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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2010-07-29 19:24:05 +0000 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2010-07-29 19:24:05 +0000 |
| commit | 8e21bf52504616024618f3386dc68e8936405dc2 (patch) | |
| tree | 74c6f1582fbf5d956a43516b69c283208678d18b | |
| parent | 3137b496985b4e2242220bdabd4de86cf5c2d36e (diff) | |
| download | postgresql-8e21bf52504616024618f3386dc68e8936405dc2.tar.gz postgresql-8e21bf52504616024618f3386dc68e8936405dc2.zip | |
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.
| -rw-r--r-- | src/backend/commands/tablecmds.c | 17 |
1 files changed, 14 insertions, 3 deletions
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c index f82109bab35..bce8750d293 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 1.142.4.13 2010/07/29 16:15:47 rhaas Exp $ + * $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.142.4.14 2010/07/29 19:24:05 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -5729,11 +5729,11 @@ static void copy_relation_data(Relation rel, SMgrRelation dst) { SMgrRelation src; + char *buf; + Page page; bool use_wal; BlockNumber nblocks; BlockNumber blkno; - char buf[BLCKSZ]; - Page page = (Page) buf; /* * Since we copy the data directly without looking at the shared @@ -5745,6 +5745,15 @@ copy_relation_data(Relation rel, SMgrRelation dst) FlushRelationBuffers(rel, 0); /* + * 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 PageSetLSN fail. + */ + buf = (char *) palloc(BLCKSZ); + page = (Page) buf; + + /* * We need to log the copied data in WAL iff WAL archiving is enabled * AND it's not a temp rel. */ @@ -5807,6 +5816,8 @@ copy_relation_data(Relation rel, SMgrRelation dst) smgrwrite(dst, 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 |