Fix multiple bugs in contrib/pgstattuple's pgstatindex() function.
Dead or half-dead index leaf pages were incorrectly reported as live, as a
consequence of a code rearrangement I made (during a moment of severe brain
fade, evidently) in commit d287818eb5.
The index metapage was not counted in index_size, causing that result to
not agree with the actual index size on-disk.
Index root pages were not counted in internal_pages, which is inconsistent
compared to the case of a root that's also a leaf (one-page index), where
the root would be counted in leaf_pages. Aside from that inconsistency,
this could lead to additional transient discrepancies between the reported
page counts and index_size, since it's possible for pgstatindex's scan to
see zero or multiple pages marked as BTP_ROOT, if the root moves due to
a split during the scan. With these fixes, index_size will always be
exactly one page more than the sum of the displayed page counts.
Also, the index_size result was incorrectly documented as being measured in
pages; it's always been measured in bytes. (While fixing that, I couldn't
resist doing some small additional wordsmithing on the pgstattuple docs.)
Including the metapage causes the reported index_size to not be zero for
an empty index. To preserve the desired property that the pgstattuple
regression test results are platform-independent (ie, BLCKSZ configuration
independent), scale the index_size result in the regression tests.
The documentation issue was reported by Otsuka Kenji, and the inconsistent
root page counting by Peter Geoghegan; the other problems noted by me.
Back-patch to all supported branches, because this has been broken for
a long time.
This commit is contained in:
Tom Lane
parent
18777c38e9
commit
48e6c943e5
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@ -41,40 +41,44 @@ select pgstattuple(relname) from pg_class where relname = 'test';
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(0,0,0,0,0,0,0,0,0)
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(1 row)
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select * from pgstatindex('test_pkey');
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select version, tree_level,
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index_size / current_setting('block_size')::int as index_size,
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root_block_no, internal_pages, leaf_pages, empty_pages, deleted_pages,
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avg_leaf_density, leaf_fragmentation
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from pgstatindex('test_pkey');
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version | tree_level | index_size | root_block_no | internal_pages | leaf_pages | empty_pages | deleted_pages | avg_leaf_density | leaf_fragmentation
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---------+------------+------------+---------------+----------------+------------+-------------+---------------+------------------+--------------------
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2 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | NaN | NaN
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2 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | NaN | NaN
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(1 row)
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select * from pgstatindex('test_pkey'::text);
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select version, tree_level,
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index_size / current_setting('block_size')::int as index_size,
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root_block_no, internal_pages, leaf_pages, empty_pages, deleted_pages,
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avg_leaf_density, leaf_fragmentation
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from pgstatindex('test_pkey'::text);
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version | tree_level | index_size | root_block_no | internal_pages | leaf_pages | empty_pages | deleted_pages | avg_leaf_density | leaf_fragmentation
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---------+------------+------------+---------------+----------------+------------+-------------+---------------+------------------+--------------------
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2 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | NaN | NaN
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2 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | NaN | NaN
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(1 row)
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select * from pgstatindex('test_pkey'::name);
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select version, tree_level,
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index_size / current_setting('block_size')::int as index_size,
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root_block_no, internal_pages, leaf_pages, empty_pages, deleted_pages,
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avg_leaf_density, leaf_fragmentation
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from pgstatindex('test_pkey'::name);
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version | tree_level | index_size | root_block_no | internal_pages | leaf_pages | empty_pages | deleted_pages | avg_leaf_density | leaf_fragmentation
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---------+------------+------------+---------------+----------------+------------+-------------+---------------+------------------+--------------------
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2 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | NaN | NaN
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2 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | NaN | NaN
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(1 row)
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select * from pgstatindex('test_pkey'::regclass);
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select version, tree_level,
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index_size / current_setting('block_size')::int as index_size,
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root_block_no, internal_pages, leaf_pages, empty_pages, deleted_pages,
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avg_leaf_density, leaf_fragmentation
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from pgstatindex('test_pkey'::regclass);
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version | tree_level | index_size | root_block_no | internal_pages | leaf_pages | empty_pages | deleted_pages | avg_leaf_density | leaf_fragmentation
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---------+------------+------------+---------------+----------------+------------+-------------+---------------+------------------+--------------------
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2 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | NaN | NaN
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(1 row)
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select pgstatindex(oid) from pg_class where relname = 'test_pkey';
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pgstatindex
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---------------------------
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(2,0,0,0,0,0,0,0,NaN,NaN)
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(1 row)
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select pgstatindex(relname) from pg_class where relname = 'test_pkey';
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pgstatindex
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---------------------------
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(2,0,0,0,0,0,0,0,NaN,NaN)
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2 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | NaN | NaN
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(1 row)
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select pg_relpages('test');
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@ -79,7 +79,6 @@ typedef struct BTIndexStat
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uint32 level;
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BlockNumber root_blkno;
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uint64 root_pages;
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uint64 internal_pages;
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uint64 leaf_pages;
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uint64 empty_pages;
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@ -185,7 +184,6 @@ pgstatindex_impl(Relation rel, FunctionCallInfo fcinfo)
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}
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/* -- init counters -- */
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indexStat.root_pages = 0;
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indexStat.internal_pages = 0;
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indexStat.leaf_pages = 0;
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indexStat.empty_pages = 0;
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@ -218,7 +216,11 @@ pgstatindex_impl(Relation rel, FunctionCallInfo fcinfo)
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/* Determine page type, and update totals */
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if (P_ISLEAF(opaque))
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if (P_ISDELETED(opaque))
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indexStat.deleted_pages++;
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else if (P_IGNORE(opaque))
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indexStat.empty_pages++; /* this is the "half dead" state */
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else if (P_ISLEAF(opaque))
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{
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int max_avail;
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@ -235,12 +237,6 @@ pgstatindex_impl(Relation rel, FunctionCallInfo fcinfo)
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if (opaque->btpo_next != P_NONE && opaque->btpo_next < blkno)
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indexStat.fragments++;
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}
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else if (P_ISDELETED(opaque))
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indexStat.deleted_pages++;
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else if (P_IGNORE(opaque))
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indexStat.empty_pages++;
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else if (P_ISROOT(opaque))
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indexStat.root_pages++;
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else
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indexStat.internal_pages++;
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@ -269,7 +265,7 @@ pgstatindex_impl(Relation rel, FunctionCallInfo fcinfo)
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values[j++] = psprintf("%d", indexStat.version);
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values[j++] = psprintf("%d", indexStat.level);
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values[j++] = psprintf(INT64_FORMAT,
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(indexStat.root_pages +
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(1 + /* include the metapage in index_size */
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indexStat.leaf_pages +
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indexStat.internal_pages +
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indexStat.deleted_pages +
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@ -15,12 +15,26 @@ select * from pgstattuple('test'::regclass);
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select pgstattuple(oid) from pg_class where relname = 'test';
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select pgstattuple(relname) from pg_class where relname = 'test';
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select * from pgstatindex('test_pkey');
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select * from pgstatindex('test_pkey'::text);
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select * from pgstatindex('test_pkey'::name);
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select * from pgstatindex('test_pkey'::regclass);
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select pgstatindex(oid) from pg_class where relname = 'test_pkey';
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select pgstatindex(relname) from pg_class where relname = 'test_pkey';
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select version, tree_level,
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index_size / current_setting('block_size')::int as index_size,
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root_block_no, internal_pages, leaf_pages, empty_pages, deleted_pages,
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avg_leaf_density, leaf_fragmentation
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from pgstatindex('test_pkey');
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select version, tree_level,
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index_size / current_setting('block_size')::int as index_size,
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root_block_no, internal_pages, leaf_pages, empty_pages, deleted_pages,
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avg_leaf_density, leaf_fragmentation
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from pgstatindex('test_pkey'::text);
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select version, tree_level,
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index_size / current_setting('block_size')::int as index_size,
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root_block_no, internal_pages, leaf_pages, empty_pages, deleted_pages,
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avg_leaf_density, leaf_fragmentation
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from pgstatindex('test_pkey'::name);
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select version, tree_level,
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index_size / current_setting('block_size')::int as index_size,
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root_block_no, internal_pages, leaf_pages, empty_pages, deleted_pages,
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avg_leaf_density, leaf_fragmentation
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from pgstatindex('test_pkey'::regclass);
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select pg_relpages('test');
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select pg_relpages('test_pkey');
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@ -130,9 +130,9 @@ free_percent | 1.95
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<listitem>
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<para>
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This is the same as <function>pgstattuple(regclass)</function>, except
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that the target relation is specified by TEXT. This function is kept
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that the target relation is specified as TEXT. This function is kept
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because of backward-compatibility so far, and will be deprecated in
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the future release.
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some future release.
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</para>
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</listitem>
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</varlistentry>
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@ -154,13 +154,13 @@ test=> SELECT * FROM pgstatindex('pg_cast_oid_index');
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-[ RECORD 1 ]------+------
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version | 2
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tree_level | 0
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index_size | 8192
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index_size | 16384
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root_block_no | 1
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internal_pages | 0
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leaf_pages | 1
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empty_pages | 0
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deleted_pages | 0
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avg_leaf_density | 50.27
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avg_leaf_density | 54.27
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leaf_fragmentation | 0
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</programlisting>
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</para>
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@ -194,13 +194,13 @@ leaf_fragmentation | 0
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<row>
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<entry><structfield>index_size</structfield></entry>
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<entry><type>bigint</type></entry>
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<entry>Total number of pages in index</entry>
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<entry>Total index size in bytes</entry>
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</row>
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<row>
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<entry><structfield>root_block_no</structfield></entry>
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<entry><type>bigint</type></entry>
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<entry>Location of root block</entry>
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<entry>Location of root page (zero if none)</entry>
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</row>
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<row>
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@ -244,6 +244,13 @@ leaf_fragmentation | 0
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</informaltable>
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</para>
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<para>
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The reported <literal>index_size</> will normally correspond to one more
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page than is accounted for by <literal>internal_pages + leaf_pages +
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empty_pages + deleted_pages</literal>, because it also includes the
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index's metapage.
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</para>
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<para>
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As with <function>pgstattuple</>, the results are accumulated
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page-by-page, and should not be expected to represent an
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@ -260,9 +267,9 @@ leaf_fragmentation | 0
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<listitem>
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<para>
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This is the same as <function>pgstatindex(regclass)</function>, except
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that the target index is specified by TEXT. This function is kept
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that the target index is specified as TEXT. This function is kept
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because of backward-compatibility so far, and will be deprecated in
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the future release.
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some future release.
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</para>
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</listitem>
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</varlistentry>
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@ -351,9 +358,9 @@ pending_tuples | 0
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<listitem>
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<para>
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This is the same as <function>pg_relpages(regclass)</function>, except
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that the target relation is specified by TEXT. This function is kept
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that the target relation is specified as TEXT. This function is kept
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because of backward-compatibility so far, and will be deprecated in
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the future release.
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some future release.
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</para>
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</listitem>
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</varlistentry>
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@ -370,7 +377,7 @@ pending_tuples | 0
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<para>
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<function>pgstattuple_approx</function> is a faster alternative to
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<function>pgstattuple</function> that returns approximate results.
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The argument is the target relation's OID.
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The argument is the target relation's name or OID.
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For example:
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<programlisting>
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test=> SELECT * FROM pgstattuple_approx('pg_catalog.pg_proc'::regclass);
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