On Sun, Feb 1, 2015 at 03:54:03PM +0100, Álvaro Hernández Tortosa wrote: > > On 31/01/15 14:55, Roger Pack wrote: > >[...] > > > >Now, the reality is that GetNewOidWithIndex() is going to keep > >incrementing the global OID counter until it finds an OID that isn't in > >the toast table. That means that if you actually get anywhere close to > >using 4B OIDs you're going to become extremely unhappy with the > >performance of toasting new data. > >OK so "system stability" doesn't degrade per se when it wraps [since > >they all use that GetNewOid method or similar [?] good to know. > > > >So basically when it gets near 4B TOAST'ed rows it may have to wrap that > >counter and search for "unused" number, and for each number it's > >querying the TOAST table to see if it's already used, degrading > >performance. > > > The problem here is that performance degrades exponentially, or > worse. Speaking here from experience, we already tested this for a > very similar case (table creation, where two oids are consumed from > a global sequence when inserting to pg_class). Have a look at > http://www.slideshare.net/nosys/billion-tables-project-nycpug-2013, > slides 43-45. We tested there this scenario and shown that table > creations per second dropped from 10K to a few per second and then > to a few per day. In the graphs you can't even realize there were > more tables been created. At around 8K tables from the theoretical > limit of 4B oids consumed, the process basically stopped (doing more > insertions).
I had a look at our FAQ about Postgres limitations and I don't see anything that needs changing: https://wiki.postgresql.org/wiki/FAQ#What_is_the_maximum_size_for_a_row.2C_a_table.2C_and_a_database.3F Maximum size for a database? unlimited (32 TB databases exist) Maximum size for a table? 32 TB Maximum size for a row? 400 GB Maximum size for a field? 1 GB Maximum number of rows in a table? unlimited Maximum number of columns in a table? 250-1600 depending on column types Maximum number of indexes on a table? unlimited We don't report the maximum number of tables per database, or the maximum number of TOAST values. Agreed? -- Bruce Momjian <br...@momjian.us> http://momjian.us EnterpriseDB http://enterprisedb.com + Everyone has their own god. + -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers