Update comments on locks.

diff --git a/src/include/storage/lock.h b/src/include/storage/lock.h
index 1c3e3ed1eb0847e68db2f1f190b3b5314105d9dd..b7ba04610b3015e5e2b762ec18e3caed9889253b 100644 (file)
--- a/src/include/storage/lock.h
+++ b/src/include/storage/lock.h
@@ -76,6 +76,14 @@ typedef int LOCKMETHOD;
 #define USER_LOCKMETHOD                2
 #define MIN_LOCKMETHOD         DEFAULT_LOCKMETHOD
 
+/* There is normally only one lock method, the default one.
+ * If user locks are enabled, an additional lock method is present
+ *
+ * LOCKMETHODCTL and LOCKMETHODTABLE are split because the first lives
+ * in shared memory.  This is because it contains a spinlock.
+ * LOCKMETHODTABLE exists in private memory.  Both are created by the
+ * postmaster and should be the same in all backends
+ */
 
 /*
  * This is the control structure for a lock table.     It