[MTOS-dev] Making MT Transaction Safe

[Alvar Freude]

Hi,

-- Hirotaka Ogawa <hirotaka.ogawa at gmail.com> wrote:


> As far as I tried this before, transactions could become too large
> when rebuilding lots of files.  That is, concurrency could be
> sacrificed in case one thread acquires such a giant lock.

with PostgreSQL and AFAIK also with InnoDB there is only a write lock on 
each row which is changed. So, reading such a row (the old one, because 
isolation level "read committed"!) is possible, only concurret writes to 
the same row in the same tabele are locked.

<http://www.postgresql.org/docs/8.3/static/mvcc-intro.html>


> Especially in SQLite, when one thread acquire a write lock (an
> exclusive lock), no other threads can write to any tables in a whole
> database file.  In such a situation, threads can easily starve.

yes, for SQLite there is an axclusive lock, but SQLite is only used for 
testing on small databases not for real big things, or does someone use 
it for real big blogs?


Ciao
  Alvar

-- 
** Alvar C.H. Freude, http://alvar.a-blast.org/
** http://www.assoziations-blaster.de/
** http://www.wen-waehlen.de/
** http://odem.org/
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