Re: Lock questions
От | Tom Lane |
---|---|
Тема | Re: Lock questions |
Дата | |
Msg-id | 9521.1069393800@sss.pgh.pa.us обсуждение исходный текст |
Ответ на | Lock questions (Fernando <proyectolsd@wanadoo.es>) |
Список | pgsql-general |
Fernando <proyectolsd@wanadoo.es> writes: > i've been reading the README file in the lmgr folder (in src/backend/storage/lmgr/) and i have a couple of questions aboutlocks: > - What's the difference between the Lightweight Locks (LWLocks) and > the Regular locks (Heavyweight Locks)? IIRC the differences are explained in that same README: no deadlock detection in LWLocks is one of the more critical ones. > For example, if i do a query and it needs a lock, would it be a lightweight one or a regular one? All user-accessible locks are regular locks. LWLocks are used for system internal processing (where, hopefully, we can prove that the access pattern can't deadlock...). As an example, the regular lock manager uses an LWLock to protect against simultaneous modifications to its own data structures. > - There are two lock methods, DEFAULT and USER. Where can I get more information about them? In the README file it says that "USER locks are non-blocking", how could this be? See contrib/userlock/ regards, tom lane
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