From 984d56b80f5a945db2bfa80499b5ed913848242b Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Thu, 29 Jul 2010 19:23:20 +0000 Subject: [PATCH] Fix another longstanding problem in copy_relation_data: it was blithely assuming that a local char[] array would be aligned on at least a word boundary. There are architectures on which that is pretty much guaranteed to NOT be the case ... and those arches also don't like non-aligned memory accesses, meaning that log_newpage() would crash if it ever got invoked. Even on Intel-ish machines there's a potential for a large performance penalty from doing I/O to an inadequately aligned buffer. So palloc it instead. Backpatch to 8.0 --- 7.4 doesn't have this code. --- src/backend/commands/tablecmds.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-) diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c index 431b06568b..b16232a0b5 100644 --- a/src/backend/commands/tablecmds.c +++ b/src/backend/commands/tablecmds.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.336 2010/07/29 11:06:34 sriggs Exp $ + * $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.337 2010/07/29 19:23:20 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -7230,11 +7230,20 @@ static void copy_relation_data(SMgrRelation src, SMgrRelation dst, ForkNumber forkNum, bool istemp) { + char *buf; + Page page; bool use_wal; BlockNumber nblocks; BlockNumber blkno; - char buf[BLCKSZ]; - Page page = (Page) buf; + + /* + * palloc the buffer so that it's MAXALIGN'd. If it were just a local + * char[] array, the compiler might align it on any byte boundary, which + * can seriously hurt transfer speed to and from the kernel; not to + * mention possibly making log_newpage's accesses to the page header fail. + */ + buf = (char *) palloc(BLCKSZ); + page = (Page) buf; /* * We need to log the copied data in WAL iff WAL archiving/streaming is @@ -7263,6 +7272,8 @@ copy_relation_data(SMgrRelation src, SMgrRelation dst, smgrextend(dst, forkNum, blkno, buf, true); } + pfree(buf); + /* * If the rel isn't temp, we must fsync it down to disk before it's safe * to commit the transaction. (For a temp rel we don't care since the rel