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5850b20f58
The new function allows to estimate bloat and other table level statics in a faster, but approximate, way. It does so by using information from the free space map for pages marked as all visible in the visibility map. The rest of the table is actually read and free space/bloat is measured accurately. In many cases that allows to get bloat information much quicker, causing less IO. Author: Abhijit Menon-Sen Reviewed-By: Andres Freund, Amit Kapila and Tomas Vondra Discussion: 20140402214144.GA28681@kea.toroid.org
19 lines
1.1 KiB
SQL
19 lines
1.1 KiB
SQL
/* contrib/pgstattuple/pgstattuple--1.2--1.3.sql */
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-- complain if script is sourced in psql, rather than via ALTER EXTENSION
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\echo Use "ALTER EXTENSION pgstattuple UPDATE TO '1.3'" to load this file. \quit
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CREATE FUNCTION pgstattuple_approx(IN reloid regclass,
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OUT table_len BIGINT, -- physical table length in bytes
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OUT scanned_percent FLOAT8, -- what percentage of the table's pages was scanned
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OUT approx_tuple_count BIGINT, -- estimated number of live tuples
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OUT approx_tuple_len BIGINT, -- estimated total length in bytes of live tuples
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OUT approx_tuple_percent FLOAT8, -- live tuples in % (based on estimate)
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OUT dead_tuple_count BIGINT, -- exact number of dead tuples
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OUT dead_tuple_len BIGINT, -- exact total length in bytes of dead tuples
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OUT dead_tuple_percent FLOAT8, -- dead tuples in % (based on estimate)
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OUT approx_free_space BIGINT, -- estimated free space in bytes
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OUT approx_free_percent FLOAT8) -- free space in % (based on estimate)
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AS 'MODULE_PATHNAME', 'pgstattuple_approx'
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LANGUAGE C STRICT;
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