Re: Allowing ALTER TYPE to change storage strategy
От | Tomas Vondra |
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Тема | Re: Allowing ALTER TYPE to change storage strategy |
Дата | |
Msg-id | 20200229213714.7osohwlvup24ugd2@development обсуждение исходный текст |
Ответ на | Re: Allowing ALTER TYPE to change storage strategy (Tom Lane <tgl@sss.pgh.pa.us>) |
Ответы |
Re: Allowing ALTER TYPE to change storage strategy
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Список | pgsql-hackers |
On Fri, Feb 28, 2020 at 08:35:33PM -0500, Tom Lane wrote: >Tomas Vondra <tomas.vondra@2ndquadrant.com> writes: >> I think we might check if there are any attributes with the given data >> type, and allow the change if there are none. That would still allow the >> change when the type is used only for things like function parameters >> etc. But we'd also have to check for domains (recursively). > >Still has race conditions. > Yeah, I have no problem believing that. >> One thing I haven't mentioned in the original message is CASCADE. It >> seems useful to optionally change storage for all attributes with the >> given data type. But I'm not sure it's actually a good idea, and the >> amount of code seems non-trivial (it'd have to copy quite a bit of code >> from ALTER TABLE). > >You'd need a moderately strong lock on each such table, which means >there'd be serious deadlock hazards. I'm dubious that it's worth >troubling with. > Yeah, I don't plan to do this in v1 (and I have no immediate plan to work on it after that). But I wonder how is the deadlock risk any different compared e.g. to DROP TYPE ... CASCADE? regards -- Tomas Vondra http://www.2ndQuadrant.com PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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