376 lines
12 KiB
C
376 lines
12 KiB
C
/*-------------------------------------------------------------------------
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*
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* transam.h
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* postgres transaction access method support code
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*
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*
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* Portions Copyright (c) 1996-2023, 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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* src/include/access/transam.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef TRANSAM_H
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#define TRANSAM_H
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#include "access/xlogdefs.h"
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/* ----------------
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* Special transaction ID values
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*
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* BootstrapTransactionId is the XID for "bootstrap" operations, and
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* FrozenTransactionId is used for very old tuples. Both should
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* always be considered valid.
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*
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* FirstNormalTransactionId is the first "normal" transaction id.
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* Note: if you need to change it, you must change pg_class.h as well.
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* ----------------
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*/
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#define InvalidTransactionId ((TransactionId) 0)
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#define BootstrapTransactionId ((TransactionId) 1)
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#define FrozenTransactionId ((TransactionId) 2)
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#define FirstNormalTransactionId ((TransactionId) 3)
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#define MaxTransactionId ((TransactionId) 0xFFFFFFFF)
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/* ----------------
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* transaction ID manipulation macros
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* ----------------
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*/
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#define TransactionIdIsValid(xid) ((xid) != InvalidTransactionId)
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#define TransactionIdIsNormal(xid) ((xid) >= FirstNormalTransactionId)
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#define TransactionIdEquals(id1, id2) ((id1) == (id2))
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#define TransactionIdStore(xid, dest) (*(dest) = (xid))
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#define StoreInvalidTransactionId(dest) (*(dest) = InvalidTransactionId)
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#define EpochFromFullTransactionId(x) ((uint32) ((x).value >> 32))
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#define XidFromFullTransactionId(x) ((uint32) (x).value)
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#define U64FromFullTransactionId(x) ((x).value)
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#define FullTransactionIdEquals(a, b) ((a).value == (b).value)
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#define FullTransactionIdPrecedes(a, b) ((a).value < (b).value)
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#define FullTransactionIdPrecedesOrEquals(a, b) ((a).value <= (b).value)
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#define FullTransactionIdFollows(a, b) ((a).value > (b).value)
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#define FullTransactionIdFollowsOrEquals(a, b) ((a).value >= (b).value)
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#define FullTransactionIdIsValid(x) TransactionIdIsValid(XidFromFullTransactionId(x))
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#define InvalidFullTransactionId FullTransactionIdFromEpochAndXid(0, InvalidTransactionId)
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#define FirstNormalFullTransactionId FullTransactionIdFromEpochAndXid(0, FirstNormalTransactionId)
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#define FullTransactionIdIsNormal(x) FullTransactionIdFollowsOrEquals(x, FirstNormalFullTransactionId)
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/*
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* A 64 bit value that contains an epoch and a TransactionId. This is
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* wrapped in a struct to prevent implicit conversion to/from TransactionId.
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* Not all values represent valid normal XIDs.
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*/
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typedef struct FullTransactionId
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{
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uint64 value;
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} FullTransactionId;
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static inline FullTransactionId
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FullTransactionIdFromEpochAndXid(uint32 epoch, TransactionId xid)
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{
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FullTransactionId result;
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result.value = ((uint64) epoch) << 32 | xid;
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return result;
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}
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static inline FullTransactionId
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FullTransactionIdFromU64(uint64 value)
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{
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FullTransactionId result;
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result.value = value;
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return result;
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}
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/* advance a transaction ID variable, handling wraparound correctly */
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#define TransactionIdAdvance(dest) \
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do { \
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(dest)++; \
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if ((dest) < FirstNormalTransactionId) \
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(dest) = FirstNormalTransactionId; \
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} while(0)
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/*
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* Retreat a FullTransactionId variable, stepping over xids that would appear
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* to be special only when viewed as 32bit XIDs.
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*/
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static inline void
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FullTransactionIdRetreat(FullTransactionId *dest)
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{
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dest->value--;
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/*
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* In contrast to 32bit XIDs don't step over the "actual" special xids.
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* For 64bit xids these can't be reached as part of a wraparound as they
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* can in the 32bit case.
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*/
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if (FullTransactionIdPrecedes(*dest, FirstNormalFullTransactionId))
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return;
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/*
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* But we do need to step over XIDs that'd appear special only for 32bit
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* XIDs.
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*/
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while (XidFromFullTransactionId(*dest) < FirstNormalTransactionId)
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dest->value--;
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}
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/*
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* Advance a FullTransactionId variable, stepping over xids that would appear
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* to be special only when viewed as 32bit XIDs.
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*/
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static inline void
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FullTransactionIdAdvance(FullTransactionId *dest)
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{
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dest->value++;
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/* see FullTransactionIdAdvance() */
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if (FullTransactionIdPrecedes(*dest, FirstNormalFullTransactionId))
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return;
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while (XidFromFullTransactionId(*dest) < FirstNormalTransactionId)
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dest->value++;
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}
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/* back up a transaction ID variable, handling wraparound correctly */
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#define TransactionIdRetreat(dest) \
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do { \
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(dest)--; \
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} while ((dest) < FirstNormalTransactionId)
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/* compare two XIDs already known to be normal; this is a macro for speed */
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#define NormalTransactionIdPrecedes(id1, id2) \
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(AssertMacro(TransactionIdIsNormal(id1) && TransactionIdIsNormal(id2)), \
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(int32) ((id1) - (id2)) < 0)
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/* compare two XIDs already known to be normal; this is a macro for speed */
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#define NormalTransactionIdFollows(id1, id2) \
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(AssertMacro(TransactionIdIsNormal(id1) && TransactionIdIsNormal(id2)), \
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(int32) ((id1) - (id2)) > 0)
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/* ----------
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* Object ID (OID) zero is InvalidOid.
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*
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* OIDs 1-9999 are reserved for manual assignment (see .dat files in
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* src/include/catalog/). Of these, 8000-9999 are reserved for
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* development purposes (such as in-progress patches and forks);
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* they should not appear in released versions.
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*
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* OIDs 10000-11999 are reserved for assignment by genbki.pl, for use
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* when the .dat files in src/include/catalog/ do not specify an OID
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* for a catalog entry that requires one. Note that genbki.pl assigns
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* these OIDs independently in each catalog, so they're not guaranteed
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* to be globally unique. Furthermore, the bootstrap backend and
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* initdb's post-bootstrap processing can also assign OIDs in this range.
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* The normal OID-generation logic takes care of any OID conflicts that
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* might arise from that.
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*
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* OIDs 12000-16383 are reserved for unpinned objects created by initdb's
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* post-bootstrap processing. initdb forces the OID generator up to
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* 12000 as soon as it's made the pinned objects it's responsible for.
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*
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* OIDs beginning at 16384 are assigned from the OID generator
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* during normal multiuser operation. (We force the generator up to
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* 16384 as soon as we are in normal operation.)
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*
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* The choices of 8000, 10000 and 12000 are completely arbitrary, and can be
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* moved if we run low on OIDs in any category. Changing the macros below,
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* and updating relevant documentation (see bki.sgml and RELEASE_CHANGES),
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* should be sufficient to do this. Moving the 16384 boundary between
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* initdb-assigned OIDs and user-defined objects would be substantially
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* more painful, however, since some user-defined OIDs will appear in
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* on-disk data; such a change would probably break pg_upgrade.
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*
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* NOTE: if the OID generator wraps around, we skip over OIDs 0-16383
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* and resume with 16384. This minimizes the odds of OID conflict, by not
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* reassigning OIDs that might have been assigned during initdb. Critically,
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* it also ensures that no user-created object will be considered pinned.
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* ----------
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*/
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#define FirstGenbkiObjectId 10000
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#define FirstUnpinnedObjectId 12000
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#define FirstNormalObjectId 16384
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/*
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* VariableCache is a data structure in shared memory that is used to track
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* OID and XID assignment state. For largely historical reasons, there is
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* just one struct with different fields that are protected by different
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* LWLocks.
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*
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* Note: xidWrapLimit and oldestXidDB are not "active" values, but are
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* used just to generate useful messages when xidWarnLimit or xidStopLimit
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* are exceeded.
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*/
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typedef struct VariableCacheData
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{
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/*
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* These fields are protected by OidGenLock.
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*/
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Oid nextOid; /* next OID to assign */
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uint32 oidCount; /* OIDs available before must do XLOG work */
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/*
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* These fields are protected by XidGenLock.
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*/
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FullTransactionId nextXid; /* next XID to assign */
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TransactionId oldestXid; /* cluster-wide minimum datfrozenxid */
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TransactionId xidVacLimit; /* start forcing autovacuums here */
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TransactionId xidWarnLimit; /* start complaining here */
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TransactionId xidStopLimit; /* refuse to advance nextXid beyond here */
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TransactionId xidWrapLimit; /* where the world ends */
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Oid oldestXidDB; /* database with minimum datfrozenxid */
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/*
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* These fields are protected by CommitTsLock
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*/
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TransactionId oldestCommitTsXid;
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TransactionId newestCommitTsXid;
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/*
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* These fields are protected by ProcArrayLock.
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*/
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FullTransactionId latestCompletedXid; /* newest full XID that has
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* committed or aborted */
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/*
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* Number of top-level transactions with xids (i.e. which may have
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* modified the database) that completed in some form since the start of
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* the server. This currently is solely used to check whether
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* GetSnapshotData() needs to recompute the contents of the snapshot, or
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* not. There are likely other users of this. Always above 1.
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*/
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uint64 xactCompletionCount;
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/*
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* These fields are protected by XactTruncationLock
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*/
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TransactionId oldestClogXid; /* oldest it's safe to look up in clog */
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} VariableCacheData;
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typedef VariableCacheData *VariableCache;
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/* ----------------
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* extern declarations
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* ----------------
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*/
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/* in transam/xact.c */
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extern bool TransactionStartedDuringRecovery(void);
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/* in transam/varsup.c */
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extern PGDLLIMPORT VariableCache ShmemVariableCache;
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/*
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* prototypes for functions in transam/transam.c
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*/
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extern bool TransactionIdDidCommit(TransactionId transactionId);
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extern bool TransactionIdDidAbort(TransactionId transactionId);
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extern void TransactionIdCommitTree(TransactionId xid, int nxids, TransactionId *xids);
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extern void TransactionIdAsyncCommitTree(TransactionId xid, int nxids, TransactionId *xids, XLogRecPtr lsn);
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extern void TransactionIdAbortTree(TransactionId xid, int nxids, TransactionId *xids);
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extern bool TransactionIdPrecedes(TransactionId id1, TransactionId id2);
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extern bool TransactionIdPrecedesOrEquals(TransactionId id1, TransactionId id2);
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extern bool TransactionIdFollows(TransactionId id1, TransactionId id2);
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extern bool TransactionIdFollowsOrEquals(TransactionId id1, TransactionId id2);
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extern TransactionId TransactionIdLatest(TransactionId mainxid,
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int nxids, const TransactionId *xids);
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extern XLogRecPtr TransactionIdGetCommitLSN(TransactionId xid);
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/* in transam/varsup.c */
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extern FullTransactionId GetNewTransactionId(bool isSubXact);
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extern void AdvanceNextFullTransactionIdPastXid(TransactionId xid);
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extern FullTransactionId ReadNextFullTransactionId(void);
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extern void SetTransactionIdLimit(TransactionId oldest_datfrozenxid,
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Oid oldest_datoid);
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extern void AdvanceOldestClogXid(TransactionId oldest_datfrozenxid);
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extern bool ForceTransactionIdLimitUpdate(void);
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extern Oid GetNewObjectId(void);
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extern void StopGeneratingPinnedObjectIds(void);
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#ifdef USE_ASSERT_CHECKING
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extern void AssertTransactionIdInAllowableRange(TransactionId xid);
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#else
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#define AssertTransactionIdInAllowableRange(xid) ((void)true)
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#endif
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/*
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* Some frontend programs include this header. For compilers that emit static
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* inline functions even when they're unused, that leads to unsatisfied
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* external references; hence hide them with #ifndef FRONTEND.
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*/
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#ifndef FRONTEND
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/*
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* For callers that just need the XID part of the next transaction ID.
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*/
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static inline TransactionId
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ReadNextTransactionId(void)
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{
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return XidFromFullTransactionId(ReadNextFullTransactionId());
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}
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/* return transaction ID backed up by amount, handling wraparound correctly */
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static inline TransactionId
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TransactionIdRetreatedBy(TransactionId xid, uint32 amount)
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{
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xid -= amount;
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while (xid < FirstNormalTransactionId)
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xid--;
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return xid;
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}
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/* return the older of the two IDs */
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static inline TransactionId
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TransactionIdOlder(TransactionId a, TransactionId b)
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{
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if (!TransactionIdIsValid(a))
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return b;
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if (!TransactionIdIsValid(b))
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return a;
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if (TransactionIdPrecedes(a, b))
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return a;
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return b;
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}
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/* return the older of the two IDs, assuming they're both normal */
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static inline TransactionId
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NormalTransactionIdOlder(TransactionId a, TransactionId b)
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{
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Assert(TransactionIdIsNormal(a));
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Assert(TransactionIdIsNormal(b));
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if (NormalTransactionIdPrecedes(a, b))
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return a;
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return b;
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}
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/* return the newer of the two IDs */
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static inline FullTransactionId
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FullTransactionIdNewer(FullTransactionId a, FullTransactionId b)
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{
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if (!FullTransactionIdIsValid(a))
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return b;
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if (!FullTransactionIdIsValid(b))
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return a;
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if (FullTransactionIdFollows(a, b))
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return a;
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return b;
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}
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#endif /* FRONTEND */
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#endif /* TRANSAM_H */
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