On Thu, Jun 24, 2021 at 7:27 AM David Rowley <dgrowle...@gmail.com> wrote: > On Wed, 23 Jun 2021 at 21:07, Amit Kapila <amit.kapil...@gmail.com> wrote: > > I noticed that while inserting directly into a partition table we > > compute the PartitionCheckExpr by traversing all the parent partitions > > via > > ExecPartitionCheck()->RelationGetPartitionQual()->generate_partition_qual(). > > We take AccessShareLock on parent tables while generating qual. > > > > Now, on the other hand, while dropping constraint on a partitioned > > table, we take the lock from parent to all the child tables. > > > > I think taking locks in opposite directions can lead to deadlock in > > these operations. > > I wonder if it's possible to do any better here? Surely when > traversing from child to parent we must lock the child before checking > what the parent relation is.
I remember there was a discussion where I proposed to document the deadlock hazard that exists when performing DML directly on partitions. The proposal didn't get enough attention, perhaps because it was in the middle of a long reply about other concerns: https://www.postgresql.org/message-id/16db1458-67cf-4add-736e-31b053115e8e%40lab.ntt.co.jp Maybe a good idea to add a line or 2 in 5.11. Table Partitioning? -- Amit Langote EDB: http://www.enterprisedb.com