SYSTEM VIEW · System view

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.

First seen PG 18Last seen PG 19Columns 15

9.0 9.1 9.2 9.3 9.4 9.5 9.6 10 11 12 13 14 15 16 17 18 19^β3

Checked column by column against a PostgreSQL 18.6 instance · Raw measurement record ↗

Columns PostgreSQL 18

pg_aios

COLUMN	TYPE	DESCRIPTION
`pid`	`integer`Documented as:`int4`	Process ID of the server process that is issuing this I/O.
`io_id`	`integer`Documented as:`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`	`bigint`Documented as:`int8`	Generation of the I/O handle.
`state`	`text`	State of the I/O handle:
`operation`	`text`	Operation performed using the I/O handle:
`off`	`bigint`Documented as:`int8`	Offset of the I/O operation.
`length`	`bigint`Documented as:`int8`	Length of the I/O operation.
`target`	`text`	What kind of object is the I/O targeting:
`handle_data_len`	`smallint`Documented as:`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`	`integer`Documented as:`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:
`target_desc`	`text`	Description of what the I/O operation is targeting.
`f_sync`	`boolean`Documented as:`bool`	Flag indicating whether the I/O is executed synchronously.
`f_localmem`	`boolean`Documented as:`bool`	Flag indicating whether the I/O references process local memory.
`f_buffered`	`boolean`Documented as:`bool`	Flag indicating whether the I/O is buffered I/O.

Columns marked "implicit" are not included in SELECT *; some early statistics views are completed from same-version source, and the extra provenance is shown in the column description.

Column evolution matrix

Hover a cell for the column type

PresentAdded / type or attribute changeRemoved

COLUMN	9.0	9.1	9.2	9.3	9.4	9.5	9.6	10	11	12	13	14	15	16	17
`pid`	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–
`io_id`	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–
`io_generation`	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–
`state`	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–
`operation`	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–
`off`	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–
`length`	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–
`target`	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–
`handle_data_len`	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–
`raw_result`	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–
`result`	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–
`target_desc`	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–
`f_sync`	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–
`f_localmem`	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–
`f_buffered`	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–

9.0 is the coverage baseline; a column already present in the baseline is not marked as added. The matrix aligns columns by name, so a rename appears as the old column removed and a new column added.

Evolution timeline

Changes between adjacent majors

PostgreSQL 18 ← 17Catalog added

+ pid+ io_id+ io_generation+ state+ operation+ off+ length+ target+ handle_data_len+ raw_result+ result+ target_desc+ f_sync+ f_localmem+ f_buffered

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FROMTOInclude description updates

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