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Don't use SGML empty tags

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For DocBook XML compatibility, don't use SGML empty tags (</>) anymore,
replace by the full tag name.  Add a warning option to catch future
occurrences.

Alexander Lakhin, Jürgen Purtz
This commit is contained in:
Peter Eisentraut
2017-10-08 21:44:17 -04:00
parent 6ecabead4b
commit c29c578908
337 changed files with 31636 additions and 31635 deletions
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106
doc/src/sgml/pgstatstatements.sgml
View File

@@ -13,20 +13,20 @@
</para>
<para>
The module must be loaded by adding <literal>pg_stat_statements</> to
The module must be loaded by adding <literal>pg_stat_statements</literal> to
<xref linkend="guc-shared-preload-libraries"> in
<filename>postgresql.conf</>, because it requires additional shared memory.
<filename>postgresql.conf</filename>, because it requires additional shared memory.
This means that a server restart is needed to add or remove the module.
</para>
<para>
When <filename>pg_stat_statements</filename> is loaded, it tracks
statistics across all databases of the server. To access and manipulate
these statistics, the module provides a view, <structname>pg_stat_statements</>,
and the utility functions <function>pg_stat_statements_reset</> and
<function>pg_stat_statements</>. These are not available globally but
these statistics, the module provides a view, <structname>pg_stat_statements</structname>,
and the utility functions <function>pg_stat_statements_reset</function> and
<function>pg_stat_statements</function>. These are not available globally but
can be enabled for a specific database with
<command>CREATE EXTENSION pg_stat_statements</>.
<command>CREATE EXTENSION pg_stat_statements</command>.
</para>
<sect2>
@@ -34,7 +34,7 @@
<para>
The statistics gathered by the module are made available via a
view named <structname>pg_stat_statements</>. This view
view named <structname>pg_stat_statements</structname>. This view
contains one row for each distinct database ID, user ID and query
ID (up to the maximum number of distinct statements that the module
can track). The columns of the view are shown in
@@ -42,7 +42,7 @@
</para>
<table id="pgstatstatements-columns">
<title><structname>pg_stat_statements</> Columns</title>
<title><structname>pg_stat_statements</structname> Columns</title>
<tgroup cols="4">
<thead>
@@ -234,9 +234,9 @@
</para>
<para>
Plannable queries (that is, <command>SELECT</>, <command>INSERT</>,
<command>UPDATE</>, and <command>DELETE</>) are combined into a single
<structname>pg_stat_statements</> entry whenever they have identical query
Plannable queries (that is, <command>SELECT</command>, <command>INSERT</command>,
<command>UPDATE</command>, and <command>DELETE</command>) are combined into a single
<structname>pg_stat_statements</structname> entry whenever they have identical query
structures according to an internal hash calculation. Typically, two
queries will be considered the same for this purpose if they are
semantically equivalent except for the values of literal constants
@@ -247,16 +247,16 @@
<para>
When a constant's value has been ignored for purposes of matching the query
to other queries, the constant is replaced by a parameter symbol, such
as <literal>$1</literal>, in the <structname>pg_stat_statements</>
as <literal>$1</literal>, in the <structname>pg_stat_statements</structname>
display.
The rest of the query text is that of the first query that had the
particular <structfield>queryid</> hash value associated with the
<structname>pg_stat_statements</> entry.
particular <structfield>queryid</structfield> hash value associated with the
<structname>pg_stat_statements</structname> entry.
</para>
<para>
In some cases, queries with visibly different texts might get merged into a
single <structname>pg_stat_statements</> entry. Normally this will happen
single <structname>pg_stat_statements</structname> entry. Normally this will happen
only for semantically equivalent queries, but there is a small chance of
hash collisions causing unrelated queries to be merged into one entry.
(This cannot happen for queries belonging to different users or databases,
@@ -264,41 +264,41 @@
</para>
<para>
Since the <structfield>queryid</> hash value is computed on the
Since the <structfield>queryid</structfield> hash value is computed on the
post-parse-analysis representation of the queries, the opposite is
also possible: queries with identical texts might appear as
separate entries, if they have different meanings as a result of
factors such as different <varname>search_path</> settings.
factors such as different <varname>search_path</varname> settings.
</para>
<para>
Consumers of <structname>pg_stat_statements</> may wish to use
<structfield>queryid</> (perhaps in combination with
<structfield>dbid</> and <structfield>userid</>) as a more stable
Consumers of <structname>pg_stat_statements</structname> may wish to use
<structfield>queryid</structfield> (perhaps in combination with
<structfield>dbid</structfield> and <structfield>userid</structfield>) as a more stable
and reliable identifier for each entry than its query text.
However, it is important to understand that there are only limited
guarantees around the stability of the <structfield>queryid</> hash
guarantees around the stability of the <structfield>queryid</structfield> hash
value. Since the identifier is derived from the
post-parse-analysis tree, its value is a function of, among other
things, the internal object identifiers appearing in this representation.
This has some counterintuitive implications. For example,
<filename>pg_stat_statements</> will consider two apparently-identical
<filename>pg_stat_statements</filename> will consider two apparently-identical
queries to be distinct, if they reference a table that was dropped
and recreated between the executions of the two queries.
The hashing process is also sensitive to differences in
machine architecture and other facets of the platform.
Furthermore, it is not safe to assume that <structfield>queryid</>
will be stable across major versions of <productname>PostgreSQL</>.
Furthermore, it is not safe to assume that <structfield>queryid</structfield>
will be stable across major versions of <productname>PostgreSQL</productname>.
</para>
<para>
As a rule of thumb, <structfield>queryid</> values can be assumed to be
As a rule of thumb, <structfield>queryid</structfield> values can be assumed to be
stable and comparable only so long as the underlying server version and
catalog metadata details stay exactly the same. Two servers
participating in replication based on physical WAL replay can be expected
to have identical <structfield>queryid</> values for the same query.
to have identical <structfield>queryid</structfield> values for the same query.
However, logical replication schemes do not promise to keep replicas
identical in all relevant details, so <structfield>queryid</> will
identical in all relevant details, so <structfield>queryid</structfield> will
not be a useful identifier for accumulating costs across a set of logical
replicas. If in doubt, direct testing is recommended.
</para>
@@ -306,13 +306,13 @@
<para>
The parameter symbols used to replace constants in
representative query texts start from the next number after the
highest <literal>$</><replaceable>n</> parameter in the original query
text, or <literal>$1</> if there was none. It's worth noting that in
highest <literal>$</literal><replaceable>n</replaceable> parameter in the original query
text, or <literal>$1</literal> if there was none. It's worth noting that in
some cases there may be hidden parameter symbols that affect this
numbering. For example, <application>PL/pgSQL</> uses hidden parameter
numbering. For example, <application>PL/pgSQL</application> uses hidden parameter
symbols to insert values of function local variables into queries, so that
a <application>PL/pgSQL</> statement like <literal>SELECT i + 1 INTO j</>
would have representative text like <literal>SELECT i + $2</>.
a <application>PL/pgSQL</application> statement like <literal>SELECT i + 1 INTO j</literal>
would have representative text like <literal>SELECT i + $2</literal>.
</para>
<para>
@@ -320,11 +320,11 @@
not consume shared memory. Therefore, even very lengthy query texts can
be stored successfully. However, if many long query texts are
accumulated, the external file might grow unmanageably large. As a
recovery method if that happens, <filename>pg_stat_statements</> may
recovery method if that happens, <filename>pg_stat_statements</filename> may
choose to discard the query texts, whereupon all existing entries in
the <structname>pg_stat_statements</> view will show
null <structfield>query</> fields, though the statistics associated with
each <structfield>queryid</> are preserved. If this happens, consider
the <structname>pg_stat_statements</structname> view will show
null <structfield>query</structfield> fields, though the statistics associated with
each <structfield>queryid</structfield> are preserved. If this happens, consider
reducing <varname>pg_stat_statements.max</varname> to prevent
recurrences.
</para>
@@ -345,7 +345,7 @@
<listitem>
<para>
<function>pg_stat_statements_reset</function> discards all statistics
gathered so far by <filename>pg_stat_statements</>.
gathered so far by <filename>pg_stat_statements</filename>.
By default, this function can only be executed by superusers.
</para>
</listitem>
@@ -363,17 +363,17 @@
<listitem>
<para>
The <structname>pg_stat_statements</structname> view is defined in
terms of a function also named <function>pg_stat_statements</>.
terms of a function also named <function>pg_stat_statements</function>.
It is possible for clients to call
the <function>pg_stat_statements</function> function directly, and by
specifying <literal>showtext := false</literal> have query text be
omitted (that is, the <literal>OUT</literal> argument that corresponds
to the view's <structfield>query</> column will return nulls). This
to the view's <structfield>query</structfield> column will return nulls). This
feature is intended to support external tools that might wish to avoid
the overhead of repeatedly retrieving query texts of indeterminate
length. Such tools can instead cache the first query text observed
for each entry themselves, since that is
all <filename>pg_stat_statements</> itself does, and then retrieve
all <filename>pg_stat_statements</filename> itself does, and then retrieve
query texts only as needed. Since the server stores query texts in a
file, this approach may reduce physical I/O for repeated examination
of the <structname>pg_stat_statements</structname> data.
@@ -396,7 +396,7 @@
<para>
<varname>pg_stat_statements.max</varname> is the maximum number of
statements tracked by the module (i.e., the maximum number of rows
in the <structname>pg_stat_statements</> view). If more distinct
in the <structname>pg_stat_statements</structname> view). If more distinct
statements than that are observed, information about the least-executed
statements is discarded.
The default value is 5000.
@@ -414,11 +414,11 @@
<para>
<varname>pg_stat_statements.track</varname> controls which statements
are counted by the module.
Specify <literal>top</> to track top-level statements (those issued
directly by clients), <literal>all</> to also track nested statements
(such as statements invoked within functions), or <literal>none</> to
Specify <literal>top</literal> to track top-level statements (those issued
directly by clients), <literal>all</literal> to also track nested statements
(such as statements invoked within functions), or <literal>none</literal> to
disable statement statistics collection.
The default value is <literal>top</>.
The default value is <literal>top</literal>.
Only superusers can change this setting.
</para>
</listitem>
@@ -433,9 +433,9 @@
<para>
<varname>pg_stat_statements.track_utility</varname> controls whether
utility commands are tracked by the module. Utility commands are
all those other than <command>SELECT</>, <command>INSERT</>,
<command>UPDATE</> and <command>DELETE</>.
The default value is <literal>on</>.
all those other than <command>SELECT</command>, <command>INSERT</command>,
<command>UPDATE</command> and <command>DELETE</command>.
The default value is <literal>on</literal>.
Only superusers can change this setting.
</para>
</listitem>
@@ -450,10 +450,10 @@
<para>
<varname>pg_stat_statements.save</varname> specifies whether to
save statement statistics across server shutdowns.
If it is <literal>off</> then statistics are not saved at
If it is <literal>off</literal> then statistics are not saved at
shutdown nor reloaded at server start.
The default value is <literal>on</>.
This parameter can only be set in the <filename>postgresql.conf</>
The default value is <literal>on</literal>.
This parameter can only be set in the <filename>postgresql.conf</filename>
file or on the server command line.
</para>
</listitem>
@@ -464,11 +464,11 @@
The module requires additional shared memory proportional to
<varname>pg_stat_statements.max</varname>. Note that this
memory is consumed whenever the module is loaded, even if
<varname>pg_stat_statements.track</> is set to <literal>none</>.
<varname>pg_stat_statements.track</varname> is set to <literal>none</literal>.
</para>
<para>
These parameters must be set in <filename>postgresql.conf</>.
These parameters must be set in <filename>postgresql.conf</filename>.
Typical usage might be:
<programlisting>