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 anddocumentation.)

identical lock mode sets. See src/include/storage/lock.h for more details.

(Lock modes are also called lock types in some places in the code and

documentation.)

There are two main methods for recording locks in shared memory. The primary

mechanism uses two main structures: the per-lockable-object LOCK struct, and