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Restructure LOCKTAG as per discussions of a couple months ago.
Essentially, we shoehorn in a lockable-object-type field by taking a byte away from the lockmethodid, which can surely fit in one byte instead of two. This allows less artificial definitions of all the other fields of LOCKTAG; we can get rid of the special pg_xactlock pseudo-relation, and also support locks on individual tuples and general database objects (including shared objects). None of those possibilities are actually exploited just yet, however. I removed pg_xactlock from pg_class, but did not force initdb for that change. At this point, relkind 's' (SPECIAL) is unused and could be removed entirely.
This commit is contained in:
Tom Lane
@@ -7,7 +7,7 @@
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* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $PostgreSQL: pgsql/src/include/storage/lock.h,v 1.84 2004/12/31 22:03:42 pgsql Exp $
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* $PostgreSQL: pgsql/src/include/storage/lock.h,v 1.85 2005/04/29 22:28:24 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@@ -58,7 +58,8 @@ typedef int LOCKMODE;
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/*
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* There is normally only one lock method, the default one.
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* If user locks are enabled, an additional lock method is present.
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* Lock methods are identified by LOCKMETHODID.
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* Lock methods are identified by LOCKMETHODID. (Despite the declaration as
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* uint16, we are constrained to 256 lockmethods by the layout of LOCKTAG.)
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*/
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typedef uint16 LOCKMETHODID;
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@@ -103,27 +104,100 @@ typedef LockMethodData *LockMethod;
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/*
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* LOCKTAG is the key information needed to look up a LOCK item in the
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* lock hashtable. A LOCKTAG value uniquely identifies a lockable object.
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*
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* The LockTagType enum defines the different kinds of objects we can lock.
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* We can handle up to 256 different LockTagTypes.
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*/
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typedef enum LockTagType
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{
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LOCKTAG_RELATION, /* whole relation */
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/* ID info for a relation is DB OID + REL OID; DB OID = 0 if shared */
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LOCKTAG_RELATION_EXTEND, /* the right to extend a relation */
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/* same ID info as RELATION */
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LOCKTAG_PAGE, /* one page of a relation */
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/* ID info for a page is RELATION info + BlockNumber */
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LOCKTAG_TUPLE, /* one physical tuple */
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/* ID info for a tuple is PAGE info + OffsetNumber */
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LOCKTAG_TRANSACTION, /* transaction (for waiting for xact done) */
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/* ID info for a transaction is its TransactionId */
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LOCKTAG_OBJECT, /* non-relation database object */
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/* ID info for an object is DB OID + CLASS OID + OBJECT OID + SUBID */
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/*
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* Note: object ID has same representation as in pg_depend and
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* pg_description, but notice that we are constraining SUBID to 16 bits.
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* Also, we use DB OID = 0 for shared objects such as tablespaces.
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*/
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LOCKTAG_USERLOCK /* reserved for contrib/userlock */
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/* ID info for a userlock is defined by user_locks.c */
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} LockTagType;
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/*
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* The LOCKTAG struct is defined with malice aforethought to fit into 16
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* bytes with no padding. Note that this would need adjustment if we were
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* to widen Oid, BlockNumber, or TransactionId to more than 32 bits.
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*
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* We include lockmethodid in the locktag so that a single hash table in
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* shared memory can store locks of different lockmethods. For largely
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* historical reasons, it's passed to the lock.c routines as a separate
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* argument and then stored into the locktag.
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*/
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typedef struct LOCKTAG
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{
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Oid relId;
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Oid dbId;
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union
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{
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BlockNumber blkno;
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TransactionId xid;
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} objId;
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/*
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* offnum should be part of objId union above, but doing that would
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* increase sizeof(LOCKTAG) due to padding. Currently used by
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* userlocks only.
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*/
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OffsetNumber offnum;
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LOCKMETHODID lockmethodid; /* needed by userlocks */
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uint32 locktag_field1; /* a 32-bit ID field */
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uint32 locktag_field2; /* a 32-bit ID field */
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uint32 locktag_field3; /* a 32-bit ID field */
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uint16 locktag_field4; /* a 16-bit ID field */
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uint8 locktag_type; /* see enum LockTagType */
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uint8 locktag_lockmethodid; /* lockmethod indicator */
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} LOCKTAG;
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/*
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* These macros define how we map logical IDs of lockable objects into
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* the physical fields of LOCKTAG. Use these to set up LOCKTAG values,
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* rather than accessing the fields directly. Note multiple eval of target!
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*/
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#define SET_LOCKTAG_RELATION(locktag,dboid,reloid) \
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((locktag).locktag_field1 = (dboid), \
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(locktag).locktag_field2 = (reloid), \
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(locktag).locktag_field3 = 0, \
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(locktag).locktag_field4 = 0, \
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(locktag).locktag_type = LOCKTAG_RELATION)
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#define SET_LOCKTAG_RELATION_EXTEND(locktag,dboid,reloid) \
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((locktag).locktag_field1 = (dboid), \
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(locktag).locktag_field2 = (reloid), \
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(locktag).locktag_field3 = 0, \
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(locktag).locktag_field4 = 0, \
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(locktag).locktag_type = LOCKTAG_RELATION_EXTEND)
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#define SET_LOCKTAG_PAGE(locktag,dboid,reloid,blocknum) \
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((locktag).locktag_field1 = (dboid), \
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(locktag).locktag_field2 = (reloid), \
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(locktag).locktag_field3 = (blocknum), \
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(locktag).locktag_field4 = 0, \
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(locktag).locktag_type = LOCKTAG_PAGE)
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#define SET_LOCKTAG_TUPLE(locktag,dboid,reloid,blocknum,offnum) \
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((locktag).locktag_field1 = (dboid), \
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(locktag).locktag_field2 = (reloid), \
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(locktag).locktag_field3 = (blocknum), \
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(locktag).locktag_field4 = (offnum), \
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(locktag).locktag_type = LOCKTAG_TUPLE)
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#define SET_LOCKTAG_TRANSACTION(locktag,xid) \
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((locktag).locktag_field1 = (xid), \
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(locktag).locktag_field2 = 0, \
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(locktag).locktag_field3 = 0, \
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(locktag).locktag_field4 = 0, \
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(locktag).locktag_type = LOCKTAG_TRANSACTION)
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#define SET_LOCKTAG_OBJECT(locktag,dboid,classoid,objoid,objsubid) \
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((locktag).locktag_field1 = (dboid), \
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(locktag).locktag_field2 = (classoid), \
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(locktag).locktag_field3 = (objoid), \
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(locktag).locktag_field4 = (objsubid), \
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(locktag).locktag_type = LOCKTAG_OBJECT)
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/*
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* Per-locked-object lock information:
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@@ -157,7 +231,7 @@ typedef struct LOCK
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int nGranted; /* total of granted[] array */
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} LOCK;
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#define LOCK_LOCKMETHOD(lock) ((lock).tag.lockmethodid)
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#define LOCK_LOCKMETHOD(lock) ((LOCKMETHODID) (lock).tag.locktag_lockmethodid)
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/*
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@@ -211,7 +285,7 @@ typedef struct PROCLOCK
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} PROCLOCK;
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#define PROCLOCK_LOCKMETHOD(proclock) \
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(((LOCK *) MAKE_PTR((proclock).tag.lock))->tag.lockmethodid)
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LOCK_LOCKMETHOD(*((LOCK *) MAKE_PTR((proclock).tag.lock)))
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/*
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* Each backend also maintains a local hash table with information about each
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@@ -253,7 +327,7 @@ typedef struct LOCALLOCK
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LOCALLOCKOWNER *lockOwners; /* dynamically resizable array */
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} LOCALLOCK;
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#define LOCALLOCK_LOCKMETHOD(llock) ((llock).tag.lock.lockmethodid)
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#define LOCALLOCK_LOCKMETHOD(llock) ((llock).tag.lock.locktag_lockmethodid)
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/*
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