diff options
Diffstat (limited to 'src/include/storage/bufpage.h')
| -rw-r--r-- | src/include/storage/bufpage.h | 60 |
1 files changed, 46 insertions, 14 deletions
diff --git a/src/include/storage/bufpage.h b/src/include/storage/bufpage.h index a9fc0f7a2a2..7a6080a1bcd 100644 --- a/src/include/storage/bufpage.h +++ b/src/include/storage/bufpage.h @@ -7,7 +7,7 @@ * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * - * $Id: bufpage.h,v 1.51 2002/08/06 19:37:10 tgl Exp $ + * $Id: bufpage.h,v 1.52 2002/09/02 01:05:06 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -97,12 +97,20 @@ typedef uint16 LocationIndex; * pd_lower - offset to start of free space. * pd_upper - offset to end of free space. * pd_special - offset to start of special space. - * pd_pagesize - size in bytes. - * Minimum possible page size is perhaps 64B to fit - * page header, opaque space and a minimal tuple; - * of course, in reality you want it much bigger. - * On the high end, we can only support pages up - * to 32KB because lp_off/lp_len are 15 bits. + * pd_pagesize_version - size in bytes and page layout version number. + * + * The page version number and page size are packed together into a single + * uint16 field. This is for historical reasons: before PostgreSQL 7.3, + * there was no concept of a page version number, and doing it this way + * lets us pretend that pre-7.3 databases have page version number zero. + * We constrain page sizes to be multiples of 256, leaving the low eight + * bytes available for a version number. + * + * Minimum possible page size is perhaps 64B to fit page header, opaque space + * and a minimal tuple; of course, in reality you want it much bigger, so + * the constraint on pagesize mod 256 is not an important restriction. + * On the high end, we can only support pages up to 32KB because lp_off/lp_len + * are 15 bits. */ typedef struct PageHeaderData { @@ -116,12 +124,18 @@ typedef struct PageHeaderData LocationIndex pd_lower; /* offset to start of free space */ LocationIndex pd_upper; /* offset to end of free space */ LocationIndex pd_special; /* offset to start of special space */ - uint16 pd_pagesize; + uint16 pd_pagesize_version; ItemIdData pd_linp[1]; /* beginning of line pointer array */ } PageHeaderData; typedef PageHeaderData *PageHeader; +/* + * Page layout version number 0 is for pre-7.3 Postgres releases. The + * current version number is 1, denoting a new HeapTupleHeader layout. + */ +#define PG_PAGE_LAYOUT_VERSION 1 + /* ---------------------------------------------------------------- * page support macros @@ -178,7 +192,7 @@ typedef PageHeaderData *PageHeader; ((char *) (&((PageHeader) (page))->pd_linp[0])) /* ---------------- - * macros to access opaque space + * macros to access page size info * ---------------- */ @@ -203,14 +217,32 @@ typedef PageHeaderData *PageHeader; * however, it can be called on a page for which there is no buffer. */ #define PageGetPageSize(page) \ - ((Size) ((PageHeader) (page))->pd_pagesize) + ((Size) (((PageHeader) (page))->pd_pagesize_version & (uint16) 0xFF00)) /* - * PageSetPageSize - * Sets the page size of a page. + * PageGetPageLayoutVersion + * Returns the page layout version of a page. + * + * this can only be called on a formatted page (unlike + * BufferGetPageSize, which can be called on an unformatted page). + * however, it can be called on a page for which there is no buffer. */ -#define PageSetPageSize(page, size) \ - (((PageHeader) (page))->pd_pagesize = (size)) +#define PageGetPageLayoutVersion(page) \ + (((PageHeader) (page))->pd_pagesize_version & 0x00FF) + +/* + * PageSetPageSizeAndVersion + * Sets the page size and page layout version number of a page. + * + * We could support setting these two values separately, but there's + * no real need for it at the moment. + */ +#define PageSetPageSizeAndVersion(page, size, version) \ +( \ + AssertMacro(((size) & 0xFF00) == (size)), \ + AssertMacro(((version) & 0x00FF) == (version)), \ + ((PageHeader) (page))->pd_pagesize_version = (size) | (version) \ +) /* ---------------- * page special data macros |