mirror of https://github.com/postgres/postgres
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/*-------------------------------------------------------------------------
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* |
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* varsup.c |
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* postgres OID & XID variables support routines |
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* |
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* Copyright (c) 2000, PostgreSQL, Inc |
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* |
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* IDENTIFICATION |
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* $Header: /cvsroot/pgsql/src/backend/access/transam/Attic/xlog_varsup.c,v 1.1 2000/11/03 11:39:35 vadim Exp $ |
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* |
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*------------------------------------------------------------------------- |
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*/ |
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#include "postgres.h" |
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#include "access/transam.h" |
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#include "storage/proc.h" |
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SPINLOCK OidGenLockId; |
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extern SPINLOCK XidGenLockId; |
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extern void XLogPutNextOid(Oid nextOid); |
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/* pointer to "variable cache" in shared memory (set up by shmem.c) */ |
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VariableCache ShmemVariableCache = NULL; |
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void |
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GetNewTransactionId(TransactionId *xid) |
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{ |
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/*
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* During bootstrap initialization, we return the special |
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* bootstrap transaction id. |
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*/ |
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if (AMI_OVERRIDE) |
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{ |
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*xid = AmiTransactionId; |
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return; |
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} |
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SpinAcquire(XidGenLockId); |
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*xid = ShmemVariableCache->nextXid; |
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(ShmemVariableCache->nextXid)++; |
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if (MyProc != (PROC *) NULL) |
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MyProc->xid = *xid; |
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SpinRelease(XidGenLockId); |
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} |
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/*
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* Like GetNewTransactionId reads nextXid but don't fetch it. |
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*/ |
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void |
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ReadNewTransactionId(TransactionId *xid) |
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{ |
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/*
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* During bootstrap initialization, we return the special |
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* bootstrap transaction id. |
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*/ |
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if (AMI_OVERRIDE) |
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{ |
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*xid = AmiTransactionId; |
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return; |
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} |
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SpinAcquire(XidGenLockId); |
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*xid = ShmemVariableCache->nextXid; |
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SpinRelease(XidGenLockId); |
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} |
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/* ----------------------------------------------------------------
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* object id generation support |
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* ---------------------------------------------------------------- |
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*/ |
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#define VAR_OID_PREFETCH 8192 |
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static Oid lastSeenOid = InvalidOid; |
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void |
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GetNewObjectId(Oid *oid_return) |
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{ |
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SpinAcquire(OidGenLockId); |
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/* If we run out of logged for use oids then we log more */ |
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if (ShmemVariableCache->oidCount == 0) |
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{ |
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XLogPutNextOid(ShmemVariableCache->nextOid + VAR_OID_PREFETCH); |
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ShmemVariableCache->oidCount = VAR_OID_PREFETCH; |
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} |
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if (PointerIsValid(oid_return)) |
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lastSeenOid = (*oid_return) = ShmemVariableCache->nextOid; |
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(ShmemVariableCache->nextOid)++; |
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(ShmemVariableCache->oidCount)--; |
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SpinRelease(OidGenLockId); |
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} |
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void |
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CheckMaxObjectId(Oid assigned_oid) |
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{ |
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if (lastSeenOid != InvalidOid && assigned_oid < lastSeenOid) |
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return; |
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SpinAcquire(OidGenLockId); |
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if (assigned_oid < ShmemVariableCache->nextOid) |
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{ |
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lastSeenOid = ShmemVariableCache->nextOid - 1; |
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SpinRelease(OidGenLockId); |
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return; |
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} |
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/* If we are in the logged oid range, just bump nextOid up */ |
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if (assigned_oid <= ShmemVariableCache->nextOid +
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ShmemVariableCache->oidCount - 1) |
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{ |
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ShmemVariableCache->oidCount -=
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assigned_oid - ShmemVariableCache->nextOid + 1; |
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ShmemVariableCache->nextOid = assigned_oid + 1; |
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SpinRelease(OidGenLockId); |
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return; |
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} |
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/*
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* We have exceeded the logged oid range. |
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* We should lock the database and kill all other backends |
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* but we are loading oid's that we can not guarantee are unique |
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* anyway, so we must rely on the user. |
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*/ |
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XLogPutNextOid(assigned_oid + VAR_OID_PREFETCH); |
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ShmemVariableCache->oidCount = VAR_OID_PREFETCH - 1; |
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ShmemVariableCache->nextOid = assigned_oid + 1; |
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SpinRelease(OidGenLockId); |
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} |
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