Adjust PageGetMaxOffsetNumber to ensure sane behavior on uninitialized
pages, even when the macro's result is stored into an unsigned variable.
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@ -7,7 +7,7 @@
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* Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
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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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* Portions Copyright (c) 1994, Regents of the University of California
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*
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*
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* $PostgreSQL: pgsql/src/include/storage/bufpage.h,v 1.57 2003/12/11 21:21:55 tgl Exp $
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* $PostgreSQL: pgsql/src/include/storage/bufpage.h,v 1.58 2004/06/05 17:42:46 tgl Exp $
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*
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*
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*-------------------------------------------------------------------------
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*-------------------------------------------------------------------------
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*/
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*/
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@ -283,13 +283,14 @@ typedef PageHeaderData *PageHeader;
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* Since offset numbers are 1-based, this is also the number
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* Since offset numbers are 1-based, this is also the number
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* of items on the page.
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* of items on the page.
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*
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*
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* NOTE: to ensure sane behavior if the page is not initialized
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* NOTE: if the page is not initialized (pd_lower == 0), we must
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* (pd_lower == 0), cast the unsigned values to int before dividing.
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* return zero to ensure sane behavior. Accept double evaluation
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* That way we get -1 or so, not a huge positive number...
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* of the argument so that we can ensure this.
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*/
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*/
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#define PageGetMaxOffsetNumber(page) \
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#define PageGetMaxOffsetNumber(page) \
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(((int) (((PageHeader) (page))->pd_lower - SizeOfPageHeaderData)) \
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(((PageHeader) (page))->pd_lower <= SizeOfPageHeaderData ? 0 : \
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/ ((int) sizeof(ItemIdData)))
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((((PageHeader) (page))->pd_lower - SizeOfPageHeaderData) \
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/ sizeof(ItemIdData)))
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#define PageGetLSN(page) \
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#define PageGetLSN(page) \
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(((PageHeader) (page))->pd_lsn)
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(((PageHeader) (page))->pd_lsn)
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