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.
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@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.142.4.13 2010/07/29 16:15:47 rhaas Exp $
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* $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.142.4.14 2010/07/29 19:24:05 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -5729,11 +5729,11 @@ static void
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copy_relation_data(Relation rel, SMgrRelation dst)
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{
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SMgrRelation src;
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char *buf;
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Page page;
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bool use_wal;
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BlockNumber nblocks;
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BlockNumber blkno;
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char buf[BLCKSZ];
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Page page = (Page) buf;
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/*
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* Since we copy the data directly without looking at the shared
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@ -5744,6 +5744,15 @@ copy_relation_data(Relation rel, SMgrRelation dst)
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*/
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FlushRelationBuffers(rel, 0);
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/*
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* palloc the buffer so that it's MAXALIGN'd. If it were just a local
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* char[] array, the compiler might align it on any byte boundary, which
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* can seriously hurt transfer speed to and from the kernel; not to
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* mention possibly making PageSetLSN fail.
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*/
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buf = (char *) palloc(BLCKSZ);
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page = (Page) buf;
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/*
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* We need to log the copied data in WAL iff WAL archiving is enabled
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* AND it's not a temp rel.
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@ -5807,6 +5816,8 @@ copy_relation_data(Relation rel, SMgrRelation dst)
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smgrwrite(dst, blkno, buf, true);
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}
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pfree(buf);
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/*
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* If the rel isn't temp, we must fsync it down to disk before it's
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* safe to commit the transaction. (For a temp rel we don't care
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