The pg_shmem_allocations view shows allocations made from the server's main shared memory segment. This includes both memory allocated by PostgreSQL itself and memory allocated by extensions using the mechanisms detailed in Section 38.10.10.
Note that this view does not include memory allocated using the dynamic shared memory infrastructure.
Table 54.26. pg_shmem_allocations Columns
The name of the shared memory allocation. NULL for unused memory and <anonymous> for anonymous allocations.
The offset at which the allocation starts. NULL for anonymous allocations, since details related to them are not known.
Size of the allocation
Size of the allocation including padding. For anonymous allocations, no information about padding is available, so the size and allocated_size columns will always be equal. Padding is not meaningful for free memory, so the columns will be equal in that case also.
Anonymous allocations are allocations that have been made with ShmemAlloc() directly, rather than via ShmemInitStruct() or ShmemInitHash().
By default, the pg_shmem_allocations view can be read only by superusers or roles with privileges of the pg_read_all_stats role.