Hi
Whenever I'm debugging some kind of corruption incident, possible visibility bug, etc, I always land up staring at integer infomasks or using a SQL helper function to decode them.
That's silly, so here's a patch to teach pageinspect how to decode infomasks to a human readable array of flag names.
Example:
SELECT t_infomask, t_infomask2, flags
FROM heap_page_items(get_raw_page('test1', 0)),
LATERAL heap_infomask_flags(t_infomask, t_infomask2, true) m(flags);
t_infomask | t_infomask2 | flags
------------+-------------+----------------------------------------------------------------------------
2816 | 2 | {HEAP_XMIN_COMMITTED,HEAP_XMIN_INVALID,HEAP_XMAX_INVALID,HEAP_XMIN_FROZEN}
(1 row)
To decode individual mask integers you can just call it directly. It's strict, so pass 0 for the other mask if you don't have both, e.g.
SELECT heap_infomask_flags(2816, 0);
The patch backports easily to older pageinspect versions for when you're debugging something old.
BTW, I used text[] not enums. That costs a fair bit of memory, but it doesn't seem worth worrying too much about in this context.
For convenience it also tests and reports HEAP_LOCKED_UPGRADED and HEAP_XMAX_IS_LOCKED_ONLY as pseudo-flags.
I decided not to filter out HEAP_XMIN_COMMITTED,HEAP_XMIN_INVALID,HEAP_XMAX_INVALID when HEAP_XMIN_FROZEN is set; that doesn't make sense when we examine HEAP_XMAX_IS_LOCKED_ONLY or HEAP_LOCKED_UPGRADED, and filtering them out could be just as confusing as leaving them in.
The infomask2 natts mask is ignored. You can bitwise-and it out in SQL pretty easily if needed. I could output it here as a constructed text datum, but it seems mostly pointless.
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