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