Re: Serializable Isolation without blocking

Again, a somewhat tardy post from a question found in review.

Markus Wanner <markus@bluegap.ch> wrote:
>> I suppose these more persistent write locks should
>> be kept out of the DEFAULT lock method, too....
> 
> I fail to understand that part. What's the DEFAULT lock method?
With some adjustment of line wrapping for email...
From src/include/storage/lock.h:
------------------------------------------------------------
/** Lock methods are identified by LOCKMETHODID.  (Despite the* declaration as uint16, we are constrained to 256
lockmethodsby* the layout of LOCKTAG.)*/
 
typedef uint16 LOCKMETHODID;

/* These identify the known lock methods */
#define DEFAULT_LOCKMETHOD    1
#define USER_LOCKMETHOD        2
------------------------------------------------------------
From the src/backend/storage/lmgr/README:
------------------------------------------------------------
Lock Data Structures
--------------------

Lock methods describe the overall locking behavior.  Currently there
are two lock methods: DEFAULT and USER.

Lock modes describe the type of the lock (read/write or shared/
exclusive).  In principle, each lock method can have its own set of
lock modes with different conflict rules, but currently DEFAULT and
USER methods use identical lock mode sets.  See
src/tools/backend/index.html and src/include/storage/lock.h for more
details.  (Lock modes are also called lock types in some places in
the code and documentation.)
------------------------------------------------------------
At least the initial implementation of the in-memory locks to
support detection of rw-dependencies will use the structures defined
in the lock.c file.
-Kevin