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pgstattuple README 2001/10/01 Tatsuo Ishii
1. What is pgstattuple?
pgstattuple returns the percentage of the "dead" tuples of a
table. This will help users to judge if vacuum is needed.
In addition, pgstattuple prints more detailed information using
NOTICE.
test=# select pgstattuple('tellers');
NOTICE: physical length: 0.08MB live tuples: 20 (0.00MB, 1.17%) dead tuples: 320 (0.01MB, 18.75%) free/reusable space: 0.01MB (18.06%) overhead: 62.02%
pgstattuple
-------------
18.75
(1 row)
Above example shows tellers table includes 18.75% dead tuples.
physical length physical size of the table in MB
live tuples information on the live tuples
dead tuples information on the dead tuples
free/reusable space available space
overhead overhead space
2. Installing pgstattuple
$ make
$ make install
$ psql -e -f /usr/local/pgsql/share/contrib/pgstattuple.sql test
3. Using pgstattuple
pgstattuple can be called as a function:
pgstattuple(NAME) RETURNS FLOAT8
The argument is the table name. pgstattuple returns the percentage
of the "dead" tuples of a table.
4. Notes
pgstattuple acquires only a read lock on the table. So concurrent
update may affect the result.
pgstattuple judges a tuple is "dead" if HeapTupleSatisfiesNow()
returns false.
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