From d9321d75a48ac8b817fa469f064c76ce54b84919 Mon Sep 17 00:00:00 2001 From: Andres Freund Date: Tue, 15 Dec 2015 19:03:10 +0100 Subject: [PATCH 2/2] Faster PageIsVerified() for the all zeroes case. That's primarily useful for testing the handling of very large relations, using sparse files. --- src/backend/storage/page/bufpage.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) diff --git a/src/backend/storage/page/bufpage.c b/src/backend/storage/page/bufpage.c index f2a07f2..1b70bfb 100644 --- a/src/backend/storage/page/bufpage.c +++ b/src/backend/storage/page/bufpage.c @@ -81,7 +81,7 @@ bool PageIsVerified(Page page, BlockNumber blkno) { PageHeader p = (PageHeader) page; - char *pagebytes; + size_t *pagebytes; int i; bool checksum_failure = false; bool header_sane = false; @@ -118,10 +118,17 @@ PageIsVerified(Page page, BlockNumber blkno) return true; } - /* Check all-zeroes case */ + /* + * Check all-zeroes case. Luckily BLCKSZ is guaranteed to always be a + * multiple of size_t - and it's much faster to compare memory using the + * native word size. + */ + StaticAssertStmt(BLCKSZ == (BLCKSZ / sizeof(size_t)) * sizeof(size_t), + "BLCKSZ has to be a multiple of sizeof(size_t)"); + all_zeroes = true; - pagebytes = (char *) page; - for (i = 0; i < BLCKSZ; i++) + pagebytes = (size_t *) page; + for (i = 0; i < (BLCKSZ / sizeof(size_t)); i++) { if (pagebytes[i] != 0) { -- 2.8.1