postgresql/contrib/pgstattuple/README.pgstattuple
Bruce Momjian a647e30ba3 New patch with corrected README attached.
Also quickly added mention that it may be a qualified schema name.

Rod Taylor
2003-06-12 08:02:57 +00:00

65 lines
1.8 KiB
Plaintext

pgstattuple README 2002/08/29 Tatsuo Ishii
1. What is pgstattuple?
pgstattuple returns the table length, percentage of the "dead"
tuples of a table and other info. This may help users to determine
whether vacuum is necessary or not. Here is an example session:
test=# \x
Expanded display is on.
test=# select * from pgstattuple('pg_catalog.pg_proc');
-[ RECORD 1 ]------+-------
table_len | 458752
tuple_count | 1470
tuple_len | 438896
tuple_percent | 95.67
dead_tuple_count | 11
dead_tuple_len | 3157
dead_tuple_percent | 0.69
free_space | 8932
free_percent | 1.95
Here are explanations for each column:
table_len -- physical table length in bytes
tuple_count -- number of live tuples
tuple_len -- total tuples length in bytes
tuple_percent -- live tuples in %
dead_tuple_len -- total dead tuples length in bytes
dead_tuple_percent -- dead tuples in %
free_space -- free space in bytes
free_percent -- free space in %
2. Installing pgstattuple
$ make
$ make install
$ psql -e -f /usr/local/pgsql/share/contrib/pgstattuple.sql test
3. Using pgstattuple
pgstattuple may be called as a table function and is
defined as follows:
CREATE OR REPLACE FUNCTION pgstattuple(text) RETURNS pgstattuple_type
AS 'MODULE_PATHNAME', 'pgstattuple'
LANGUAGE 'c' STRICT;
CREATE OR REPLACE FUNCTION pgstattuple(oid) RETURNS pgstattuple_type
AS 'MODULE_PATHNAME', 'pgstattuplebyid'
LANGUAGE 'c' STRICT;
The argument is the table name (optionally it may be qualified)
or the OID of the table. Note that pgstattuple only returns
one row.
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.