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HOT updates. When we update a tuple without changing any of its indexed

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columns, and the new version can be stored on the same heap page, we no longer
generate extra index entries for the new version.  Instead, index searches
follow the HOT-chain links to ensure they find the correct tuple version.

In addition, this patch introduces the ability to "prune" dead tuples on a
per-page basis, without having to do a complete VACUUM pass to recover space.
VACUUM is still needed to clean up dead index entries, however.

Pavan Deolasee, with help from a bunch of other people.
This commit is contained in:
Tom Lane
2007-09-20 17:56:33 +00:00
parent bbf4fdc253
commit 282d2a03dd
65 changed files with 3517 additions and 514 deletions
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42
doc/src/sgml/monitoring.sgml
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@@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/monitoring.sgml,v 1.51 2007/06/28 00:02:37 tgl Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/monitoring.sgml,v 1.52 2007/09/20 17:56:30 tgl Exp $ -->
<chapter id="monitoring">
<title>Monitoring Database Activity</title>
@@ -276,6 +276,8 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
scans, number of index scans initiated (over all indexes
belonging to the table), number of live rows fetched by index
scans, numbers of row insertions, updates, and deletions,
number of row updates that were HOT (i.e., no separate index update),
numbers of live and dead rows,
the last time the table was vacuumed manually,
the last time it was vacuumed by the autovacuum daemon,
the last time it was analyzed manually,
@@ -580,7 +582,7 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
<entry><literal><function>pg_stat_get_tuples_updated</function>(<type>oid</type>)</literal></entry>
<entry><type>bigint</type></entry>
<entry>
Number of rows updated in table
Number of rows updated in table (includes HOT updates)
</entry>
</row>
@@ -592,6 +594,30 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
</entry>
</row>
<row>
<entry><literal><function>pg_stat_get_tuples_hot_updated</function>(<type>oid</type>)</literal></entry>
<entry><type>bigint</type></entry>
<entry>
Number of rows HOT-updated in table
</entry>
</row>
<row>
<entry><literal><function>pg_stat_get_live_tuples</function>(<type>oid</type>)</literal></entry>
<entry><type>bigint</type></entry>
<entry>
Number of live rows in table
</entry>
</row>
<row>
<entry><literal><function>pg_stat_get_dead_tuples</function>(<type>oid</type>)</literal></entry>
<entry><type>bigint</type></entry>
<entry>
Number of dead rows in table
</entry>
</row>
<row>
<entry><literal><function>pg_stat_get_blocks_fetched</function>(<type>oid</type>)</literal></entry>
<entry><type>bigint</type></entry>
@@ -716,6 +742,18 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
</entry>
</row>
<row>
<entry><literal><function>pg_stat_get_backend_xact_start</function>(<type>integer</type>)</literal></entry>
<entry><type>timestamp with time zone</type></entry>
<entry>
The time at which the given server process' currently
executing transaction was started, but only if the
current user is a superuser or the same user as that of
the session being queried (and
<varname>stats_command_string</varname> is on)
</entry>
</row>
<row>
<entry><literal><function>pg_stat_get_backend_start</function>(<type>integer</type>)</literal></entry>
<entry><type>timestamp with time zone</type></entry>