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66 lines
1.6 KiB
C
66 lines
1.6 KiB
C
/*-------------------------------------------------------------------------
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*
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* pos.h
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* POSTGRES "position" definitions.
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*
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*
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* Portions Copyright (c) 1996-2003, 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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* $Id: pos.h,v 1.15 2003/08/04 02:40:15 momjian Exp $
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef POS_H
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#define POS_H
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#include "storage/off.h"
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/*
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* a 'position' used to be <pagenumber, offset> in postgres. this has
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* been changed to just <offset> as the notion of having multiple pages
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* within a block has been removed.
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*
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* the 'offset' abstraction is somewhat confusing. it is NOT a byte
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* offset within the page; instead, it is an offset into the line
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* pointer array contained on every page that store (heap or index)
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* tuples.
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*/
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typedef bits16 PositionIdData;
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typedef PositionIdData *PositionId;
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/* ----------------
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* support macros
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* ----------------
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*/
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/*
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* PositionIdIsValid
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* True iff the position identifier is valid.
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*/
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#define PositionIdIsValid(positionId) \
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PointerIsValid(positionId)
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/*
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* PositionIdSetInvalid
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* Make an invalid position.
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*/
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#define PositionIdSetInvalid(positionId) \
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*(positionId) = (bits16) 0
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/*
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* PositionIdSet
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* Sets a position identifier to the specified value.
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*/
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#define PositionIdSet(positionId, offsetNumber) \
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*(positionId) = (offsetNumber)
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/*
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* PositionIdGetOffsetNumber
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* Retrieve the offset number from a position identifier.
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*/
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#define PositionIdGetOffsetNumber(positionId) \
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((OffsetNumber) *(positionId))
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#endif /* POS_H */
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