diff options
Diffstat (limited to 'contrib/pageinspect/rawpage.c')
| -rw-r--r-- | contrib/pageinspect/rawpage.c | 38 |
1 files changed, 38 insertions, 0 deletions
diff --git a/contrib/pageinspect/rawpage.c b/contrib/pageinspect/rawpage.c index a2ac078d404..102f360c6f7 100644 --- a/contrib/pageinspect/rawpage.c +++ b/contrib/pageinspect/rawpage.c @@ -15,6 +15,8 @@ #include "postgres.h" +#include "pageinspect.h" + #include "access/htup_details.h" #include "catalog/catalog.h" #include "catalog/namespace.h" @@ -158,6 +160,42 @@ get_raw_page_internal(text *relname, ForkNumber forknum, BlockNumber blkno) return raw_page; } + +/* + * get_page_from_raw + * + * Get a palloc'd, maxalign'ed page image from the result of get_raw_page() + * + * On machines with MAXALIGN = 8, the payload of a bytea is not maxaligned, + * since it will start 4 bytes into a palloc'd value. On alignment-picky + * machines, this will cause failures in accesses to 8-byte-wide values + * within the page. We don't need to worry if accessing only 4-byte or + * smaller fields, but when examining a struct that contains 8-byte fields, + * use this function for safety. + */ +Page +get_page_from_raw(bytea *raw_page) +{ + Page page; + int raw_page_size; + + raw_page_size = VARSIZE(raw_page) - VARHDRSZ; + + if (raw_page_size != BLCKSZ) + ereport(ERROR, + (errcode(ERRCODE_INVALID_PARAMETER_VALUE), + errmsg("invalid page size"), + errdetail("Expected %d bytes, got %d.", + BLCKSZ, raw_page_size))); + + page = palloc(raw_page_size); + + memcpy(page, VARDATA(raw_page), raw_page_size); + + return page; +} + + /* * page_header * |