4451 lines
136 KiB
C
4451 lines
136 KiB
C
/*-------------------------------------------------------------------------
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*
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* predicate.c
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* POSTGRES predicate locking
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* to support full serializable transaction isolation
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*
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*
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* The approach taken is to implement Serializable Snapshot Isolation (SSI)
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* as initially described in this paper:
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*
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* Michael J. Cahill, Uwe Röhm, and Alan D. Fekete. 2008.
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* Serializable isolation for snapshot databases.
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* In SIGMOD ’08: Proceedings of the 2008 ACM SIGMOD
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* international conference on Management of data,
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* pages 729–738, New York, NY, USA. ACM.
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* http://doi.acm.org/10.1145/1376616.1376690
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*
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* and further elaborated in Cahill's doctoral thesis:
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*
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* Michael James Cahill. 2009.
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* Serializable Isolation for Snapshot Databases.
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* Sydney Digital Theses.
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* University of Sydney, School of Information Technologies.
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* http://hdl.handle.net/2123/5353
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*
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*
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* Predicate locks for Serializable Snapshot Isolation (SSI) are SIREAD
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* locks, which are so different from normal locks that a distinct set of
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* structures is required to handle them. They are needed to detect
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* rw-conflicts when the read happens before the write. (When the write
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* occurs first, the reading transaction can check for a conflict by
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* examining the MVCC data.)
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*
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* (1) Besides tuples actually read, they must cover ranges of tuples
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* which would have been read based on the predicate. This will
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* require modelling the predicates through locks against database
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* objects such as pages, index ranges, or entire tables.
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*
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* (2) They must be kept in RAM for quick access. Because of this, it
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* isn't possible to always maintain tuple-level granularity -- when
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* the space allocated to store these approaches exhaustion, a
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* request for a lock may need to scan for situations where a single
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* transaction holds many fine-grained locks which can be coalesced
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* into a single coarser-grained lock.
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*
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* (3) They never block anything; they are more like flags than locks
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* in that regard; although they refer to database objects and are
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* used to identify rw-conflicts with normal write locks.
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*
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* (4) While they are associated with a transaction, they must survive
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* a successful COMMIT of that transaction, and remain until all
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* overlapping transactions complete. This even means that they
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* must survive termination of the transaction's process. If a
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* top level transaction is rolled back, however, it is immediately
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* flagged so that it can be ignored, and its SIREAD locks can be
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* released any time after that.
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*
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* (5) The only transactions which create SIREAD locks or check for
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* conflicts with them are serializable transactions.
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*
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* (6) When a write lock for a top level transaction is found to cover
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* an existing SIREAD lock for the same transaction, the SIREAD lock
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* can be deleted.
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*
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* (7) A write from a serializable transaction must ensure that a xact
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* record exists for the transaction, with the same lifespan (until
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* all concurrent transaction complete or the transaction is rolled
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* back) so that rw-dependencies to that transaction can be
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* detected.
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*
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* We use an optimization for read-only transactions. Under certain
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* circumstances, a read-only transaction's snapshot can be shown to
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* never have conflicts with other transactions. This is referred to
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* as a "safe" snapshot (and one known not to be is "unsafe").
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* However, it can't be determined whether a snapshot is safe until
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* all concurrent read/write transactions complete.
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*
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* Once a read-only transaction is known to have a safe snapshot, it
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* can release its predicate locks and exempt itself from further
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* predicate lock tracking. READ ONLY DEFERRABLE transactions run only
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* on safe snapshots, waiting as necessary for one to be available.
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*
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*
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* Lightweight locks to manage access to the predicate locking shared
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* memory objects must be taken in this order, and should be released in
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* reverse order:
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*
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* SerializableFinishedListLock
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* - Protects the list of transactions which have completed but which
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* may yet matter because they overlap still-active transactions.
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*
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* SerializablePredicateLockListLock
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* - Protects the linked list of locks held by a transaction. Note
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* that the locks themselves are also covered by the partition
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* locks of their respective lock targets; this lock only affects
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* the linked list connecting the locks related to a transaction.
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* - All transactions share this single lock (with no partitioning).
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* - There is never a need for a process other than the one running
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* an active transaction to walk the list of locks held by that
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* transaction.
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* - It is relatively infrequent that another process needs to
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* modify the list for a transaction, but it does happen for such
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* things as index page splits for pages with predicate locks and
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* freeing of predicate locked pages by a vacuum process. When
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* removing a lock in such cases, the lock itself contains the
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* pointers needed to remove it from the list. When adding a
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* lock in such cases, the lock can be added using the anchor in
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* the transaction structure. Neither requires walking the list.
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* - Cleaning up the list for a terminated transaction is sometimes
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* not done on a retail basis, in which case no lock is required.
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* - Due to the above, a process accessing its active transaction's
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* list always uses a shared lock, regardless of whether it is
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* walking or maintaining the list. This improves concurrency
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* for the common access patterns.
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* - A process which needs to alter the list of a transaction other
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* than its own active transaction must acquire an exclusive
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* lock.
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*
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* FirstPredicateLockMgrLock based partition locks
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* - The same lock protects a target, all locks on that target, and
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* the linked list of locks on the target..
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* - When more than one is needed, acquire in ascending order.
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*
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* SerializableXactHashLock
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* - Protects both PredXact and SerializableXidHash.
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*
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* PredicateLockNextRowLinkLock
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* - Protects the priorVersionOfRow and nextVersionOfRow fields of
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* PREDICATELOCKTARGET when linkage is being created or destroyed.
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*
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*
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* Portions Copyright (c) 1996-2011, 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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*
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* IDENTIFICATION
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* src/backend/storage/lmgr/predicate.c
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*
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*-------------------------------------------------------------------------
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*/
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/*
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* INTERFACE ROUTINES
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*
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* housekeeping for setting up shared memory predicate lock structures
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* InitPredicateLocks(void)
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* PredicateLockShmemSize(void)
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*
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* predicate lock reporting
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* GetPredicateLockStatusData(void)
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* PageIsPredicateLocked(Relation relation, BlockNumber blkno)
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*
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* predicate lock maintenance
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* RegisterSerializableTransaction(Snapshot snapshot)
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* RegisterPredicateLockingXid(void)
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* PredicateLockRelation(Relation relation)
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* PredicateLockPage(Relation relation, BlockNumber blkno)
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* PredicateLockTuple(Relation relation, HeapTuple tuple)
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* PredicateLockPageSplit(Relation relation, BlockNumber oldblkno,
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* BlockNumber newblkno);
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* PredicateLockPageCombine(Relation relation, BlockNumber oldblkno,
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* BlockNumber newblkno);
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* PredicateLockTupleRowVersionLink(const Relation relation,
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* const HeapTuple oldTuple,
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* const HeapTuple newTuple)
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* ReleasePredicateLocks(bool isCommit)
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*
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* conflict detection (may also trigger rollback)
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* CheckForSerializableConflictOut(bool visible, Relation relation,
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* HeapTupleData *tup, Buffer buffer)
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* CheckForSerializableConflictIn(Relation relation, HeapTupleData *tup,
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* Buffer buffer)
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*
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* final rollback checking
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* PreCommit_CheckForSerializationFailure(void)
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*
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* two-phase commit support
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* AtPrepare_PredicateLocks(void);
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* PostPrepare_PredicateLocks(TransactionId xid);
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* PredicateLockTwoPhaseFinish(TransactionId xid, bool isCommit);
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* predicatelock_twophase_recover(TransactionId xid, uint16 info,
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* void *recdata, uint32 len);
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*/
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#include "postgres.h"
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#include "access/slru.h"
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#include "access/subtrans.h"
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#include "access/transam.h"
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#include "access/twophase.h"
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#include "access/twophase_rmgr.h"
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#include "access/xact.h"
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#include "miscadmin.h"
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#include "storage/bufmgr.h"
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#include "storage/predicate.h"
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#include "storage/predicate_internals.h"
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#include "storage/procarray.h"
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#include "utils/rel.h"
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#include "utils/snapmgr.h"
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#include "utils/tqual.h"
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/* Uncomment the next line to test the graceful degradation code. */
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/* #define TEST_OLDSERXID */
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/*
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* Test the most selective fields first, for performance.
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*
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* a is covered by b if all of the following hold:
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* 1) a.database = b.database
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* 2) a.relation = b.relation
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* 3) b.offset is invalid (b is page-granularity or higher)
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* 4) either of the following:
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* 4a) a.offset is valid (a is tuple-granularity) and a.page = b.page
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* or 4b) a.offset is invalid and b.page is invalid (a is
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* page-granularity and b is relation-granularity
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*/
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#define TargetTagIsCoveredBy(covered_target, covering_target) \
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((GET_PREDICATELOCKTARGETTAG_RELATION(covered_target) == /* (2) */ \
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GET_PREDICATELOCKTARGETTAG_RELATION(covering_target)) \
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&& (GET_PREDICATELOCKTARGETTAG_OFFSET(covering_target) == \
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InvalidOffsetNumber) /* (3) */ \
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&& (((GET_PREDICATELOCKTARGETTAG_OFFSET(covered_target) != \
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InvalidOffsetNumber) /* (4a) */ \
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&& (GET_PREDICATELOCKTARGETTAG_PAGE(covering_target) == \
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GET_PREDICATELOCKTARGETTAG_PAGE(covered_target))) \
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|| ((GET_PREDICATELOCKTARGETTAG_PAGE(covering_target) == \
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InvalidBlockNumber) /* (4b) */ \
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&& (GET_PREDICATELOCKTARGETTAG_PAGE(covered_target) \
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!= InvalidBlockNumber))) \
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&& (GET_PREDICATELOCKTARGETTAG_DB(covered_target) == /* (1) */ \
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GET_PREDICATELOCKTARGETTAG_DB(covering_target)))
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/*
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* The predicate locking target and lock shared hash tables are partitioned to
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* reduce contention. To determine which partition a given target belongs to,
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* compute the tag's hash code with PredicateLockTargetTagHashCode(), then
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* apply one of these macros.
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* NB: NUM_PREDICATELOCK_PARTITIONS must be a power of 2!
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*/
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#define PredicateLockHashPartition(hashcode) \
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((hashcode) % NUM_PREDICATELOCK_PARTITIONS)
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#define PredicateLockHashPartitionLock(hashcode) \
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((LWLockId) (FirstPredicateLockMgrLock + PredicateLockHashPartition(hashcode)))
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#define NPREDICATELOCKTARGETENTS() \
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mul_size(max_predicate_locks_per_xact, add_size(MaxBackends, max_prepared_xacts))
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#define SxactIsOnFinishedList(sxact) (!SHMQueueIsDetached(&((sxact)->finishedLink)))
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#define SxactIsPrepared(sxact) (((sxact)->flags & SXACT_FLAG_PREPARED) != 0)
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#define SxactIsCommitted(sxact) (((sxact)->flags & SXACT_FLAG_COMMITTED) != 0)
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#define SxactIsRolledBack(sxact) (((sxact)->flags & SXACT_FLAG_ROLLED_BACK) != 0)
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#define SxactIsReadOnly(sxact) (((sxact)->flags & SXACT_FLAG_READ_ONLY) != 0)
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#define SxactHasSummaryConflictIn(sxact) (((sxact)->flags & SXACT_FLAG_SUMMARY_CONFLICT_IN) != 0)
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#define SxactHasSummaryConflictOut(sxact) (((sxact)->flags & SXACT_FLAG_SUMMARY_CONFLICT_OUT) != 0)
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#define SxactHasConflictOut(sxact) (((sxact)->flags & SXACT_FLAG_CONFLICT_OUT) != 0)
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#define SxactIsDeferrableWaiting(sxact) (((sxact)->flags & SXACT_FLAG_DEFERRABLE_WAITING) != 0)
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#define SxactIsROSafe(sxact) (((sxact)->flags & SXACT_FLAG_RO_SAFE) != 0)
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#define SxactIsROUnsafe(sxact) (((sxact)->flags & SXACT_FLAG_RO_UNSAFE) != 0)
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#define SxactIsMarkedForDeath(sxact) (((sxact)->flags & SXACT_FLAG_MARKED_FOR_DEATH) != 0)
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/*
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* When a public interface method is called for a split on an index relation,
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* this is the test to see if we should do a quick return.
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*/
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#define SkipSplitTracking(relation) \
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(((relation)->rd_id < FirstBootstrapObjectId) \
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|| RelationUsesLocalBuffers(relation))
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/*
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* When a public interface method is called for serializing a relation within
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* the current transaction, this is the test to see if we should do a quick
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* return.
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*/
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#define SkipSerialization(relation) \
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((!IsolationIsSerializable()) \
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|| ((MySerializableXact == InvalidSerializableXact)) \
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|| ReleasePredicateLocksIfROSafe() \
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|| SkipSplitTracking(relation))
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/*
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* Compute the hash code associated with a PREDICATELOCKTARGETTAG.
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*
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* To avoid unnecessary recomputations of the hash code, we try to do this
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* just once per function, and then pass it around as needed. Aside from
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* passing the hashcode to hash_search_with_hash_value(), we can extract
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* the lock partition number from the hashcode.
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*/
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#define PredicateLockTargetTagHashCode(predicatelocktargettag) \
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(tag_hash((predicatelocktargettag), sizeof(PREDICATELOCKTARGETTAG)))
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/*
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* Given a predicate lock tag, and the hash for its target,
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* compute the lock hash.
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*
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* To make the hash code also depend on the transaction, we xor the sxid
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* struct's address into the hash code, left-shifted so that the
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* partition-number bits don't change. Since this is only a hash, we
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* don't care if we lose high-order bits of the address; use an
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* intermediate variable to suppress cast-pointer-to-int warnings.
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*/
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#define PredicateLockHashCodeFromTargetHashCode(predicatelocktag, targethash) \
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((targethash) ^ ((uint32) PointerGetDatum((predicatelocktag)->myXact)) \
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<< LOG2_NUM_PREDICATELOCK_PARTITIONS)
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/*
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* The SLRU buffer area through which we access the old xids.
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*/
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static SlruCtlData OldSerXidSlruCtlData;
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#define OldSerXidSlruCtl (&OldSerXidSlruCtlData)
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#define OLDSERXID_PAGESIZE BLCKSZ
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#define OLDSERXID_ENTRYSIZE sizeof(SerCommitSeqNo)
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#define OLDSERXID_ENTRIESPERPAGE (OLDSERXID_PAGESIZE / OLDSERXID_ENTRYSIZE)
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#define OLDSERXID_MAX_PAGE (SLRU_PAGES_PER_SEGMENT * 0x10000 - 1)
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#define OldSerXidNextPage(page) (((page) >= OLDSERXID_MAX_PAGE) ? 0 : (page) + 1)
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#define OldSerXidValue(slotno, xid) (*((SerCommitSeqNo *) \
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(OldSerXidSlruCtl->shared->page_buffer[slotno] + \
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((((uint32) (xid)) % OLDSERXID_ENTRIESPERPAGE) * OLDSERXID_ENTRYSIZE))))
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#define OldSerXidPage(xid) ((((uint32) (xid)) / OLDSERXID_ENTRIESPERPAGE) % (OLDSERXID_MAX_PAGE + 1))
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#define OldSerXidSegment(page) ((page) / SLRU_PAGES_PER_SEGMENT)
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typedef struct OldSerXidControlData
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{
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int headPage;
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int tailSegment;
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TransactionId headXid;
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TransactionId tailXid;
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bool warningIssued;
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} OldSerXidControlData;
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typedef struct OldSerXidControlData *OldSerXidControl;
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static OldSerXidControl oldSerXidControl;
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/*
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* When the oldest committed transaction on the "finished" list is moved to
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* SLRU, its predicate locks will be moved to this "dummy" transaction,
|
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* collapsing duplicate targets. When a duplicate is found, the later
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* commitSeqNo is used.
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*/
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static SERIALIZABLEXACT *OldCommittedSxact;
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||
|
||
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/* This configuration variable is used to set the predicate lock table size */
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int max_predicate_locks_per_xact; /* set by guc.c */
|
||
|
||
/*
|
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* This provides a list of objects in order to track transactions
|
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* participating in predicate locking. Entries in the list are fixed size,
|
||
* and reside in shared memory. The memory address of an entry must remain
|
||
* fixed during its lifetime. The list will be protected from concurrent
|
||
* update externally; no provision is made in this code to manage that. The
|
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* number of entries in the list, and the size allowed for each entry is
|
||
* fixed upon creation.
|
||
*/
|
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static PredXactList PredXact;
|
||
|
||
/*
|
||
* This provides a pool of RWConflict data elements to use in conflict lists
|
||
* between transactions.
|
||
*/
|
||
static RWConflictPoolHeader RWConflictPool;
|
||
|
||
/*
|
||
* The predicate locking hash tables are in shared memory.
|
||
* Each backend keeps pointers to them.
|
||
*/
|
||
static HTAB *SerializableXidHash;
|
||
static HTAB *PredicateLockTargetHash;
|
||
static HTAB *PredicateLockHash;
|
||
static SHM_QUEUE *FinishedSerializableTransactions;
|
||
|
||
/*
|
||
* Tag for a reserved entry in PredicateLockTargetHash; used to ensure
|
||
* there's an element available for scratch space if we need it,
|
||
* e.g. in PredicateLockPageSplit. This is an otherwise-invalid tag.
|
||
*/
|
||
static const PREDICATELOCKTARGETTAG ReservedTargetTag = {0, 0, 0, 0, 0};
|
||
|
||
/*
|
||
* The local hash table used to determine when to combine multiple fine-
|
||
* grained locks into a single courser-grained lock.
|
||
*/
|
||
static HTAB *LocalPredicateLockHash = NULL;
|
||
|
||
/*
|
||
* Keep a pointer to the currently-running serializable transaction (if any)
|
||
* for quick reference.
|
||
* TODO SSI: Remove volatile qualifier and the then-unnecessary casts?
|
||
*/
|
||
static volatile SERIALIZABLEXACT *MySerializableXact = InvalidSerializableXact;
|
||
|
||
/* local functions */
|
||
|
||
static SERIALIZABLEXACT *CreatePredXact(void);
|
||
static void ReleasePredXact(SERIALIZABLEXACT *sxact);
|
||
static SERIALIZABLEXACT *FirstPredXact(void);
|
||
static SERIALIZABLEXACT *NextPredXact(SERIALIZABLEXACT *sxact);
|
||
|
||
static bool RWConflictExists(const SERIALIZABLEXACT *reader, const SERIALIZABLEXACT *writer);
|
||
static void SetRWConflict(SERIALIZABLEXACT *reader, SERIALIZABLEXACT *writer);
|
||
static void SetPossibleUnsafeConflict(SERIALIZABLEXACT *roXact, SERIALIZABLEXACT *activeXact);
|
||
static void ReleaseRWConflict(RWConflict conflict);
|
||
static void FlagSxactUnsafe(SERIALIZABLEXACT *sxact);
|
||
|
||
static bool OldSerXidPagePrecedesLogically(int p, int q);
|
||
static void OldSerXidInit(void);
|
||
static void OldSerXidAdd(TransactionId xid, SerCommitSeqNo minConflictCommitSeqNo);
|
||
static SerCommitSeqNo OldSerXidGetMinConflictCommitSeqNo(TransactionId xid);
|
||
static void OldSerXidSetActiveSerXmin(TransactionId xid);
|
||
|
||
static uint32 predicatelock_hash(const void *key, Size keysize);
|
||
static void SummarizeOldestCommittedSxact(void);
|
||
static Snapshot GetSafeSnapshot(Snapshot snapshot);
|
||
static Snapshot RegisterSerializableTransactionInt(Snapshot snapshot);
|
||
static bool PredicateLockExists(const PREDICATELOCKTARGETTAG *targettag);
|
||
static bool GetParentPredicateLockTag(const PREDICATELOCKTARGETTAG *tag,
|
||
PREDICATELOCKTARGETTAG *parent);
|
||
static bool CoarserLockCovers(const PREDICATELOCKTARGETTAG *newtargettag);
|
||
static void RemoveTargetIfNoLongerUsed(PREDICATELOCKTARGET *target,
|
||
uint32 targettaghash);
|
||
static void DeleteChildTargetLocks(const PREDICATELOCKTARGETTAG *newtargettag);
|
||
static int PredicateLockPromotionThreshold(const PREDICATELOCKTARGETTAG *tag);
|
||
static bool CheckAndPromotePredicateLockRequest(const PREDICATELOCKTARGETTAG *reqtag);
|
||
static void DecrementParentLocks(const PREDICATELOCKTARGETTAG *targettag);
|
||
static void CreatePredicateLock(const PREDICATELOCKTARGETTAG *targettag,
|
||
uint32 targettaghash,
|
||
SERIALIZABLEXACT *sxact);
|
||
static void DeleteLockTarget(PREDICATELOCKTARGET *target, uint32 targettaghash);
|
||
static bool TransferPredicateLocksToNewTarget(const PREDICATELOCKTARGETTAG oldtargettag,
|
||
const PREDICATELOCKTARGETTAG newtargettag,
|
||
bool removeOld);
|
||
static void PredicateLockAcquire(const PREDICATELOCKTARGETTAG *targettag);
|
||
static void SetNewSxactGlobalXmin(void);
|
||
static bool ReleasePredicateLocksIfROSafe(void);
|
||
static void ClearOldPredicateLocks(void);
|
||
static void ReleaseOneSerializableXact(SERIALIZABLEXACT *sxact, bool partial,
|
||
bool summarize);
|
||
static bool XidIsConcurrent(TransactionId xid);
|
||
static void CheckTargetForConflictsIn(PREDICATELOCKTARGETTAG *targettag);
|
||
static bool CheckSingleTargetForConflictsIn(PREDICATELOCKTARGETTAG *targettag,
|
||
PREDICATELOCKTARGETTAG *nexttargettag);
|
||
static void FlagRWConflict(SERIALIZABLEXACT *reader, SERIALIZABLEXACT *writer);
|
||
static void OnConflict_CheckForSerializationFailure(const SERIALIZABLEXACT *reader,
|
||
SERIALIZABLEXACT *writer);
|
||
|
||
/*------------------------------------------------------------------------*/
|
||
|
||
/*
|
||
* These functions are a simple implementation of a list for this specific
|
||
* type of struct. If there is ever a generalized shared memory list, we
|
||
* should probably switch to that.
|
||
*/
|
||
static SERIALIZABLEXACT *
|
||
CreatePredXact(void)
|
||
{
|
||
PredXactListElement ptle;
|
||
|
||
ptle = (PredXactListElement)
|
||
SHMQueueNext(&PredXact->availableList,
|
||
&PredXact->availableList,
|
||
offsetof(PredXactListElementData, link));
|
||
if (!ptle)
|
||
return NULL;
|
||
|
||
SHMQueueDelete(&ptle->link);
|
||
SHMQueueInsertBefore(&PredXact->activeList, &ptle->link);
|
||
return &ptle->sxact;
|
||
}
|
||
|
||
static void
|
||
ReleasePredXact(SERIALIZABLEXACT *sxact)
|
||
{
|
||
PredXactListElement ptle;
|
||
|
||
Assert(ShmemAddrIsValid(sxact));
|
||
|
||
ptle = (PredXactListElement)
|
||
(((char *) sxact)
|
||
- offsetof(PredXactListElementData, sxact)
|
||
+offsetof(PredXactListElementData, link));
|
||
SHMQueueDelete(&ptle->link);
|
||
SHMQueueInsertBefore(&PredXact->availableList, &ptle->link);
|
||
}
|
||
|
||
static SERIALIZABLEXACT *
|
||
FirstPredXact(void)
|
||
{
|
||
PredXactListElement ptle;
|
||
|
||
ptle = (PredXactListElement)
|
||
SHMQueueNext(&PredXact->activeList,
|
||
&PredXact->activeList,
|
||
offsetof(PredXactListElementData, link));
|
||
if (!ptle)
|
||
return NULL;
|
||
|
||
return &ptle->sxact;
|
||
}
|
||
|
||
static SERIALIZABLEXACT *
|
||
NextPredXact(SERIALIZABLEXACT *sxact)
|
||
{
|
||
PredXactListElement ptle;
|
||
|
||
Assert(ShmemAddrIsValid(sxact));
|
||
|
||
ptle = (PredXactListElement)
|
||
(((char *) sxact)
|
||
- offsetof(PredXactListElementData, sxact)
|
||
+offsetof(PredXactListElementData, link));
|
||
ptle = (PredXactListElement)
|
||
SHMQueueNext(&PredXact->activeList,
|
||
&ptle->link,
|
||
offsetof(PredXactListElementData, link));
|
||
if (!ptle)
|
||
return NULL;
|
||
|
||
return &ptle->sxact;
|
||
}
|
||
|
||
/*------------------------------------------------------------------------*/
|
||
|
||
/*
|
||
* These functions manage primitive access to the RWConflict pool and lists.
|
||
*/
|
||
static bool
|
||
RWConflictExists(const SERIALIZABLEXACT *reader, const SERIALIZABLEXACT *writer)
|
||
{
|
||
RWConflict conflict;
|
||
|
||
Assert(reader != writer);
|
||
|
||
/* Check the ends of the purported conflict first. */
|
||
if (SxactIsRolledBack(reader)
|
||
|| SxactIsRolledBack(writer)
|
||
|| SHMQueueEmpty(&reader->outConflicts)
|
||
|| SHMQueueEmpty(&writer->inConflicts))
|
||
return false;
|
||
|
||
/* A conflict is possible; walk the list to find out. */
|
||
conflict = (RWConflict)
|
||
SHMQueueNext(&reader->outConflicts,
|
||
&reader->outConflicts,
|
||
offsetof(RWConflictData, outLink));
|
||
while (conflict)
|
||
{
|
||
if (conflict->sxactIn == writer)
|
||
return true;
|
||
conflict = (RWConflict)
|
||
SHMQueueNext(&reader->outConflicts,
|
||
&conflict->outLink,
|
||
offsetof(RWConflictData, outLink));
|
||
}
|
||
|
||
/* No conflict found. */
|
||
return false;
|
||
}
|
||
|
||
static void
|
||
SetRWConflict(SERIALIZABLEXACT *reader, SERIALIZABLEXACT *writer)
|
||
{
|
||
RWConflict conflict;
|
||
|
||
Assert(reader != writer);
|
||
Assert(!RWConflictExists(reader, writer));
|
||
|
||
conflict = (RWConflict)
|
||
SHMQueueNext(&RWConflictPool->availableList,
|
||
&RWConflictPool->availableList,
|
||
offsetof(RWConflictData, outLink));
|
||
if (!conflict)
|
||
ereport(ERROR,
|
||
(errcode(ERRCODE_OUT_OF_MEMORY),
|
||
errmsg("not enough elements in RWConflictPool to record a rw-conflict"),
|
||
errhint("You might need to run fewer transactions at a time or increase max_connections.")));
|
||
|
||
SHMQueueDelete(&conflict->outLink);
|
||
|
||
conflict->sxactOut = reader;
|
||
conflict->sxactIn = writer;
|
||
SHMQueueInsertBefore(&reader->outConflicts, &conflict->outLink);
|
||
SHMQueueInsertBefore(&writer->inConflicts, &conflict->inLink);
|
||
}
|
||
|
||
static void
|
||
SetPossibleUnsafeConflict(SERIALIZABLEXACT *roXact,
|
||
SERIALIZABLEXACT *activeXact)
|
||
{
|
||
RWConflict conflict;
|
||
|
||
Assert(roXact != activeXact);
|
||
Assert(SxactIsReadOnly(roXact));
|
||
Assert(!SxactIsReadOnly(activeXact));
|
||
|
||
conflict = (RWConflict)
|
||
SHMQueueNext(&RWConflictPool->availableList,
|
||
&RWConflictPool->availableList,
|
||
offsetof(RWConflictData, outLink));
|
||
if (!conflict)
|
||
ereport(ERROR,
|
||
(errcode(ERRCODE_OUT_OF_MEMORY),
|
||
errmsg("not enough elements in RWConflictPool to record a potential rw-conflict"),
|
||
errhint("You might need to run fewer transactions at a time or increase max_connections.")));
|
||
|
||
SHMQueueDelete(&conflict->outLink);
|
||
|
||
conflict->sxactOut = activeXact;
|
||
conflict->sxactIn = roXact;
|
||
SHMQueueInsertBefore(&activeXact->possibleUnsafeConflicts,
|
||
&conflict->outLink);
|
||
SHMQueueInsertBefore(&roXact->possibleUnsafeConflicts,
|
||
&conflict->inLink);
|
||
}
|
||
|
||
static void
|
||
ReleaseRWConflict(RWConflict conflict)
|
||
{
|
||
SHMQueueDelete(&conflict->inLink);
|
||
SHMQueueDelete(&conflict->outLink);
|
||
SHMQueueInsertBefore(&RWConflictPool->availableList, &conflict->outLink);
|
||
}
|
||
|
||
static void
|
||
FlagSxactUnsafe(SERIALIZABLEXACT *sxact)
|
||
{
|
||
RWConflict conflict,
|
||
nextConflict;
|
||
|
||
Assert(SxactIsReadOnly(sxact));
|
||
Assert(!SxactIsROSafe(sxact));
|
||
|
||
sxact->flags |= SXACT_FLAG_RO_UNSAFE;
|
||
|
||
/*
|
||
* We know this isn't a safe snapshot, so we can stop looking for other
|
||
* potential conflicts.
|
||
*/
|
||
conflict = (RWConflict)
|
||
SHMQueueNext(&sxact->possibleUnsafeConflicts,
|
||
&sxact->possibleUnsafeConflicts,
|
||
offsetof(RWConflictData, inLink));
|
||
while (conflict)
|
||
{
|
||
nextConflict = (RWConflict)
|
||
SHMQueueNext(&sxact->possibleUnsafeConflicts,
|
||
&conflict->inLink,
|
||
offsetof(RWConflictData, inLink));
|
||
|
||
Assert(!SxactIsReadOnly(conflict->sxactOut));
|
||
Assert(sxact == conflict->sxactIn);
|
||
|
||
ReleaseRWConflict(conflict);
|
||
|
||
conflict = nextConflict;
|
||
}
|
||
}
|
||
|
||
/*------------------------------------------------------------------------*/
|
||
|
||
/*
|
||
* We will work on the page range of 0..OLDSERXID_MAX_PAGE.
|
||
* Compares using wraparound logic, as is required by slru.c.
|
||
*/
|
||
static bool
|
||
OldSerXidPagePrecedesLogically(int p, int q)
|
||
{
|
||
int diff;
|
||
|
||
/*
|
||
* We have to compare modulo (OLDSERXID_MAX_PAGE+1)/2. Both inputs should
|
||
* be in the range 0..OLDSERXID_MAX_PAGE.
|
||
*/
|
||
Assert(p >= 0 && p <= OLDSERXID_MAX_PAGE);
|
||
Assert(q >= 0 && q <= OLDSERXID_MAX_PAGE);
|
||
|
||
diff = p - q;
|
||
if (diff >= ((OLDSERXID_MAX_PAGE + 1) / 2))
|
||
diff -= OLDSERXID_MAX_PAGE + 1;
|
||
else if (diff < -((OLDSERXID_MAX_PAGE + 1) / 2))
|
||
diff += OLDSERXID_MAX_PAGE + 1;
|
||
return diff < 0;
|
||
}
|
||
|
||
/*
|
||
* Initialize for the tracking of old serializable committed xids.
|
||
*/
|
||
static void
|
||
OldSerXidInit(void)
|
||
{
|
||
bool found;
|
||
|
||
/*
|
||
* Set up SLRU management of the pg_serial data.
|
||
*/
|
||
OldSerXidSlruCtl->PagePrecedes = OldSerXidPagePrecedesLogically;
|
||
SimpleLruInit(OldSerXidSlruCtl, "OldSerXid SLRU Ctl", NUM_OLDSERXID_BUFFERS, 0,
|
||
OldSerXidLock, "pg_serial");
|
||
/* Override default assumption that writes should be fsync'd */
|
||
OldSerXidSlruCtl->do_fsync = false;
|
||
|
||
/*
|
||
* Create or attach to the OldSerXidControl structure.
|
||
*/
|
||
oldSerXidControl = (OldSerXidControl)
|
||
ShmemInitStruct("OldSerXidControlData", sizeof(OldSerXidControlData), &found);
|
||
|
||
if (!found)
|
||
{
|
||
/*
|
||
* Set control information to reflect empty SLRU.
|
||
*/
|
||
oldSerXidControl->headPage = -1;
|
||
oldSerXidControl->tailSegment = -1;
|
||
oldSerXidControl->headXid = InvalidTransactionId;
|
||
oldSerXidControl->tailXid = InvalidTransactionId;
|
||
oldSerXidControl->warningIssued = false;
|
||
}
|
||
}
|
||
|
||
/*
|
||
* Record a committed read write serializable xid and the minimum
|
||
* commitSeqNo of any transactions to which this xid had a rw-conflict out.
|
||
* A zero seqNo means that there were no conflicts out from xid.
|
||
*
|
||
* The return value is normally false -- true means that we're about to
|
||
* wrap around our space for tracking these xids, so the caller might want
|
||
* to take action to prevent that.
|
||
*/
|
||
static void
|
||
OldSerXidAdd(TransactionId xid, SerCommitSeqNo minConflictCommitSeqNo)
|
||
{
|
||
TransactionId tailXid;
|
||
int targetPage;
|
||
int slotno;
|
||
int page;
|
||
int xidSpread;
|
||
bool isNewPage;
|
||
|
||
Assert(TransactionIdIsValid(xid));
|
||
|
||
targetPage = OldSerXidPage(xid);
|
||
|
||
LWLockAcquire(OldSerXidLock, LW_EXCLUSIVE);
|
||
|
||
/*
|
||
* If no serializable transactions are active, there shouldn't be anything
|
||
* to push out to this SLRU. Hitting this assert would mean there's
|
||
* something wrong with the earlier cleanup logic.
|
||
*/
|
||
tailXid = oldSerXidControl->tailXid;
|
||
Assert(TransactionIdIsValid(tailXid));
|
||
|
||
if (oldSerXidControl->headPage < 0)
|
||
{
|
||
page = OldSerXidPage(tailXid);
|
||
oldSerXidControl->tailSegment = OldSerXidSegment(page);
|
||
page = oldSerXidControl->tailSegment * OLDSERXID_ENTRIESPERPAGE;
|
||
isNewPage = true;
|
||
}
|
||
else
|
||
{
|
||
page = OldSerXidNextPage(oldSerXidControl->headPage);
|
||
isNewPage = OldSerXidPagePrecedesLogically(oldSerXidControl->headPage, targetPage);
|
||
}
|
||
|
||
if (!TransactionIdIsValid(oldSerXidControl->headXid)
|
||
|| TransactionIdFollows(xid, oldSerXidControl->headXid))
|
||
oldSerXidControl->headXid = xid;
|
||
if (oldSerXidControl->headPage < 0
|
||
|| OldSerXidPagePrecedesLogically(oldSerXidControl->headPage, targetPage))
|
||
oldSerXidControl->headPage = targetPage;
|
||
|
||
xidSpread = (((uint32) xid) - ((uint32) tailXid));
|
||
if (oldSerXidControl->warningIssued)
|
||
{
|
||
if (xidSpread < 800000000)
|
||
oldSerXidControl->warningIssued = false;
|
||
}
|
||
else if (xidSpread >= 1000000000)
|
||
{
|
||
oldSerXidControl->warningIssued = true;
|
||
ereport(WARNING,
|
||
(errmsg("memory for serializable conflict tracking is nearly exhausted"),
|
||
errhint("There may be an idle transaction or a forgotten prepared transaction causing this.")));
|
||
}
|
||
|
||
if (isNewPage)
|
||
{
|
||
/* Initialize intervening pages. */
|
||
while (page != targetPage)
|
||
{
|
||
(void) SimpleLruZeroPage(OldSerXidSlruCtl, page);
|
||
page = OldSerXidNextPage(page);
|
||
}
|
||
slotno = SimpleLruZeroPage(OldSerXidSlruCtl, targetPage);
|
||
}
|
||
else
|
||
slotno = SimpleLruReadPage(OldSerXidSlruCtl, targetPage, true, xid);
|
||
|
||
OldSerXidValue(slotno, xid) = minConflictCommitSeqNo;
|
||
|
||
LWLockRelease(OldSerXidLock);
|
||
}
|
||
|
||
/*
|
||
* Get the minimum commitSeqNo for any conflict out for the given xid. For
|
||
* a transaction which exists but has no conflict out, InvalidSerCommitSeqNo
|
||
* will be returned.
|
||
*/
|
||
static SerCommitSeqNo
|
||
OldSerXidGetMinConflictCommitSeqNo(TransactionId xid)
|
||
{
|
||
TransactionId headXid;
|
||
TransactionId tailXid;
|
||
SerCommitSeqNo val;
|
||
int slotno;
|
||
|
||
Assert(TransactionIdIsValid(xid));
|
||
|
||
LWLockAcquire(OldSerXidLock, LW_SHARED);
|
||
headXid = oldSerXidControl->headXid;
|
||
tailXid = oldSerXidControl->tailXid;
|
||
LWLockRelease(OldSerXidLock);
|
||
|
||
if (!TransactionIdIsValid(headXid))
|
||
return 0;
|
||
|
||
Assert(TransactionIdIsValid(tailXid));
|
||
|
||
if (TransactionIdPrecedes(xid, tailXid)
|
||
|| TransactionIdFollows(xid, headXid))
|
||
return 0;
|
||
|
||
/*
|
||
* The following function must be called without holding OldSerXidLock,
|
||
* but will return with that lock held, which must then be released.
|
||
*/
|
||
slotno = SimpleLruReadPage_ReadOnly(OldSerXidSlruCtl,
|
||
OldSerXidPage(xid), xid);
|
||
val = OldSerXidValue(slotno, xid);
|
||
LWLockRelease(OldSerXidLock);
|
||
return val;
|
||
}
|
||
|
||
/*
|
||
* Call this whenever there is a new xmin for active serializable
|
||
* transactions. We don't need to keep information on transactions which
|
||
* preceed that. InvalidTransactionId means none active, so everything in
|
||
* the SLRU should be discarded.
|
||
*/
|
||
static void
|
||
OldSerXidSetActiveSerXmin(TransactionId xid)
|
||
{
|
||
int newTailPage;
|
||
int newTailSegment;
|
||
|
||
LWLockAcquire(OldSerXidLock, LW_EXCLUSIVE);
|
||
|
||
/*
|
||
* When no sxacts are active, nothing overlaps, set the xid values to
|
||
* invalid to show that there are no valid entries. Don't clear the
|
||
* segment/page information, though. A new xmin might still land in an
|
||
* existing segment, and we don't want to repeatedly delete and re-create
|
||
* the same segment file.
|
||
*/
|
||
if (!TransactionIdIsValid(xid))
|
||
{
|
||
if (TransactionIdIsValid(oldSerXidControl->tailXid))
|
||
{
|
||
oldSerXidControl->headXid = InvalidTransactionId;
|
||
oldSerXidControl->tailXid = InvalidTransactionId;
|
||
}
|
||
LWLockRelease(OldSerXidLock);
|
||
return;
|
||
}
|
||
|
||
/*
|
||
* When we're recovering prepared transactions, the global xmin might move
|
||
* backwards depending on the order they're recovered. Normally that's not
|
||
* OK, but during recovery no serializable transactions will commit, so
|
||
* the SLRU is empty and we can get away with it.
|
||
*/
|
||
if (RecoveryInProgress())
|
||
{
|
||
Assert(oldSerXidControl->headPage < 0);
|
||
if (!TransactionIdIsValid(oldSerXidControl->tailXid)
|
||
|| TransactionIdPrecedes(xid, oldSerXidControl->tailXid))
|
||
oldSerXidControl->tailXid = xid;
|
||
LWLockRelease(OldSerXidLock);
|
||
return;
|
||
}
|
||
|
||
Assert(!TransactionIdIsValid(oldSerXidControl->tailXid)
|
||
|| TransactionIdFollows(xid, oldSerXidControl->tailXid));
|
||
|
||
oldSerXidControl->tailXid = xid;
|
||
|
||
/* Exit quickly if there are no segments active. */
|
||
if (oldSerXidControl->headPage < 0)
|
||
{
|
||
LWLockRelease(OldSerXidLock);
|
||
return;
|
||
}
|
||
|
||
newTailPage = OldSerXidPage(xid);
|
||
newTailSegment = OldSerXidSegment(newTailPage);
|
||
|
||
/* Exit quickly if we're still on the same segment. */
|
||
if (newTailSegment == oldSerXidControl->tailSegment)
|
||
{
|
||
LWLockRelease(OldSerXidLock);
|
||
return;
|
||
}
|
||
|
||
oldSerXidControl->tailSegment = newTailSegment;
|
||
|
||
/* See if that has cleared the last segment. */
|
||
if (OldSerXidPagePrecedesLogically(oldSerXidControl->headPage,
|
||
newTailSegment * SLRU_PAGES_PER_SEGMENT))
|
||
{
|
||
oldSerXidControl->headXid = InvalidTransactionId;
|
||
oldSerXidControl->headPage = -1;
|
||
oldSerXidControl->tailSegment = -1;
|
||
}
|
||
|
||
LWLockRelease(OldSerXidLock);
|
||
|
||
SimpleLruTruncate(OldSerXidSlruCtl, newTailPage);
|
||
}
|
||
|
||
/*------------------------------------------------------------------------*/
|
||
|
||
/*
|
||
* InitPredicateLocks -- Initialize the predicate locking data structures.
|
||
*
|
||
* This is called from CreateSharedMemoryAndSemaphores(), which see for
|
||
* more comments. In the normal postmaster case, the shared hash tables
|
||
* are created here. Backends inherit the pointers
|
||
* to the shared tables via fork(). In the EXEC_BACKEND case, each
|
||
* backend re-executes this code to obtain pointers to the already existing
|
||
* shared hash tables.
|
||
*/
|
||
void
|
||
InitPredicateLocks(void)
|
||
{
|
||
HASHCTL info;
|
||
int hash_flags;
|
||
long init_table_size,
|
||
max_table_size;
|
||
Size requestSize;
|
||
bool found;
|
||
|
||
/*
|
||
* Compute init/max size to request for predicate lock target hashtable.
|
||
* Note these calculations must agree with PredicateLockShmemSize!
|
||
*/
|
||
max_table_size = NPREDICATELOCKTARGETENTS();
|
||
init_table_size = max_table_size / 2;
|
||
|
||
/*
|
||
* Allocate hash table for PREDICATELOCKTARGET structs. This stores
|
||
* per-predicate-lock-target information.
|
||
*/
|
||
MemSet(&info, 0, sizeof(info));
|
||
info.keysize = sizeof(PREDICATELOCKTARGETTAG);
|
||
info.entrysize = sizeof(PREDICATELOCKTARGET);
|
||
info.hash = tag_hash;
|
||
info.num_partitions = NUM_PREDICATELOCK_PARTITIONS;
|
||
hash_flags = (HASH_ELEM | HASH_FUNCTION | HASH_PARTITION);
|
||
|
||
PredicateLockTargetHash = ShmemInitHash("PREDICATELOCKTARGET hash",
|
||
init_table_size,
|
||
max_table_size,
|
||
&info,
|
||
hash_flags);
|
||
|
||
/* Assume an average of 2 xacts per target */
|
||
max_table_size *= 2;
|
||
init_table_size *= 2;
|
||
|
||
/*
|
||
* Reserve an entry in the hash table; we use it to make sure there's
|
||
* always one entry available when we need to split or combine a page,
|
||
* because running out of space there could mean aborting a
|
||
* non-serializable transaction.
|
||
*/
|
||
hash_search(PredicateLockTargetHash, &ReservedTargetTag,
|
||
HASH_ENTER, NULL);
|
||
|
||
|
||
/*
|
||
* Allocate hash table for PREDICATELOCK structs. This stores per
|
||
* xact-lock-of-a-target information.
|
||
*/
|
||
MemSet(&info, 0, sizeof(info));
|
||
info.keysize = sizeof(PREDICATELOCKTAG);
|
||
info.entrysize = sizeof(PREDICATELOCK);
|
||
info.hash = predicatelock_hash;
|
||
info.num_partitions = NUM_PREDICATELOCK_PARTITIONS;
|
||
hash_flags = (HASH_ELEM | HASH_FUNCTION | HASH_PARTITION);
|
||
|
||
PredicateLockHash = ShmemInitHash("PREDICATELOCK hash",
|
||
init_table_size,
|
||
max_table_size,
|
||
&info,
|
||
hash_flags);
|
||
|
||
/*
|
||
* Compute init/max size to request for serializable transaction
|
||
* hashtable. Note these calculations must agree with
|
||
* PredicateLockShmemSize!
|
||
*/
|
||
max_table_size = (MaxBackends + max_prepared_xacts);
|
||
|
||
/*
|
||
* Allocate a list to hold information on transactions participating in
|
||
* predicate locking.
|
||
*
|
||
* Assume an average of 10 predicate locking transactions per backend.
|
||
* This allows aggressive cleanup while detail is present before data must
|
||
* be summarized for storage in SLRU and the "dummy" transaction.
|
||
*/
|
||
max_table_size *= 10;
|
||
|
||
PredXact = ShmemInitStruct("PredXactList",
|
||
PredXactListDataSize,
|
||
&found);
|
||
if (!found)
|
||
{
|
||
int i;
|
||
|
||
SHMQueueInit(&PredXact->availableList);
|
||
SHMQueueInit(&PredXact->activeList);
|
||
PredXact->SxactGlobalXmin = InvalidTransactionId;
|
||
PredXact->SxactGlobalXminCount = 0;
|
||
PredXact->WritableSxactCount = 0;
|
||
PredXact->LastSxactCommitSeqNo = FirstNormalSerCommitSeqNo - 1;
|
||
PredXact->CanPartialClearThrough = 0;
|
||
PredXact->HavePartialClearedThrough = 0;
|
||
PredXact->NeedTargetLinkCleanup = false;
|
||
requestSize = mul_size((Size) max_table_size,
|
||
PredXactListElementDataSize);
|
||
PredXact->element = ShmemAlloc(requestSize);
|
||
if (PredXact->element == NULL)
|
||
ereport(ERROR,
|
||
(errcode(ERRCODE_OUT_OF_MEMORY),
|
||
errmsg("not enough shared memory for elements of data structure"
|
||
" \"%s\" (%lu bytes requested)",
|
||
"PredXactList", (unsigned long) requestSize)));
|
||
/* Add all elements to available list, clean. */
|
||
memset(PredXact->element, 0, requestSize);
|
||
for (i = 0; i < max_table_size; i++)
|
||
{
|
||
SHMQueueInsertBefore(&(PredXact->availableList),
|
||
&(PredXact->element[i].link));
|
||
}
|
||
PredXact->OldCommittedSxact = CreatePredXact();
|
||
SetInvalidVirtualTransactionId(PredXact->OldCommittedSxact->vxid);
|
||
PredXact->OldCommittedSxact->commitSeqNo = 0;
|
||
PredXact->OldCommittedSxact->SeqNo.lastCommitBeforeSnapshot = 0;
|
||
SHMQueueInit(&PredXact->OldCommittedSxact->outConflicts);
|
||
SHMQueueInit(&PredXact->OldCommittedSxact->inConflicts);
|
||
SHMQueueInit(&PredXact->OldCommittedSxact->predicateLocks);
|
||
SHMQueueInit(&PredXact->OldCommittedSxact->finishedLink);
|
||
SHMQueueInit(&PredXact->OldCommittedSxact->possibleUnsafeConflicts);
|
||
PredXact->OldCommittedSxact->topXid = InvalidTransactionId;
|
||
PredXact->OldCommittedSxact->finishedBefore = InvalidTransactionId;
|
||
PredXact->OldCommittedSxact->xmin = InvalidTransactionId;
|
||
PredXact->OldCommittedSxact->flags = SXACT_FLAG_COMMITTED;
|
||
PredXact->OldCommittedSxact->pid = 0;
|
||
}
|
||
/* This never changes, so let's keep a local copy. */
|
||
OldCommittedSxact = PredXact->OldCommittedSxact;
|
||
|
||
/*
|
||
* Allocate hash table for SERIALIZABLEXID structs. This stores per-xid
|
||
* information for serializable transactions which have accessed data.
|
||
*/
|
||
MemSet(&info, 0, sizeof(info));
|
||
info.keysize = sizeof(SERIALIZABLEXIDTAG);
|
||
info.entrysize = sizeof(SERIALIZABLEXID);
|
||
info.hash = tag_hash;
|
||
hash_flags = (HASH_ELEM | HASH_FUNCTION);
|
||
|
||
SerializableXidHash = ShmemInitHash("SERIALIZABLEXID hash",
|
||
max_table_size,
|
||
max_table_size,
|
||
&info,
|
||
hash_flags);
|
||
|
||
/*
|
||
* Allocate space for tracking rw-conflicts in lists attached to the
|
||
* transactions.
|
||
*
|
||
* Assume an average of 5 conflicts per transaction. Calculations suggest
|
||
* that this will prevent resource exhaustion in even the most pessimal
|
||
* loads up to max_connections = 200 with all 200 connections pounding the
|
||
* database with serializable transactions. Beyond that, there may be
|
||
* occassional transactions canceled when trying to flag conflicts. That's
|
||
* probably OK.
|
||
*/
|
||
max_table_size *= 5;
|
||
|
||
RWConflictPool = ShmemInitStruct("RWConflictPool",
|
||
RWConflictPoolHeaderDataSize,
|
||
&found);
|
||
if (!found)
|
||
{
|
||
int i;
|
||
|
||
SHMQueueInit(&RWConflictPool->availableList);
|
||
requestSize = mul_size((Size) max_table_size,
|
||
RWConflictDataSize);
|
||
RWConflictPool->element = ShmemAlloc(requestSize);
|
||
if (RWConflictPool->element == NULL)
|
||
ereport(ERROR,
|
||
(errcode(ERRCODE_OUT_OF_MEMORY),
|
||
errmsg("not enough shared memory for elements of data structure"
|
||
" \"%s\" (%lu bytes requested)",
|
||
"RWConflictPool", (unsigned long) requestSize)));
|
||
/* Add all elements to available list, clean. */
|
||
memset(RWConflictPool->element, 0, requestSize);
|
||
for (i = 0; i < max_table_size; i++)
|
||
{
|
||
SHMQueueInsertBefore(&(RWConflictPool->availableList),
|
||
&(RWConflictPool->element[i].outLink));
|
||
}
|
||
}
|
||
|
||
/*
|
||
* Create or attach to the header for the list of finished serializable
|
||
* transactions.
|
||
*/
|
||
FinishedSerializableTransactions = (SHM_QUEUE *)
|
||
ShmemInitStruct("FinishedSerializableTransactions",
|
||
sizeof(SHM_QUEUE),
|
||
&found);
|
||
if (!found)
|
||
SHMQueueInit(FinishedSerializableTransactions);
|
||
|
||
/*
|
||
* Initialize the SLRU storage for old committed serializable
|
||
* transactions.
|
||
*/
|
||
OldSerXidInit();
|
||
}
|
||
|
||
/*
|
||
* Estimate shared-memory space used for predicate lock table
|
||
*/
|
||
Size
|
||
PredicateLockShmemSize(void)
|
||
{
|
||
Size size = 0;
|
||
long max_table_size;
|
||
|
||
/* predicate lock target hash table */
|
||
max_table_size = NPREDICATELOCKTARGETENTS();
|
||
size = add_size(size, hash_estimate_size(max_table_size,
|
||
sizeof(PREDICATELOCKTARGET)));
|
||
|
||
/* predicate lock hash table */
|
||
max_table_size *= 2;
|
||
size = add_size(size, hash_estimate_size(max_table_size,
|
||
sizeof(PREDICATELOCK)));
|
||
|
||
/*
|
||
* Since NPREDICATELOCKTARGETENTS is only an estimate, add 10% safety
|
||
* margin.
|
||
*/
|
||
size = add_size(size, size / 10);
|
||
|
||
/* transaction list */
|
||
max_table_size = MaxBackends + max_prepared_xacts;
|
||
max_table_size *= 10;
|
||
size = add_size(size, PredXactListDataSize);
|
||
size = add_size(size, mul_size((Size) max_table_size,
|
||
PredXactListElementDataSize));
|
||
|
||
/* transaction xid table */
|
||
size = add_size(size, hash_estimate_size(max_table_size,
|
||
sizeof(SERIALIZABLEXID)));
|
||
|
||
/* rw-conflict pool */
|
||
max_table_size *= 5;
|
||
size = add_size(size, RWConflictPoolHeaderDataSize);
|
||
size = add_size(size, mul_size((Size) max_table_size,
|
||
RWConflictDataSize));
|
||
|
||
/* Head for list of finished serializable transactions. */
|
||
size = add_size(size, sizeof(SHM_QUEUE));
|
||
|
||
/* Shared memory structures for SLRU tracking of old committed xids. */
|
||
size = add_size(size, sizeof(OldSerXidControlData));
|
||
size = add_size(size, SimpleLruShmemSize(NUM_OLDSERXID_BUFFERS, 0));
|
||
|
||
return size;
|
||
}
|
||
|
||
|
||
/*
|
||
* Compute the hash code associated with a PREDICATELOCKTAG.
|
||
*
|
||
* Because we want to use just one set of partition locks for both the
|
||
* PREDICATELOCKTARGET and PREDICATELOCK hash tables, we have to make sure
|
||
* that PREDICATELOCKs fall into the same partition number as their
|
||
* associated PREDICATELOCKTARGETs. dynahash.c expects the partition number
|
||
* to be the low-order bits of the hash code, and therefore a
|
||
* PREDICATELOCKTAG's hash code must have the same low-order bits as the
|
||
* associated PREDICATELOCKTARGETTAG's hash code. We achieve this with this
|
||
* specialized hash function.
|
||
*/
|
||
static uint32
|
||
predicatelock_hash(const void *key, Size keysize)
|
||
{
|
||
const PREDICATELOCKTAG *predicatelocktag = (const PREDICATELOCKTAG *) key;
|
||
uint32 targethash;
|
||
|
||
Assert(keysize == sizeof(PREDICATELOCKTAG));
|
||
|
||
/* Look into the associated target object, and compute its hash code */
|
||
targethash = PredicateLockTargetTagHashCode(&predicatelocktag->myTarget->tag);
|
||
|
||
return PredicateLockHashCodeFromTargetHashCode(predicatelocktag, targethash);
|
||
}
|
||
|
||
|
||
/*
|
||
* GetPredicateLockStatusData
|
||
* Return a table containing the internal state of the predicate
|
||
* lock manager for use in pg_lock_status.
|
||
*
|
||
* Like GetLockStatusData, this function tries to hold the partition LWLocks
|
||
* for as short a time as possible by returning two arrays that simply
|
||
* contain the PREDICATELOCKTARGETTAG and SERIALIZABLEXACT for each lock
|
||
* table entry. Multiple copies of the same PREDICATELOCKTARGETTAG and
|
||
* SERIALIZABLEXACT will likely appear.
|
||
*/
|
||
PredicateLockData *
|
||
GetPredicateLockStatusData(void)
|
||
{
|
||
PredicateLockData *data;
|
||
int i;
|
||
int els,
|
||
el;
|
||
HASH_SEQ_STATUS seqstat;
|
||
PREDICATELOCK *predlock;
|
||
|
||
data = (PredicateLockData *) palloc(sizeof(PredicateLockData));
|
||
|
||
/*
|
||
* To ensure consistency, take simultaneous locks on all partition locks
|
||
* in ascending order, then SerializableXactHashLock.
|
||
*/
|
||
for (i = 0; i < NUM_PREDICATELOCK_PARTITIONS; i++)
|
||
LWLockAcquire(FirstPredicateLockMgrLock + i, LW_SHARED);
|
||
LWLockAcquire(SerializableXactHashLock, LW_SHARED);
|
||
|
||
/* Get number of locks and allocate appropriately-sized arrays. */
|
||
els = hash_get_num_entries(PredicateLockHash);
|
||
data->nelements = els;
|
||
data->locktags = (PREDICATELOCKTARGETTAG *)
|
||
palloc(sizeof(PREDICATELOCKTARGETTAG) * els);
|
||
data->xacts = (SERIALIZABLEXACT *)
|
||
palloc(sizeof(SERIALIZABLEXACT) * els);
|
||
|
||
|
||
/* Scan through PredicateLockHash and copy contents */
|
||
hash_seq_init(&seqstat, PredicateLockHash);
|
||
|
||
el = 0;
|
||
|
||
while ((predlock = (PREDICATELOCK *) hash_seq_search(&seqstat)))
|
||
{
|
||
data->locktags[el] = predlock->tag.myTarget->tag;
|
||
data->xacts[el] = *predlock->tag.myXact;
|
||
el++;
|
||
}
|
||
|
||
Assert(el == els);
|
||
|
||
/* Release locks in reverse order */
|
||
LWLockRelease(SerializableXactHashLock);
|
||
for (i = NUM_PREDICATELOCK_PARTITIONS - 1; i >= 0; i--)
|
||
LWLockRelease(FirstPredicateLockMgrLock + i);
|
||
|
||
return data;
|
||
}
|
||
|
||
/*
|
||
* Free up shared memory structures by pushing the oldest sxact (the one at
|
||
* the front of the SummarizeOldestCommittedSxact queue) into summary form.
|
||
* Each call will free exactly one SERIALIZABLEXACT structure and may also
|
||
* free one or more of these structures: SERIALIZABLEXID, PREDICATELOCK,
|
||
* PREDICATELOCKTARGET, RWConflictData.
|
||
*/
|
||
static void
|
||
SummarizeOldestCommittedSxact(void)
|
||
{
|
||
SERIALIZABLEXACT *sxact;
|
||
|
||
LWLockAcquire(SerializableFinishedListLock, LW_EXCLUSIVE);
|
||
|
||
#ifdef TEST_OLDSERXID
|
||
if (SHMQueueEmpty(FinishedSerializableTransactions))
|
||
{
|
||
LWLockRelease(SerializableFinishedListLock);
|
||
return;
|
||
}
|
||
#else
|
||
Assert(!SHMQueueEmpty(FinishedSerializableTransactions));
|
||
#endif
|
||
|
||
/*
|
||
* Grab the first sxact off the finished list -- this will be the earliest
|
||
* commit. Remove it from the list.
|
||
*/
|
||
sxact = (SERIALIZABLEXACT *)
|
||
SHMQueueNext(FinishedSerializableTransactions,
|
||
FinishedSerializableTransactions,
|
||
offsetof(SERIALIZABLEXACT, finishedLink));
|
||
SHMQueueDelete(&(sxact->finishedLink));
|
||
|
||
/* Add to SLRU summary information. */
|
||
if (TransactionIdIsValid(sxact->topXid) && !SxactIsReadOnly(sxact))
|
||
OldSerXidAdd(sxact->topXid, SxactHasConflictOut(sxact)
|
||
? sxact->SeqNo.earliestOutConflictCommit : InvalidSerCommitSeqNo);
|
||
|
||
/* Summarize and release the detail. */
|
||
ReleaseOneSerializableXact(sxact, false, true);
|
||
|
||
LWLockRelease(SerializableFinishedListLock);
|
||
}
|
||
|
||
/*
|
||
* GetSafeSnapshot
|
||
* Obtain and register a snapshot for a READ ONLY DEFERRABLE
|
||
* transaction. Ensures that the snapshot is "safe", i.e. a
|
||
* read-only transaction running on it can execute serializably
|
||
* without further checks. This requires waiting for concurrent
|
||
* transactions to complete, and retrying with a new snapshot if
|
||
* one of them could possibly create a conflict.
|
||
*/
|
||
static Snapshot
|
||
GetSafeSnapshot(Snapshot origSnapshot)
|
||
{
|
||
Snapshot snapshot;
|
||
|
||
Assert(XactReadOnly && XactDeferrable);
|
||
|
||
while (true)
|
||
{
|
||
/*
|
||
* RegisterSerializableTransactionInt is going to call
|
||
* GetSnapshotData, so we need to provide it the static snapshot our
|
||
* caller passed to us. It returns a copy of that snapshot and
|
||
* registers it on TopTransactionResourceOwner.
|
||
*/
|
||
snapshot = RegisterSerializableTransactionInt(origSnapshot);
|
||
|
||
if (MySerializableXact == InvalidSerializableXact)
|
||
return snapshot; /* no concurrent r/w xacts; it's safe */
|
||
|
||
MySerializableXact->flags |= SXACT_FLAG_DEFERRABLE_WAITING;
|
||
|
||
/*
|
||
* Wait for concurrent transactions to finish. Stop early if one of
|
||
* them marked us as conflicted.
|
||
*/
|
||
while (!(SHMQueueEmpty((SHM_QUEUE *)
|
||
&MySerializableXact->possibleUnsafeConflicts) ||
|
||
SxactIsROUnsafe(MySerializableXact)))
|
||
ProcWaitForSignal();
|
||
|
||
MySerializableXact->flags &= ~SXACT_FLAG_DEFERRABLE_WAITING;
|
||
if (!SxactIsROUnsafe(MySerializableXact))
|
||
break; /* success */
|
||
|
||
/* else, need to retry... */
|
||
ereport(DEBUG2,
|
||
(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
|
||
errmsg("deferrable snapshot was unsafe; trying a new one")));
|
||
ReleasePredicateLocks(false);
|
||
UnregisterSnapshotFromOwner(snapshot,
|
||
TopTransactionResourceOwner);
|
||
}
|
||
|
||
/*
|
||
* Now we have a safe snapshot, so we don't need to do any further checks.
|
||
*/
|
||
Assert(SxactIsROSafe(MySerializableXact));
|
||
ReleasePredicateLocks(false);
|
||
|
||
return snapshot;
|
||
}
|
||
|
||
/*
|
||
* Acquire and register a snapshot which can be used for this transaction..
|
||
* Make sure we have a SERIALIZABLEXACT reference in MySerializableXact.
|
||
* It should be current for this process and be contained in PredXact.
|
||
*/
|
||
Snapshot
|
||
RegisterSerializableTransaction(Snapshot snapshot)
|
||
{
|
||
Assert(IsolationIsSerializable());
|
||
|
||
/*
|
||
* A special optimization is available for SERIALIZABLE READ ONLY
|
||
* DEFERRABLE transactions -- we can wait for a suitable snapshot and
|
||
* thereby avoid all SSI overhead once it's running..
|
||
*/
|
||
if (XactReadOnly && XactDeferrable)
|
||
return GetSafeSnapshot(snapshot);
|
||
|
||
return RegisterSerializableTransactionInt(snapshot);
|
||
}
|
||
|
||
static Snapshot
|
||
RegisterSerializableTransactionInt(Snapshot snapshot)
|
||
{
|
||
PGPROC *proc;
|
||
VirtualTransactionId vxid;
|
||
SERIALIZABLEXACT *sxact,
|
||
*othersxact;
|
||
HASHCTL hash_ctl;
|
||
|
||
/* We only do this for serializable transactions. Once. */
|
||
Assert(MySerializableXact == InvalidSerializableXact);
|
||
|
||
Assert(!RecoveryInProgress());
|
||
|
||
proc = MyProc;
|
||
Assert(proc != NULL);
|
||
GET_VXID_FROM_PGPROC(vxid, *proc);
|
||
|
||
/*
|
||
* First we get the sxact structure, which may involve looping and access
|
||
* to the "finished" list to free a structure for use.
|
||
*/
|
||
#ifdef TEST_OLDSERXID
|
||
SummarizeOldestCommittedSxact();
|
||
#endif
|
||
LWLockAcquire(SerializableXactHashLock, LW_EXCLUSIVE);
|
||
do
|
||
{
|
||
sxact = CreatePredXact();
|
||
/* If null, push out committed sxact to SLRU summary & retry. */
|
||
if (!sxact)
|
||
{
|
||
LWLockRelease(SerializableXactHashLock);
|
||
SummarizeOldestCommittedSxact();
|
||
LWLockAcquire(SerializableXactHashLock, LW_EXCLUSIVE);
|
||
}
|
||
} while (!sxact);
|
||
|
||
/* Get and register a snapshot */
|
||
snapshot = GetSnapshotData(snapshot);
|
||
snapshot = RegisterSnapshotOnOwner(snapshot, TopTransactionResourceOwner);
|
||
|
||
/*
|
||
* If there are no serializable transactions which are not read-only, we
|
||
* can "opt out" of predicate locking and conflict checking for a
|
||
* read-only transaction.
|
||
*
|
||
* The reason this is safe is that a read-only transaction can only become
|
||
* part of a dangerous structure if it overlaps a writable transaction
|
||
* which in turn overlaps a writable transaction which committed before
|
||
* the read-only transaction started. A new writable transaction can
|
||
* overlap this one, but it can't meet the other condition of overlapping
|
||
* a transaction which committed before this one started.
|
||
*/
|
||
if (XactReadOnly && PredXact->WritableSxactCount == 0)
|
||
{
|
||
ReleasePredXact(sxact);
|
||
LWLockRelease(SerializableXactHashLock);
|
||
return snapshot;
|
||
}
|
||
|
||
/* Maintain serializable global xmin info. */
|
||
if (!TransactionIdIsValid(PredXact->SxactGlobalXmin))
|
||
{
|
||
Assert(PredXact->SxactGlobalXminCount == 0);
|
||
PredXact->SxactGlobalXmin = snapshot->xmin;
|
||
PredXact->SxactGlobalXminCount = 1;
|
||
OldSerXidSetActiveSerXmin(snapshot->xmin);
|
||
}
|
||
else if (TransactionIdEquals(snapshot->xmin, PredXact->SxactGlobalXmin))
|
||
{
|
||
Assert(PredXact->SxactGlobalXminCount > 0);
|
||
PredXact->SxactGlobalXminCount++;
|
||
}
|
||
else
|
||
{
|
||
Assert(TransactionIdFollows(snapshot->xmin, PredXact->SxactGlobalXmin));
|
||
}
|
||
|
||
/* Initialize the structure. */
|
||
sxact->vxid = vxid;
|
||
sxact->SeqNo.lastCommitBeforeSnapshot = PredXact->LastSxactCommitSeqNo;
|
||
sxact->commitSeqNo = InvalidSerCommitSeqNo;
|
||
SHMQueueInit(&(sxact->outConflicts));
|
||
SHMQueueInit(&(sxact->inConflicts));
|
||
SHMQueueInit(&(sxact->possibleUnsafeConflicts));
|
||
sxact->topXid = GetTopTransactionIdIfAny();
|
||
sxact->finishedBefore = InvalidTransactionId;
|
||
sxact->xmin = snapshot->xmin;
|
||
sxact->pid = MyProcPid;
|
||
SHMQueueInit(&(sxact->predicateLocks));
|
||
SHMQueueElemInit(&(sxact->finishedLink));
|
||
sxact->flags = 0;
|
||
if (XactReadOnly)
|
||
{
|
||
sxact->flags |= SXACT_FLAG_READ_ONLY;
|
||
|
||
/*
|
||
* Register all concurrent r/w transactions as possible conflicts; if
|
||
* all of them commit without any outgoing conflicts to earlier
|
||
* transactions then this snapshot can be deemed safe (and we can run
|
||
* without tracking predicate locks).
|
||
*/
|
||
for (othersxact = FirstPredXact();
|
||
othersxact != NULL;
|
||
othersxact = NextPredXact(othersxact))
|
||
{
|
||
if (!SxactIsOnFinishedList(othersxact) &&
|
||
!SxactIsReadOnly(othersxact))
|
||
{
|
||
SetPossibleUnsafeConflict(sxact, othersxact);
|
||
}
|
||
}
|
||
}
|
||
else
|
||
{
|
||
++(PredXact->WritableSxactCount);
|
||
Assert(PredXact->WritableSxactCount <=
|
||
(MaxBackends + max_prepared_xacts));
|
||
}
|
||
|
||
MySerializableXact = sxact;
|
||
|
||
LWLockRelease(SerializableXactHashLock);
|
||
|
||
/* Initialize the backend-local hash table of parent locks */
|
||
Assert(LocalPredicateLockHash == NULL);
|
||
MemSet(&hash_ctl, 0, sizeof(hash_ctl));
|
||
hash_ctl.keysize = sizeof(PREDICATELOCKTARGETTAG);
|
||
hash_ctl.entrysize = sizeof(LOCALPREDICATELOCK);
|
||
hash_ctl.hash = tag_hash;
|
||
LocalPredicateLockHash = hash_create("Local predicate lock",
|
||
max_predicate_locks_per_xact,
|
||
&hash_ctl,
|
||
HASH_ELEM | HASH_FUNCTION);
|
||
|
||
return snapshot;
|
||
}
|
||
|
||
/*
|
||
* Register the top level XID in SerializableXidHash.
|
||
* Also store it for easy reference in MySerializableXact.
|
||
*/
|
||
void
|
||
RegisterPredicateLockingXid(const TransactionId xid)
|
||
{
|
||
SERIALIZABLEXIDTAG sxidtag;
|
||
SERIALIZABLEXID *sxid;
|
||
bool found;
|
||
|
||
/*
|
||
* If we're not tracking predicate lock data for this transaction, we
|
||
* should ignore the request and return quickly.
|
||
*/
|
||
if (MySerializableXact == InvalidSerializableXact)
|
||
return;
|
||
|
||
/* This should only be done once per transaction. */
|
||
Assert(MySerializableXact->topXid == InvalidTransactionId);
|
||
|
||
/* We should have a valid XID and be at the top level. */
|
||
Assert(TransactionIdIsValid(xid));
|
||
|
||
MySerializableXact->topXid = xid;
|
||
|
||
sxidtag.xid = xid;
|
||
LWLockAcquire(SerializableXactHashLock, LW_EXCLUSIVE);
|
||
sxid = (SERIALIZABLEXID *) hash_search(SerializableXidHash,
|
||
&sxidtag,
|
||
HASH_ENTER, &found);
|
||
if (!sxid)
|
||
/* This should not be possible, based on allocation. */
|
||
ereport(ERROR,
|
||
(errcode(ERRCODE_OUT_OF_MEMORY),
|
||
errmsg("out of shared memory")));
|
||
|
||
Assert(!found);
|
||
|
||
/* Initialize the structure. */
|
||
sxid->myXact = (SERIALIZABLEXACT *) MySerializableXact;
|
||
LWLockRelease(SerializableXactHashLock);
|
||
}
|
||
|
||
|
||
/*
|
||
* Check whether there are any predicate locks held by any transaction
|
||
* for the page at the given block number.
|
||
*
|
||
* Note that the transaction may be completed but not yet subject to
|
||
* cleanup due to overlapping serializable transactions. This must
|
||
* return valid information regardless of transaction isolation level.
|
||
*
|
||
* Also note that this doesn't check for a conflicting relation lock,
|
||
* just a lock specifically on the given page.
|
||
*
|
||
* One use is to support proper behavior during GiST index vacuum.
|
||
*/
|
||
bool
|
||
PageIsPredicateLocked(const Relation relation, const BlockNumber blkno)
|
||
{
|
||
PREDICATELOCKTARGETTAG targettag;
|
||
uint32 targettaghash;
|
||
LWLockId partitionLock;
|
||
PREDICATELOCKTARGET *target;
|
||
|
||
SET_PREDICATELOCKTARGETTAG_PAGE(targettag,
|
||
relation->rd_node.dbNode,
|
||
relation->rd_id,
|
||
blkno);
|
||
|
||
targettaghash = PredicateLockTargetTagHashCode(&targettag);
|
||
partitionLock = PredicateLockHashPartitionLock(targettaghash);
|
||
LWLockAcquire(partitionLock, LW_SHARED);
|
||
target = (PREDICATELOCKTARGET *)
|
||
hash_search_with_hash_value(PredicateLockTargetHash,
|
||
&targettag, targettaghash,
|
||
HASH_FIND, NULL);
|
||
LWLockRelease(partitionLock);
|
||
|
||
return (target != NULL);
|
||
}
|
||
|
||
|
||
/*
|
||
* Check whether a particular lock is held by this transaction.
|
||
*
|
||
* Important note: this function may return false even if the lock is
|
||
* being held, because it uses the local lock table which is not
|
||
* updated if another transaction modifies our lock list (e.g. to
|
||
* split an index page). However, it will never return true if the
|
||
* lock is not held. We only use this function in circumstances where
|
||
* such false negatives are acceptable.
|
||
*/
|
||
static bool
|
||
PredicateLockExists(const PREDICATELOCKTARGETTAG *targettag)
|
||
{
|
||
LOCALPREDICATELOCK *lock;
|
||
|
||
/* check local hash table */
|
||
lock = (LOCALPREDICATELOCK *) hash_search(LocalPredicateLockHash,
|
||
targettag,
|
||
HASH_FIND, NULL);
|
||
|
||
if (!lock)
|
||
return false;
|
||
|
||
/*
|
||
* Found entry in the table, but still need to check whether it's actually
|
||
* held -- it could just be a parent of some held lock.
|
||
*/
|
||
return lock->held;
|
||
}
|
||
|
||
/*
|
||
* Return the parent lock tag in the lock hierarchy: the next coarser
|
||
* lock that covers the provided tag.
|
||
*
|
||
* Returns true and sets *parent to the parent tag if one exists,
|
||
* returns false if none exists.
|
||
*/
|
||
static bool
|
||
GetParentPredicateLockTag(const PREDICATELOCKTARGETTAG *tag,
|
||
PREDICATELOCKTARGETTAG *parent)
|
||
{
|
||
switch (GET_PREDICATELOCKTARGETTAG_TYPE(*tag))
|
||
{
|
||
case PREDLOCKTAG_RELATION:
|
||
/* relation locks have no parent lock */
|
||
return false;
|
||
|
||
case PREDLOCKTAG_PAGE:
|
||
/* parent lock is relation lock */
|
||
SET_PREDICATELOCKTARGETTAG_RELATION(*parent,
|
||
GET_PREDICATELOCKTARGETTAG_DB(*tag),
|
||
GET_PREDICATELOCKTARGETTAG_RELATION(*tag));
|
||
|
||
return true;
|
||
|
||
case PREDLOCKTAG_TUPLE:
|
||
/* parent lock is page lock */
|
||
SET_PREDICATELOCKTARGETTAG_PAGE(*parent,
|
||
GET_PREDICATELOCKTARGETTAG_DB(*tag),
|
||
GET_PREDICATELOCKTARGETTAG_RELATION(*tag),
|
||
GET_PREDICATELOCKTARGETTAG_PAGE(*tag));
|
||
return true;
|
||
}
|
||
|
||
/* not reachable */
|
||
Assert(false);
|
||
return false;
|
||
}
|
||
|
||
/*
|
||
* Check whether the lock we are considering is already covered by a
|
||
* coarser lock for our transaction.
|
||
*/
|
||
static bool
|
||
CoarserLockCovers(const PREDICATELOCKTARGETTAG *newtargettag)
|
||
{
|
||
PREDICATELOCKTARGETTAG targettag,
|
||
parenttag;
|
||
|
||
targettag = *newtargettag;
|
||
|
||
/* check parents iteratively until no more */
|
||
while (GetParentPredicateLockTag(&targettag, &parenttag))
|
||
{
|
||
targettag = parenttag;
|
||
if (PredicateLockExists(&targettag))
|
||
return true;
|
||
}
|
||
|
||
/* no more parents to check; lock is not covered */
|
||
return false;
|
||
}
|
||
|
||
/*
|
||
* Check whether both the list of related predicate locks and the pointer to
|
||
* a prior version of the row (if this is a tuple lock target) are empty for
|
||
* a predicate lock target, and remove the target if they are.
|
||
*/
|
||
static void
|
||
RemoveTargetIfNoLongerUsed(PREDICATELOCKTARGET *target, uint32 targettaghash)
|
||
{
|
||
PREDICATELOCKTARGET *rmtarget;
|
||
PREDICATELOCKTARGET *next;
|
||
|
||
Assert(LWLockHeldByMe(SerializablePredicateLockListLock));
|
||
|
||
/* Can't remove it until no locks at this target. */
|
||
if (!SHMQueueEmpty(&target->predicateLocks))
|
||
return;
|
||
|
||
/* Can't remove it if there are locks for a prior row version. */
|
||
LWLockAcquire(PredicateLockNextRowLinkLock, LW_EXCLUSIVE);
|
||
if (target->priorVersionOfRow != NULL)
|
||
{
|
||
LWLockRelease(PredicateLockNextRowLinkLock);
|
||
return;
|
||
}
|
||
|
||
/*
|
||
* We are going to release this target, This requires that we let the
|
||
* next version of the row (if any) know that it's previous version is
|
||
* done.
|
||
*
|
||
* It might be that the link was all that was keeping the other target
|
||
* from cleanup, but we can't clean that up here -- LW locking is all
|
||
* wrong for that. We'll pass the HTAB in the general cleanup function to
|
||
* get rid of such "dead" targets.
|
||
*/
|
||
next = target->nextVersionOfRow;
|
||
if (next != NULL)
|
||
{
|
||
next->priorVersionOfRow = NULL;
|
||
if (SHMQueueEmpty(&next->predicateLocks))
|
||
PredXact->NeedTargetLinkCleanup = true;
|
||
}
|
||
LWLockRelease(PredicateLockNextRowLinkLock);
|
||
|
||
/* Actually remove the target. */
|
||
rmtarget = hash_search_with_hash_value(PredicateLockTargetHash,
|
||
&target->tag,
|
||
targettaghash,
|
||
HASH_REMOVE, NULL);
|
||
Assert(rmtarget == target);
|
||
}
|
||
|
||
/*
|
||
* Delete child target locks owned by this process.
|
||
* This implementation is assuming that the usage of each target tag field
|
||
* is uniform. No need to make this hard if we don't have to.
|
||
*
|
||
* We aren't acquiring lightweight locks for the predicate lock or lock
|
||
* target structures associated with this transaction unless we're going
|
||
* to modify them, because no other process is permitted to modify our
|
||
* locks.
|
||
*/
|
||
static void
|
||
DeleteChildTargetLocks(const PREDICATELOCKTARGETTAG *newtargettag)
|
||
{
|
||
SERIALIZABLEXACT *sxact;
|
||
PREDICATELOCK *predlock;
|
||
|
||
LWLockAcquire(SerializablePredicateLockListLock, LW_SHARED);
|
||
sxact = (SERIALIZABLEXACT *) MySerializableXact;
|
||
predlock = (PREDICATELOCK *)
|
||
SHMQueueNext(&(sxact->predicateLocks),
|
||
&(sxact->predicateLocks),
|
||
offsetof(PREDICATELOCK, xactLink));
|
||
while (predlock)
|
||
{
|
||
SHM_QUEUE *predlocksxactlink;
|
||
PREDICATELOCK *nextpredlock;
|
||
PREDICATELOCKTAG oldlocktag;
|
||
PREDICATELOCKTARGET *oldtarget;
|
||
PREDICATELOCKTARGETTAG oldtargettag;
|
||
|
||
predlocksxactlink = &(predlock->xactLink);
|
||
nextpredlock = (PREDICATELOCK *)
|
||
SHMQueueNext(&(sxact->predicateLocks),
|
||
predlocksxactlink,
|
||
offsetof(PREDICATELOCK, xactLink));
|
||
|
||
oldlocktag = predlock->tag;
|
||
Assert(oldlocktag.myXact == sxact);
|
||
oldtarget = oldlocktag.myTarget;
|
||
oldtargettag = oldtarget->tag;
|
||
|
||
if (TargetTagIsCoveredBy(oldtargettag, *newtargettag))
|
||
{
|
||
uint32 oldtargettaghash;
|
||
LWLockId partitionLock;
|
||
PREDICATELOCK *rmpredlock;
|
||
|
||
oldtargettaghash = PredicateLockTargetTagHashCode(&oldtargettag);
|
||
partitionLock = PredicateLockHashPartitionLock(oldtargettaghash);
|
||
|
||
LWLockAcquire(partitionLock, LW_EXCLUSIVE);
|
||
|
||
SHMQueueDelete(predlocksxactlink);
|
||
SHMQueueDelete(&(predlock->targetLink));
|
||
rmpredlock = hash_search_with_hash_value
|
||
(PredicateLockHash,
|
||
&oldlocktag,
|
||
PredicateLockHashCodeFromTargetHashCode(&oldlocktag,
|
||
oldtargettaghash),
|
||
HASH_REMOVE, NULL);
|
||
Assert(rmpredlock == predlock);
|
||
|
||
RemoveTargetIfNoLongerUsed(oldtarget, oldtargettaghash);
|
||
|
||
LWLockRelease(partitionLock);
|
||
|
||
DecrementParentLocks(&oldtargettag);
|
||
}
|
||
|
||
predlock = nextpredlock;
|
||
}
|
||
LWLockRelease(SerializablePredicateLockListLock);
|
||
}
|
||
|
||
/*
|
||
* Returns the promotion threshold for a given predicate lock
|
||
* target. This is the number of descendant locks required to promote
|
||
* to the specified tag. Note that the threshold includes non-direct
|
||
* descendants, e.g. both tuples and pages for a relation lock.
|
||
*
|
||
* TODO SSI: We should do something more intelligent about what the
|
||
* thresholds are, either making it proportional to the number of
|
||
* tuples in a page & pages in a relation, or at least making it a
|
||
* GUC. Currently the threshold is 3 for a page lock, and
|
||
* max_pred_locks_per_transaction/2 for a relation lock, chosen
|
||
* entirely arbitrarily (and without benchmarking).
|
||
*/
|
||
static int
|
||
PredicateLockPromotionThreshold(const PREDICATELOCKTARGETTAG *tag)
|
||
{
|
||
switch (GET_PREDICATELOCKTARGETTAG_TYPE(*tag))
|
||
{
|
||
case PREDLOCKTAG_RELATION:
|
||
return max_predicate_locks_per_xact / 2;
|
||
|
||
case PREDLOCKTAG_PAGE:
|
||
return 3;
|
||
|
||
case PREDLOCKTAG_TUPLE:
|
||
|
||
/*
|
||
* not reachable: nothing is finer-granularity than a tuple, so we
|
||
* should never try to promote to it.
|
||
*/
|
||
Assert(false);
|
||
return 0;
|
||
}
|
||
|
||
/* not reachable */
|
||
Assert(false);
|
||
return 0;
|
||
}
|
||
|
||
/*
|
||
* For all ancestors of a newly-acquired predicate lock, increment
|
||
* their child count in the parent hash table. If any of them have
|
||
* more descendants than their promotion threshold, acquire the
|
||
* coarsest such lock.
|
||
*
|
||
* Returns true if a parent lock was acquired and false otherwise.
|
||
*/
|
||
static bool
|
||
CheckAndPromotePredicateLockRequest(const PREDICATELOCKTARGETTAG *reqtag)
|
||
{
|
||
PREDICATELOCKTARGETTAG targettag,
|
||
nexttag,
|
||
promotiontag;
|
||
LOCALPREDICATELOCK *parentlock;
|
||
bool found,
|
||
promote;
|
||
|
||
promote = false;
|
||
|
||
targettag = *reqtag;
|
||
|
||
/* check parents iteratively */
|
||
while (GetParentPredicateLockTag(&targettag, &nexttag))
|
||
{
|
||
targettag = nexttag;
|
||
parentlock = (LOCALPREDICATELOCK *) hash_search(LocalPredicateLockHash,
|
||
&targettag,
|
||
HASH_ENTER,
|
||
&found);
|
||
if (!found)
|
||
{
|
||
parentlock->held = false;
|
||
parentlock->childLocks = 1;
|
||
}
|
||
else
|
||
parentlock->childLocks++;
|
||
|
||
if (parentlock->childLocks >=
|
||
PredicateLockPromotionThreshold(&targettag))
|
||
{
|
||
/*
|
||
* We should promote to this parent lock. Continue to check its
|
||
* ancestors, however, both to get their child counts right and to
|
||
* check whether we should just go ahead and promote to one of
|
||
* them.
|
||
*/
|
||
promotiontag = targettag;
|
||
promote = true;
|
||
}
|
||
}
|
||
|
||
if (promote)
|
||
{
|
||
/* acquire coarsest ancestor eligible for promotion */
|
||
PredicateLockAcquire(&promotiontag);
|
||
return true;
|
||
}
|
||
else
|
||
return false;
|
||
}
|
||
|
||
/*
|
||
* When releasing a lock, decrement the child count on all ancestor
|
||
* locks.
|
||
*
|
||
* This is called only when releasing a lock via
|
||
* DeleteChildTargetLocks (i.e. when a lock becomes redundant because
|
||
* we've acquired its parent, possibly due to promotion) or when a new
|
||
* MVCC write lock makes the predicate lock unnecessary. There's no
|
||
* point in calling it when locks are released at transaction end, as
|
||
* this information is no longer needed.
|
||
*/
|
||
static void
|
||
DecrementParentLocks(const PREDICATELOCKTARGETTAG *targettag)
|
||
{
|
||
PREDICATELOCKTARGETTAG parenttag,
|
||
nexttag;
|
||
|
||
parenttag = *targettag;
|
||
|
||
while (GetParentPredicateLockTag(&parenttag, &nexttag))
|
||
{
|
||
uint32 targettaghash;
|
||
LOCALPREDICATELOCK *parentlock,
|
||
*rmlock;
|
||
|
||
parenttag = nexttag;
|
||
targettaghash = PredicateLockTargetTagHashCode(&parenttag);
|
||
parentlock = (LOCALPREDICATELOCK *)
|
||
hash_search_with_hash_value(LocalPredicateLockHash,
|
||
&parenttag, targettaghash,
|
||
HASH_FIND, NULL);
|
||
|
||
/*
|
||
* There's a small chance the parent lock doesn't exist in the lock
|
||
* table. This can happen if we prematurely removed it because an
|
||
* index split caused the child refcount to be off.
|
||
*/
|
||
if (parentlock == NULL)
|
||
continue;
|
||
|
||
parentlock->childLocks--;
|
||
|
||
/*
|
||
* Under similar circumstances the parent lock's refcount might be
|
||
* zero. This only happens if we're holding that lock (otherwise we
|
||
* would have removed the entry).
|
||
*/
|
||
if (parentlock->childLocks < 0)
|
||
{
|
||
Assert(parentlock->held);
|
||
parentlock->childLocks = 0;
|
||
}
|
||
|
||
if ((parentlock->childLocks == 0) && (!parentlock->held))
|
||
{
|
||
rmlock = (LOCALPREDICATELOCK *)
|
||
hash_search_with_hash_value(LocalPredicateLockHash,
|
||
&parenttag, targettaghash,
|
||
HASH_REMOVE, NULL);
|
||
Assert(rmlock == parentlock);
|
||
}
|
||
}
|
||
}
|
||
|
||
/*
|
||
* Indicate that a predicate lock on the given target is held by the
|
||
* specified transaction. Has no effect if the lock is already held.
|
||
*
|
||
* This updates the lock table and the sxact's lock list, and creates
|
||
* the lock target if necessary, but does *not* do anything related to
|
||
* granularity promotion or the local lock table. See
|
||
* PredicateLockAcquire for that.
|
||
*/
|
||
static void
|
||
CreatePredicateLock(const PREDICATELOCKTARGETTAG *targettag,
|
||
uint32 targettaghash,
|
||
SERIALIZABLEXACT *sxact)
|
||
{
|
||
PREDICATELOCKTARGET *target;
|
||
PREDICATELOCKTAG locktag;
|
||
PREDICATELOCK *lock;
|
||
LWLockId partitionLock;
|
||
bool found;
|
||
|
||
partitionLock = PredicateLockHashPartitionLock(targettaghash);
|
||
|
||
LWLockAcquire(SerializablePredicateLockListLock, LW_SHARED);
|
||
LWLockAcquire(partitionLock, LW_EXCLUSIVE);
|
||
|
||
/* Make sure that the target is represented. */
|
||
target = (PREDICATELOCKTARGET *)
|
||
hash_search_with_hash_value(PredicateLockTargetHash,
|
||
targettag, targettaghash,
|
||
HASH_ENTER, &found);
|
||
if (!target)
|
||
ereport(ERROR,
|
||
(errcode(ERRCODE_OUT_OF_MEMORY),
|
||
errmsg("out of shared memory"),
|
||
errhint("You might need to increase max_pred_locks_per_transaction.")));
|
||
if (!found)
|
||
{
|
||
SHMQueueInit(&(target->predicateLocks));
|
||
target->priorVersionOfRow = NULL;
|
||
target->nextVersionOfRow = NULL;
|
||
}
|
||
|
||
/* We've got the sxact and target, make sure they're joined. */
|
||
locktag.myTarget = target;
|
||
locktag.myXact = sxact;
|
||
lock = (PREDICATELOCK *)
|
||
hash_search_with_hash_value(PredicateLockHash, &locktag,
|
||
PredicateLockHashCodeFromTargetHashCode(&locktag, targettaghash),
|
||
HASH_ENTER, &found);
|
||
if (!lock)
|
||
ereport(ERROR,
|
||
(errcode(ERRCODE_OUT_OF_MEMORY),
|
||
errmsg("out of shared memory"),
|
||
errhint("You might need to increase max_pred_locks_per_transaction.")));
|
||
|
||
if (!found)
|
||
{
|
||
SHMQueueInsertBefore(&(target->predicateLocks), &(lock->targetLink));
|
||
SHMQueueInsertBefore(&(sxact->predicateLocks),
|
||
&(lock->xactLink));
|
||
lock->commitSeqNo = 0;
|
||
}
|
||
|
||
LWLockRelease(partitionLock);
|
||
LWLockRelease(SerializablePredicateLockListLock);
|
||
}
|
||
|
||
/*
|
||
* Acquire a predicate lock on the specified target for the current
|
||
* connection if not already held. This updates the local lock table
|
||
* and uses it to implement granularity promotion. It will consolidate
|
||
* multiple locks into a coarser lock if warranted, and will release
|
||
* any finer-grained locks covered by the new one.
|
||
*/
|
||
static void
|
||
PredicateLockAcquire(const PREDICATELOCKTARGETTAG *targettag)
|
||
{
|
||
uint32 targettaghash;
|
||
bool found;
|
||
LOCALPREDICATELOCK *locallock;
|
||
|
||
/* Do we have the lock already, or a covering lock? */
|
||
if (PredicateLockExists(targettag))
|
||
return;
|
||
|
||
if (CoarserLockCovers(targettag))
|
||
return;
|
||
|
||
/* the same hash and LW lock apply to the lock target and the local lock. */
|
||
targettaghash = PredicateLockTargetTagHashCode(targettag);
|
||
|
||
/* Acquire lock in local table */
|
||
locallock = (LOCALPREDICATELOCK *)
|
||
hash_search_with_hash_value(LocalPredicateLockHash,
|
||
targettag, targettaghash,
|
||
HASH_ENTER, &found);
|
||
/* We should not hold the lock (but its entry might still exist) */
|
||
Assert(!found || !locallock->held);
|
||
locallock->held = true;
|
||
if (!found)
|
||
locallock->childLocks = 0;
|
||
|
||
/* Actually create the lock */
|
||
CreatePredicateLock(targettag, targettaghash,
|
||
(SERIALIZABLEXACT *) MySerializableXact);
|
||
|
||
/*
|
||
* Lock has been acquired. Check whether it should be promoted to a
|
||
* coarser granularity, or whether there are finer-granularity locks to
|
||
* clean up.
|
||
*/
|
||
if (CheckAndPromotePredicateLockRequest(targettag))
|
||
{
|
||
/*
|
||
* Lock request was promoted to a coarser-granularity lock, and that
|
||
* lock was acquired. It will delete this lock and any of its
|
||
* children, so we're done.
|
||
*/
|
||
}
|
||
else
|
||
{
|
||
/* Clean up any finer-granularity locks */
|
||
if (GET_PREDICATELOCKTARGETTAG_TYPE(*targettag) != PREDLOCKTAG_TUPLE)
|
||
DeleteChildTargetLocks(targettag);
|
||
}
|
||
}
|
||
|
||
|
||
/*
|
||
* PredicateLockRelation
|
||
*
|
||
* Gets a predicate lock at the relation level.
|
||
* Skip if not in full serializable transaction isolation level.
|
||
* Skip if this is a temporary table.
|
||
* Clear any finer-grained predicate locks this session has on the relation.
|
||
*/
|
||
void
|
||
PredicateLockRelation(const Relation relation)
|
||
{
|
||
PREDICATELOCKTARGETTAG tag;
|
||
|
||
if (SkipSerialization(relation))
|
||
return;
|
||
|
||
SET_PREDICATELOCKTARGETTAG_RELATION(tag,
|
||
relation->rd_node.dbNode,
|
||
relation->rd_id);
|
||
PredicateLockAcquire(&tag);
|
||
}
|
||
|
||
/*
|
||
* PredicateLockPage
|
||
*
|
||
* Gets a predicate lock at the page level.
|
||
* Skip if not in full serializable transaction isolation level.
|
||
* Skip if this is a temporary table.
|
||
* Skip if a coarser predicate lock already covers this page.
|
||
* Clear any finer-grained predicate locks this session has on the relation.
|
||
*/
|
||
void
|
||
PredicateLockPage(const Relation relation, const BlockNumber blkno)
|
||
{
|
||
PREDICATELOCKTARGETTAG tag;
|
||
|
||
if (SkipSerialization(relation))
|
||
return;
|
||
|
||
SET_PREDICATELOCKTARGETTAG_PAGE(tag,
|
||
relation->rd_node.dbNode,
|
||
relation->rd_id,
|
||
blkno);
|
||
PredicateLockAcquire(&tag);
|
||
}
|
||
|
||
/*
|
||
* PredicateLockTuple
|
||
*
|
||
* Gets a predicate lock at the tuple level.
|
||
* Skip if not in full serializable transaction isolation level.
|
||
* Skip if this is a temporary table.
|
||
*/
|
||
void
|
||
PredicateLockTuple(const Relation relation, const HeapTuple tuple)
|
||
{
|
||
PREDICATELOCKTARGETTAG tag;
|
||
ItemPointer tid;
|
||
|
||
if (SkipSerialization(relation))
|
||
return;
|
||
|
||
/*
|
||
* If it's a heap tuple, return if this xact wrote it.
|
||
*/
|
||
if (relation->rd_index == NULL)
|
||
{
|
||
TransactionId myxid = GetTopTransactionIdIfAny();
|
||
|
||
if (TransactionIdIsValid(myxid))
|
||
{
|
||
TransactionId xid = HeapTupleHeaderGetXmin(tuple->t_data);
|
||
|
||
if (TransactionIdFollowsOrEquals(xid, TransactionXmin))
|
||
{
|
||
xid = SubTransGetTopmostTransaction(xid);
|
||
if (TransactionIdEquals(xid, myxid))
|
||
{
|
||
/* We wrote it; we already have a write lock. */
|
||
return;
|
||
}
|
||
}
|
||
}
|
||
}
|
||
|
||
/*
|
||
* Do quick-but-not-definitive test for a relation lock first. This will
|
||
* never cause a return when the relation is *not* locked, but will
|
||
* occasionally let the check continue when there really *is* a relation
|
||
* level lock.
|
||
*/
|
||
SET_PREDICATELOCKTARGETTAG_RELATION(tag,
|
||
relation->rd_node.dbNode,
|
||
relation->rd_id);
|
||
if (PredicateLockExists(&tag))
|
||
return;
|
||
|
||
tid = &(tuple->t_self);
|
||
SET_PREDICATELOCKTARGETTAG_TUPLE(tag,
|
||
relation->rd_node.dbNode,
|
||
relation->rd_id,
|
||
ItemPointerGetBlockNumber(tid),
|
||
ItemPointerGetOffsetNumber(tid));
|
||
PredicateLockAcquire(&tag);
|
||
}
|
||
|
||
/*
|
||
* If the old tuple has any predicate locks, create a lock target for the
|
||
* new tuple and point them at each other. Conflict detection needs to
|
||
* look for locks against prior versions of the row.
|
||
*/
|
||
void
|
||
PredicateLockTupleRowVersionLink(const Relation relation,
|
||
const HeapTuple oldTuple,
|
||
const HeapTuple newTuple)
|
||
{
|
||
PREDICATELOCKTARGETTAG oldtargettag;
|
||
PREDICATELOCKTARGETTAG newtargettag;
|
||
PREDICATELOCKTARGET *oldtarget;
|
||
PREDICATELOCKTARGET *newtarget;
|
||
PREDICATELOCKTARGET *next;
|
||
uint32 oldtargettaghash;
|
||
LWLockId oldpartitionLock;
|
||
uint32 newtargettaghash;
|
||
LWLockId newpartitionLock;
|
||
bool found;
|
||
|
||
SET_PREDICATELOCKTARGETTAG_TUPLE(oldtargettag,
|
||
relation->rd_node.dbNode,
|
||
relation->rd_id,
|
||
ItemPointerGetBlockNumber(&(oldTuple->t_self)),
|
||
ItemPointerGetOffsetNumber(&(oldTuple->t_self)));
|
||
oldtargettaghash = PredicateLockTargetTagHashCode(&oldtargettag);
|
||
oldpartitionLock = PredicateLockHashPartitionLock(oldtargettaghash);
|
||
|
||
SET_PREDICATELOCKTARGETTAG_TUPLE(newtargettag,
|
||
relation->rd_node.dbNode,
|
||
relation->rd_id,
|
||
ItemPointerGetBlockNumber(&(newTuple->t_self)),
|
||
ItemPointerGetOffsetNumber(&(newTuple->t_self)));
|
||
newtargettaghash = PredicateLockTargetTagHashCode(&newtargettag);
|
||
newpartitionLock = PredicateLockHashPartitionLock(newtargettaghash);
|
||
|
||
/* Lock lower numbered partition first. */
|
||
if (oldpartitionLock < newpartitionLock)
|
||
{
|
||
LWLockAcquire(oldpartitionLock, LW_SHARED);
|
||
LWLockAcquire(newpartitionLock, LW_EXCLUSIVE);
|
||
}
|
||
else if (newpartitionLock < oldpartitionLock)
|
||
{
|
||
LWLockAcquire(newpartitionLock, LW_EXCLUSIVE);
|
||
LWLockAcquire(oldpartitionLock, LW_SHARED);
|
||
}
|
||
else
|
||
LWLockAcquire(newpartitionLock, LW_EXCLUSIVE);
|
||
|
||
oldtarget = (PREDICATELOCKTARGET *)
|
||
hash_search_with_hash_value(PredicateLockTargetHash,
|
||
&oldtargettag, oldtargettaghash,
|
||
HASH_FIND, NULL);
|
||
|
||
/* Only need to link if there is an old target already. */
|
||
if (oldtarget)
|
||
{
|
||
LWLockAcquire(PredicateLockNextRowLinkLock, LW_EXCLUSIVE);
|
||
|
||
/* Guard against stale pointers from rollback. */
|
||
next = oldtarget->nextVersionOfRow;
|
||
if (next != NULL)
|
||
{
|
||
next->priorVersionOfRow = NULL;
|
||
oldtarget->nextVersionOfRow = NULL;
|
||
}
|
||
|
||
/* Find or create the new target, and link old and new. */
|
||
newtarget = (PREDICATELOCKTARGET *)
|
||
hash_search_with_hash_value(PredicateLockTargetHash,
|
||
&newtargettag, newtargettaghash,
|
||
HASH_ENTER, &found);
|
||
if (!newtarget)
|
||
ereport(ERROR,
|
||
(errcode(ERRCODE_OUT_OF_MEMORY),
|
||
errmsg("out of shared memory"),
|
||
errhint("You might need to increase max_pred_locks_per_transaction.")));
|
||
if (!found)
|
||
{
|
||
SHMQueueInit(&(newtarget->predicateLocks));
|
||
newtarget->nextVersionOfRow = NULL;
|
||
}
|
||
else
|
||
Assert(newtarget->priorVersionOfRow == NULL);
|
||
|
||
newtarget->priorVersionOfRow = oldtarget;
|
||
oldtarget->nextVersionOfRow = newtarget;
|
||
|
||
LWLockRelease(PredicateLockNextRowLinkLock);
|
||
}
|
||
|
||
/* Release lower number partition last. */
|
||
if (oldpartitionLock < newpartitionLock)
|
||
{
|
||
LWLockRelease(newpartitionLock);
|
||
LWLockRelease(oldpartitionLock);
|
||
}
|
||
else if (newpartitionLock < oldpartitionLock)
|
||
{
|
||
LWLockRelease(oldpartitionLock);
|
||
LWLockRelease(newpartitionLock);
|
||
}
|
||
else
|
||
LWLockRelease(newpartitionLock);
|
||
}
|
||
|
||
|
||
/*
|
||
* DeleteLockTarget
|
||
*
|
||
* Remove a predicate lock target along with any locks held for it.
|
||
*
|
||
* Caller must hold SerializablePredicateLockListLock and the
|
||
* appropriate hash partition lock for the target.
|
||
*/
|
||
static void
|
||
DeleteLockTarget(PREDICATELOCKTARGET *target, uint32 targettaghash)
|
||
{
|
||
PREDICATELOCK *predlock;
|
||
SHM_QUEUE *predlocktargetlink;
|
||
PREDICATELOCK *nextpredlock;
|
||
bool found;
|
||
|
||
Assert(LWLockHeldByMe(SerializablePredicateLockListLock));
|
||
Assert(LWLockHeldByMe(PredicateLockHashPartitionLock(targettaghash)));
|
||
|
||
predlock = (PREDICATELOCK *)
|
||
SHMQueueNext(&(target->predicateLocks),
|
||
&(target->predicateLocks),
|
||
offsetof(PREDICATELOCK, targetLink));
|
||
LWLockAcquire(SerializableXactHashLock, LW_EXCLUSIVE);
|
||
while (predlock)
|
||
{
|
||
predlocktargetlink = &(predlock->targetLink);
|
||
nextpredlock = (PREDICATELOCK *)
|
||
SHMQueueNext(&(target->predicateLocks),
|
||
predlocktargetlink,
|
||
offsetof(PREDICATELOCK, targetLink));
|
||
|
||
SHMQueueDelete(&(predlock->xactLink));
|
||
SHMQueueDelete(&(predlock->targetLink));
|
||
|
||
hash_search_with_hash_value
|
||
(PredicateLockHash,
|
||
&predlock->tag,
|
||
PredicateLockHashCodeFromTargetHashCode(&predlock->tag,
|
||
targettaghash),
|
||
HASH_REMOVE, &found);
|
||
Assert(found);
|
||
|
||
predlock = nextpredlock;
|
||
}
|
||
LWLockRelease(SerializableXactHashLock);
|
||
|
||
/* Remove the target itself, if possible. */
|
||
RemoveTargetIfNoLongerUsed(target, targettaghash);
|
||
}
|
||
|
||
|
||
/*
|
||
* TransferPredicateLocksToNewTarget
|
||
*
|
||
* Move or copy all the predicate locks for a lock target, for use by
|
||
* index page splits/combines and other things that create or replace
|
||
* lock targets. If 'removeOld' is true, the old locks and the target
|
||
* will be removed.
|
||
*
|
||
* Returns true on success, or false if we ran out of shared memory to
|
||
* allocate the new target or locks. Guaranteed to always succeed if
|
||
* removeOld is set (by using the reserved entry in
|
||
* PredicateLockTargetHash for scratch space).
|
||
*
|
||
* Caller must hold SerializablePredicateLockListLock.
|
||
*/
|
||
static bool
|
||
TransferPredicateLocksToNewTarget(const PREDICATELOCKTARGETTAG oldtargettag,
|
||
const PREDICATELOCKTARGETTAG newtargettag,
|
||
bool removeOld)
|
||
{
|
||
uint32 oldtargettaghash;
|
||
LWLockId oldpartitionLock;
|
||
PREDICATELOCKTARGET *oldtarget;
|
||
uint32 newtargettaghash;
|
||
LWLockId newpartitionLock;
|
||
bool found;
|
||
bool outOfShmem = false;
|
||
uint32 reservedtargettaghash;
|
||
LWLockId reservedpartitionLock;
|
||
|
||
|
||
Assert(LWLockHeldByMe(SerializablePredicateLockListLock));
|
||
|
||
oldtargettaghash = PredicateLockTargetTagHashCode(&oldtargettag);
|
||
newtargettaghash = PredicateLockTargetTagHashCode(&newtargettag);
|
||
oldpartitionLock = PredicateLockHashPartitionLock(oldtargettaghash);
|
||
newpartitionLock = PredicateLockHashPartitionLock(newtargettaghash);
|
||
|
||
reservedtargettaghash = 0; /* Quiet compiler warnings. */
|
||
reservedpartitionLock = 0; /* Quiet compiler warnings. */
|
||
|
||
if (removeOld)
|
||
{
|
||
/*
|
||
* Remove the reserved entry to give us scratch space, so we know
|
||
* we'll be able to create the new lock target.
|
||
*/
|
||
reservedtargettaghash = PredicateLockTargetTagHashCode(&ReservedTargetTag);
|
||
reservedpartitionLock = PredicateLockHashPartitionLock(reservedtargettaghash);
|
||
LWLockAcquire(reservedpartitionLock, LW_EXCLUSIVE);
|
||
hash_search_with_hash_value(PredicateLockTargetHash,
|
||
&ReservedTargetTag,
|
||
reservedtargettaghash,
|
||
HASH_REMOVE, &found);
|
||
Assert(found);
|
||
LWLockRelease(reservedpartitionLock);
|
||
}
|
||
|
||
/*
|
||
* We must get the partition locks in ascending sequence to avoid
|
||
* deadlocks. If old and new partitions are the same, we must request the
|
||
* lock only once.
|
||
*/
|
||
if (oldpartitionLock < newpartitionLock)
|
||
{
|
||
LWLockAcquire(oldpartitionLock,
|
||
(removeOld ? LW_EXCLUSIVE : LW_SHARED));
|
||
LWLockAcquire(newpartitionLock, LW_EXCLUSIVE);
|
||
}
|
||
else if (oldpartitionLock > newpartitionLock)
|
||
{
|
||
LWLockAcquire(newpartitionLock, LW_EXCLUSIVE);
|
||
LWLockAcquire(oldpartitionLock,
|
||
(removeOld ? LW_EXCLUSIVE : LW_SHARED));
|
||
}
|
||
else
|
||
LWLockAcquire(newpartitionLock, LW_EXCLUSIVE);
|
||
|
||
/*
|
||
* Look for the old target. If not found, that's OK; no predicate locks
|
||
* are affected, so we can just clean up and return. If it does exist,
|
||
* walk its list of predicate locks and move or copy them to the new
|
||
* target.
|
||
*/
|
||
oldtarget = hash_search_with_hash_value(PredicateLockTargetHash,
|
||
&oldtargettag,
|
||
oldtargettaghash,
|
||
HASH_FIND, NULL);
|
||
|
||
if (oldtarget)
|
||
{
|
||
PREDICATELOCKTARGET *newtarget;
|
||
PREDICATELOCK *oldpredlock;
|
||
PREDICATELOCKTAG newpredlocktag;
|
||
|
||
newtarget = hash_search_with_hash_value(PredicateLockTargetHash,
|
||
&newtargettag,
|
||
newtargettaghash,
|
||
HASH_ENTER_NULL, &found);
|
||
|
||
if (!newtarget)
|
||
{
|
||
/* Failed to allocate due to insufficient shmem */
|
||
outOfShmem = true;
|
||
goto exit;
|
||
}
|
||
|
||
/* If we created a new entry, initialize it */
|
||
if (!found)
|
||
{
|
||
SHMQueueInit(&(newtarget->predicateLocks));
|
||
newtarget->priorVersionOfRow = NULL;
|
||
newtarget->nextVersionOfRow = NULL;
|
||
}
|
||
|
||
newpredlocktag.myTarget = newtarget;
|
||
|
||
oldpredlock = (PREDICATELOCK *)
|
||
SHMQueueNext(&(oldtarget->predicateLocks),
|
||
&(oldtarget->predicateLocks),
|
||
offsetof(PREDICATELOCK, targetLink));
|
||
LWLockAcquire(SerializableXactHashLock, LW_EXCLUSIVE);
|
||
while (oldpredlock)
|
||
{
|
||
SHM_QUEUE *predlocktargetlink;
|
||
PREDICATELOCK *nextpredlock;
|
||
PREDICATELOCK *newpredlock;
|
||
|
||
predlocktargetlink = &(oldpredlock->targetLink);
|
||
nextpredlock = (PREDICATELOCK *)
|
||
SHMQueueNext(&(oldtarget->predicateLocks),
|
||
predlocktargetlink,
|
||
offsetof(PREDICATELOCK, targetLink));
|
||
newpredlocktag.myXact = oldpredlock->tag.myXact;
|
||
|
||
if (removeOld)
|
||
{
|
||
SHMQueueDelete(&(oldpredlock->xactLink));
|
||
SHMQueueDelete(&(oldpredlock->targetLink));
|
||
|
||
hash_search_with_hash_value
|
||
(PredicateLockHash,
|
||
&oldpredlock->tag,
|
||
PredicateLockHashCodeFromTargetHashCode(&oldpredlock->tag,
|
||
oldtargettaghash),
|
||
HASH_REMOVE, &found);
|
||
Assert(found);
|
||
}
|
||
|
||
|
||
newpredlock = (PREDICATELOCK *)
|
||
hash_search_with_hash_value
|
||
(PredicateLockHash,
|
||
&newpredlocktag,
|
||
PredicateLockHashCodeFromTargetHashCode(&newpredlocktag,
|
||
newtargettaghash),
|
||
HASH_ENTER_NULL, &found);
|
||
if (!newpredlock)
|
||
{
|
||
/* Out of shared memory. Undo what we've done so far. */
|
||
LWLockRelease(SerializableXactHashLock);
|
||
DeleteLockTarget(newtarget, newtargettaghash);
|
||
outOfShmem = true;
|
||
goto exit;
|
||
}
|
||
if (!found)
|
||
{
|
||
SHMQueueInsertBefore(&(newtarget->predicateLocks),
|
||
&(newpredlock->targetLink));
|
||
SHMQueueInsertBefore(&(newpredlocktag.myXact->predicateLocks),
|
||
&(newpredlock->xactLink));
|
||
newpredlock->commitSeqNo = InvalidSerCommitSeqNo;
|
||
}
|
||
|
||
oldpredlock = nextpredlock;
|
||
}
|
||
LWLockRelease(SerializableXactHashLock);
|
||
|
||
if (removeOld)
|
||
{
|
||
Assert(SHMQueueEmpty(&oldtarget->predicateLocks));
|
||
RemoveTargetIfNoLongerUsed(oldtarget, oldtargettaghash);
|
||
}
|
||
}
|
||
|
||
|
||
exit:
|
||
/* Release partition locks in reverse order of acquisition. */
|
||
if (oldpartitionLock < newpartitionLock)
|
||
{
|
||
LWLockRelease(newpartitionLock);
|
||
LWLockRelease(oldpartitionLock);
|
||
}
|
||
else if (oldpartitionLock > newpartitionLock)
|
||
{
|
||
LWLockRelease(oldpartitionLock);
|
||
LWLockRelease(newpartitionLock);
|
||
}
|
||
else
|
||
LWLockRelease(newpartitionLock);
|
||
|
||
if (removeOld)
|
||
{
|
||
/* We shouldn't run out of memory if we're moving locks */
|
||
Assert(!outOfShmem);
|
||
|
||
/* Put the reserved entry back */
|
||
LWLockAcquire(reservedpartitionLock, LW_EXCLUSIVE);
|
||
hash_search_with_hash_value(PredicateLockTargetHash,
|
||
&ReservedTargetTag,
|
||
reservedtargettaghash,
|
||
HASH_ENTER, &found);
|
||
Assert(!found);
|
||
LWLockRelease(reservedpartitionLock);
|
||
}
|
||
|
||
return !outOfShmem;
|
||
}
|
||
|
||
|
||
/*
|
||
* PredicateLockPageSplit
|
||
*
|
||
* Copies any predicate locks for the old page to the new page.
|
||
* Skip if this is a temporary table or toast table.
|
||
*
|
||
* NOTE: A page split (or overflow) affects all serializable transactions,
|
||
* even if it occurs in the context of another transaction isolation level.
|
||
*
|
||
* NOTE: This currently leaves the local copy of the locks without
|
||
* information on the new lock which is in shared memory. This could cause
|
||
* problems if enough page splits occur on locked pages without the processes
|
||
* which hold the locks getting in and noticing.
|
||
*/
|
||
void
|
||
PredicateLockPageSplit(const Relation relation, const BlockNumber oldblkno,
|
||
const BlockNumber newblkno)
|
||
{
|
||
PREDICATELOCKTARGETTAG oldtargettag;
|
||
PREDICATELOCKTARGETTAG newtargettag;
|
||
bool success;
|
||
|
||
if (SkipSplitTracking(relation))
|
||
return;
|
||
|
||
Assert(oldblkno != newblkno);
|
||
Assert(BlockNumberIsValid(oldblkno));
|
||
Assert(BlockNumberIsValid(newblkno));
|
||
|
||
SET_PREDICATELOCKTARGETTAG_PAGE(oldtargettag,
|
||
relation->rd_node.dbNode,
|
||
relation->rd_id,
|
||
oldblkno);
|
||
SET_PREDICATELOCKTARGETTAG_PAGE(newtargettag,
|
||
relation->rd_node.dbNode,
|
||
relation->rd_id,
|
||
newblkno);
|
||
|
||
LWLockAcquire(SerializablePredicateLockListLock, LW_EXCLUSIVE);
|
||
|
||
/*
|
||
* Try copying the locks over to the new page's tag, creating it if
|
||
* necessary.
|
||
*/
|
||
success = TransferPredicateLocksToNewTarget(oldtargettag,
|
||
newtargettag,
|
||
false);
|
||
|
||
if (!success)
|
||
{
|
||
/*
|
||
* No more predicate lock entries are available. Failure isn't an
|
||
* option here, so promote the page lock to a relation lock.
|
||
*/
|
||
|
||
/* Get the parent relation lock's lock tag */
|
||
success = GetParentPredicateLockTag(&oldtargettag,
|
||
&newtargettag);
|
||
Assert(success);
|
||
|
||
/* Move the locks to the parent. This shouldn't fail. */
|
||
success = TransferPredicateLocksToNewTarget(oldtargettag,
|
||
newtargettag,
|
||
true);
|
||
Assert(success);
|
||
}
|
||
|
||
LWLockRelease(SerializablePredicateLockListLock);
|
||
}
|
||
|
||
/*
|
||
* PredicateLockPageCombine
|
||
*
|
||
* Combines predicate locks for two existing pages.
|
||
* Skip if this is a temporary table or toast table.
|
||
*
|
||
* NOTE: A page combine affects all serializable transactions, even if it
|
||
* occurs in the context of another transaction isolation level.
|
||
*/
|
||
void
|
||
PredicateLockPageCombine(const Relation relation, const BlockNumber oldblkno,
|
||
const BlockNumber newblkno)
|
||
{
|
||
PREDICATELOCKTARGETTAG oldtargettag;
|
||
PREDICATELOCKTARGETTAG newtargettag;
|
||
bool success;
|
||
|
||
|
||
if (SkipSplitTracking(relation))
|
||
return;
|
||
|
||
Assert(oldblkno != newblkno);
|
||
Assert(BlockNumberIsValid(oldblkno));
|
||
Assert(BlockNumberIsValid(newblkno));
|
||
|
||
SET_PREDICATELOCKTARGETTAG_PAGE(oldtargettag,
|
||
relation->rd_node.dbNode,
|
||
relation->rd_id,
|
||
oldblkno);
|
||
SET_PREDICATELOCKTARGETTAG_PAGE(newtargettag,
|
||
relation->rd_node.dbNode,
|
||
relation->rd_id,
|
||
newblkno);
|
||
|
||
LWLockAcquire(SerializablePredicateLockListLock, LW_EXCLUSIVE);
|
||
|
||
/* Move the locks. This shouldn't fail. */
|
||
success = TransferPredicateLocksToNewTarget(oldtargettag,
|
||
newtargettag,
|
||
true);
|
||
Assert(success);
|
||
|
||
LWLockRelease(SerializablePredicateLockListLock);
|
||
}
|
||
|
||
/*
|
||
* Walk the hash table and find the new xmin.
|
||
*/
|
||
static void
|
||
SetNewSxactGlobalXmin(void)
|
||
{
|
||
SERIALIZABLEXACT *sxact;
|
||
|
||
Assert(LWLockHeldByMe(SerializableXactHashLock));
|
||
|
||
PredXact->SxactGlobalXmin = InvalidTransactionId;
|
||
PredXact->SxactGlobalXminCount = 0;
|
||
|
||
for (sxact = FirstPredXact(); sxact != NULL; sxact = NextPredXact(sxact))
|
||
{
|
||
if (!SxactIsRolledBack(sxact)
|
||
&& !SxactIsCommitted(sxact)
|
||
&& sxact != OldCommittedSxact)
|
||
{
|
||
Assert(sxact->xmin != InvalidTransactionId);
|
||
if (!TransactionIdIsValid(PredXact->SxactGlobalXmin)
|
||
|| TransactionIdPrecedes(sxact->xmin,
|
||
PredXact->SxactGlobalXmin))
|
||
{
|
||
PredXact->SxactGlobalXmin = sxact->xmin;
|
||
PredXact->SxactGlobalXminCount = 1;
|
||
}
|
||
else if (TransactionIdEquals(sxact->xmin,
|
||
PredXact->SxactGlobalXmin))
|
||
PredXact->SxactGlobalXminCount++;
|
||
}
|
||
}
|
||
|
||
OldSerXidSetActiveSerXmin(PredXact->SxactGlobalXmin);
|
||
}
|
||
|
||
/*
|
||
* ReleasePredicateLocks
|
||
*
|
||
* Releases predicate locks based on completion of the current transaction,
|
||
* whether committed or rolled back. It can also be called for a read only
|
||
* transaction when it becomes impossible for the transaction to become
|
||
* part of a dangerous structure.
|
||
*
|
||
* We do nothing unless this is a serializable transaction.
|
||
*
|
||
* This method must ensure that shared memory hash tables are cleaned
|
||
* up in some relatively timely fashion.
|
||
*
|
||
* If this transaction is committing and is holding any predicate locks,
|
||
* it must be added to a list of completed serializable transaction still
|
||
* holding locks.
|
||
*/
|
||
void
|
||
ReleasePredicateLocks(const bool isCommit)
|
||
{
|
||
bool needToClear;
|
||
RWConflict conflict,
|
||
nextConflict,
|
||
possibleUnsafeConflict;
|
||
SERIALIZABLEXACT *roXact;
|
||
|
||
/*
|
||
* We can't trust XactReadOnly here, because a transaction which started
|
||
* as READ WRITE can show as READ ONLY later, e.g., within
|
||
* substransactions. We want to flag a transaction as READ ONLY if it
|
||
* commits without writing so that de facto READ ONLY transactions get the
|
||
* benefit of some RO optimizations, so we will use this local variable to
|
||
* get some cleanup logic right which is based on whether the transaction
|
||
* was declared READ ONLY at the top level.
|
||
*/
|
||
bool topLevelIsDeclaredReadOnly;
|
||
|
||
if (MySerializableXact == InvalidSerializableXact)
|
||
{
|
||
Assert(LocalPredicateLockHash == NULL);
|
||
return;
|
||
}
|
||
|
||
Assert(!isCommit || SxactIsPrepared(MySerializableXact));
|
||
Assert(!SxactIsRolledBack(MySerializableXact));
|
||
Assert(!SxactIsCommitted(MySerializableXact));
|
||
|
||
/* may not be serializable during COMMIT/ROLLBACK PREPARED */
|
||
if (MySerializableXact->pid != 0)
|
||
Assert(IsolationIsSerializable());
|
||
|
||
/* We'd better not already be on the cleanup list. */
|
||
Assert(!SxactIsOnFinishedList((SERIALIZABLEXACT *) MySerializableXact));
|
||
|
||
topLevelIsDeclaredReadOnly = SxactIsReadOnly(MySerializableXact);
|
||
|
||
LWLockAcquire(SerializableXactHashLock, LW_EXCLUSIVE);
|
||
|
||
/*
|
||
* We don't hold a lock here, assuming that TransactionId is atomic!
|
||
*
|
||
* If this value is changing, we don't care that much whether we get the
|
||
* old or new value -- it is just used to determine how far
|
||
* GlobalSerizableXmin must advance before this transaction can be cleaned
|
||
* fully cleaned up. The worst that could happen is we wait for ome more
|
||
* transaction to complete before freeing some RAM; correctness of visible
|
||
* behavior is not affected.
|
||
*/
|
||
MySerializableXact->finishedBefore = ShmemVariableCache->nextXid;
|
||
|
||
/*
|
||
* If it's not a commit it's a rollback, and we can clear our locks
|
||
* immediately.
|
||
*/
|
||
if (isCommit)
|
||
{
|
||
MySerializableXact->flags |= SXACT_FLAG_COMMITTED;
|
||
MySerializableXact->commitSeqNo = ++(PredXact->LastSxactCommitSeqNo);
|
||
/* Recognize implicit read-only transaction (commit without write). */
|
||
if (!(MySerializableXact->flags & SXACT_FLAG_DID_WRITE))
|
||
MySerializableXact->flags |= SXACT_FLAG_READ_ONLY;
|
||
}
|
||
else
|
||
{
|
||
MySerializableXact->flags |= SXACT_FLAG_ROLLED_BACK;
|
||
}
|
||
|
||
if (!topLevelIsDeclaredReadOnly)
|
||
{
|
||
Assert(PredXact->WritableSxactCount > 0);
|
||
if (--(PredXact->WritableSxactCount) == 0)
|
||
{
|
||
/*
|
||
* Release predicate locks and rw-conflicts in for all committed
|
||
* transactions. There are no longer any transactions which might
|
||
* conflict with the locks and no chance for new transactions to
|
||
* overlap. Similarly, existing conflicts in can't cause pivots,
|
||
* and any conflicts in which could have completed a dangerous
|
||
* structure would already have caused a rollback, so any
|
||
* remaining ones must be benign.
|
||
*/
|
||
PredXact->CanPartialClearThrough = PredXact->LastSxactCommitSeqNo;
|
||
}
|
||
}
|
||
else
|
||
{
|
||
/*
|
||
* Read-only transactions: clear the list of transactions that might
|
||
* make us unsafe. Note that we use 'inLink' for the iteration as
|
||
* opposed to 'outLink' for the r/w xacts.
|
||
*/
|
||
possibleUnsafeConflict = (RWConflict)
|
||
SHMQueueNext((SHM_QUEUE *) &MySerializableXact->possibleUnsafeConflicts,
|
||
(SHM_QUEUE *) &MySerializableXact->possibleUnsafeConflicts,
|
||
offsetof(RWConflictData, inLink));
|
||
while (possibleUnsafeConflict)
|
||
{
|
||
nextConflict = (RWConflict)
|
||
SHMQueueNext((SHM_QUEUE *) &MySerializableXact->possibleUnsafeConflicts,
|
||
&possibleUnsafeConflict->inLink,
|
||
offsetof(RWConflictData, inLink));
|
||
|
||
Assert(!SxactIsReadOnly(possibleUnsafeConflict->sxactOut));
|
||
Assert(MySerializableXact == possibleUnsafeConflict->sxactIn);
|
||
|
||
ReleaseRWConflict(possibleUnsafeConflict);
|
||
|
||
possibleUnsafeConflict = nextConflict;
|
||
}
|
||
}
|
||
|
||
/* Check for conflict out to old committed transactions. */
|
||
if (isCommit
|
||
&& !SxactIsReadOnly(MySerializableXact)
|
||
&& SxactHasSummaryConflictOut(MySerializableXact))
|
||
{
|
||
MySerializableXact->SeqNo.earliestOutConflictCommit =
|
||
FirstNormalSerCommitSeqNo;
|
||
MySerializableXact->flags |= SXACT_FLAG_CONFLICT_OUT;
|
||
}
|
||
|
||
/*
|
||
* Release all outConflicts to committed transactions. If we're rolling
|
||
* back clear them all. Set SXACT_FLAG_CONFLICT_OUT if any point to
|
||
* previously committed transactions.
|
||
*/
|
||
conflict = (RWConflict)
|
||
SHMQueueNext((SHM_QUEUE *) &MySerializableXact->outConflicts,
|
||
(SHM_QUEUE *) &MySerializableXact->outConflicts,
|
||
offsetof(RWConflictData, outLink));
|
||
while (conflict)
|
||
{
|
||
nextConflict = (RWConflict)
|
||
SHMQueueNext((SHM_QUEUE *) &MySerializableXact->outConflicts,
|
||
&conflict->outLink,
|
||
offsetof(RWConflictData, outLink));
|
||
|
||
if (isCommit
|
||
&& !SxactIsReadOnly(MySerializableXact)
|
||
&& SxactIsCommitted(conflict->sxactIn))
|
||
{
|
||
if ((MySerializableXact->flags & SXACT_FLAG_CONFLICT_OUT) == 0
|
||
|| conflict->sxactIn->commitSeqNo < MySerializableXact->SeqNo.earliestOutConflictCommit)
|
||
MySerializableXact->SeqNo.earliestOutConflictCommit = conflict->sxactIn->commitSeqNo;
|
||
MySerializableXact->flags |= SXACT_FLAG_CONFLICT_OUT;
|
||
}
|
||
|
||
if (!isCommit
|
||
|| SxactIsCommitted(conflict->sxactIn)
|
||
|| (conflict->sxactIn->SeqNo.lastCommitBeforeSnapshot >= PredXact->LastSxactCommitSeqNo))
|
||
ReleaseRWConflict(conflict);
|
||
|
||
conflict = nextConflict;
|
||
}
|
||
|
||
/*
|
||
* Release all inConflicts from committed and read-only transactions. If
|
||
* we're rolling back, clear them all.
|
||
*/
|
||
conflict = (RWConflict)
|
||
SHMQueueNext((SHM_QUEUE *) &MySerializableXact->inConflicts,
|
||
(SHM_QUEUE *) &MySerializableXact->inConflicts,
|
||
offsetof(RWConflictData, inLink));
|
||
while (conflict)
|
||
{
|
||
nextConflict = (RWConflict)
|
||
SHMQueueNext((SHM_QUEUE *) &MySerializableXact->inConflicts,
|
||
&conflict->inLink,
|
||
offsetof(RWConflictData, inLink));
|
||
|
||
if (!isCommit
|
||
|| SxactIsCommitted(conflict->sxactOut)
|
||
|| SxactIsReadOnly(conflict->sxactOut))
|
||
ReleaseRWConflict(conflict);
|
||
|
||
conflict = nextConflict;
|
||
}
|
||
|
||
if (!topLevelIsDeclaredReadOnly)
|
||
{
|
||
/*
|
||
* Remove ourselves from the list of possible conflicts for concurrent
|
||
* READ ONLY transactions, flagging them as unsafe if we have a
|
||
* conflict out. If any are waiting DEFERRABLE transactions, wake them
|
||
* up if they are known safe or known unsafe.
|
||
*/
|
||
possibleUnsafeConflict = (RWConflict)
|
||
SHMQueueNext((SHM_QUEUE *) &MySerializableXact->possibleUnsafeConflicts,
|
||
(SHM_QUEUE *) &MySerializableXact->possibleUnsafeConflicts,
|
||
offsetof(RWConflictData, outLink));
|
||
while (possibleUnsafeConflict)
|
||
{
|
||
nextConflict = (RWConflict)
|
||
SHMQueueNext((SHM_QUEUE *) &MySerializableXact->possibleUnsafeConflicts,
|
||
&possibleUnsafeConflict->outLink,
|
||
offsetof(RWConflictData, outLink));
|
||
|
||
roXact = possibleUnsafeConflict->sxactIn;
|
||
Assert(MySerializableXact == possibleUnsafeConflict->sxactOut);
|
||
Assert(SxactIsReadOnly(roXact));
|
||
|
||
/* Mark conflicted if necessary. */
|
||
if (isCommit
|
||
&& (MySerializableXact->flags & SXACT_FLAG_DID_WRITE)
|
||
&& SxactHasConflictOut(MySerializableXact)
|
||
&& (MySerializableXact->SeqNo.earliestOutConflictCommit
|
||
<= roXact->SeqNo.lastCommitBeforeSnapshot))
|
||
{
|
||
/*
|
||
* This releases possibleUnsafeConflict (as well as all other
|
||
* possible conflicts for roXact)
|
||
*/
|
||
FlagSxactUnsafe(roXact);
|
||
}
|
||
else
|
||
{
|
||
ReleaseRWConflict(possibleUnsafeConflict);
|
||
|
||
/*
|
||
* If we were the last possible conflict, flag it safe. The
|
||
* transaction can now safely release its predicate locks (but
|
||
* that transaction's backend has to do that itself).
|
||
*/
|
||
if (SHMQueueEmpty(&roXact->possibleUnsafeConflicts))
|
||
roXact->flags |= SXACT_FLAG_RO_SAFE;
|
||
}
|
||
|
||
/*
|
||
* Wake up the process for a waiting DEFERRABLE transaction if we
|
||
* now know it's either safe or conflicted.
|
||
*/
|
||
if (SxactIsDeferrableWaiting(roXact) &&
|
||
(SxactIsROUnsafe(roXact) || SxactIsROSafe(roXact)))
|
||
ProcSendSignal(roXact->pid);
|
||
|
||
possibleUnsafeConflict = nextConflict;
|
||
}
|
||
}
|
||
|
||
/*
|
||
* Check whether it's time to clean up old transactions. This can only be
|
||
* done when the last serializable transaction with the oldest xmin among
|
||
* serializable transactions completes. We then find the "new oldest"
|
||
* xmin and purge any transactions which finished before this transaction
|
||
* was launched.
|
||
*/
|
||
needToClear = false;
|
||
if (TransactionIdEquals(MySerializableXact->xmin, PredXact->SxactGlobalXmin))
|
||
{
|
||
Assert(PredXact->SxactGlobalXminCount > 0);
|
||
if (--(PredXact->SxactGlobalXminCount) == 0)
|
||
{
|
||
SetNewSxactGlobalXmin();
|
||
needToClear = true;
|
||
}
|
||
}
|
||
|
||
LWLockRelease(SerializableXactHashLock);
|
||
|
||
LWLockAcquire(SerializableFinishedListLock, LW_EXCLUSIVE);
|
||
|
||
/* Add this to the list of transactions to check for later cleanup. */
|
||
if (isCommit)
|
||
SHMQueueInsertBefore(FinishedSerializableTransactions,
|
||
(SHM_QUEUE *) &(MySerializableXact->finishedLink));
|
||
|
||
if (!isCommit)
|
||
ReleaseOneSerializableXact((SERIALIZABLEXACT *) MySerializableXact,
|
||
false, false);
|
||
|
||
LWLockRelease(SerializableFinishedListLock);
|
||
|
||
if (needToClear)
|
||
ClearOldPredicateLocks();
|
||
|
||
MySerializableXact = InvalidSerializableXact;
|
||
|
||
/* Delete per-transaction lock table */
|
||
if (LocalPredicateLockHash != NULL)
|
||
{
|
||
hash_destroy(LocalPredicateLockHash);
|
||
LocalPredicateLockHash = NULL;
|
||
}
|
||
}
|
||
|
||
/*
|
||
* ReleasePredicateLocksIfROSafe
|
||
* Check if the current transaction is read only and operating on
|
||
* a safe snapshot. If so, release predicate locks and return
|
||
* true.
|
||
*
|
||
* A transaction is flagged as RO_SAFE if all concurrent R/W
|
||
* transactions commit without having conflicts out to an earlier
|
||
* snapshot, thus ensuring that no conflicts are possible for this
|
||
* transaction. Thus, we call this function as part of the
|
||
* SkipSerialization check on all public interface methods.
|
||
*/
|
||
static bool
|
||
ReleasePredicateLocksIfROSafe(void)
|
||
{
|
||
if (SxactIsROSafe(MySerializableXact))
|
||
{
|
||
ReleasePredicateLocks(false);
|
||
return true;
|
||
}
|
||
else
|
||
return false;
|
||
}
|
||
|
||
/*
|
||
* Clear old predicate locks.
|
||
*/
|
||
static void
|
||
ClearOldPredicateLocks(void)
|
||
{
|
||
SERIALIZABLEXACT *finishedSxact;
|
||
PREDICATELOCK *predlock;
|
||
int i;
|
||
HASH_SEQ_STATUS seqstat;
|
||
PREDICATELOCKTARGET *locktarget;
|
||
|
||
LWLockAcquire(SerializableFinishedListLock, LW_EXCLUSIVE);
|
||
finishedSxact = (SERIALIZABLEXACT *)
|
||
SHMQueueNext(FinishedSerializableTransactions,
|
||
FinishedSerializableTransactions,
|
||
offsetof(SERIALIZABLEXACT, finishedLink));
|
||
LWLockAcquire(SerializableXactHashLock, LW_SHARED);
|
||
while (finishedSxact)
|
||
{
|
||
SERIALIZABLEXACT *nextSxact;
|
||
|
||
nextSxact = (SERIALIZABLEXACT *)
|
||
SHMQueueNext(FinishedSerializableTransactions,
|
||
&(finishedSxact->finishedLink),
|
||
offsetof(SERIALIZABLEXACT, finishedLink));
|
||
if (!TransactionIdIsValid(PredXact->SxactGlobalXmin)
|
||
|| TransactionIdPrecedesOrEquals(finishedSxact->finishedBefore,
|
||
PredXact->SxactGlobalXmin))
|
||
{
|
||
LWLockRelease(SerializableXactHashLock);
|
||
SHMQueueDelete(&(finishedSxact->finishedLink));
|
||
ReleaseOneSerializableXact(finishedSxact, false, false);
|
||
LWLockAcquire(SerializableXactHashLock, LW_SHARED);
|
||
}
|
||
else if (finishedSxact->commitSeqNo > PredXact->HavePartialClearedThrough
|
||
&& finishedSxact->commitSeqNo <= PredXact->CanPartialClearThrough)
|
||
{
|
||
LWLockRelease(SerializableXactHashLock);
|
||
ReleaseOneSerializableXact(finishedSxact,
|
||
!SxactIsReadOnly(finishedSxact),
|
||
false);
|
||
PredXact->HavePartialClearedThrough = finishedSxact->commitSeqNo;
|
||
LWLockAcquire(SerializableXactHashLock, LW_SHARED);
|
||
}
|
||
else
|
||
break;
|
||
finishedSxact = nextSxact;
|
||
}
|
||
LWLockRelease(SerializableXactHashLock);
|
||
|
||
/*
|
||
* Loop through predicate locks on dummy transaction for summarized data.
|
||
*/
|
||
predlock = (PREDICATELOCK *)
|
||
SHMQueueNext(&OldCommittedSxact->predicateLocks,
|
||
&OldCommittedSxact->predicateLocks,
|
||
offsetof(PREDICATELOCK, xactLink));
|
||
LWLockAcquire(SerializablePredicateLockListLock, LW_SHARED);
|
||
while (predlock)
|
||
{
|
||
PREDICATELOCK *nextpredlock;
|
||
bool canDoPartialCleanup;
|
||
|
||
nextpredlock = (PREDICATELOCK *)
|
||
SHMQueueNext(&OldCommittedSxact->predicateLocks,
|
||
&predlock->xactLink,
|
||
offsetof(PREDICATELOCK, xactLink));
|
||
|
||
LWLockAcquire(SerializableXactHashLock, LW_SHARED);
|
||
canDoPartialCleanup = (predlock->commitSeqNo <= PredXact->CanPartialClearThrough);
|
||
LWLockRelease(SerializableXactHashLock);
|
||
|
||
if (canDoPartialCleanup)
|
||
{
|
||
PREDICATELOCKTAG tag;
|
||
SHM_QUEUE *targetLink;
|
||
PREDICATELOCKTARGET *target;
|
||
PREDICATELOCKTARGETTAG targettag;
|
||
uint32 targettaghash;
|
||
LWLockId partitionLock;
|
||
|
||
tag = predlock->tag;
|
||
targetLink = &(predlock->targetLink);
|
||
target = tag.myTarget;
|
||
targettag = target->tag;
|
||
targettaghash = PredicateLockTargetTagHashCode(&targettag);
|
||
partitionLock = PredicateLockHashPartitionLock(targettaghash);
|
||
|
||
LWLockAcquire(partitionLock, LW_EXCLUSIVE);
|
||
|
||
SHMQueueDelete(targetLink);
|
||
SHMQueueDelete(&(predlock->xactLink));
|
||
|
||
hash_search_with_hash_value(PredicateLockHash, &tag,
|
||
PredicateLockHashCodeFromTargetHashCode(&tag,
|
||
targettaghash),
|
||
HASH_REMOVE, NULL);
|
||
RemoveTargetIfNoLongerUsed(target, targettaghash);
|
||
|
||
LWLockRelease(partitionLock);
|
||
}
|
||
|
||
predlock = nextpredlock;
|
||
}
|
||
|
||
LWLockRelease(SerializablePredicateLockListLock);
|
||
LWLockRelease(SerializableFinishedListLock);
|
||
|
||
if (!PredXact->NeedTargetLinkCleanup)
|
||
return;
|
||
|
||
/*
|
||
* Clean up any targets which were disconnected from a prior version with
|
||
* no predicate locks attached.
|
||
*/
|
||
for (i = 0; i < NUM_PREDICATELOCK_PARTITIONS; i++)
|
||
LWLockAcquire(FirstPredicateLockMgrLock + i, LW_EXCLUSIVE);
|
||
LWLockAcquire(PredicateLockNextRowLinkLock, LW_SHARED);
|
||
|
||
hash_seq_init(&seqstat, PredicateLockTargetHash);
|
||
while ((locktarget = (PREDICATELOCKTARGET *) hash_seq_search(&seqstat)))
|
||
{
|
||
if (SHMQueueEmpty(&locktarget->predicateLocks)
|
||
&& locktarget->priorVersionOfRow == NULL
|
||
&& locktarget->nextVersionOfRow == NULL)
|
||
{
|
||
hash_search(PredicateLockTargetHash, &locktarget->tag,
|
||
HASH_REMOVE, NULL);
|
||
}
|
||
}
|
||
|
||
PredXact->NeedTargetLinkCleanup = false;
|
||
|
||
LWLockRelease(PredicateLockNextRowLinkLock);
|
||
for (i = NUM_PREDICATELOCK_PARTITIONS - 1; i >= 0; i--)
|
||
LWLockRelease(FirstPredicateLockMgrLock + i);
|
||
}
|
||
|
||
/*
|
||
* This is the normal way to delete anything from any of the predicate
|
||
* locking hash tables. Given a transaction which we know can be deleted:
|
||
* delete all predicate locks held by that transaction and any predicate
|
||
* lock targets which are now unreferenced by a lock; delete all conflicts
|
||
* for the transaction; delete all xid values for the transaction; then
|
||
* delete the transaction.
|
||
*
|
||
* When the partial flag is set, we can release all predicate locks and
|
||
* out-conflict information -- we've established that there are no longer
|
||
* any overlapping read write transactions for which this transaction could
|
||
* matter.
|
||
*
|
||
* When the summarize flag is set, we've run short of room for sxact data
|
||
* and must summarize to the SLRU. Predicate locks are transferred to a
|
||
* dummy "old" transaction, with duplicate locks on a single target
|
||
* collapsing to a single lock with the "latest" commitSeqNo from among
|
||
* the conflicting locks..
|
||
*/
|
||
static void
|
||
ReleaseOneSerializableXact(SERIALIZABLEXACT *sxact, bool partial,
|
||
bool summarize)
|
||
{
|
||
PREDICATELOCK *predlock;
|
||
SERIALIZABLEXIDTAG sxidtag;
|
||
RWConflict conflict,
|
||
nextConflict;
|
||
|
||
Assert(sxact != NULL);
|
||
Assert(SxactIsRolledBack(sxact) || SxactIsCommitted(sxact));
|
||
Assert(LWLockHeldByMe(SerializableFinishedListLock));
|
||
|
||
LWLockAcquire(SerializablePredicateLockListLock, LW_SHARED);
|
||
predlock = (PREDICATELOCK *)
|
||
SHMQueueNext(&(sxact->predicateLocks),
|
||
&(sxact->predicateLocks),
|
||
offsetof(PREDICATELOCK, xactLink));
|
||
while (predlock)
|
||
{
|
||
PREDICATELOCK *nextpredlock;
|
||
PREDICATELOCKTAG tag;
|
||
SHM_QUEUE *targetLink;
|
||
PREDICATELOCKTARGET *target;
|
||
PREDICATELOCKTARGETTAG targettag;
|
||
uint32 targettaghash;
|
||
LWLockId partitionLock;
|
||
|
||
nextpredlock = (PREDICATELOCK *)
|
||
SHMQueueNext(&(sxact->predicateLocks),
|
||
&(predlock->xactLink),
|
||
offsetof(PREDICATELOCK, xactLink));
|
||
|
||
tag = predlock->tag;
|
||
targetLink = &(predlock->targetLink);
|
||
target = tag.myTarget;
|
||
targettag = target->tag;
|
||
targettaghash = PredicateLockTargetTagHashCode(&targettag);
|
||
partitionLock = PredicateLockHashPartitionLock(targettaghash);
|
||
|
||
LWLockAcquire(partitionLock, LW_EXCLUSIVE);
|
||
|
||
SHMQueueDelete(targetLink);
|
||
|
||
hash_search_with_hash_value(PredicateLockHash, &tag,
|
||
PredicateLockHashCodeFromTargetHashCode(&tag,
|
||
targettaghash),
|
||
HASH_REMOVE, NULL);
|
||
if (summarize)
|
||
{
|
||
bool found;
|
||
|
||
/* Fold into dummy transaction list. */
|
||
tag.myXact = OldCommittedSxact;
|
||
predlock = hash_search_with_hash_value(PredicateLockHash, &tag,
|
||
PredicateLockHashCodeFromTargetHashCode(&tag,
|
||
targettaghash),
|
||
HASH_ENTER, &found);
|
||
if (!predlock)
|
||
ereport(ERROR,
|
||
(errcode(ERRCODE_OUT_OF_MEMORY),
|
||
errmsg("out of shared memory"),
|
||
errhint("You might need to increase max_pred_locks_per_transaction.")));
|
||
if (found)
|
||
{
|
||
if (predlock->commitSeqNo < sxact->commitSeqNo)
|
||
predlock->commitSeqNo = sxact->commitSeqNo;
|
||
}
|
||
else
|
||
{
|
||
SHMQueueInsertBefore(&(target->predicateLocks),
|
||
&(predlock->targetLink));
|
||
SHMQueueInsertBefore(&(OldCommittedSxact->predicateLocks),
|
||
&(predlock->xactLink));
|
||
predlock->commitSeqNo = sxact->commitSeqNo;
|
||
}
|
||
}
|
||
else
|
||
RemoveTargetIfNoLongerUsed(target, targettaghash);
|
||
|
||
LWLockRelease(partitionLock);
|
||
|
||
predlock = nextpredlock;
|
||
}
|
||
|
||
/*
|
||
* Rather than retail removal, just re-init the head after we've run
|
||
* through the list.
|
||
*/
|
||
SHMQueueInit(&sxact->predicateLocks);
|
||
|
||
LWLockRelease(SerializablePredicateLockListLock);
|
||
|
||
sxidtag.xid = sxact->topXid;
|
||
LWLockAcquire(SerializableXactHashLock, LW_EXCLUSIVE);
|
||
|
||
if (!partial)
|
||
{
|
||
/* Release all outConflicts. */
|
||
conflict = (RWConflict)
|
||
SHMQueueNext(&sxact->outConflicts,
|
||
&sxact->outConflicts,
|
||
offsetof(RWConflictData, outLink));
|
||
while (conflict)
|
||
{
|
||
nextConflict = (RWConflict)
|
||
SHMQueueNext(&sxact->outConflicts,
|
||
&conflict->outLink,
|
||
offsetof(RWConflictData, outLink));
|
||
if (summarize)
|
||
conflict->sxactIn->flags |= SXACT_FLAG_SUMMARY_CONFLICT_IN;
|
||
ReleaseRWConflict(conflict);
|
||
conflict = nextConflict;
|
||
}
|
||
}
|
||
|
||
/* Release all inConflicts. */
|
||
conflict = (RWConflict)
|
||
SHMQueueNext(&sxact->inConflicts,
|
||
&sxact->inConflicts,
|
||
offsetof(RWConflictData, inLink));
|
||
while (conflict)
|
||
{
|
||
nextConflict = (RWConflict)
|
||
SHMQueueNext(&sxact->inConflicts,
|
||
&conflict->inLink,
|
||
offsetof(RWConflictData, inLink));
|
||
if (summarize)
|
||
conflict->sxactOut->flags |= SXACT_FLAG_SUMMARY_CONFLICT_OUT;
|
||
ReleaseRWConflict(conflict);
|
||
conflict = nextConflict;
|
||
}
|
||
|
||
if (!partial)
|
||
{
|
||
/* Get rid of the xid and the record of the transaction itself. */
|
||
if (sxidtag.xid != InvalidTransactionId)
|
||
hash_search(SerializableXidHash, &sxidtag, HASH_REMOVE, NULL);
|
||
ReleasePredXact(sxact);
|
||
}
|
||
|
||
LWLockRelease(SerializableXactHashLock);
|
||
}
|
||
|
||
/*
|
||
* Tests whether the given top level transaction is concurrent with
|
||
* (overlaps) our current transaction.
|
||
*
|
||
* We need to identify the top level transaction for SSI, anyway, so pass
|
||
* that to this function to save the overhead of checking the snapshot's
|
||
* subxip array.
|
||
*/
|
||
static bool
|
||
XidIsConcurrent(TransactionId xid)
|
||
{
|
||
Snapshot snap;
|
||
uint32 i;
|
||
|
||
Assert(TransactionIdIsValid(xid));
|
||
Assert(!TransactionIdEquals(xid, GetTopTransactionIdIfAny()));
|
||
|
||
snap = GetTransactionSnapshot();
|
||
|
||
if (TransactionIdPrecedes(xid, snap->xmin))
|
||
return false;
|
||
|
||
if (TransactionIdFollowsOrEquals(xid, snap->xmax))
|
||
return true;
|
||
|
||
for (i = 0; i < snap->xcnt; i++)
|
||
{
|
||
if (xid == snap->xip[i])
|
||
return true;
|
||
}
|
||
|
||
return false;
|
||
}
|
||
|
||
/*
|
||
* CheckForSerializableConflictOut
|
||
* We are reading a tuple which has been modified. If it is visible to
|
||
* us but has been deleted, that indicates a rw-conflict out. If it's
|
||
* not visible and was created by a concurrent (overlapping)
|
||
* serializable transaction, that is also a rw-conflict out,
|
||
*
|
||
* We will determine the top level xid of the writing transaction with which
|
||
* we may be in conflict, and check for overlap with our own transaction.
|
||
* If the transactions overlap (i.e., they cannot see each other's writes),
|
||
* then we have a conflict out.
|
||
*
|
||
* This function should be called just about anywhere in heapam.c that a
|
||
* tuple has been read. There is currently no known reason to call this
|
||
* function from an index AM.
|
||
*/
|
||
void
|
||
CheckForSerializableConflictOut(const bool visible, const Relation relation,
|
||
const HeapTuple tuple, const Buffer buffer)
|
||
{
|
||
TransactionId xid;
|
||
SERIALIZABLEXIDTAG sxidtag;
|
||
SERIALIZABLEXID *sxid;
|
||
SERIALIZABLEXACT *sxact;
|
||
HTSV_Result htsvResult;
|
||
|
||
if (SkipSerialization(relation))
|
||
return;
|
||
|
||
if (SxactIsMarkedForDeath(MySerializableXact))
|
||
{
|
||
ereport(ERROR,
|
||
(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
|
||
errmsg("could not serialize access due to read/write dependencies among transactions"),
|
||
errdetail("Cancelled on identification as a pivot, during conflict out checking."),
|
||
errhint("The transaction might succeed if retried.")));
|
||
}
|
||
|
||
/*
|
||
* Check to see whether the tuple has been written to by a concurrent
|
||
* transaction, either to create it not visible to us, or to delete it
|
||
* while it is visible to us. The "visible" bool indicates whether the
|
||
* tuple is visible to us, while HeapTupleSatisfiesVacuum checks what else
|
||
* is going on with it.
|
||
*/
|
||
htsvResult = HeapTupleSatisfiesVacuum(tuple->t_data, TransactionXmin, buffer);
|
||
switch (htsvResult)
|
||
{
|
||
case HEAPTUPLE_LIVE:
|
||
if (visible)
|
||
return;
|
||
xid = HeapTupleHeaderGetXmin(tuple->t_data);
|
||
break;
|
||
case HEAPTUPLE_RECENTLY_DEAD:
|
||
if (!visible)
|
||
return;
|
||
xid = HeapTupleHeaderGetXmax(tuple->t_data);
|
||
break;
|
||
case HEAPTUPLE_DELETE_IN_PROGRESS:
|
||
xid = HeapTupleHeaderGetXmax(tuple->t_data);
|
||
break;
|
||
case HEAPTUPLE_INSERT_IN_PROGRESS:
|
||
xid = HeapTupleHeaderGetXmin(tuple->t_data);
|
||
break;
|
||
case HEAPTUPLE_DEAD:
|
||
return;
|
||
default:
|
||
|
||
/*
|
||
* The only way to get to this default clause is if a new value is
|
||
* added to the enum type without adding it to this switch
|
||
* statement. That's a bug, so elog.
|
||
*/
|
||
elog(ERROR, "unrecognized return value from HeapTupleSatisfiesVacuum: %u", htsvResult);
|
||
|
||
/*
|
||
* In spite of having all enum values covered and calling elog on
|
||
* this default, some compilers think this is a code path which
|
||
* allows xid to be used below without initialization. Silence
|
||
* that warning.
|
||
*/
|
||
xid = InvalidTransactionId;
|
||
}
|
||
Assert(TransactionIdIsValid(xid));
|
||
Assert(TransactionIdFollowsOrEquals(xid, TransactionXmin));
|
||
|
||
/*
|
||
* Find top level xid. Bail out if xid is too early to be a conflict, or
|
||
* if it's our own xid.
|
||
*/
|
||
if (TransactionIdEquals(xid, GetTopTransactionIdIfAny()))
|
||
return;
|
||
xid = SubTransGetTopmostTransaction(xid);
|
||
if (TransactionIdPrecedes(xid, TransactionXmin))
|
||
return;
|
||
if (TransactionIdEquals(xid, GetTopTransactionIdIfAny()))
|
||
return;
|
||
|
||
/*
|
||
* Find sxact or summarized info for the top level xid.
|
||
*/
|
||
sxidtag.xid = xid;
|
||
LWLockAcquire(SerializableXactHashLock, LW_EXCLUSIVE);
|
||
sxid = (SERIALIZABLEXID *)
|
||
hash_search(SerializableXidHash, &sxidtag, HASH_FIND, NULL);
|
||
if (!sxid)
|
||
{
|
||
/*
|
||
* Transaction not found in "normal" SSI structures. Check whether it
|
||
* got pushed out to SLRU storage for "old committed" transactions.
|
||
*/
|
||
SerCommitSeqNo conflictCommitSeqNo;
|
||
|
||
conflictCommitSeqNo = OldSerXidGetMinConflictCommitSeqNo(xid);
|
||
if (conflictCommitSeqNo != 0)
|
||
{
|
||
if (conflictCommitSeqNo != InvalidSerCommitSeqNo
|
||
&& (!SxactIsReadOnly(MySerializableXact)
|
||
|| conflictCommitSeqNo
|
||
<= MySerializableXact->SeqNo.lastCommitBeforeSnapshot))
|
||
ereport(ERROR,
|
||
(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
|
||
errmsg("could not serialize access due to read/write dependencies among transactions"),
|
||
errdetail("Cancelled on conflict out to old pivot %u.", xid),
|
||
errhint("The transaction might succeed if retried.")));
|
||
|
||
if (SxactHasSummaryConflictIn(MySerializableXact)
|
||
|| !SHMQueueEmpty((SHM_QUEUE *) &MySerializableXact->inConflicts))
|
||
ereport(ERROR,
|
||
(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
|
||
errmsg("could not serialize access due to read/write dependencies among transactions"),
|
||
errdetail("Cancelled on identification as a pivot, with conflict out to old committed transaction %u.", xid),
|
||
errhint("The transaction might succeed if retried.")));
|
||
|
||
MySerializableXact->flags |= SXACT_FLAG_SUMMARY_CONFLICT_OUT;
|
||
}
|
||
|
||
/* It's not serializable or otherwise not important. */
|
||
LWLockRelease(SerializableXactHashLock);
|
||
return;
|
||
}
|
||
sxact = sxid->myXact;
|
||
Assert(TransactionIdEquals(sxact->topXid, xid));
|
||
if (sxact == MySerializableXact
|
||
|| SxactIsRolledBack(sxact)
|
||
|| SxactIsMarkedForDeath(sxact))
|
||
{
|
||
/* We can't conflict with our own transaction or one rolled back. */
|
||
LWLockRelease(SerializableXactHashLock);
|
||
return;
|
||
}
|
||
|
||
/*
|
||
* We have a conflict out to a transaction which has a conflict out to a
|
||
* summarized transaction. That summarized transaction must have
|
||
* committed first, and we can't tell when it committed in relation to our
|
||
* snapshot acquisition, so something needs to be cancelled.
|
||
*/
|
||
if (SxactHasSummaryConflictOut(sxact))
|
||
{
|
||
if (!SxactIsPrepared(sxact))
|
||
{
|
||
sxact->flags |= SXACT_FLAG_MARKED_FOR_DEATH;
|
||
LWLockRelease(SerializableXactHashLock);
|
||
return;
|
||
}
|
||
else
|
||
{
|
||
LWLockRelease(SerializableXactHashLock);
|
||
ereport(ERROR,
|
||
(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
|
||
errmsg("could not serialize access due to read/write dependencies among transactions"),
|
||
errdetail("Cancelled on conflict out to old pivot."),
|
||
errhint("The transaction might succeed if retried.")));
|
||
}
|
||
}
|
||
|
||
/*
|
||
* If this is a read-only transaction and the writing transaction has
|
||
* committed, and it doesn't have a rw-conflict to a transaction which
|
||
* committed before it, no conflict.
|
||
*/
|
||
if (SxactIsReadOnly(MySerializableXact)
|
||
&& SxactIsCommitted(sxact)
|
||
&& !SxactHasSummaryConflictOut(sxact)
|
||
&& (!SxactHasConflictOut(sxact)
|
||
|| MySerializableXact->SeqNo.lastCommitBeforeSnapshot < sxact->SeqNo.earliestOutConflictCommit))
|
||
{
|
||
/* Read-only transaction will appear to run first. No conflict. */
|
||
LWLockRelease(SerializableXactHashLock);
|
||
return;
|
||
}
|
||
|
||
if (!XidIsConcurrent(xid))
|
||
{
|
||
/* This write was already in our snapshot; no conflict. */
|
||
LWLockRelease(SerializableXactHashLock);
|
||
return;
|
||
}
|
||
|
||
if (RWConflictExists((SERIALIZABLEXACT *) MySerializableXact, sxact))
|
||
{
|
||
/* We don't want duplicate conflict records in the list. */
|
||
LWLockRelease(SerializableXactHashLock);
|
||
return;
|
||
}
|
||
|
||
/*
|
||
* Flag the conflict. But first, if this conflict creates a dangerous
|
||
* structure, ereport an error.
|
||
*/
|
||
FlagRWConflict((SERIALIZABLEXACT *) MySerializableXact, sxact);
|
||
LWLockRelease(SerializableXactHashLock);
|
||
}
|
||
|
||
/*
|
||
* Check a particular target for rw-dependency conflict in. This will
|
||
* also check prior versions of a tuple, if any.
|
||
*/
|
||
static void
|
||
CheckTargetForConflictsIn(PREDICATELOCKTARGETTAG *targettag)
|
||
{
|
||
PREDICATELOCKTARGETTAG nexttargettag = { 0 };
|
||
PREDICATELOCKTARGETTAG thistargettag;
|
||
|
||
for (;;)
|
||
{
|
||
if (!CheckSingleTargetForConflictsIn(targettag, &nexttargettag))
|
||
break;
|
||
thistargettag = nexttargettag;
|
||
targettag = &thistargettag;
|
||
}
|
||
}
|
||
|
||
/*
|
||
* Check a particular target for rw-dependency conflict in. If the tuple
|
||
* has prior versions, returns true and *nexttargettag is set to the tag
|
||
* of the prior tuple version.
|
||
*/
|
||
static bool
|
||
CheckSingleTargetForConflictsIn(PREDICATELOCKTARGETTAG *targettag,
|
||
PREDICATELOCKTARGETTAG *nexttargettag)
|
||
{
|
||
uint32 targettaghash;
|
||
LWLockId partitionLock;
|
||
PREDICATELOCKTARGET *target;
|
||
PREDICATELOCK *predlock;
|
||
bool hasnexttarget = false;
|
||
|
||
Assert(MySerializableXact != InvalidSerializableXact);
|
||
|
||
/*
|
||
* The same hash and LW lock apply to the lock target and the lock itself.
|
||
*/
|
||
targettaghash = PredicateLockTargetTagHashCode(targettag);
|
||
partitionLock = PredicateLockHashPartitionLock(targettaghash);
|
||
LWLockAcquire(partitionLock, LW_SHARED);
|
||
LWLockAcquire(PredicateLockNextRowLinkLock, LW_SHARED);
|
||
target = (PREDICATELOCKTARGET *)
|
||
hash_search_with_hash_value(PredicateLockTargetHash,
|
||
targettag, targettaghash,
|
||
HASH_FIND, NULL);
|
||
if (!target)
|
||
{
|
||
/* Nothing has this target locked; we're done here. */
|
||
LWLockRelease(PredicateLockNextRowLinkLock);
|
||
LWLockRelease(partitionLock);
|
||
return false;
|
||
}
|
||
|
||
/*
|
||
* If the target is linked to a prior version of the row, save the tag so
|
||
* that it can be used for iterative calls to this function.
|
||
*/
|
||
if (target->priorVersionOfRow != NULL)
|
||
{
|
||
*nexttargettag = target->priorVersionOfRow->tag;
|
||
hasnexttarget = true;
|
||
}
|
||
LWLockRelease(PredicateLockNextRowLinkLock);
|
||
|
||
/*
|
||
* Each lock for an overlapping transaction represents a conflict: a
|
||
* rw-dependency in to this transaction.
|
||
*/
|
||
predlock = (PREDICATELOCK *)
|
||
SHMQueueNext(&(target->predicateLocks),
|
||
&(target->predicateLocks),
|
||
offsetof(PREDICATELOCK, targetLink));
|
||
LWLockAcquire(SerializableXactHashLock, LW_SHARED);
|
||
while (predlock)
|
||
{
|
||
SHM_QUEUE *predlocktargetlink;
|
||
PREDICATELOCK *nextpredlock;
|
||
SERIALIZABLEXACT *sxact;
|
||
|
||
predlocktargetlink = &(predlock->targetLink);
|
||
nextpredlock = (PREDICATELOCK *)
|
||
SHMQueueNext(&(target->predicateLocks),
|
||
predlocktargetlink,
|
||
offsetof(PREDICATELOCK, targetLink));
|
||
|
||
sxact = predlock->tag.myXact;
|
||
if (sxact == MySerializableXact)
|
||
{
|
||
/*
|
||
* If we're getting a write lock on the tuple, we don't need a
|
||
* predicate (SIREAD) lock. At this point our transaction already
|
||
* has an ExclusiveRowLock on the relation, so we are OK to drop
|
||
* the predicate lock on the tuple, if found, without fearing that
|
||
* another write against the tuple will occur before the MVCC
|
||
* information makes it to the buffer.
|
||
*/
|
||
if (GET_PREDICATELOCKTARGETTAG_OFFSET(*targettag))
|
||
{
|
||
uint32 predlockhashcode;
|
||
PREDICATELOCKTARGET *rmtarget = NULL;
|
||
PREDICATELOCK *rmpredlock;
|
||
LOCALPREDICATELOCK *locallock,
|
||
*rmlocallock;
|
||
|
||
/*
|
||
* This is a tuple on which we have a tuple predicate lock. We
|
||
* only have shared LW locks now; release those, and get
|
||
* exclusive locks only while we modify things.
|
||
*/
|
||
LWLockRelease(SerializableXactHashLock);
|
||
LWLockRelease(partitionLock);
|
||
LWLockAcquire(SerializablePredicateLockListLock, LW_SHARED);
|
||
LWLockAcquire(partitionLock, LW_EXCLUSIVE);
|
||
LWLockAcquire(SerializableXactHashLock, LW_EXCLUSIVE);
|
||
|
||
/*
|
||
* Remove the predicate lock from shared memory, if it wasn't
|
||
* removed while the locks were released. One way that could
|
||
* happen is from autovacuum cleaning up an index.
|
||
*/
|
||
predlockhashcode = PredicateLockHashCodeFromTargetHashCode
|
||
(&(predlock->tag), targettaghash);
|
||
rmpredlock = (PREDICATELOCK *)
|
||
hash_search_with_hash_value(PredicateLockHash,
|
||
&(predlock->tag),
|
||
predlockhashcode,
|
||
HASH_FIND, NULL);
|
||
if (rmpredlock)
|
||
{
|
||
Assert(rmpredlock == predlock);
|
||
|
||
SHMQueueDelete(predlocktargetlink);
|
||
SHMQueueDelete(&(predlock->xactLink));
|
||
|
||
rmpredlock = (PREDICATELOCK *)
|
||
hash_search_with_hash_value(PredicateLockHash,
|
||
&(predlock->tag),
|
||
predlockhashcode,
|
||
HASH_REMOVE, NULL);
|
||
Assert(rmpredlock == predlock);
|
||
|
||
RemoveTargetIfNoLongerUsed(target, targettaghash);
|
||
|
||
LWLockRelease(SerializableXactHashLock);
|
||
LWLockRelease(partitionLock);
|
||
LWLockRelease(SerializablePredicateLockListLock);
|
||
|
||
locallock = (LOCALPREDICATELOCK *)
|
||
hash_search_with_hash_value(LocalPredicateLockHash,
|
||
targettag, targettaghash,
|
||
HASH_FIND, NULL);
|
||
Assert(locallock != NULL);
|
||
Assert(locallock->held);
|
||
locallock->held = false;
|
||
|
||
if (locallock->childLocks == 0)
|
||
{
|
||
rmlocallock = (LOCALPREDICATELOCK *)
|
||
hash_search_with_hash_value(LocalPredicateLockHash,
|
||
targettag, targettaghash,
|
||
HASH_REMOVE, NULL);
|
||
Assert(rmlocallock == locallock);
|
||
}
|
||
|
||
DecrementParentLocks(targettag);
|
||
|
||
/*
|
||
* If we've cleaned up the last of the predicate locks for
|
||
* the target, bail out before re-acquiring the locks.
|
||
*/
|
||
if (rmtarget)
|
||
return hasnexttarget;
|
||
|
||
/*
|
||
* The list has been altered. Start over at the front.
|
||
*/
|
||
LWLockAcquire(partitionLock, LW_SHARED);
|
||
nextpredlock = (PREDICATELOCK *)
|
||
SHMQueueNext(&(target->predicateLocks),
|
||
&(target->predicateLocks),
|
||
offsetof(PREDICATELOCK, targetLink));
|
||
|
||
LWLockAcquire(SerializableXactHashLock, LW_SHARED);
|
||
}
|
||
else
|
||
{
|
||
/*
|
||
* The predicate lock was cleared while we were attempting
|
||
* to upgrade our lightweight locks. Revert to the shared
|
||
* locks.
|
||
*/
|
||
LWLockRelease(SerializableXactHashLock);
|
||
LWLockRelease(partitionLock);
|
||
LWLockRelease(SerializablePredicateLockListLock);
|
||
LWLockAcquire(partitionLock, LW_SHARED);
|
||
LWLockAcquire(SerializableXactHashLock, LW_SHARED);
|
||
}
|
||
}
|
||
}
|
||
else if (!SxactIsRolledBack(sxact)
|
||
&& (!SxactIsCommitted(sxact)
|
||
|| TransactionIdPrecedes(GetTransactionSnapshot()->xmin,
|
||
sxact->finishedBefore))
|
||
&& !RWConflictExists(sxact, (SERIALIZABLEXACT *) MySerializableXact))
|
||
{
|
||
LWLockRelease(SerializableXactHashLock);
|
||
LWLockAcquire(SerializableXactHashLock, LW_EXCLUSIVE);
|
||
|
||
FlagRWConflict(sxact, (SERIALIZABLEXACT *) MySerializableXact);
|
||
|
||
LWLockRelease(SerializableXactHashLock);
|
||
LWLockAcquire(SerializableXactHashLock, LW_SHARED);
|
||
}
|
||
|
||
predlock = nextpredlock;
|
||
}
|
||
LWLockRelease(SerializableXactHashLock);
|
||
LWLockRelease(partitionLock);
|
||
|
||
return hasnexttarget;
|
||
}
|
||
|
||
/*
|
||
* CheckForSerializableConflictIn
|
||
* We are writing the given tuple. If that indicates a rw-conflict
|
||
* in from another serializable transaction, take appropriate action.
|
||
*
|
||
* Skip checking for any granularity for which a parameter is missing.
|
||
*
|
||
* A tuple update or delete is in conflict if we have a predicate lock
|
||
* against the relation or page in which the tuple exists, or against the
|
||
* tuple itself.
|
||
*/
|
||
void
|
||
CheckForSerializableConflictIn(const Relation relation, const HeapTuple tuple,
|
||
const Buffer buffer)
|
||
{
|
||
PREDICATELOCKTARGETTAG targettag;
|
||
|
||
if (SkipSerialization(relation))
|
||
return;
|
||
|
||
if (SxactIsMarkedForDeath(MySerializableXact))
|
||
ereport(ERROR,
|
||
(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
|
||
errmsg("could not serialize access due to read/write dependencies among transactions"),
|
||
errdetail("Cancelled on identification as a pivot, during conflict in checking."),
|
||
errhint("The transaction might succeed if retried.")));
|
||
|
||
MySerializableXact->flags |= SXACT_FLAG_DID_WRITE;
|
||
|
||
/*
|
||
* It is important that we check for locks from the finest granularity to
|
||
* the coarsest granularity, so that granularity promotion doesn't cause
|
||
* us to miss a lock. The new (coarser) lock will be acquired before the
|
||
* old (finer) locks are released.
|
||
*
|
||
* It is not possible to take and hold a lock across the checks for all
|
||
* granularities because each target could be in a separate partition.
|
||
*/
|
||
if (tuple != NULL)
|
||
{
|
||
SET_PREDICATELOCKTARGETTAG_TUPLE(targettag,
|
||
relation->rd_node.dbNode,
|
||
relation->rd_id,
|
||
ItemPointerGetBlockNumber(&(tuple->t_data->t_ctid)),
|
||
ItemPointerGetOffsetNumber(&(tuple->t_data->t_ctid)));
|
||
CheckTargetForConflictsIn(&targettag);
|
||
}
|
||
|
||
if (BufferIsValid(buffer))
|
||
{
|
||
SET_PREDICATELOCKTARGETTAG_PAGE(targettag,
|
||
relation->rd_node.dbNode,
|
||
relation->rd_id,
|
||
BufferGetBlockNumber(buffer));
|
||
CheckTargetForConflictsIn(&targettag);
|
||
}
|
||
|
||
SET_PREDICATELOCKTARGETTAG_RELATION(targettag,
|
||
relation->rd_node.dbNode,
|
||
relation->rd_id);
|
||
CheckTargetForConflictsIn(&targettag);
|
||
}
|
||
|
||
/*
|
||
* Flag a rw-dependency between two serializable transactions.
|
||
*
|
||
* The caller is responsible for ensuring that we have a LW lock on
|
||
* the transaction hash table.
|
||
*/
|
||
static void
|
||
FlagRWConflict(SERIALIZABLEXACT *reader, SERIALIZABLEXACT *writer)
|
||
{
|
||
Assert(reader != writer);
|
||
|
||
/* First, see if this conflict causes failure. */
|
||
OnConflict_CheckForSerializationFailure(reader, writer);
|
||
|
||
/* Actually do the conflict flagging. */
|
||
if (reader == OldCommittedSxact)
|
||
writer->flags |= SXACT_FLAG_SUMMARY_CONFLICT_IN;
|
||
else if (writer == OldCommittedSxact)
|
||
reader->flags |= SXACT_FLAG_SUMMARY_CONFLICT_OUT;
|
||
else
|
||
SetRWConflict(reader, writer);
|
||
}
|
||
|
||
/*
|
||
* Check whether we should roll back one of these transactions
|
||
* instead of flagging a new rw-conflict.
|
||
*/
|
||
static void
|
||
OnConflict_CheckForSerializationFailure(const SERIALIZABLEXACT *reader,
|
||
SERIALIZABLEXACT *writer)
|
||
{
|
||
bool failure;
|
||
RWConflict conflict;
|
||
|
||
Assert(LWLockHeldByMe(SerializableXactHashLock));
|
||
|
||
failure = false;
|
||
|
||
/*
|
||
* Check for already-committed writer with rw-conflict out flagged. This
|
||
* means that the reader must immediately fail.
|
||
*/
|
||
if (SxactIsCommitted(writer)
|
||
&& (SxactHasConflictOut(writer) || SxactHasSummaryConflictOut(writer)))
|
||
failure = true;
|
||
|
||
/*
|
||
* Check whether the reader has become a pivot with a committed writer. If
|
||
* so, we must roll back unless every in-conflict either committed before
|
||
* the writer committed or is READ ONLY and overlaps the writer.
|
||
*/
|
||
if (!failure && SxactIsCommitted(writer) && !SxactIsReadOnly(reader))
|
||
{
|
||
if (SxactHasSummaryConflictIn(reader))
|
||
{
|
||
failure = true;
|
||
conflict = NULL;
|
||
}
|
||
else
|
||
conflict = (RWConflict)
|
||
SHMQueueNext(&reader->inConflicts,
|
||
&reader->inConflicts,
|
||
offsetof(RWConflictData, inLink));
|
||
while (conflict)
|
||
{
|
||
if (!SxactIsRolledBack(conflict->sxactOut)
|
||
&& (!SxactIsCommitted(conflict->sxactOut)
|
||
|| conflict->sxactOut->commitSeqNo >= writer->commitSeqNo)
|
||
&& (!SxactIsReadOnly(conflict->sxactOut)
|
||
|| conflict->sxactOut->SeqNo.lastCommitBeforeSnapshot >= writer->commitSeqNo))
|
||
{
|
||
failure = true;
|
||
break;
|
||
}
|
||
conflict = (RWConflict)
|
||
SHMQueueNext(&reader->inConflicts,
|
||
&conflict->inLink,
|
||
offsetof(RWConflictData, inLink));
|
||
}
|
||
}
|
||
|
||
/*
|
||
* Check whether the writer has become a pivot with an out-conflict
|
||
* committed transaction, while neither reader nor writer is committed. If
|
||
* the reader is a READ ONLY transaction, there is only a serialization
|
||
* failure if an out-conflict transaction causing the pivot committed
|
||
* before the reader acquired its snapshot. (That is, the reader must not
|
||
* have been concurrent with the out-conflict transaction.)
|
||
*/
|
||
if (!failure && !SxactIsCommitted(writer))
|
||
{
|
||
if (SxactHasSummaryConflictOut(reader))
|
||
{
|
||
failure = true;
|
||
conflict = NULL;
|
||
}
|
||
else
|
||
conflict = (RWConflict)
|
||
SHMQueueNext(&writer->outConflicts,
|
||
&writer->outConflicts,
|
||
offsetof(RWConflictData, outLink));
|
||
while (conflict)
|
||
{
|
||
if ((reader == conflict->sxactIn && SxactIsCommitted(reader))
|
||
|| (SxactIsCommitted(conflict->sxactIn)
|
||
&& !SxactIsCommitted(reader)
|
||
&& (!SxactIsReadOnly(reader)
|
||
|| conflict->sxactIn->commitSeqNo <= reader->SeqNo.lastCommitBeforeSnapshot)))
|
||
{
|
||
failure = true;
|
||
break;
|
||
}
|
||
conflict = (RWConflict)
|
||
SHMQueueNext(&writer->outConflicts,
|
||
&conflict->outLink,
|
||
offsetof(RWConflictData, outLink));
|
||
}
|
||
}
|
||
|
||
if (failure)
|
||
{
|
||
if (MySerializableXact == writer)
|
||
{
|
||
LWLockRelease(SerializableXactHashLock);
|
||
ereport(ERROR,
|
||
(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
|
||
errmsg("could not serialize access due to read/write dependencies among transactions"),
|
||
errdetail("Cancelled on identification as pivot, during write."),
|
||
errhint("The transaction might succeed if retried.")));
|
||
}
|
||
else if (SxactIsPrepared(writer))
|
||
{
|
||
LWLockRelease(SerializableXactHashLock);
|
||
ereport(ERROR,
|
||
(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
|
||
errmsg("could not serialize access due to read/write dependencies among transactions"),
|
||
errdetail("Cancelled on conflict out to pivot %u, during read.", writer->topXid),
|
||
errhint("The transaction might succeed if retried.")));
|
||
}
|
||
writer->flags |= SXACT_FLAG_MARKED_FOR_DEATH;
|
||
}
|
||
}
|
||
|
||
/*
|
||
* PreCommit_CheckForSerializableConflicts
|
||
* Check for dangerous structures in a serializable transaction
|
||
* at commit.
|
||
*
|
||
* We're checking for a dangerous structure as each conflict is recorded.
|
||
* The only way we could have a problem at commit is if this is the "out"
|
||
* side of a pivot, and neither the "in" side nor the pivot has yet
|
||
* committed.
|
||
*
|
||
* If a dangerous structure is found, the pivot (the near conflict) is
|
||
* marked for death, because rolling back another transaction might mean
|
||
* that we flail without ever making progress. This transaction is
|
||
* committing writes, so letting it commit ensures progress. If we
|
||
* cancelled the far conflict, it might immediately fail again on retry.
|
||
*/
|
||
void
|
||
PreCommit_CheckForSerializationFailure(void)
|
||
{
|
||
RWConflict nearConflict;
|
||
|
||
if (MySerializableXact == InvalidSerializableXact)
|
||
return;
|
||
|
||
Assert(IsolationIsSerializable());
|
||
|
||
LWLockAcquire(SerializableXactHashLock, LW_EXCLUSIVE);
|
||
|
||
if (SxactIsMarkedForDeath(MySerializableXact))
|
||
{
|
||
LWLockRelease(SerializableXactHashLock);
|
||
ereport(ERROR,
|
||
(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
|
||
errmsg("could not serialize access due to read/write dependencies among transactions"),
|
||
errdetail("Cancelled on identification as a pivot, during commit attempt."),
|
||
errhint("The transaction might succeed if retried.")));
|
||
}
|
||
|
||
nearConflict = (RWConflict)
|
||
SHMQueueNext((SHM_QUEUE *) &MySerializableXact->inConflicts,
|
||
(SHM_QUEUE *) &MySerializableXact->inConflicts,
|
||
offsetof(RWConflictData, inLink));
|
||
while (nearConflict)
|
||
{
|
||
if (!SxactIsCommitted(nearConflict->sxactOut)
|
||
&& !SxactIsRolledBack(nearConflict->sxactOut)
|
||
&& !SxactIsMarkedForDeath(nearConflict->sxactOut))
|
||
{
|
||
RWConflict farConflict;
|
||
|
||
farConflict = (RWConflict)
|
||
SHMQueueNext(&nearConflict->sxactOut->inConflicts,
|
||
&nearConflict->sxactOut->inConflicts,
|
||
offsetof(RWConflictData, inLink));
|
||
while (farConflict)
|
||
{
|
||
if (farConflict->sxactOut == MySerializableXact
|
||
|| (!SxactIsCommitted(farConflict->sxactOut)
|
||
&& !SxactIsReadOnly(farConflict->sxactOut)
|
||
&& !SxactIsRolledBack(farConflict->sxactOut)
|
||
&& !SxactIsMarkedForDeath(farConflict->sxactOut)))
|
||
{
|
||
nearConflict->sxactOut->flags |= SXACT_FLAG_MARKED_FOR_DEATH;
|
||
break;
|
||
}
|
||
farConflict = (RWConflict)
|
||
SHMQueueNext(&nearConflict->sxactOut->inConflicts,
|
||
&farConflict->inLink,
|
||
offsetof(RWConflictData, inLink));
|
||
}
|
||
}
|
||
|
||
nearConflict = (RWConflict)
|
||
SHMQueueNext((SHM_QUEUE *) &MySerializableXact->inConflicts,
|
||
&nearConflict->inLink,
|
||
offsetof(RWConflictData, inLink));
|
||
}
|
||
|
||
MySerializableXact->flags |= SXACT_FLAG_PREPARED;
|
||
|
||
LWLockRelease(SerializableXactHashLock);
|
||
}
|
||
|
||
/*------------------------------------------------------------------------*/
|
||
|
||
/*
|
||
* Two-phase commit support
|
||
*/
|
||
|
||
/*
|
||
* AtPrepare_Locks
|
||
* Do the preparatory work for a PREPARE: make 2PC state file
|
||
* records for all predicate locks currently held.
|
||
*/
|
||
void
|
||
AtPrepare_PredicateLocks(void)
|
||
{
|
||
PREDICATELOCK *predlock;
|
||
SERIALIZABLEXACT *sxact;
|
||
TwoPhasePredicateRecord record;
|
||
TwoPhasePredicateXactRecord *xactRecord;
|
||
TwoPhasePredicateLockRecord *lockRecord;
|
||
|
||
sxact = (SERIALIZABLEXACT *) MySerializableXact;
|
||
xactRecord = &(record.data.xactRecord);
|
||
lockRecord = &(record.data.lockRecord);
|
||
|
||
if (MySerializableXact == InvalidSerializableXact)
|
||
return;
|
||
|
||
/* Generate a xact record for our SERIALIZABLEXACT */
|
||
record.type = TWOPHASEPREDICATERECORD_XACT;
|
||
xactRecord->xmin = MySerializableXact->xmin;
|
||
xactRecord->flags = MySerializableXact->flags;
|
||
|
||
/*
|
||
* Tweak the flags. Since we're not going to output the inConflicts and
|
||
* outConflicts lists, if they're non-empty we'll represent that by
|
||
* setting the appropriate summary conflict flags.
|
||
*/
|
||
if (!SHMQueueEmpty((SHM_QUEUE *) &MySerializableXact->inConflicts))
|
||
xactRecord->flags |= SXACT_FLAG_SUMMARY_CONFLICT_IN;
|
||
if (!SHMQueueEmpty((SHM_QUEUE *) &MySerializableXact->outConflicts))
|
||
xactRecord->flags |= SXACT_FLAG_SUMMARY_CONFLICT_OUT;
|
||
|
||
RegisterTwoPhaseRecord(TWOPHASE_RM_PREDICATELOCK_ID, 0,
|
||
&record, sizeof(record));
|
||
|
||
/*
|
||
* Generate a lock record for each lock.
|
||
*
|
||
* To do this, we need to walk the predicate lock list in our sxact rather
|
||
* than using the local predicate lock table because the latter is not
|
||
* guaranteed to be accurate.
|
||
*/
|
||
LWLockAcquire(SerializablePredicateLockListLock, LW_SHARED);
|
||
|
||
predlock = (PREDICATELOCK *)
|
||
SHMQueueNext(&(sxact->predicateLocks),
|
||
&(sxact->predicateLocks),
|
||
offsetof(PREDICATELOCK, xactLink));
|
||
|
||
while (predlock != NULL)
|
||
{
|
||
record.type = TWOPHASEPREDICATERECORD_LOCK;
|
||
lockRecord->target = predlock->tag.myTarget->tag;
|
||
|
||
RegisterTwoPhaseRecord(TWOPHASE_RM_PREDICATELOCK_ID, 0,
|
||
&record, sizeof(record));
|
||
|
||
predlock = (PREDICATELOCK *)
|
||
SHMQueueNext(&(sxact->predicateLocks),
|
||
&(predlock->xactLink),
|
||
offsetof(PREDICATELOCK, xactLink));
|
||
}
|
||
|
||
LWLockRelease(SerializablePredicateLockListLock);
|
||
}
|
||
|
||
/*
|
||
* PostPrepare_Locks
|
||
* Clean up after successful PREPARE. Unlike the non-predicate
|
||
* lock manager, we do not need to transfer locks to a dummy
|
||
* PGPROC because our SERIALIZABLEXACT will stay around
|
||
* anyway. We only need to clean up our local state.
|
||
*/
|
||
void
|
||
PostPrepare_PredicateLocks(TransactionId xid)
|
||
{
|
||
if (MySerializableXact == InvalidSerializableXact)
|
||
return;
|
||
|
||
Assert(SxactIsPrepared(MySerializableXact));
|
||
|
||
MySerializableXact->pid = 0;
|
||
|
||
hash_destroy(LocalPredicateLockHash);
|
||
LocalPredicateLockHash = NULL;
|
||
|
||
MySerializableXact = InvalidSerializableXact;
|
||
}
|
||
|
||
/*
|
||
* PredicateLockTwoPhaseFinish
|
||
* Release a prepared transaction's predicate locks once it
|
||
* commits or aborts.
|
||
*/
|
||
void
|
||
PredicateLockTwoPhaseFinish(TransactionId xid, bool isCommit)
|
||
{
|
||
SERIALIZABLEXID *sxid;
|
||
SERIALIZABLEXIDTAG sxidtag;
|
||
|
||
sxidtag.xid = xid;
|
||
|
||
LWLockAcquire(SerializableXactHashLock, LW_SHARED);
|
||
sxid = (SERIALIZABLEXID *)
|
||
hash_search(SerializableXidHash, &sxidtag, HASH_FIND, NULL);
|
||
LWLockRelease(SerializableXactHashLock);
|
||
|
||
/* xid will not be found if it wasn't a serializable transaction */
|
||
if (sxid == NULL)
|
||
return;
|
||
|
||
/* Release its locks */
|
||
MySerializableXact = sxid->myXact;
|
||
ReleasePredicateLocks(isCommit);
|
||
}
|
||
|
||
/*
|
||
* Re-acquire a predicate lock belonging to a transaction that was prepared.
|
||
*/
|
||
void
|
||
predicatelock_twophase_recover(TransactionId xid, uint16 info,
|
||
void *recdata, uint32 len)
|
||
{
|
||
TwoPhasePredicateRecord *record;
|
||
|
||
Assert(len == sizeof(TwoPhasePredicateRecord));
|
||
|
||
record = (TwoPhasePredicateRecord *) recdata;
|
||
|
||
Assert((record->type == TWOPHASEPREDICATERECORD_XACT) ||
|
||
(record->type == TWOPHASEPREDICATERECORD_LOCK));
|
||
|
||
if (record->type == TWOPHASEPREDICATERECORD_XACT)
|
||
{
|
||
/* Per-transaction record. Set up a SERIALIZABLEXACT. */
|
||
TwoPhasePredicateXactRecord *xactRecord;
|
||
SERIALIZABLEXACT *sxact;
|
||
SERIALIZABLEXID *sxid;
|
||
SERIALIZABLEXIDTAG sxidtag;
|
||
bool found;
|
||
|
||
xactRecord = (TwoPhasePredicateXactRecord *) &record->data.xactRecord;
|
||
|
||
LWLockAcquire(SerializableXactHashLock, LW_EXCLUSIVE);
|
||
sxact = CreatePredXact();
|
||
if (!sxact)
|
||
ereport(ERROR,
|
||
(errcode(ERRCODE_OUT_OF_MEMORY),
|
||
errmsg("out of shared memory")));
|
||
|
||
/* vxid for a prepared xact is InvalidBackendId/xid; no pid */
|
||
sxact->vxid.backendId = InvalidBackendId;
|
||
sxact->vxid.localTransactionId = (LocalTransactionId) xid;
|
||
sxact->pid = 0;
|
||
|
||
/* a prepared xact hasn't committed yet */
|
||
sxact->commitSeqNo = InvalidSerCommitSeqNo;
|
||
sxact->finishedBefore = InvalidTransactionId;
|
||
|
||
sxact->SeqNo.lastCommitBeforeSnapshot = RecoverySerCommitSeqNo;
|
||
|
||
|
||
/*
|
||
* We don't need the details of a prepared transaction's conflicts,
|
||
* just whether it had conflicts in or out (which we get from the
|
||
* flags)
|
||
*/
|
||
SHMQueueInit(&(sxact->outConflicts));
|
||
SHMQueueInit(&(sxact->inConflicts));
|
||
|
||
/*
|
||
* Don't need to track this; no transactions running at the time the
|
||
* recovered xact started are still active, except possibly other
|
||
* prepared xacts and we don't care whether those are RO_SAFE or not.
|
||
*/
|
||
SHMQueueInit(&(sxact->possibleUnsafeConflicts));
|
||
|
||
SHMQueueInit(&(sxact->predicateLocks));
|
||
SHMQueueElemInit(&(sxact->finishedLink));
|
||
|
||
sxact->topXid = xid;
|
||
sxact->xmin = xactRecord->xmin;
|
||
sxact->flags = xactRecord->flags;
|
||
Assert(SxactIsPrepared(sxact));
|
||
if (!SxactIsReadOnly(sxact))
|
||
{
|
||
++(PredXact->WritableSxactCount);
|
||
Assert(PredXact->WritableSxactCount <=
|
||
(MaxBackends + max_prepared_xacts));
|
||
}
|
||
|
||
/* Register the transaction's xid */
|
||
sxidtag.xid = xid;
|
||
sxid = (SERIALIZABLEXID *) hash_search(SerializableXidHash,
|
||
&sxidtag,
|
||
HASH_ENTER, &found);
|
||
if (!sxid)
|
||
ereport(ERROR,
|
||
(errcode(ERRCODE_OUT_OF_MEMORY),
|
||
errmsg("out of shared memory")));
|
||
Assert(!found);
|
||
sxid->myXact = (SERIALIZABLEXACT *) sxact;
|
||
|
||
/*
|
||
* Update global xmin. Note that this is a special case compared to
|
||
* registering a normal transaction, because the global xmin might go
|
||
* backwards. That's OK, because until recovery is over we're not
|
||
* going to complete any transactions or create any non-prepared
|
||
* transactions, so there's no danger of throwing away.
|
||
*/
|
||
if ((!TransactionIdIsValid(PredXact->SxactGlobalXmin)) ||
|
||
(TransactionIdFollows(PredXact->SxactGlobalXmin, sxact->xmin)))
|
||
{
|
||
PredXact->SxactGlobalXmin = sxact->xmin;
|
||
PredXact->SxactGlobalXminCount = 1;
|
||
OldSerXidSetActiveSerXmin(sxact->xmin);
|
||
}
|
||
else if (TransactionIdEquals(sxact->xmin, PredXact->SxactGlobalXmin))
|
||
{
|
||
Assert(PredXact->SxactGlobalXminCount > 0);
|
||
PredXact->SxactGlobalXminCount++;
|
||
}
|
||
|
||
LWLockRelease(SerializableXactHashLock);
|
||
}
|
||
else if (record->type == TWOPHASEPREDICATERECORD_LOCK)
|
||
{
|
||
/* Lock record. Recreate the PREDICATELOCK */
|
||
TwoPhasePredicateLockRecord *lockRecord;
|
||
SERIALIZABLEXID *sxid;
|
||
SERIALIZABLEXACT *sxact;
|
||
SERIALIZABLEXIDTAG sxidtag;
|
||
uint32 targettaghash;
|
||
|
||
lockRecord = (TwoPhasePredicateLockRecord *) &record->data.lockRecord;
|
||
targettaghash = PredicateLockTargetTagHashCode(&lockRecord->target);
|
||
|
||
LWLockAcquire(SerializableXactHashLock, LW_SHARED);
|
||
sxidtag.xid = xid;
|
||
sxid = (SERIALIZABLEXID *)
|
||
hash_search(SerializableXidHash, &sxidtag, HASH_FIND, NULL);
|
||
LWLockRelease(SerializableXactHashLock);
|
||
|
||
Assert(sxid != NULL);
|
||
sxact = sxid->myXact;
|
||
Assert(sxact != InvalidSerializableXact);
|
||
|
||
CreatePredicateLock(&lockRecord->target, targettaghash, sxact);
|
||
}
|
||
}
|