granicus.if.org Git - postgresql/blob - src/backend/access/transam/varsup.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * varsup.c
   4  *        postgres OID & XID variables support routines
   5  *
   6  * Copyright (c) 2000, PostgreSQL Global Development Group
   7  *
   8  * IDENTIFICATION
   9  *        $Header: /cvsroot/pgsql/src/backend/access/transam/varsup.c,v 1.35 2001/01/24 19:42:51 momjian Exp $
  10  *
  11  *-------------------------------------------------------------------------
  12  */
  13
  14 #include "postgres.h"
  15
  16 #include "access/transam.h"
  17 #include "storage/proc.h"
  18
  19 SPINLOCK OidGenLockId;
  20
  21 extern SPINLOCK XidGenLockId;
  22 extern void XLogPutNextOid(Oid nextOid);
  23
  24 /* pointer to "variable cache" in shared memory (set up by shmem.c) */
  25 VariableCache ShmemVariableCache = NULL;
  26
  27 void
  28 GetNewTransactionId(TransactionId *xid)
  29 {
  30         /*
  31          * During bootstrap initialization, we return the special
  32          * bootstrap transaction id.
  33          */
  34         if (AMI_OVERRIDE)
  35         {
  36                 *xid = AmiTransactionId;
  37                 return;
  38         }
  39
  40         SpinAcquire(XidGenLockId);
  41         *xid = ShmemVariableCache->nextXid;
  42         (ShmemVariableCache->nextXid)++;
  43
  44         if (MyProc != (PROC *) NULL)
  45                 MyProc->xid = *xid;
  46
  47         SpinRelease(XidGenLockId);
  48
  49 }
  50
  51 /*
  52  * Like GetNewTransactionId reads nextXid but don't fetch it.
  53  */
  54 void
  55 ReadNewTransactionId(TransactionId *xid)
  56 {
  57
  58         /*
  59          * During bootstrap initialization, we return the special
  60          * bootstrap transaction id.
  61          */
  62         if (AMI_OVERRIDE)
  63         {
  64                 *xid = AmiTransactionId;
  65                 return;
  66         }
  67
  68         SpinAcquire(XidGenLockId);
  69         *xid = ShmemVariableCache->nextXid;
  70         SpinRelease(XidGenLockId);
  71
  72 }
  73
  74 /* ----------------------------------------------------------------
  75  *                                      object id generation support
  76  * ----------------------------------------------------------------
  77  */
  78
  79 #define VAR_OID_PREFETCH                8192
  80 static Oid lastSeenOid = InvalidOid;
  81
  82 void
  83 GetNewObjectId(Oid *oid_return)
  84 {
  85         SpinAcquire(OidGenLockId);
  86
  87         /* If we run out of logged for use oids then we log more */
  88         if (ShmemVariableCache->oidCount == 0)
  89         {
  90                 XLogPutNextOid(ShmemVariableCache->nextOid + VAR_OID_PREFETCH);
  91                 ShmemVariableCache->oidCount = VAR_OID_PREFETCH;
  92         }
  93
  94         if (PointerIsValid(oid_return))
  95                 lastSeenOid = (*oid_return) = ShmemVariableCache->nextOid;
  96
  97         (ShmemVariableCache->nextOid)++;
  98         (ShmemVariableCache->oidCount)--;
  99
 100         SpinRelease(OidGenLockId);
 101 }
 102
 103 void
 104 CheckMaxObjectId(Oid assigned_oid)
 105 {
 106
 107         if (lastSeenOid != InvalidOid && assigned_oid < lastSeenOid)
 108                 return;
 109
 110         SpinAcquire(OidGenLockId);
 111         if (assigned_oid < ShmemVariableCache->nextOid)
 112         {
 113                 lastSeenOid = ShmemVariableCache->nextOid - 1;
 114                 SpinRelease(OidGenLockId);
 115                 return;
 116         }
 117
 118         /* If we are in the logged oid range, just bump nextOid up */
 119         if (assigned_oid <= ShmemVariableCache->nextOid +
 120                                                 ShmemVariableCache->oidCount - 1)
 121         {
 122                 ShmemVariableCache->oidCount -=
 123                         assigned_oid - ShmemVariableCache->nextOid + 1;
 124                 ShmemVariableCache->nextOid = assigned_oid + 1;
 125                 SpinRelease(OidGenLockId);
 126                 return;
 127         }
 128
 129         /*
 130          * We have exceeded the logged oid range.
 131          * We should lock the database and kill all other backends
 132          * but we are loading oid's that we can not guarantee are unique
 133          * anyway, so we must rely on the user.
 134          */
 135
 136         XLogPutNextOid(assigned_oid + VAR_OID_PREFETCH);
 137         ShmemVariableCache->oidCount = VAR_OID_PREFETCH - 1;
 138         ShmemVariableCache->nextOid = assigned_oid + 1;
 139
 140         SpinRelease(OidGenLockId);
 141
 142 }