From: | "Qingqing Zhou" <zhouqq(at)cs(dot)toronto(dot)edu> |
---|---|
To: | pgsql-general(at)postgresql(dot)org |
Subject: | Re: index and MVCC |
Date: | 2006-01-11 21:01:44 |
Message-ID: | dq3rlc$lo2$1@news.hub.org |
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Lists: | pgsql-general |
<chenb1981(at)sohu(dot)com> wrote
>a table is created and an index is created on that table
>
> then one row is updated
>
> what happens to the index file?
> ( is the index to old row deleted?)
>
Nothing happened to the index file. The index row is not deleted since there
is no MVCC information associated with index. See the comments in
ExecDelete():
* Note: Normally one would think that we have to delete index tuples
* associated with the heap tuple now...
*
* ... but in POSTGRES, we have no need to do this because VACUUM will
* take care of it later. We can't delete index tuples immediately
* anyway, since the tuple is still visible to other transactions.
Regards,
Qingqing
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