The ECPG and main 2PC tests have been using rather-generic names for the
prepared transactions they generate. This commit switches the 2PC
transactions to use more complex GIDs, reducing the risk of naming
conflicts.
The main 2PC tests also include scans of pg_prepared_xacts that do not
apply filters on the GID of the prepared transactions, making it
possible to fail the test when any 2PC transaction runs concurrently.
The CI has been able to see such failures with an installcheck
running the ECPG and the main regression test suites in parallel. The
queries on pg_prepared_xacts gain quals to only look after the GIDs
generated locally.
The race is very hard to reproduce, so no backbatch is done for now.
Reported-by: Richard Guo
Discussion: https://postgr.es/m/CAMbWs4-mWCGbbE_bne5=AfqjYGDaUZmjCw2+soLjrdNA0xUDFw@mail.gmail.com
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