Unreproducible bug in snapshot import code

Hi All,

    I have not been able to reproduce this error, but wanted to report this in case it might be useful.

    Commit -id: 0f39d5050dc0dce99258381f33f1832c437aff85

    Configure options:
    --prefix=/mnt/storage/gurjeet/dev/builds//master/db --enable-debug --enable-cassert CFLAGS=-O0 --enable-depend --enable-thread-safety --with-openssl

    Used VPATH to build postgres.

    Attached files: terminal1.txt termonal2.txt config.log

    Starting from line 89 of terminal1.txt we see this snippet:

postgres=# rollback;
ROLLBACK
postgres=# begin TRANSACTION ;
BEGIN
postgres=# set transaction snapshot '000002C8-1';
ERROR:  SET TRANSACTION SNAPSHOT must be called before any query
postgres=# rollback;
ROLLBACK


    As you can see the SET TRANSACTION SNAPSHOT was the first statement in that transaction, and yet the ERROR message says that it is not. That snapshot id was generated in another session (terminal2.txt), and was generated outside any transaction; that's the only peculiar thing I can say about that snapshot-id.

    As is evident from the rest of the lines in terminal1.txt, I have not been able to reproduce this error again; I tried even with a clean build of the sources.

    I have taken a look at the code and everything tells me that the error should have been:

ERROR:  a snapshot-importing transaction must have isolation level SERIALIZABLE or REPEATABLE READ

    Maybe it was not a clean build the first time, and the code may have wrongly linked with previously compiled .o files.

Regards,
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