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897083715b
prevents embarassments such as having the table dropped or truncated partway through the scan. Also, fix free space calculation to include pages that currently contain no tuples.
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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