Usage

To make your extension use the interface, include the header file and declare magic signature:

#include <dynpgext.h>

DYNPGEXT_MAGIC;

Allocating shared memory

You can request shared memory in _Dynpgext_init callback you can define:

void _Dynpgext_init(const dynpgext_handle *handle) {
      handle->allocate_shmem(handle, /* name */ "my_ext:0.1:value", /* size */ 1024,
                         /* callback */ cb, /* callback payload */ NULL,
                         /* flags */ DYNPGEXT_SCOPE_DATABASE_LOCAL /* or DYNPGEXT_SCOPE_GLOBAL */);
}

A particularly useful feature is the ability to scope the allocation per database so that every database provisioned will get its own allocation of the specified size.

Once allocated, the pointer to allocated memory can be found using dynpgext_lookup_shmem(name):

void *ptr = dynpgext_lookup_shmem("my_ext:0.1:value");

Registering background worker

You can register a background worker to be started in `_Dynpgext_init:

BackgroundWorker bgw = {.bgw_name = "worker",
                          .bgw_type = "worker",
                          .bgw_function_name = "worker",
                          .bgw_flags = BGWORKER_SHMEM_ACCESS,
                          .bgw_start_time = BgWorkerStart_RecoveryFinished};
strncpy(bgw.bgw_library_name, handle->library_name, BGW_MAXLEN);
handle->register_bgworker(handle, &bgw, NULL, NULL,
                           DYNPGEXT_REGISTER_BGWORKER_NOTIFY | DYNPGEXT_SCOPE_GLOBAL /* can also take DYNPGEXT_SCOPE_DATABASE_LOCAL */);

Just like shared memory allocations, background workers can be either global or provisioned per database.

Caveat: bgw_restart_time is always BGW_NEVER_RESTART

Since omni_ext manages the startup of the background workers, BackgroundWorker.bgw_restart_time value is ignored and is always effectively set to BGW_NEVER_RESTART so that Postgres never attempts to restart them itself.