PostgreSQL has the ability to report the progress of
certain commands during command execution. Currently, the only command
which supports progress reporting is VACUUM. This may be
expanded in the future.
Whenever VACUUM is running, the
pg_stat_progress_vacuum view will contain
one row for each backend (including autovacuum worker processes) that is
currently vacuuming. The tables below describe the information
that will be reported and provide information about how to interpret it.
Progress reporting is not currently supported for VACUUM FULL
and backends running VACUUM FULL will not be listed in this
view.
Table 28.21. pg_stat_progress_vacuum View
| Column | Type | Description |
|---|---|---|
pid | integer | Process ID of backend. |
datid | oid | OID of the database to which this backend is connected. |
datname | name | Name of the database to which this backend is connected. |
relid | oid | OID of the table being vacuumed. |
phase | text | Current processing phase of vacuum. See Table 28.22. |
heap_blks_total | bigint |
Total number of heap blocks in the table. This number is reported
as of the beginning of the scan; blocks added later will not be (and
need not be) visited by this VACUUM.
|
heap_blks_scanned | bigint |
Number of heap blocks scanned. Because the
visibility map is used to optimize scans,
some blocks will be skipped without inspection; skipped blocks are
included in this total, so that this number will eventually become
equal to heap_blks_total when the vacuum is complete.
This counter only advances when the phase is scanning heap.
|
heap_blks_vacuumed | bigint |
Number of heap blocks vacuumed. Unless the table has no indexes, this
counter only advances when the phase is vacuuming heap.
Blocks that contain no dead tuples are skipped, so the counter may
sometimes skip forward in large increments.
|
index_vacuum_count | bigint | Number of completed index vacuum cycles. |
max_dead_tuples | bigint | Number of dead tuples that we can store before needing to perform an index vacuum cycle, based on maintenance_work_mem. |
num_dead_tuples | bigint | Number of dead tuples collected since the last index vacuum cycle. |
Table 28.22. VACUUM phases
| Phase | Description |
|---|---|
initializing |
VACUUM is preparing to begin scanning the heap. This
phase is expected to be very brief.
|
scanning heap |
VACUUM is currently scanning the heap. It will prune and
defragment each page if required, and possibly perform freezing
activity. The heap_blks_scanned column can be used
to monitor the progress of the scan.
|
vacuuming indexes |
VACUUM is currently vacuuming the indexes. If a table has
any indexes, this will happen at least once per vacuum, after the heap
has been completely scanned. It may happen multiple times per vacuum
if maintenance_work_mem is insufficient to
store the number of dead tuples found.
|
vacuuming heap |
VACUUM is currently vacuuming the heap. Vacuuming the heap
is distinct from scanning the heap, and occurs after each instance of
vacuuming indexes. If heap_blks_scanned is less than
heap_blks_total, the system will return to scanning
the heap after this phase is completed; otherwise, it will begin
cleaning up indexes after this phase is completed.
|
cleaning up indexes |
VACUUM is currently cleaning up indexes. This occurs after
the heap has been completely scanned and all vacuuming of the indexes
and the heap has been completed.
|
truncating heap |
VACUUM is currently truncating the heap so as to return
empty pages at the end of the relation to the operating system. This
occurs after cleaning up indexes.
|
performing final cleanup |
VACUUM is performing final cleanup. During this phase,
VACUUM will vacuum the free space map, update statistics
in pg_class, and report statistics to the statistics
collector. When this phase is completed, VACUUM will end.
|