Re: pg_get_indexdef() modification to use TxnSnapshot

kuroda.keisuke@nttcom.co.jp writes:
> On 2023-06-14 15:31, vignesh C wrote:
>> I have attempted to convert pg_get_indexdef() to use
>> systable_beginscan() based on transaction-snapshot rather than using
>> SearchSysCache().

Has anybody thought about the fact that ALTER TABLE ALTER TYPE
(specifically RememberIndexForRebuilding) absolutely requires seeing
the latest version of the index's definition?

>>> it would be going to be a large refactoring and potentially make the
>>> future implementations such as pg_get_tabledef() etc hard. Have you
>>> considered changes to the SearchSysCache() family so that they
>>> internally use a transaction snapshot that is registered in advance.

A very significant fraction of other SearchSysCache callers likewise
cannot afford to see stale data.  We might be able to fix things so
that the SQL-accessible ruleutils functionality works differently, but
we can't just up and change the behavior of cache lookups everywhere.

            regards, tom lane