Hi Alvaro, > From: Alvaro Herrera <alvhe...@alvh.no-ip.org> > Subject: RE: [EXTERNAL]Initial Schema Sync for Logical Replication > On 2023-Mar-15, Kumar, Sachin wrote: > > > 1. In CreateSubscription() when we create replication > > slot(walrcv_create_slot()), should use CRS_EXPORT_SNAPSHOT, So that we > can use this snapshot later in the pg_dump. > > > > 2. Now we can call pg_dump with above snapshot from CreateSubscription. > > Overall I'm not on board with the idea that logical replication would depend > on > pg_dump; that seems like it could run into all sorts of trouble (what if > calling > external binaries requires additional security setup? what about pg_hba > connection requirements? what about max_connections in tight > circumstances?). > what if calling external binaries requires additional security setup I am not sure what kind of security restriction would apply in this case, maybe pg_dump binary can be changed ? > what about pg_hba connection requirements? We will use the same connection string which subscriber process uses to connect to the publisher. >what about max_connections in tight circumstances? Right that might be a issue, but I don’t think it will be a big issue, We will create dump of database in CreateSubscription() function itself , So before tableSync process even starts if we have reached max_connections while calling pg_dump itself , tableSync wont be successful. > It would be much better, I think, to handle this internally in the publisher > instead: > similar to how DDL sync would work, except it'd somehow generate the CREATE > statements from the existing tables instead of waiting for DDL events to > occur. I > grant that this does require writing a bunch of new code for each object > type, a > lot of which would duplicate the pg_dump logic, but it would probably be a lot > more robust. Agree , But we might have a lots of code duplication essentially almost all of pg_dump Code needs to be duplicated, which might cause issue when modifying/adding new DDLs. I am not sure but if it's possible to move dependent code of pg_dump to common/ folder , to avoid duplication.
Regards Sachin
