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Update lock manager README.

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Bruce Momjian 1998-07-06 18:16:07 +00:00
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src/backend/storage/lmgr/README
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$Header: /cvsroot/pgsql/src/backend/storage/lmgr/README,v 1.2 1998/01/28 02:29:26 momjian Exp $
$Header: /cvsroot/pgsql/src/backend/storage/lmgr/README,v 1.3 1998/07/06 18:16:07 momjian Exp $
This file is an attempt to save me (and future code maintainers) some
time and a lot of headaches. The existing lock manager code at the time
of this writing (June 16 1992) can best be described as confusing. The
complexity seems inherent in lock manager functionality, but variable
names chosen in the current implementation really confuse me everytime
I have to track down a bug. Also, what gets done where and by whom isn't
always clear....
There are two fundemental lock structures. Lock methods describe the
locking behavior. We currently only support multi-level locking. Lock
modes describe the mode of the lock(read/write or shared/exclusive).
See src/tools/backend/index.html and src/include/storage/lock.h for more
details.
Starting with the data structures the lock manager relies upon...
(NOTE - these will undoubtedly change over time and it is likely
that this file won't always be updated along with the structs.)
---------------------------------------------------------------------------
The lock manager's LOCK:
@ -90,10 +85,3 @@ activeHolders -
---------------------------------------------------------------------------
Locks are accessed in two ways. Each PROC structure has a lockQueue,
that is a circular linked list of LOCK pointers that this process holds
or is waiting on.
Second, there is a hash table that can do a lookup by combined LOCK
address and transaction id(xid) which allows a process to see what
type of locks it holds on that table.