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53.2. `pg_aios`
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53.2. `pg_aios`#

Thepg_aios view lists allAsynchronous 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 ofPostgres Pro, but may also be useful when tuningPostgres Pro.

Table 53.2. pg_aios Columns

Column Type Description
`pidint4` Process ID of the server process that is issuing this I/O.
`io_idint4` 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_generationint8` Generation of the I/O handle.
`statetext` 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
`operationtext` Operation performed using the I/O handle: `invalid`, not yet known `readv`, a vectored read `writev`, a vectored write
`offint8` Offset of the I/O operation.
`lengthint8` Length of the I/O operation.
`targettext` What kind of object is the I/O targeting: `smgr`, I/O on relations
`handle_data_lenint2` Length of the data associated with the I/O operation. For I/O to/fromshared_buffers andtemp_buffers, this indicates the number of buffers the I/O is operating on.
`raw_resultint4` Low-level result of the I/O operation, or NULL if the operation has not yet completed.
`resulttext` 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 withzero_damaged_pages enabled. `ERROR` means the I/O failed with an error.
`target_desctext` Description of what the I/O operation is targeting.
`f_syncbool` Flag indicating whether the I/O is executed synchronously.
`f_localmembool` Flag indicating whether the I/O references process local memory.
`f_bufferedbool` Flag indicating whether the I/O is buffered I/O.

Column Type

Description

pidint4

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

io_idint4

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 reusepg_aios.io_generation is incremented.

io_generationint8

Generation of the I/O handle.

statetext

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

operationtext

Operation performed using the I/O handle:

invalid, not yet known
readv, a vectored read
writev, a vectored write

offint8

Offset of the I/O operation.

lengthint8

Length of the I/O operation.

targettext

What kind of object is the I/O targeting:

smgr, I/O on relations

handle_data_lenint2

Length of the data associated with the I/O operation. For I/O to/fromshared_buffers andtemp_buffers, this indicates the number of buffers the I/O is operating on.

raw_resultint4

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

resulttext

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 withzero_damaged_pages enabled.
ERROR means the I/O failed with an error.

target_desctext

Description of what the I/O operation is targeting.

f_syncbool

Flag indicating whether the I/O is executed synchronously.

f_localmembool

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

f_bufferedbool

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

Thepg_aios view is read-only.

By default, thepg_aios view can be read only by superusers or roles with privileges of thepg_read_all_stats role.

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53.2. pg_aios#

53.2. `pg_aios`#