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That means you can now set your options in either or all of $PGDATA/configuration, some postmaster option (--enable-fsync=off), or set a SET command. The list of options is in backend/utils/misc/guc.c, documentation will be written post haste. pg_options is gone, so is that pq_geqo config file. Also removed were backend -K, -Q, and -T options (no longer applicable, although -d0 does the same as -Q). Added to configure an --enable-syslog option. changed all callers from TPRINTF to elog(DEBUG) |
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lmgr.c | ||
lock.c | ||
Makefile | ||
multi.c | ||
proc.c | ||
README | ||
single.c |
$Header: /cvsroot/pgsql/src/backend/storage/lmgr/README,v 1.3 1998/07/06 18:16:07 momjian Exp $ 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. --------------------------------------------------------------------------- The lock manager's LOCK: tag - The key fields that are used for hashing locks in the shared memory lock hash table. This is kept as a separate struct to ensure that we always zero out the correct number of bytes. This is a problem as part of the tag is an itempointer which is 6 bytes and causes 2 additional bytes to be added as padding. tag.relId - Uniquely identifies the relation that the lock corresponds to. tag.dbId - Uniquely identifies the database in which the relation lives. If this is a shared system relation (e.g. pg_user) the dbId should be set to 0. tag.tupleId - Uniquely identifies the block/page within the relation and the tuple within the block. If we are setting a table level lock both the blockId and tupleId (in an item pointer this is called the position) are set to invalid, if it is a page level lock the blockId is valid, while the tuleId is still invalid. Finally if this is a tuple level lock (we currently never do this) then both the blockId and tupleId are set to valid specifications. This is how we get the appearance of a multi-level lock table while using only a single table (see Gray's paper on 2 phase locking if you are puzzled about how multi-level lock tables work). mask - This field indicates what types of locks are currently held in the given lock. It is used (against the lock table's conflict table) to determine if the new lock request will conflict with existing lock types held. Conficts are determined by bitwise AND operations between the mask and the conflict table entry for the given lock type to be set. The current representation is that each bit (1 through 5) is set when that lock type (WRITE, READ, WRITE INTENT, READ INTENT, EXTEND) has been acquired for the lock. waitProcs - This is a shared memory queue of all process structures corresponding to a backend that is waiting (sleeping) until another backend releases this lock. The process structure holds the information needed to determine if it should be woken up when this lock is released. If, for example, we are releasing a read lock and the process is sleeping trying to acquire a read lock then there is no point in waking it since the lock being released isn't what caused it to sleep in the first place. There will be more on this below (when I get to releasing locks and waking sleeping process routines). nHolding - Keeps a count of how many times this lock has been attempted to be acquired. The count includes attempts by processes which were put to sleep due to conflicts. It also counts the same backend twice if, for example, a backend process first acquires a read and then acquires a write. holders - Keeps a count of how many locks of each type have been attempted. Only elements 1 through MAX_LOCK_TYPES are used as they correspond to the lock type defined constants (WRITE through EXTEND). Summing the values of holders should come out equal to nHolding. nActive - Keeps a count of how many times this lock has been succesfully acquired. This count does not include attempts that were rejected due to conflicts, but can count the same backend twice (e.g. a read then a write -- since its the same transaction this won't cause a conflict) activeHolders - Keeps a count of how locks of each type are currently held. Once again only elements 1 through MAX_LOCK_TYPES are used (0 is not). Also, like holders, summing the values of activeHolders should total to the value of nActive. ---------------------------------------------------------------------------