Comparing pairs of rows in a table

I could use some remedial help on a query that compares rows in the same table. I'm revamping our code for pushing to Postgres, and have set up a test bed to push using our old and new code. The row counts are fine, but that doesn't tell me if the data is the same. For that, I realized I can use built-in features to get a hash of the row. Here's one of my simple tables as a start:

CREATE TABLE IF NOT EXISTS data.hsys (
    "id" uuid NOT NULL DEFAULT NULL,
    "marked_for_deletion" boolean NOT NULL DEFAULT false,
    "name_" citext NOT NULL DEFAULT NULL,

CONSTRAINT hsys_id_pkey
    PRIMARY KEY ("id")
);

The hash then just takes this line:

select hashtext(hsys::text) from hsys;

What I want to do is store the ID, hash, code version and table name for each row after each test push into a small table:

CREATE TABLE IF NOT EXISTS data.row_check (
    id         uuid NOT NULL DEFAULT NULL,
    version    int8 NOT NULL DEFAULT NULL,
    row_hash   int8 NOT NULL DEFAULT NULL,
    table_name text NOT NULL DEFAULT NULL,

CONSTRAINT row_check_pkey
    PRIMARY KEY (id, version)
);

Inserting the data into row_check isn't hard. The proof-of-concept query looks like this:

select 
   id,
    0 as version,
    hashtext(hsys::text)  as row_hash,
   'hsys' as table_name,
from hsys;

A working insert query looks like this:

INSERT INTO row_check (id,version,row_hash,table_name)
            SELECT id, 0, hashtext(hsys::text),'hsys' 
            FROM hsys

            ON CONFLICT ON CONSTRAINT row_check_pkey DO UPDATE SET
                row_hash   = EXCLUDED.row_hash,
                table_name = EXCLUDED.table_name;

Once the data is in place, I can then see it like this:

select * from row_check
order by 1,2
limit 6;

id                                    version   row_hash    table_name
17ea1ed4-87b0-0840-912f-d29de2a06f5d    0      -1853961325  hsys
17ea1ed4-87b0-0840-912f-d29de2a06f5d    1      -1853961325  hsys
2200d1da-73e7-419c-9e4c-efe020834e6f    0      -482794730   hsys
2200d1da-73e7-419c-9e4c-efe020834e6f    1       482794730   hsys   <--- Different from version 0
47f4a50e-2358-434b-b30d-1f707ea9ee1b    0      -1539190835  hsys
47f4a50e-2358-434b-b30d-1f707ea9ee1b    1      -1539190835  hsys

What I'd ideally like from a sample like that is:

table_name id                                       v0         v1
hsys       2200d1da-73e7-419c-9e4c-efe020834e6f 0   -482794730  482794730

But even this minimal result would be helpful:

2200d1da-73e7-419c-9e4c-efe020834e6f    hsys

And this is where I'm stumped. What I would like to build is a query on row_check that spots any IDs where the hash is different between versions. I've got versions 0 and 1 above. Can someone point me in the right direction for grouping and/or joining to get only the rows that don't match across versions? Those are my red flags that I need to spot and track down. I really need the ID and table name back, the version and hash are of secondary importance. I've got a few constraints going into this, some of which help:

• The ID values are unique across all tables.

• I'll only compare two versions at a time.

• I have dozens of tables to test.

• Some of the tables have millions of rows.

That last point might matter. I though of using SELECT DISTINCT id in a CTE, but I didn't get far with that.

Thanks for advice.