Re: pg_serial early wraparound

From: Anastasia Lubennikova <lubennikovaav(at)gmail(dot)com>
To: pgsql-hackers(at)postgresql(dot)org
Cc: Thomas Munro <munro(at)ip9(dot)org>
Subject: Re: pg_serial early wraparound
Date: 2017-03-24 14:11:22
Message-ID: 20170324141122.22419.63945.pgcf@coridan.postgresql.org
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The following review has been posted through the commitfest application:
make installcheck-world: not tested
Implements feature: not tested
Spec compliant: not tested
Documentation: not tested

Hi, I've tried to review this patch, but it seems that I miss something essential.
You claim that SLRUs now support five digit segment name, while in slru.h
at current master I see the following:

* Note: slru.c currently assumes that segment file names will be four hex
* digits. This sets a lower bound on the segment size (64K transactions
* for 32-bit TransactionIds).
*/
#define SLRU_PAGES_PER_SEGMENT 32

/* Maximum length of an SLRU name */
#define SLRU_MAX_NAME_LENGTH 32

Could you please clarify the idea of the patch? Is it still relevant?

I've also run your test script.
pg_clog was renamed to pg_xact, so it need to be changed accordingly
echo "Contents of pg_clog:"
ls $PGDATA/pg_xact/

The test shows failed assertion:

========== setting next xid to 1073741824 =========
Transaction log reset
waiting for server to start....2017-03-24 17:05:19.897 MSK [1181] LOG: listening on IPv4 address "127.0.0.1", port 5432
2017-03-24 17:05:19.981 MSK [1181] LOG: listening on Unix socket "/tmp/.s.PGSQL.5432"
2017-03-24 17:05:20.081 MSK [1183] LOG: database system was shut down at 2017-03-24 17:05:19 MSK
2017-03-24 17:05:20.221 MSK [1181] LOG: database system is ready to accept connections
done
server started
vacuumdb: vacuuming database "postgres"
vacuumdb: vacuuming database "template0"
vacuumdb: vacuuming database "template1"
TRAP: FailedAssertion("!(TransactionIdPrecedesOrEquals(oldestXact, ShmemVariableCache->oldestXid))", File: "clog.c", Line: 669)
vacuumdb: vacuuming of database "template1" failed: server closed the connection unexpectedly
This probably means the server terminated abnormally
before or while processing the request.
2017-03-24 17:05:21.541 MSK [1181] LOG: server process (PID 1202) was terminated by signal 6: Aborted
2017-03-24 17:05:21.541 MSK [1181] DETAIL: Failed process was running: VACUUM (FREEZE);

The new status of this patch is: Waiting on Author

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