diff --git a/src/backend/access/transam/multixact.c b/src/backend/access/transam/multixact.c index 6f86961..1301d85 100644 --- a/src/backend/access/transam/multixact.c +++ b/src/backend/access/transam/multixact.c @@ -51,6 +51,8 @@ #include "access/multixact.h" #include "access/slru.h" #include "access/transam.h" +#include "access/twophase.h" +#include "access/twophase_rmgr.h" #include "access/xact.h" #include "miscadmin.h" #include "pg_trace.h" @@ -117,9 +119,12 @@ typedef struct MultiXactStateData /* * Per-backend data starts here. We have two arrays stored in the area - * immediately following the MultiXactStateData struct. Each is indexed by - * BackendId. (Note: valid BackendIds run from 1 to MaxBackends; element - * zero of each array is never used.) + * immediately following the MultiXactStateData struct. Each is indexed + * by BackendId. + * + * In both arrays, there's a slot for all normal backends (1..MaxBackends) + * followed by a slot for all max_prepared_xacts prepared transactions. + * Valid BackendIds start from 1; element zero of each array is never used. * * OldestMemberMXactId[k] is the oldest MultiXactId each backend's current * transaction(s) could possibly be a member of, or InvalidMultiXactId @@ -152,6 +157,12 @@ typedef struct MultiXactStateData MultiXactId perBackendXactIds[1]; /* VARIABLE LENGTH ARRAY */ } MultiXactStateData; +/* + * Last element of OldestMemberMXactID and OldestVisibleMXactId arrays. + * Valid elements are (1..MaxOldestSlot); element 0 is never used. + */ +#define MaxOldestSlot (MaxBackends + max_prepared_xacts) + /* Pointers to the state data in shared memory */ static MultiXactStateData *MultiXactState; static MultiXactId *OldestMemberMXactId; @@ -539,7 +550,7 @@ MultiXactIdSetOldestVisible(void) if (oldestMXact < FirstMultiXactId) oldestMXact = FirstMultiXactId; - for (i = 1; i <= MaxBackends; i++) + for (i = 1; i <= MaxOldestSlot; i++) { MultiXactId thisoldest = OldestMemberMXactId[i]; @@ -1276,6 +1287,119 @@ AtEOXact_MultiXact(void) } /* + * AtPrepare_MultiXact + * Save multixact state at 2PC tranasction prepare. + * + * In this phase, we only store our OldestMemberMXactId value in the two-phase + * state file. + */ +void +AtPrepare_MultiXact(void) +{ + MultiXactId myOldestMember = OldestMemberMXactId[MyBackendId]; + + if (MultiXactIdIsValid(myOldestMember)) + RegisterTwoPhaseRecord(TWOPHASE_RM_MULTIXACT_ID, 0, + &myOldestMember, sizeof(MultiXactId)); +} + +/* + * PostPrepare_MultiXact + * Clean up after successful PREPARE TRANSACTION + */ +void +PostPrepare_MultiXact(TransactionId xid) +{ + MultiXactId myOldestMember; + + /* + * Transfer our OldestMemberMXactId value to the slot reserved for the + * prepared transaction. + */ + myOldestMember = OldestMemberMXactId[MyBackendId]; + if (MultiXactIdIsValid(myOldestMember)) + { + BackendId dummyBackendId = TwoPhaseGetDummyBackendId(xid); + + /* + * Even though storing MultiXactId is atomic, acquire lock to make sure + * others see both changes, not just the reset of the slot of the + * current backend. Using a volatile pointer might suffice, but this + * isn't a hot spot. + */ + LWLockAcquire(MultiXactGenLock, LW_EXCLUSIVE); + + OldestMemberMXactId[dummyBackendId] = myOldestMember; + OldestMemberMXactId[MyBackendId] = InvalidMultiXactId; + + LWLockRelease(MultiXactGenLock); + } + + /* + * We don't need to transfer OldestVisibleMXactId value, because the + * transaction is not going to be looking at any more multixacts once + * it's prepared. + * + * We assume that storing a MultiXactId is atomic and so we need not take + * MultiXactGenLock to do this. + */ + OldestVisibleMXactId[MyBackendId] = InvalidMultiXactId; + + /* + * Discard the local MultiXactId cache like in AtEOX_MultiXact + */ + MXactContext = NULL; + MXactCache = NULL; +} + +/* + * multixact_twophase_recover + * recover the state of a prepared transaction at startup. + */ +void +multixact_twophase_recover(TransactionId xid, uint16 info, + void *recdata, uint32 len) +{ + BackendId dummyBackendId = TwoPhaseGetDummyBackendId(xid); + MultiXactId oldestMember; + + /* + * Get the oldest member XID from the state file record, and set it in + * the OldestMemberMXactId slot reserved for this prepared transaction. + */ + Assert(len == sizeof(MultiXactId)); + oldestMember = *((MultiXactId *)recdata); + + OldestMemberMXactId[dummyBackendId] = oldestMember; +} + +/* + * multixact_twophase_postcommit + * similar to AtEOX_MultiXact but for COMMIT PREPARED + */ +void +multixact_twophase_postcommit(TransactionId xid, uint16 info, + void *recdata, uint32 len) +{ + BackendId dummyBackendId = TwoPhaseGetDummyBackendId(xid); + + Assert(len == sizeof(MultiXactId)); + + OldestMemberMXactId[dummyBackendId] = InvalidMultiXactId; +} + +/* + * multixact_twophase_postabort + * this is actually just the same as the COMMIT case. + */ +void +multixact_twophase_postabort(TransactionId xid, uint16 info, + void *recdata, uint32 len) +{ + multixact_twophase_postcommit(xid, info, recdata, len); +} + +/* * Initialization of shared memory for MultiXact. We use two SLRU areas, * thus double memory. Also, reserve space for the shared MultiXactState * struct and the per-backend MultiXactId arrays (two of those, too). @@ -1287,7 +1411,7 @@ MultiXactShmemSize(void) #define SHARED_MULTIXACT_STATE_SIZE \ add_size(sizeof(MultiXactStateData), \ - mul_size(sizeof(MultiXactId) * 2, MaxBackends)) + mul_size(sizeof(MultiXactId) * 2, MaxOldestSlot)) size = SHARED_MULTIXACT_STATE_SIZE; size = add_size(size, SimpleLruShmemSize(NUM_MXACTOFFSET_BUFFERS, 0)); @@ -1329,10 +1453,10 @@ MultiXactShmemInit(void) /* * Set up array pointers. Note that perBackendXactIds[0] is wasted space - * since we only use indexes 1..MaxBackends in each array. + * since we only use indexes 1..MaxOldestSlot in each array. */ OldestMemberMXactId = MultiXactState->perBackendXactIds; - OldestVisibleMXactId = OldestMemberMXactId + MaxBackends; + OldestVisibleMXactId = OldestMemberMXactId + MaxOldestSlot; } /* @@ -1702,7 +1826,7 @@ TruncateMultiXact(void) nextMXact = FirstMultiXactId; oldestMXact = nextMXact; - for (i = 1; i <= MaxBackends; i++) + for (i = 1; i <= MaxOldestSlot; i++) { MultiXactId thisoldest; diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.c index 195c90c..bafa006 100644 --- a/src/backend/access/transam/twophase.c +++ b/src/backend/access/transam/twophase.c @@ -109,6 +109,7 @@ int max_prepared_xacts = 0; typedef struct GlobalTransactionData { PGPROC proc; /* dummy proc */ + BackendId dummyBackendId; /* similar to backend id for backends */ TimestampTz prepared_at; /* time of preparation */ XLogRecPtr prepare_lsn; /* XLOG offset of prepare record */ Oid owner; /* ID of user that executed the xact */ @@ -200,6 +201,20 @@ TwoPhaseShmemInit(void) { gxacts[i].proc.links.next = (SHM_QUEUE *) TwoPhaseState->freeGXacts; TwoPhaseState->freeGXacts = &gxacts[i]; + + /* + * Assign a unique ID for each dummy proc, so that the range of + * dummy backend IDs immediately follows the range of normal + * backend IDs. We don't dare to assign a real backend ID to + * dummy procs, because prepared transactions don't take part in + * cache invalidation like a real backend ID would imply, but + * having a unique ID for them is nevertheless handy. This + * arrangement allows you to allocate an array of size + * (MaxBackends + max_prepared_xacts + 1), and have a slot for + * every backend and prepared transaction. Currently multixact.c + * uses that technique. + */ + gxacts[i].dummyBackendId = MaxBackends + 1 + i; } } else @@ -649,6 +664,22 @@ pg_prepared_xact(PG_FUNCTION_ARGS) /* * TwoPhaseGetDummyProc + * Get the dummy backend ID for prepared transaction specified by XID + * + * Dummy backend IDs are similar to real backend IDs of real backends. + * They start at MaxBackends + 1, and are unique across all currently active + * real backends and prepared transactions. + */ +BackendId +TwoPhaseGetDummyBackendId(TransactionId xid) +{ + PGPROC *proc = TwoPhaseGetDummyProc(xid); + + return ((GlobalTransaction) proc)->dummyBackendId; +} + +/* + * TwoPhaseGetDummyProc * Get the PGPROC that represents a prepared transaction specified by XID */ PGPROC * diff --git a/src/backend/access/transam/twophase_rmgr.c b/src/backend/access/transam/twophase_rmgr.c index 4ff9549..f019868 100644 --- a/src/backend/access/transam/twophase_rmgr.c +++ b/src/backend/access/transam/twophase_rmgr.c @@ -14,6 +14,7 @@ */ #include "postgres.h" +#include "access/multixact.h" #include "access/twophase_rmgr.h" #include "commands/async.h" #include "pgstat.h" @@ -27,7 +28,8 @@ const TwoPhaseCallback twophase_recover_callbacks[TWOPHASE_RM_MAX_ID + 1] = lock_twophase_recover, /* Lock */ NULL, /* Inval */ NULL, /* notify/listen */ - NULL /* pgstat */ + NULL, /* pgstat */ + multixact_twophase_recover /* MultiXact */ }; const TwoPhaseCallback twophase_postcommit_callbacks[TWOPHASE_RM_MAX_ID + 1] = @@ -36,7 +38,8 @@ const TwoPhaseCallback twophase_postcommit_callbacks[TWOPHASE_RM_MAX_ID + 1] = lock_twophase_postcommit, /* Lock */ inval_twophase_postcommit, /* Inval */ notify_twophase_postcommit, /* notify/listen */ - pgstat_twophase_postcommit /* pgstat */ + pgstat_twophase_postcommit, /* pgstat */ + multixact_twophase_postcommit /* MultiXact */ }; const TwoPhaseCallback twophase_postabort_callbacks[TWOPHASE_RM_MAX_ID + 1] = @@ -45,5 +48,6 @@ const TwoPhaseCallback twophase_postabort_callbacks[TWOPHASE_RM_MAX_ID + 1] = lock_twophase_postabort, /* Lock */ NULL, /* Inval */ NULL, /* notify/listen */ - pgstat_twophase_postabort /* pgstat */ + pgstat_twophase_postabort, /* pgstat */ + multixact_twophase_postabort /* MultiXact */ }; diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c index c3606e0..777bd17 100644 --- a/src/backend/access/transam/xact.c +++ b/src/backend/access/transam/xact.c @@ -1856,6 +1856,7 @@ PrepareTransaction(void) AtPrepare_Inval(); AtPrepare_Locks(); AtPrepare_PgStat(); + AtPrepare_MultiXact(); /* * Here is where we really truly prepare. @@ -1909,7 +1910,7 @@ PrepareTransaction(void) PostPrepare_smgr(); - AtEOXact_MultiXact(); + PostPrepare_MultiXact(xid); PostPrepare_Locks(xid); diff --git a/src/include/access/multixact.h b/src/include/access/multixact.h index 7ffc15a..72425bf 100644 --- a/src/include/access/multixact.h +++ b/src/include/access/multixact.h @@ -52,6 +52,8 @@ extern void MultiXactIdSetOldestMember(void); extern int GetMultiXactIdMembers(MultiXactId multi, TransactionId **xids); extern void AtEOXact_MultiXact(void); +extern void AtPrepare_MultiXact(void); +extern void PostPrepare_MultiXact(TransactionId xid); extern Size MultiXactShmemSize(void); extern void MultiXactShmemInit(void); @@ -67,6 +69,13 @@ extern void MultiXactSetNextMXact(MultiXactId nextMulti, extern void MultiXactAdvanceNextMXact(MultiXactId minMulti, MultiXactOffset minMultiOffset); +extern void multixact_twophase_recover(TransactionId xid, uint16 info, + void *recdata, uint32 len); +extern void multixact_twophase_postcommit(TransactionId xid, uint16 info, + void *recdata, uint32 len); +extern void multixact_twophase_postabort(TransactionId xid, uint16 info, + void *recdata, uint32 len); + extern void multixact_redo(XLogRecPtr lsn, XLogRecord *record); extern void multixact_desc(StringInfo buf, uint8 xl_info, char *rec); diff --git a/src/include/access/twophase.h b/src/include/access/twophase.h index 64dba0c..a3a1492 100644 --- a/src/include/access/twophase.h +++ b/src/include/access/twophase.h @@ -15,6 +15,7 @@ #define TWOPHASE_H #include "access/xlogdefs.h" +#include "storage/backendid.h" #include "storage/proc.h" #include "utils/timestamp.h" @@ -31,6 +32,7 @@ extern Size TwoPhaseShmemSize(void); extern void TwoPhaseShmemInit(void); extern PGPROC *TwoPhaseGetDummyProc(TransactionId xid); +extern BackendId TwoPhaseGetDummyBackendId(TransactionId xid); extern GlobalTransaction MarkAsPreparing(TransactionId xid, const char *gid, TimestampTz prepared_at, diff --git a/src/include/access/twophase_rmgr.h b/src/include/access/twophase_rmgr.h index 20c2b2f..86acc8e 100644 --- a/src/include/access/twophase_rmgr.h +++ b/src/include/access/twophase_rmgr.h @@ -26,7 +26,8 @@ typedef uint8 TwoPhaseRmgrId; #define TWOPHASE_RM_INVAL_ID 2 #define TWOPHASE_RM_NOTIFY_ID 3 #define TWOPHASE_RM_PGSTAT_ID 4 -#define TWOPHASE_RM_MAX_ID TWOPHASE_RM_PGSTAT_ID +#define TWOPHASE_RM_MULTIXACT_ID 5 +#define TWOPHASE_RM_MAX_ID TWOPHASE_RM_MULTIXACT_ID extern const TwoPhaseCallback twophase_recover_callbacks[]; extern const TwoPhaseCallback twophase_postcommit_callbacks[];