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Re: Making type Datum be 8 bytes everywhere

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Peter Eisentraut <peter@eisentraut.org>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Joe Conway <mail@joeconway.com>, Michael Paquier <michael@paquier.xyz>, pgsql-hackers@lists.postgresql.org, Robert Haas <robertmhaas@gmail.com>
Date: 2025-08-12T14:11:15Z
Lists: pgsql-hackers 
Hi,

On 2025-08-12 08:30:43 +0200, Peter Eisentraut wrote:
> I'm also thinking, as a follow-on project, we could get rid of typbyval and
> require that typbyval == (typlen > 0 && typlen <= 8).  Something to think
> about.

We currently have types that aren't typbyval despite fitting those criteria:

postgres[1606972][1]=# SELECT oid::regtype, typlen FROM pg_type WHERE typlen > 0 and typlen <= 8 and not typbyval;
┌──────────┬────────┐
│   oid    │ typlen │
├──────────┼────────┤
│ tid      │      6 │
│ macaddr  │      6 │
│ macaddr8 │      8 │
└──────────┴────────┘
(3 rows)


Greetings,

Andres Freund

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Avoid faulty alignment of Datums in build_sorted_items().

  2. Grab the low-hanging fruit from forcing USE_FLOAT8_BYVAL to true.

  3. Grab the low-hanging fruit from forcing sizeof(Datum) to 8.

  4. Make type Datum be 8 bytes wide everywhere.

  5. Mop-up for Datum conversion cleanups.