pg_shmem_allocations — PostgreSQL system view

The PostgreSQL pg_shmem_allocations system view: full column reference (names, types, descriptions), catalog relationships and version support.

The Sev-1 Admin
The Sev-1 Admin  ·  2 min read

Summary

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 xfunc_shared_addin.

(Description quoted from the official PostgreSQL documentation.)

Columns

The pg_shmem_allocations system view exposes the following columns (names, types and descriptions are taken verbatim from the PostgreSQL documentation):

  • name text
    The name of the shared memory allocation. NULL for unused memory and <anonymous> for anonymous allocations.
  • off int8
    The offset at which the allocation starts. NULL for anonymous allocations, since details related to them are not known.
  • size int8
    Size of the allocation in bytes
  • allocated_size int8
    Size of the allocation in bytes 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.

Version applicability

Present in PostgreSQL 17, 18, 19 (verified against each release’s documentation). This is a long-standing system object that also exists in earlier PostgreSQL releases.

Related & references

Reference: PostgreSQL documentation — pg_shmem_allocations.