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diff --git a/contrib/pgstattuple/README.pgstattuple b/contrib/pgstattuple/README.pgstattuple new file mode 100644 index 0000000000..c54f97e82f --- /dev/null +++ b/contrib/pgstattuple/README.pgstattuple @@ -0,0 +1,47 @@ +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 tables 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 does not lock the target table at all. So concurrent + update may affect the result. + + pgstattuple judges a tuple is "dead" if HeapTupleSatisfiesNow() + returns false. |