Re: [COMMITTERS] pgsql-server: Rearrange pg_subtrans handling

On 8/25/2004 1:32 AM, Greg Stark wrote:

> A dirty read is a read that includes data that hasn't been committed yet. Or
> as the SQL 92 standard puts it:

[...]

> It could also be useful for referential integrity checks since, for example,
> it would let you see if someone has deleted the referenced record but not
> committed the delete yet.
> 
> But that alone wouldn't let you avoid locking the record, TODO items are
> mostly just pointers to old threads on the mailing lists. They don't contain
> the complete story. You could maybe find more information searching the
> pgsql-hackers archive on the web site.

Plus ... wouldn't doing the "on delete" lookup as dirty reads let 
referencing rows that have been deleted but still could come back 
through a rollback disappear? What you want to see are new tuples of 
uncommitted insert/update as well as old tuples of uncommitted 
delete/update. I don't think there is any term in the standard for that 
read mode, so we should call it dusty-reads because they see everything 
vacuum is interested in.


Jan

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