53.2. pg_aios #

   The pg_aios view lists all Asynchronous I/O handles that are currently
   in-use. An I/O handle is used to reference an I/O operation that is
   being prepared, executed or is in the process of completing. pg_aios
   contains one row for each I/O handle.

   This view is mainly useful for developers of PostgreSQL, but may also
   be useful when tuning PostgreSQL.

   Table 53.2. pg_aios Columns

   Column Type

   Description

   pid int4

   Process ID of the server process that is issuing this I/O.

   io_id int4

   Identifier of the I/O handle. Handles are reused once the I/O completed
   (or if the handle is released before I/O is started). On reuse
   pg_aios.io_generation is incremented.

   io_generation int8

   Generation of the I/O handle.

   state text

   State of the I/O handle:
     * HANDED_OUT, referenced by code but not yet used
     * DEFINED, information necessary for execution is known
     * STAGED, ready for execution
     * SUBMITTED, submitted for execution
     * COMPLETED_IO, finished, but result has not yet been processed
     * COMPLETED_SHARED, shared completion processing completed
     * COMPLETED_LOCAL, backend local completion processing completed

   operation text

   Operation performed using the I/O handle:
     * invalid, not yet known
     * readv, a vectored read
     * writev, a vectored write

   off int8

   Offset of the I/O operation.

   length int8

   Length of the I/O operation.

   target text

   What kind of object is the I/O targeting:
     * smgr, I/O on relations

   handle_data_len int2

   Length of the data associated with the I/O operation. For I/O to/from
   shared_buffers and temp_buffers, this indicates the number of buffers
   the I/O is operating on.

   raw_result int4

   Low-level result of the I/O operation, or NULL if the operation has not
   yet completed.

   result text

   High-level result of the I/O operation:
     * UNKNOWN means that the result of the operation is not yet known.
     * OK means the I/O completed successfully.
     * PARTIAL means that the I/O completed without error, but did not
       process all data. Commonly callers will need to retry and perform
       the remainder of the work in a separate I/O.
     * WARNING means that the I/O completed without error, but that
       execution of the IO triggered a warning. E.g. when encountering a
       corrupted buffer with zero_damaged_pages enabled.
     * ERROR means the I/O failed with an error.

   target_desc text

   Description of what the I/O operation is targeting.

   f_sync bool

   Flag indicating whether the I/O is executed synchronously.

   f_localmem bool

   Flag indicating whether the I/O references process local memory.

   f_buffered bool

   Flag indicating whether the I/O is buffered I/O.

   The pg_aios view is read-only.

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