Hi! On Mon, 11 Aug 2025 at 09:46, Amit Kapila <amit.kapil...@gmail.com> wrote: > > Hi, > > Background and Motivation > ------------------------------------- > In high-throughput systems, where hundreds of sessions generate data > on the publisher, the subscriber's apply process often becomes a > bottleneck due to the single apply worker model. While users can > mitigate this by creating multiple publication-subscription pairs, > this approach has scalability and usability limitations. > > Currently, PostgreSQL supports parallel apply only for large streaming > transactions (streaming=parallel). This proposal aims to extend > parallelism to non-streaming transactions, thereby improving > replication performance in workloads dominated by smaller, frequent > transactions.
Sure. > Design Overview > ------------------------ > To safely parallelize non-streaming transactions, we must ensure that > transaction dependencies are respected to avoid failures and > deadlocks. Consider the following scenarios to understand it better: > (a) Transaction failures: Say, if we insert a row in the first > transaction and update it in the second transaction on the publisher, > then allowing the subscriber to apply both in parallel can lead to > failure in the update; (b) Deadlocks - allowing transactions that > update the same set of rows in a table in the opposite order in > parallel can lead to deadlocks. > Build-in subsystem for transaction dependency tracking would be highly beneficial for physical replication speedup projects like[0] > > Thoughts? Surely we need to give it a try. [0] https://github.com/koichi-szk/postgres -- Best regards, Kirill Reshke
