diff options
Diffstat (limited to 'src/include/storage/bufpage.h')
| -rw-r--r-- | src/include/storage/bufpage.h | 30 |
1 files changed, 18 insertions, 12 deletions
diff --git a/src/include/storage/bufpage.h b/src/include/storage/bufpage.h index 727ec508a3b..21148c9937b 100644 --- a/src/include/storage/bufpage.h +++ b/src/include/storage/bufpage.h @@ -7,7 +7,7 @@ * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * - * $PostgreSQL: pgsql/src/include/storage/bufpage.h,v 1.59 2004/07/01 00:51:43 tgl Exp $ + * $PostgreSQL: pgsql/src/include/storage/bufpage.h,v 1.60 2004/07/21 22:31:26 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -87,13 +87,22 @@ typedef uint16 LocationIndex; /* * disk page organization + * * space management information generic to any page * + * pd_lsn - identifies xlog record for last change to this page. + * pd_tli - ditto. * 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_version - size in bytes and page layout version number. * + * The LSN is used by the buffer manager to enforce the basic rule of WAL: + * "thou shalt write xlog before data". A dirty buffer cannot be dumped + * to disk until xlog has been flushed at least as far as the page's LSN. + * We also store the TLI for identification purposes (it is not clear that + * this is actually necessary, but it seems like a good idea). + * * 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 @@ -109,13 +118,10 @@ typedef uint16 LocationIndex; */ typedef struct PageHeaderData { - /* XXX LSN is member of *any* block, not */ - /* only page-organized - 'll change later */ - XLogRecPtr pd_lsn; /* LSN: next byte after last byte of xlog */ - /* record for last change of this page */ - StartUpID pd_sui; /* SUI of last changes (currently it's */ - /* used by heap AM only) */ - + /* XXX LSN is member of *any* block, not only page-organized ones */ + XLogRecPtr pd_lsn; /* LSN: next byte after last byte of xlog + * record for last change to this page */ + TimeLineID pd_tli; /* TLI of last change */ 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 */ @@ -298,10 +304,10 @@ typedef PageHeaderData *PageHeader; #define PageSetLSN(page, lsn) \ (((PageHeader) (page))->pd_lsn = (lsn)) -#define PageGetSUI(page) \ - (((PageHeader) (page))->pd_sui) -#define PageSetSUI(page, sui) \ - (((PageHeader) (page))->pd_sui = (StartUpID) (sui)) +#define PageGetTLI(page) \ + (((PageHeader) (page))->pd_tli) +#define PageSetTLI(page, tli) \ + (((PageHeader) (page))->pd_tli = (tli)) /* ---------------------------------------------------------------- * extern declarations |