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Postgres FD Implementation
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Abuhujair Javed
Postgres FD Implementation
Commits
dad0e20f
Commit
dad0e20f
authored
Jun 21, 2002
by
Bruce Momjian
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Mention "PostgreSQL"'s hashes as slower/similar to btree.
parent
1415a838
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doc/src/sgml/diskusage.sgml
doc/src/sgml/diskusage.sgml
+11
-9
doc/src/sgml/indices.sgml
doc/src/sgml/indices.sgml
+6
-5
doc/src/sgml/ref/create_index.sgml
doc/src/sgml/ref/create_index.sgml
+6
-5
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doc/src/sgml/diskusage.sgml
View file @
dad0e20f
<!--
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/diskusage.sgml,v 1.
1 2002/06/13 05:15:22
momjian Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/diskusage.sgml,v 1.
2 2002/06/21 19:06:44
momjian Exp $
-->
-->
<chapter id="diskusage">
<chapter id="diskusage">
...
@@ -22,10 +22,12 @@ $Header: /cvsroot/pgsql/doc/src/sgml/diskusage.sgml,v 1.1 2002/06/13 05:15:22 mo
...
@@ -22,10 +22,12 @@ $Header: /cvsroot/pgsql/doc/src/sgml/diskusage.sgml,v 1.1 2002/06/13 05:15:22 mo
</para>
</para>
<para>
<para>
You can monitor disk space from two places; from inside
You can monitor disk space from three places: from
<application>psql</> and from the command line using
<application>psql</> using <command>VACUUM</> information, from
<application>contrib/oid2name</>. Using <application>psql</> you can
<application>psql</> using <application>contrib/dbsize</>, and from
issue queries to see the disk usage for any table:
the command line using <application>contrib/oid2name</>. Using
<application>psql</> on a recently vacuumed (or analyzed) database,
you can issue queries to see the disk usage of any table:
<programlisting>
<programlisting>
play=# SELECT relfilenode, relpages
play=# SELECT relfilenode, relpages
play-# FROM pg_class
play-# FROM pg_class
...
@@ -38,10 +40,10 @@ play-# WHERE relname = 'customer';
...
@@ -38,10 +40,10 @@ play-# WHERE relname = 'customer';
</para>
</para>
<para>
<para>
Each page is typically 8 kilobytes.
<literal>relpages</> is only
Each page is typically 8 kilobytes.
(Remember, <literal>relpages</>
updated by <command>VACUUM</> and <command>ANALYZE</>. To show the
is only updated by <command>VACUUM</> and <command>ANALYZE</>.) To
s
pace used by <acronym>TOAST</> tables, use a query based on the heap
s
how the space used by <acronym>TOAST</> tables, use a query based on
relfilenod
e:
the heap relfilenode shown abov
e:
<programlisting>
<programlisting>
play=# SELECT relname, relpages
play=# SELECT relname, relpages
play-# FROM pg_class
play-# FROM pg_class
...
...
doc/src/sgml/indices.sgml
View file @
dad0e20f
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/indices.sgml,v 1.3
3 2002/06/21 16:52:00
momjian Exp $ -->
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/indices.sgml,v 1.3
4 2002/06/21 19:06:44
momjian Exp $ -->
<chapter id="indexes">
<chapter id="indexes">
<title id="indexes-title">Indexes</title>
<title id="indexes-title">Indexes</title>
...
@@ -181,10 +181,11 @@ CREATE INDEX <replaceable>name</replaceable> ON <replaceable>table</replaceable>
...
@@ -181,10 +181,11 @@ CREATE INDEX <replaceable>name</replaceable> ON <replaceable>table</replaceable>
</synopsis>
</synopsis>
<note>
<note>
<para>
<para>
Testing has shown hash indexes to be similar or slower than btree
Testing has shown PostgreSQL's hash indexes to be similar or slower
indexes, and the index size and build time for hash indexes is much
than btree indexes, and the index size and build time for hash
worse. Hash indexes also suffer poor performance under high
indexes is much worse. Hash indexes also suffer poor performance
concurrency. For these reasons, hash index use is discouraged.
under high concurrency. For these reasons, hash index use is
discouraged.
</para>
</para>
</note>
</note>
</para>
</para>
...
...
doc/src/sgml/ref/create_index.sgml
View file @
dad0e20f
<!--
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_index.sgml,v 1.3
3 2002/06/21 16:52:00
momjian Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_index.sgml,v 1.3
4 2002/06/21 19:06:44
momjian Exp $
PostgreSQL documentation
PostgreSQL documentation
-->
-->
...
@@ -330,10 +330,11 @@ ERROR: Cannot create index: 'index_name' already exists.
...
@@ -330,10 +330,11 @@ ERROR: Cannot create index: 'index_name' already exists.
the <literal>=</literal> operator.
the <literal>=</literal> operator.
</para>
</para>
<para>
<para>
Testing has shown hash indexes to be similar or slower than btree
Testing has shown PostgreSQL's hash indexes to be similar or slower
indexes, and the index size and build time for hash indexes is much
than btree indexes, and the index size and build time for hash
worse. Hash indexes also suffer poor performance under high
indexes is much worse. Hash indexes also suffer poor performance
concurrency. For these reasons, hash index use is discouraged.
under high concurrency. For these reasons, hash index use is
discouraged.
</para>
</para>
<para>
<para>
...
...
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