On Mon, Feb 27, 2017 at 7:28 PM, Thomas Munro <thomas.mu...@enterprisedb.com> wrote: > On Wed, Nov 9, 2016 at 11:07 AM, Thomas Munro > <thomas.mu...@enterprisedb.com> wrote: >> The SLRU managed by predicate.c can wrap around and overwrite data if >> you have more than 1 billion active XIDs. That's because when SSI was >> implemented, slru.c was limited to four digit segment names, which >> implied a page limit that wasn't enough for pg_serial to have space >> for every possible XID. We should probably rip that code out, because >> SLRUs now support five digit segment names. Something like the >> attached. I'll post a test script to demonstrate correct wraparound >> behaviour around in time for one of the later CFs. > > Here is a shell script that shows a full rotation through xid space if > you build PostgreSQL with TEST_OLDSERXID, which you can do by > uncommenting a line in predicate.c. On master we see the SLRU > segments go around the clock twice for each time xid goes around. > With the patch it goes around just once, adding an extra character to > the segment name to double the space.
I attached the wrong version. Here is the right one. -- Thomas Munro http://www.enterprisedb.com
ssi-slru-wraparound-test.sh
Description: Bourne shell script
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