On 11/17/2014 10:37 AM, Andres Freund wrote:
On 2014-11-13 22:23:02 -0500, Steve Singer wrote:Also since updating (to 2c267e47afa4f9a7c) I've seen a assertion failure in a normal client connection, not the walsender #3 0x00000000006b4978 in GetSerializableTransactionSnapshotInt ( snapshot=snapshot@entry=0xbfa8a0 <CurrentSnapshotData>, sourcexid=sourcexid@entry=0) at predicate.c:1738 #4 0x00000000006b66c3 in GetSafeSnapshot (origSnapshot=<optimized out>) at predicate.c:1517 #5 GetSerializableTransactionSnapshot ( snapshot=0xbfa8a0 <CurrentSnapshotData>) at predicate.c:1598 #6 0x00000000007d16dd in GetTransactionSnapshot () at snapmgr.c:200 #7 0x00000000006c0e35 in exec_simple_query ( query_string=0x1fd01b8 "select ev_origin, ev_seqno, ev_timestamp, ev_snapshot, \"pg_catalog\".txid_snapshot_xmin(ev_snapshot), \"pg_catalog\".txid_snapshot_xmax(ev_snapshot), coalesce(ev_provider_xid,\""...) at postgres.c:959 #8 PostgresMain (argc=<optimized out>, argv=argv@entry=0x1f5ab50, I have no idea if this has anything to do with your recent changes or some other change. I haven't so far been able to replicate that since the first time I saw it. That crash is decidedly odd. Any chance you still have the full backtrace around?
Yes I still have the core file
This is in the SSI code... I'm not immediately seeing how this could be related to logical decoding. It can't even be a imported snapshot, because the exported snapshot is marked repeatable read. Are you actually using serializable transactions? If so, how and why?
Yes, the test client that performs the 'simulated workload' does some serializable transactions. It connects as a normal client via JDBC and does a prepareStatement("SET TRANSACTION ISOLATION LEVEL SERIALIZABLE") and then does some DML. Why? because it seemed like a good thing to include in the test suite.
Your right this might have nothing to do with logical decoding. I haven't been able to reproduce again either, I can't even say if this problem was introduced to 9.4 in the past month or if it has been around much longer and I just haven't hit it before.
Greetings, Andres Freund
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