On Wed, Aug 31, 2016 at 1:05 PM, Amit Langote <langote_amit...@lab.ntt.co.jp> wrote: >> However, it seems a lot better to make it a property of the parent >> from a performance point of view. Suppose there are 1000 partitions. >> Reading one toasted value for pg_class and running stringToNode() on >> it is probably a lot faster than scanning pg_inherits to find all of >> the child partitions and then doing an index scan to find the pg_class >> tuple for each and then decoding all of those tuples and assembling >> them into some data structure. > > Seems worth trying. One point that bothers me a bit is how do we enforce > partition bound condition on individual partition basis. For example when > a row is inserted into a partition directly, we better check that it does > not fall outside the bounds and issue an error otherwise. With current > approach, we just look up a partition's bound from the catalog and gin up > a check constraint expression (and cache in relcache) to be enforced in > ExecConstraints(). With the new approach, I guess we would need to look > up the parent's partition descriptor. Note that the checking in > ExecConstraints() is turned off when routing a tuple from the parent.
[ Sorry for the slow response. ] Yeah, that's a problem. Maybe it's best to associate this data with the childrels after all - or halfway in between, e.g. augment pg_inherits with this information. After all, the performance problem I was worried about above isn't really much of an issue: each backend will build a relcache entry for the parent just once and then use it for the lifetime of the session unless some invalidation occurs. So if that takes a small amount of extra time, it's probably not really a big deal. On the other hand, if we can't build the implicit constraint for the child table without opening the parent, that's probably going to cause us some serious inconvenience. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (email@example.com) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers