-s represent custom types. It would be great if pg-types could support ranges of type id-s for parsers, so we could say something like typeId > 65535 => my custom type parser, or something like that.

If this is the case then it may be possible to integrate automatic parsing for tuples, although it wouldn’t be trivial, because the format itself isn’t.

Either way, you would need a proper parser for this. And I don’t know of any module that can do it today.

[FbN]

If someone land here a simple parser that auto load types from Postgres https://www.npmjs.com/package/pg-tuple-types