| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Andres Freund <andres(at)anarazel(dot)de> |
| Cc: | pgsql-hackers(at)postgresql(dot)org, Albe Laurenz <laurenz(dot)albe(at)wien(dot)gv(dot)at>, "Kevin Grittner *EXTERN*" <Kevin(dot)Grittner(at)wicourts(dot)gov> |
| Subject: | Re: Update on true serializable techniques in MVCC |
| Date: | 2009-12-16 15:36:52 |
| Message-ID: | 603c8f070912160736v1f12acaeif7d9096190c792b7@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Wed, Dec 16, 2009 at 10:29 AM, Andres Freund <andres(at)anarazel(dot)de> wrote:
> On Wednesday 16 December 2009 16:24:42 Robert Haas wrote:
>> > Inserts and deletes follow the same protocol, obtaining an exclusive
>> > lock on the row after the one being inserted or deleted. The result
>> > of this locking protocol is that a range scan prevents concurrent
>> > inserts or delete within the range of the scan, and vice versa.
>> >
>> > That sounds like it should actually work.
>>
>> Only if you can guarantee that the database will access the rows using
>> some particular index. If it gets to the data some other way it might
>> accidentally circumvent the lock. That's kind of a killer in terms of
>> making this work for PostgreSQL.
> Isnt the whole topic only relevant for writing access? There you have to
> access the index anyway.
Yeah, I guess you have to insert the new tuple. I guess while you
were at it you might check whether the next tuple is locked...
...Robert
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