53.5. pg_backend_memory_contexts #

   The view pg_backend_memory_contexts displays all the memory contexts of
   the server process attached to the current session.

   pg_backend_memory_contexts contains one row for each memory context.

   Table 53.5. pg_backend_memory_contexts Columns

   Column Type

   Description

   name text

   Name of the memory context

   ident text

   Identification information of the memory context. This field is
   truncated at 1024 bytes

   type text

   Type of the memory context

   level int4

   The 1-based level of the context in the memory context hierarchy. The
   level of a context also shows the position of that context in the path
   column.

   path int4[]

   Array of transient numerical identifiers to describe the memory context
   hierarchy. The first element is for TopMemoryContext, subsequent
   elements contain intermediate parents and the final element contains
   the identifier for the current context.

   total_bytes int8

   Total bytes allocated for this memory context

   total_nblocks int8

   Total number of blocks allocated for this memory context

   free_bytes int8

   Free space in bytes

   free_chunks int8

   Total number of free chunks

   used_bytes int8

   Used space in bytes

   By default, the pg_backend_memory_contexts view can be read only by
   superusers or roles with the privileges of the pg_read_all_stats role.

   Since memory contexts are created and destroyed during the running of a
   query, the identifiers stored in the path column can be unstable
   between multiple invocations of the view in the same query. The example
   below demonstrates an effective usage of this column and calculates the
   total number of bytes used by CacheMemoryContext and all of its
   children:
WITH memory_contexts AS (
    SELECT * FROM pg_backend_memory_contexts
)
SELECT sum(c1.total_bytes)
FROM memory_contexts c1, memory_contexts c2
WHERE c2.name = 'CacheMemoryContext'
AND c1.path[c2.level] = c2.path[c2.level];

   The Common Table Expression is used to ensure the context IDs in the
   path column match between both evaluations of the view.