shmem_request_hook
A hook for requesting additional shared memory
shmem_request_hook is a hook for extensions loaded into memory which request additional shared memory.
shmem_request_hook was added in PostgreSQL 15.
Change history
- PostgreSQL 15
- added (commit 4f2400cb)
Examples
Usage example for shmem_request_hook:
/*
* Module load callback
*/
void
_PG_init(void)
{
if (!process_shared_preload_libraries_in_progress)
return;
/*
* Install hooks.
*/
#if (PG_VERSION_NUM >= 150000)
prev_shmem_request_hook = shmem_request_hook;
shmem_request_hook = extension_shmem_request;
#endif
prev_shmem_startup_hook = shmem_startup_hook;
shmem_startup_hook = extension_shmem_startup;
/* ... */
}
#if (PG_VERSION_NUM >= 150000)
/*
* shmem_requst_hook: request shared memory
*/
static void
extension_shmem_request(void)
{
if (prev_shmem_request_hook)
prev_shmem_request_hook();
RequestAddinShmemSpace(MAXALIGN(sizeof(extensionSharedState)));
RequestNamedLWLockTranche(TRANCHE_NAME, 1);
}
#endif
References
- PostgreSQL documentation: Shared Memory and LWLocks
Useful links
- PostgreSQL 15: _PG_init() and shmem_request_hook - May 2022 blog article by Ian Barwick
