diff options
Diffstat (limited to 'src/include/access/transam.h')
| -rw-r--r-- | src/include/access/transam.h | 30 |
1 files changed, 27 insertions, 3 deletions
diff --git a/src/include/access/transam.h b/src/include/access/transam.h index 98850cc0d3b..0408038124c 100644 --- a/src/include/access/transam.h +++ b/src/include/access/transam.h @@ -7,7 +7,7 @@ * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * - * $PostgreSQL: pgsql/src/include/access/transam.h,v 1.61 2007/08/01 22:45:09 tgl Exp $ + * $PostgreSQL: pgsql/src/include/access/transam.h,v 1.62 2007/09/08 20:31:15 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -43,6 +43,7 @@ #define TransactionIdEquals(id1, id2) ((id1) == (id2)) #define TransactionIdStore(xid, dest) (*(dest) = (xid)) #define StoreInvalidTransactionId(dest) (*(dest) = InvalidTransactionId) + /* advance a transaction ID variable, handling wraparound correctly */ #define TransactionIdAdvance(dest) \ do { \ @@ -51,6 +52,12 @@ (dest) = FirstNormalTransactionId; \ } while(0) +/* back up a transaction ID variable, handling wraparound correctly */ +#define TransactionIdRetreat(dest) \ + do { \ + (dest)--; \ + } while ((dest) < FirstNormalTransactionId) + /* ---------- * Object ID (OID) zero is InvalidOid. @@ -78,8 +85,10 @@ #define FirstNormalObjectId 16384 /* - * VariableCache is placed in shmem and used by - * backends to get next available OID & XID. + * VariableCache is a data structure in shared memory that is used to track + * OID and XID assignment state. For largely historical reasons, there is + * just one struct with different fields that are protected by different + * LWLocks. * * Note: xidWrapLimit and limit_datname are not "active" values, but are * used just to generate useful messages when xidWarnLimit or xidStopLimit @@ -87,8 +96,15 @@ */ typedef struct VariableCacheData { + /* + * These fields are protected by OidGenLock. + */ Oid nextOid; /* next OID to assign */ uint32 oidCount; /* OIDs available before must do XLOG work */ + + /* + * These fields are protected by XidGenLock. + */ TransactionId nextXid; /* next XID to assign */ TransactionId oldestXid; /* cluster-wide minimum datfrozenxid */ @@ -97,6 +113,12 @@ typedef struct VariableCacheData TransactionId xidStopLimit; /* refuse to advance nextXid beyond here */ TransactionId xidWrapLimit; /* where the world ends */ NameData limit_datname; /* database that needs vacuumed first */ + + /* + * These fields are protected by ProcArrayLock. + */ + TransactionId latestCompletedXid; /* newest XID that has committed or + * aborted */ } VariableCacheData; typedef VariableCacheData *VariableCache; @@ -127,6 +149,8 @@ extern bool TransactionIdPrecedes(TransactionId id1, TransactionId id2); extern bool TransactionIdPrecedesOrEquals(TransactionId id1, TransactionId id2); extern bool TransactionIdFollows(TransactionId id1, TransactionId id2); extern bool TransactionIdFollowsOrEquals(TransactionId id1, TransactionId id2); +extern TransactionId TransactionIdLatest(TransactionId mainxid, + int nxids, const TransactionId *xids); extern XLogRecPtr TransactionIdGetCommitLSN(TransactionId xid); /* in transam/varsup.c */ |