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Fix core dump in ReorderBufferRestoreChange on alignment-picky platforms.
When re-reading an update involving both an old tuple and a new tuple from disk, reorderbuffer.c was careless about whether the new tuple is suitably aligned for direct access --- in general, it isn't. We'd missed seeing this in the buildfarm because the contrib/test_decoding tests exercise this code path only a few times, and by chance all of those cases have old tuples with length a multiple of 4, which is usually enough to make the access to the new tuple's t_len safe. For some still-not-entirely-clear reason, however, Debian's sparc build gets a bus error, as reported by Christoph Berg; perhaps it's assuming 8-byte alignment of the pointer? The lack of previous field reports is probably because you need all of these conditions to trigger a crash: an alignment-picky platform (not Intel), a transaction large enough to spill to disk, an update within that xact that changes a primary-key field and has an odd-length old tuple, and of course logical decoding tracing the transaction. Avoid the alignment assumption by using memcpy instead of fetching t_len directly, and add a test case that exposes the crash on picky platforms. Back-patch to 9.4 where the bug was introduced. Discussion: <20160413094117.GC21485@msg.credativ.de>
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@ -233,6 +233,8 @@ SELECT 'tx logical msg' FROM pg_logical_emit_message(true, 'test', 'tx logical m
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DELETE FROM tr_etoomuch WHERE id < 5000;
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UPDATE tr_etoomuch SET data = - data WHERE id > 5000;
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CREATE TABLE tr_oddlength (id text primary key, data text);
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INSERT INTO tr_oddlength VALUES('ab', 'foo');
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COMMIT;
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/* display results, but hide most of the output */
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SELECT count(*), min(data), max(data)
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@ -244,13 +246,16 @@ ORDER BY 1,2;
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1 | BEGIN | BEGIN
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1 | COMMIT | COMMIT
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1 | message: transactional: 1 prefix: test, sz: 14 content:tx logical msg | message: transactional: 1 prefix: test, sz: 14 content:tx logical msg
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1 | table public.tr_oddlength: INSERT: id[text]:'ab' data[text]:'foo' | table public.tr_oddlength: INSERT: id[text]:'ab' data[text]:'foo'
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20467 | table public.tr_etoomuch: DELETE: id[integer]:1 | table public.tr_etoomuch: UPDATE: id[integer]:9999 data[integer]:-9999
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(4 rows)
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(5 rows)
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-- check updates of primary keys work correctly
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BEGIN;
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CREATE TABLE spoolme AS SELECT g.i FROM generate_series(1, 5000) g(i);
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UPDATE tr_etoomuch SET id = -id WHERE id = 5000;
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UPDATE tr_oddlength SET id = 'x', data = 'quux';
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UPDATE tr_oddlength SET id = 'yy', data = 'a';
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DELETE FROM spoolme;
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DROP TABLE spoolme;
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COMMIT;
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@ -260,7 +265,9 @@ WHERE data ~ 'UPDATE';
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data
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-------------------------------------------------------------------------------------------------------------
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table public.tr_etoomuch: UPDATE: old-key: id[integer]:5000 new-tuple: id[integer]:-5000 data[integer]:5000
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(1 row)
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table public.tr_oddlength: UPDATE: old-key: id[text]:'ab' new-tuple: id[text]:'x' data[text]:'quux'
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table public.tr_oddlength: UPDATE: old-key: id[text]:'x' new-tuple: id[text]:'yy' data[text]:'a'
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(3 rows)
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-- check that a large, spooled, upsert works
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INSERT INTO tr_etoomuch (id, data)
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