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postgresql/src/include/access/multixact.h

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Implement sharable row-level locks, and use them for foreign key references to eliminate unnecessary deadlocks. This commit adds SELECT ... FOR SHARE paralleling SELECT ... FOR UPDATE. The implementation uses a new SLRU data structure (managed much like pg_subtrans) to represent multiple- transaction-ID sets. When more than one transaction is holding a shared lock on a particular row, we create a MultiXactId representing that set of transactions and store its ID in the row's XMAX. This scheme allows an effectively unlimited number of row locks, just as we did before, while not costing any extra overhead except when a shared lock actually has to be shared. Still TODO: use the regular lock manager to control the grant order when multiple backends are waiting for a row lock. Alvaro Herrera and Tom Lane.
2005-04-28 23:47:18 +02:00
/*
* multixact.h
*
* PostgreSQL multi-transaction-log manager
*
Update copyright for the year 2010.
2010-01-02 17:58:17 +01:00
* Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
Implement sharable row-level locks, and use them for foreign key references to eliminate unnecessary deadlocks. This commit adds SELECT ... FOR SHARE paralleling SELECT ... FOR UPDATE. The implementation uses a new SLRU data structure (managed much like pg_subtrans) to represent multiple- transaction-ID sets. When more than one transaction is holding a shared lock on a particular row, we create a MultiXactId representing that set of transactions and store its ID in the row's XMAX. This scheme allows an effectively unlimited number of row locks, just as we did before, while not costing any extra overhead except when a shared lock actually has to be shared. Still TODO: use the regular lock manager to control the grant order when multiple backends are waiting for a row lock. Alvaro Herrera and Tom Lane.
2005-04-28 23:47:18 +02:00
* Portions Copyright (c) 1994, Regents of the University of California
*
Update copyright for the year 2010.
2010-01-02 17:58:17 +01:00
* $PostgreSQL: pgsql/src/include/access/multixact.h,v 1.16 2010/01/02 16:58:00 momjian Exp $
Implement sharable row-level locks, and use them for foreign key references to eliminate unnecessary deadlocks. This commit adds SELECT ... FOR SHARE paralleling SELECT ... FOR UPDATE. The implementation uses a new SLRU data structure (managed much like pg_subtrans) to represent multiple- transaction-ID sets. When more than one transaction is holding a shared lock on a particular row, we create a MultiXactId representing that set of transactions and store its ID in the row's XMAX. This scheme allows an effectively unlimited number of row locks, just as we did before, while not costing any extra overhead except when a shared lock actually has to be shared. Still TODO: use the regular lock manager to control the grant order when multiple backends are waiting for a row lock. Alvaro Herrera and Tom Lane.
2005-04-28 23:47:18 +02:00
*/
#ifndef MULTIXACT_H
#define MULTIXACT_H
Change WAL-logging scheme for multixacts to be more like regular transaction IDs, rather than like subtrans; in particular, the information now survives a database restart. Per previous discussion, this is essential for PITR log shipping and for 2PC.
2005-06-08 17:50:28 +02:00
#include "access/xlog.h"
Implement sharable row-level locks, and use them for foreign key references to eliminate unnecessary deadlocks. This commit adds SELECT ... FOR SHARE paralleling SELECT ... FOR UPDATE. The implementation uses a new SLRU data structure (managed much like pg_subtrans) to represent multiple- transaction-ID sets. When more than one transaction is holding a shared lock on a particular row, we create a MultiXactId representing that set of transactions and store its ID in the row's XMAX. This scheme allows an effectively unlimited number of row locks, just as we did before, while not costing any extra overhead except when a shared lock actually has to be shared. Still TODO: use the regular lock manager to control the grant order when multiple backends are waiting for a row lock. Alvaro Herrera and Tom Lane.
2005-04-28 23:47:18 +02:00
#define InvalidMultiXactId ((MultiXactId) 0)
#define FirstMultiXactId ((MultiXactId) 1)
#define MultiXactIdIsValid(multi) ((multi) != InvalidMultiXactId)
Get rid of slru.c's hardwired insistence on a fixed number of slots per SLRU area. The number of slots is still a compile-time constant (someday we might want to change that), but at least it's a different constant for each SLRU area. Increase number of subtrans buffers to 32 based on experimentation with a heavily subtrans-bashing test case, and increase number of multixact member buffers to 16, since it's obviously silly for it not to be at least twice the number of multixact offset buffers.
2005-12-07 00:08:34 +01:00
/* Number of SLRU buffers to use for multixact */
#define NUM_MXACTOFFSET_BUFFERS 8
#define NUM_MXACTMEMBER_BUFFERS 16
Change WAL-logging scheme for multixacts to be more like regular transaction IDs, rather than like subtrans; in particular, the information now survives a database restart. Per previous discussion, this is essential for PITR log shipping and for 2PC.
2005-06-08 17:50:28 +02:00
/* ----------------
* multixact-related XLOG entries
* ----------------
*/
#define XLOG_MULTIXACT_ZERO_OFF_PAGE 0x00
#define XLOG_MULTIXACT_ZERO_MEM_PAGE 0x10
#define XLOG_MULTIXACT_CREATE_ID 0x20
typedef struct xl_multixact_create
{
Standard pgindent run for 8.1.
2005-10-15 04:49:52 +02:00
MultiXactId mid; /* new MultiXact's ID */
MultiXactOffset moff; /* its starting offset in members file */
int32 nxids; /* number of member XIDs */
TransactionId xids[1]; /* VARIABLE LENGTH ARRAY */
Change WAL-logging scheme for multixacts to be more like regular transaction IDs, rather than like subtrans; in particular, the information now survives a database restart. Per previous discussion, this is essential for PITR log shipping and for 2PC.
2005-06-08 17:50:28 +02:00
} xl_multixact_create;
#define MinSizeOfMultiXactCreate offsetof(xl_multixact_create, xids)
Clean up MultiXactIdExpand's API by separating out the case where we are creating a new MultiXactId from two regular XIDs. The original coding was unnecessarily complicated and didn't save any code anyway.
2005-05-03 21:42:41 +02:00
extern MultiXactId MultiXactIdCreate(TransactionId xid1, TransactionId xid2);
extern MultiXactId MultiXactIdExpand(MultiXactId multi, TransactionId xid);
Implement sharable row-level locks, and use them for foreign key references to eliminate unnecessary deadlocks. This commit adds SELECT ... FOR SHARE paralleling SELECT ... FOR UPDATE. The implementation uses a new SLRU data structure (managed much like pg_subtrans) to represent multiple- transaction-ID sets. When more than one transaction is holding a shared lock on a particular row, we create a MultiXactId representing that set of transactions and store its ID in the row's XMAX. This scheme allows an effectively unlimited number of row locks, just as we did before, while not costing any extra overhead except when a shared lock actually has to be shared. Still TODO: use the regular lock manager to control the grant order when multiple backends are waiting for a row lock. Alvaro Herrera and Tom Lane.
2005-04-28 23:47:18 +02:00
extern bool MultiXactIdIsRunning(MultiXactId multi);
Repair two related errors in heap_lock_tuple: it was failing to recognize cases where we already hold the desired lock "indirectly", either via membership in a MultiXact or because the lock was originally taken by a different subtransaction of the current transaction. These cases must be accounted for to avoid needless deadlocks and/or inappropriate replacement of an exclusive lock with a shared lock. Per report from Clarence Gardner and subsequent investigation.
2006-11-17 19:00:15 +01:00
extern bool MultiXactIdIsCurrent(MultiXactId multi);
Clean up MultiXactIdExpand's API by separating out the case where we are creating a new MultiXactId from two regular XIDs. The original coding was unnecessarily complicated and didn't save any code anyway.
2005-05-03 21:42:41 +02:00
extern void MultiXactIdWait(MultiXactId multi);
Add NOWAIT option to SELECT FOR UPDATE/SHARE. Original patch by Hans-Juergen Schoenig, revisions by Karel Zak and Tom Lane.
2005-08-01 22:31:16 +02:00
extern bool ConditionalMultiXactIdWait(MultiXactId multi);
Implement sharable row-level locks, and use them for foreign key references to eliminate unnecessary deadlocks. This commit adds SELECT ... FOR SHARE paralleling SELECT ... FOR UPDATE. The implementation uses a new SLRU data structure (managed much like pg_subtrans) to represent multiple- transaction-ID sets. When more than one transaction is holding a shared lock on a particular row, we create a MultiXactId representing that set of transactions and store its ID in the row's XMAX. This scheme allows an effectively unlimited number of row locks, just as we did before, while not costing any extra overhead except when a shared lock actually has to be shared. Still TODO: use the regular lock manager to control the grant order when multiple backends are waiting for a row lock. Alvaro Herrera and Tom Lane.
2005-04-28 23:47:18 +02:00
extern void MultiXactIdSetOldestMember(void);
Standard pgindent run for 8.1.
2005-10-15 04:49:52 +02:00
extern int GetMultiXactIdMembers(MultiXactId multi, TransactionId **xids);
Implement sharable row-level locks, and use them for foreign key references to eliminate unnecessary deadlocks. This commit adds SELECT ... FOR SHARE paralleling SELECT ... FOR UPDATE. The implementation uses a new SLRU data structure (managed much like pg_subtrans) to represent multiple- transaction-ID sets. When more than one transaction is holding a shared lock on a particular row, we create a MultiXactId representing that set of transactions and store its ID in the row's XMAX. This scheme allows an effectively unlimited number of row locks, just as we did before, while not costing any extra overhead except when a shared lock actually has to be shared. Still TODO: use the regular lock manager to control the grant order when multiple backends are waiting for a row lock. Alvaro Herrera and Tom Lane.
2005-04-28 23:47:18 +02:00
extern void AtEOXact_MultiXact(void);
Fix an old bug in multixact and two-phase commit. Prepared transactions can be part of multixacts, so allocate a slot for each prepared transaction in the "oldest member" array in multixact.c. On PREPARE TRANSACTION, transfer the oldest member value from the current backends slot to the prepared xact slot. Also save and recover the value from the 2pc state file. The symptom of the bug was that after a transaction prepared, a shared lock still held by the prepared transaction was sometimes ignored by other transactions. Fix back to 8.1, where both 2PC and multixact were introduced.
2009-11-23 10:58:36 +01:00
extern void AtPrepare_MultiXact(void);
extern void PostPrepare_MultiXact(TransactionId xid);
Implement sharable row-level locks, and use them for foreign key references to eliminate unnecessary deadlocks. This commit adds SELECT ... FOR SHARE paralleling SELECT ... FOR UPDATE. The implementation uses a new SLRU data structure (managed much like pg_subtrans) to represent multiple- transaction-ID sets. When more than one transaction is holding a shared lock on a particular row, we create a MultiXactId representing that set of transactions and store its ID in the row's XMAX. This scheme allows an effectively unlimited number of row locks, just as we did before, while not costing any extra overhead except when a shared lock actually has to be shared. Still TODO: use the regular lock manager to control the grant order when multiple backends are waiting for a row lock. Alvaro Herrera and Tom Lane.
2005-04-28 23:47:18 +02:00
Convert the arithmetic for shared memory size calculation from 'int' to 'Size' (that is, size_t), and install overflow detection checks in it. This allows us to remove the former arbitrary restrictions on NBuffers etc. It won't make any difference in a 32-bit machine, but in a 64-bit machine you could theoretically have terabytes of shared buffers. (How efficiently we could manage 'em remains to be seen.) Similarly, num_temp_buffers, work_mem, and maintenance_work_mem can be set above 2Gb on a 64-bit machine. Original patch from Koichi Suzuki, additional work by moi.
2005-08-21 01:26:37 +02:00
extern Size MultiXactShmemSize(void);
Implement sharable row-level locks, and use them for foreign key references to eliminate unnecessary deadlocks. This commit adds SELECT ... FOR SHARE paralleling SELECT ... FOR UPDATE. The implementation uses a new SLRU data structure (managed much like pg_subtrans) to represent multiple- transaction-ID sets. When more than one transaction is holding a shared lock on a particular row, we create a MultiXactId representing that set of transactions and store its ID in the row's XMAX. This scheme allows an effectively unlimited number of row locks, just as we did before, while not costing any extra overhead except when a shared lock actually has to be shared. Still TODO: use the regular lock manager to control the grant order when multiple backends are waiting for a row lock. Alvaro Herrera and Tom Lane.
2005-04-28 23:47:18 +02:00
extern void MultiXactShmemInit(void);
extern void BootStrapMultiXact(void);
extern void StartupMultiXact(void);
extern void ShutdownMultiXact(void);
Change WAL-logging scheme for multixacts to be more like regular transaction IDs, rather than like subtrans; in particular, the information now survives a database restart. Per previous discussion, this is essential for PITR log shipping and for 2PC.
2005-06-08 17:50:28 +02:00
extern void MultiXactGetCheckptMulti(bool is_shutdown,
Standard pgindent run for 8.1.
2005-10-15 04:49:52 +02:00
MultiXactId *nextMulti,
MultiXactOffset *nextMultiOffset);
Implement sharable row-level locks, and use them for foreign key references to eliminate unnecessary deadlocks. This commit adds SELECT ... FOR SHARE paralleling SELECT ... FOR UPDATE. The implementation uses a new SLRU data structure (managed much like pg_subtrans) to represent multiple- transaction-ID sets. When more than one transaction is holding a shared lock on a particular row, we create a MultiXactId representing that set of transactions and store its ID in the row's XMAX. This scheme allows an effectively unlimited number of row locks, just as we did before, while not costing any extra overhead except when a shared lock actually has to be shared. Still TODO: use the regular lock manager to control the grant order when multiple backends are waiting for a row lock. Alvaro Herrera and Tom Lane.
2005-04-28 23:47:18 +02:00
extern void CheckPointMultiXact(void);
Change WAL-logging scheme for multixacts to be more like regular transaction IDs, rather than like subtrans; in particular, the information now survives a database restart. Per previous discussion, this is essential for PITR log shipping and for 2PC.
2005-06-08 17:50:28 +02:00
extern void MultiXactSetNextMXact(MultiXactId nextMulti,
Standard pgindent run for 8.1.
2005-10-15 04:49:52 +02:00
MultiXactOffset nextMultiOffset);
Change WAL-logging scheme for multixacts to be more like regular transaction IDs, rather than like subtrans; in particular, the information now survives a database restart. Per previous discussion, this is essential for PITR log shipping and for 2PC.
2005-06-08 17:50:28 +02:00
extern void MultiXactAdvanceNextMXact(MultiXactId minMulti,
Standard pgindent run for 8.1.
2005-10-15 04:49:52 +02:00
MultiXactOffset minMultiOffset);
Change WAL-logging scheme for multixacts to be more like regular transaction IDs, rather than like subtrans; in particular, the information now survives a database restart. Per previous discussion, this is essential for PITR log shipping and for 2PC.
2005-06-08 17:50:28 +02:00
Fix an old bug in multixact and two-phase commit. Prepared transactions can be part of multixacts, so allocate a slot for each prepared transaction in the "oldest member" array in multixact.c. On PREPARE TRANSACTION, transfer the oldest member value from the current backends slot to the prepared xact slot. Also save and recover the value from the 2pc state file. The symptom of the bug was that after a transaction prepared, a shared lock still held by the prepared transaction was sometimes ignored by other transactions. Fix back to 8.1, where both 2PC and multixact were introduced.
2009-11-23 10:58:36 +01:00
extern void multixact_twophase_recover(TransactionId xid, uint16 info,
void *recdata, uint32 len);
extern void multixact_twophase_postcommit(TransactionId xid, uint16 info,
void *recdata, uint32 len);
extern void multixact_twophase_postabort(TransactionId xid, uint16 info,
void *recdata, uint32 len);
Change WAL-logging scheme for multixacts to be more like regular transaction IDs, rather than like subtrans; in particular, the information now survives a database restart. Per previous discussion, this is essential for PITR log shipping and for 2PC.
2005-06-08 17:50:28 +02:00
extern void multixact_redo(XLogRecPtr lsn, XLogRecord *record);
Arrange to emit a description of the current XLOG record as error context when an error occurs during xlog replay. Also, replace the former risky 'write into a fixed-size buffer with no overflow detection' API for XLOG record description routines; use an expansible StringInfo instead. (The latter accounts for most of the patch bulk.) Qingqing Zhou
2006-03-24 05:32:13 +01:00
extern void multixact_desc(StringInfo buf, uint8 xl_info, char *rec);
Implement sharable row-level locks, and use them for foreign key references to eliminate unnecessary deadlocks. This commit adds SELECT ... FOR SHARE paralleling SELECT ... FOR UPDATE. The implementation uses a new SLRU data structure (managed much like pg_subtrans) to represent multiple- transaction-ID sets. When more than one transaction is holding a shared lock on a particular row, we create a MultiXactId representing that set of transactions and store its ID in the row's XMAX. This scheme allows an effectively unlimited number of row locks, just as we did before, while not costing any extra overhead except when a shared lock actually has to be shared. Still TODO: use the regular lock manager to control the grant order when multiple backends are waiting for a row lock. Alvaro Herrera and Tom Lane.
2005-04-28 23:47:18 +02:00
#endif /* MULTIXACT_H */