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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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164
doc/src/sgml/ref/create_aggregate.sgml
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@@ -98,7 +98,7 @@ CREATE AGGREGATE <replaceable class="parameter">name</replaceable> (
<para>
If a schema name is given (for example, <literal>CREATE AGGREGATE
myschema.myagg ...</>) then the aggregate function is created in the
myschema.myagg ...</literal>) then the aggregate function is created in the
specified schema. Otherwise it is created in the current schema.
</para>
@@ -191,57 +191,57 @@ CREATE AGGREGATE <replaceable class="parameter">name</replaceable> (
is polymorphic and the state value's data type would be inadequate to
pin down the result type. These extra parameters are always passed as
NULL (and so the final function must not be strict when
the <literal>FINALFUNC_EXTRA</> option is used), but nonetheless they
the <literal>FINALFUNC_EXTRA</literal> option is used), but nonetheless they
are valid parameters. The final function could for example make use
of <function>get_fn_expr_argtype</> to identify the actual argument type
of <function>get_fn_expr_argtype</function> to identify the actual argument type
in the current call.
</para>
<para>
An aggregate can optionally support <firstterm>moving-aggregate mode</>,
An aggregate can optionally support <firstterm>moving-aggregate mode</firstterm>,
as described in <xref linkend="xaggr-moving-aggregates">. This requires
specifying the <literal>MSFUNC</>, <literal>MINVFUNC</>,
and <literal>MSTYPE</> parameters, and optionally
the <literal>MSPACE</>, <literal>MFINALFUNC</>,
<literal>MFINALFUNC_EXTRA</>, <literal>MFINALFUNC_MODIFY</>,
and <literal>MINITCOND</> parameters. Except for <literal>MINVFUNC</>,
specifying the <literal>MSFUNC</literal>, <literal>MINVFUNC</literal>,
and <literal>MSTYPE</literal> parameters, and optionally
the <literal>MSPACE</literal>, <literal>MFINALFUNC</literal>,
<literal>MFINALFUNC_EXTRA</literal>, <literal>MFINALFUNC_MODIFY</literal>,
and <literal>MINITCOND</literal> parameters. Except for <literal>MINVFUNC</literal>,
these parameters work like the corresponding simple-aggregate parameters
without <literal>M</>; they define a separate implementation of the
without <literal>M</literal>; they define a separate implementation of the
aggregate that includes an inverse transition function.
</para>
<para>
The syntax with <literal>ORDER BY</literal> in the parameter list creates
a special type of aggregate called an <firstterm>ordered-set
aggregate</firstterm>; or if <literal>HYPOTHETICAL</> is specified, then
aggregate</firstterm>; or if <literal>HYPOTHETICAL</literal> is specified, then
a <firstterm>hypothetical-set aggregate</firstterm> is created. These
aggregates operate over groups of sorted values in order-dependent ways,
so that specification of an input sort order is an essential part of a
call. Also, they can have <firstterm>direct</> arguments, which are
call. Also, they can have <firstterm>direct</firstterm> arguments, which are
arguments that are evaluated only once per aggregation rather than once
per input row. Hypothetical-set aggregates are a subclass of ordered-set
aggregates in which some of the direct arguments are required to match,
in number and data types, the aggregated argument columns. This allows
the values of those direct arguments to be added to the collection of
aggregate-input rows as an additional <quote>hypothetical</> row.
aggregate-input rows as an additional <quote>hypothetical</quote> row.
</para>
<para>
An aggregate can optionally support <firstterm>partial aggregation</>,
An aggregate can optionally support <firstterm>partial aggregation</firstterm>,
as described in <xref linkend="xaggr-partial-aggregates">.
This requires specifying the <literal>COMBINEFUNC</> parameter.
This requires specifying the <literal>COMBINEFUNC</literal> parameter.
If the <replaceable class="parameter">state_data_type</replaceable>
is <type>internal</>, it's usually also appropriate to provide the
<literal>SERIALFUNC</> and <literal>DESERIALFUNC</> parameters so that
is <type>internal</type>, it's usually also appropriate to provide the
<literal>SERIALFUNC</literal> and <literal>DESERIALFUNC</literal> parameters so that
parallel aggregation is possible. Note that the aggregate must also be
marked <literal>PARALLEL SAFE</> to enable parallel aggregation.
marked <literal>PARALLEL SAFE</literal> to enable parallel aggregation.
</para>
<para>
Aggregates that behave like <function>MIN</> or <function>MAX</> can
Aggregates that behave like <function>MIN</function> or <function>MAX</function> can
sometimes be optimized by looking into an index instead of scanning every
input row. If this aggregate can be so optimized, indicate it by
specifying a <firstterm>sort operator</>. The basic requirement is that
specifying a <firstterm>sort operator</firstterm>. The basic requirement is that
the aggregate must yield the first element in the sort ordering induced by
the operator; in other words:
<programlisting>
@@ -253,9 +253,9 @@ SELECT col FROM tab ORDER BY col USING sortop LIMIT 1;
</programlisting>
Further assumptions are that the aggregate ignores null inputs, and that
it delivers a null result if and only if there were no non-null inputs.
Ordinarily, a data type's <literal>&lt;</> operator is the proper sort
operator for <function>MIN</>, and <literal>&gt;</> is the proper sort
operator for <function>MAX</>. Note that the optimization will never
Ordinarily, a data type's <literal>&lt;</literal> operator is the proper sort
operator for <function>MIN</function>, and <literal>&gt;</literal> is the proper sort
operator for <function>MAX</function>. Note that the optimization will never
actually take effect unless the specified operator is the <quote>less
than</quote> or <quote>greater than</quote> strategy member of a B-tree
index operator class.
@@ -288,10 +288,10 @@ SELECT col FROM tab ORDER BY col USING sortop LIMIT 1;
<listitem>
<para>
The mode of an argument: <literal>IN</> or <literal>VARIADIC</>.
(Aggregate functions do not support <literal>OUT</> arguments.)
If omitted, the default is <literal>IN</>. Only the last argument
can be marked <literal>VARIADIC</>.
The mode of an argument: <literal>IN</literal> or <literal>VARIADIC</literal>.
(Aggregate functions do not support <literal>OUT</literal> arguments.)
If omitted, the default is <literal>IN</literal>. Only the last argument
can be marked <literal>VARIADIC</literal>.
</para>
</listitem>
</varlistentry>
@@ -312,7 +312,7 @@ SELECT col FROM tab ORDER BY col USING sortop LIMIT 1;
<listitem>
<para>
An input data type on which this aggregate function operates.
To create a zero-argument aggregate function, write <literal>*</>
To create a zero-argument aggregate function, write <literal>*</literal>
in place of the list of argument specifications. (An example of such an
aggregate is <function>count(*)</function>.)
</para>
@@ -323,12 +323,12 @@ SELECT col FROM tab ORDER BY col USING sortop LIMIT 1;
<term><replaceable class="parameter">base_type</replaceable></term>
<listitem>
<para>
In the old syntax for <command>CREATE AGGREGATE</>, the input data type
is specified by a <literal>basetype</> parameter rather than being
In the old syntax for <command>CREATE AGGREGATE</command>, the input data type
is specified by a <literal>basetype</literal> parameter rather than being
written next to the aggregate name. Note that this syntax allows
only one input parameter. To define a zero-argument aggregate function
with this syntax, specify the <literal>basetype</> as
<literal>"ANY"</> (not <literal>*</>).
with this syntax, specify the <literal>basetype</literal> as
<literal>"ANY"</literal> (not <literal>*</literal>).
Ordered-set aggregates cannot be defined with the old syntax.
</para>
</listitem>
@@ -339,9 +339,9 @@ SELECT col FROM tab ORDER BY col USING sortop LIMIT 1;
<listitem>
<para>
The name of the state transition function to be called for each
input row. For a normal <replaceable class="parameter">N</>-argument
aggregate function, the <replaceable class="parameter">sfunc</>
must take <replaceable class="parameter">N</>+1 arguments,
input row. For a normal <replaceable class="parameter">N</replaceable>-argument
aggregate function, the <replaceable class="parameter">sfunc</replaceable>
must take <replaceable class="parameter">N</replaceable>+1 arguments,
the first being of type <replaceable
class="parameter">state_data_type</replaceable> and the rest
matching the declared input data type(s) of the aggregate.
@@ -375,7 +375,7 @@ SELECT col FROM tab ORDER BY col USING sortop LIMIT 1;
<para>
The approximate average size (in bytes) of the aggregate's state value.
If this parameter is omitted or is zero, a default estimate is used
based on the <replaceable>state_data_type</>.
based on the <replaceable>state_data_type</replaceable>.
The planner uses this value to estimate the memory required for a
grouped aggregate query. The planner will consider using hash
aggregation for such a query only if the hash table is estimated to fit
@@ -408,7 +408,7 @@ SELECT col FROM tab ORDER BY col USING sortop LIMIT 1;
</para>
<para>
If <literal>FINALFUNC_EXTRA</> is specified, then in addition to the
If <literal>FINALFUNC_EXTRA</literal> is specified, then in addition to the
final state value and any direct arguments, the final function
receives extra NULL values corresponding to the aggregate's regular
(aggregated) arguments. This is mainly useful to allow correct
@@ -419,16 +419,16 @@ SELECT col FROM tab ORDER BY col USING sortop LIMIT 1;
</varlistentry>
<varlistentry>
<term><literal>FINALFUNC_MODIFY</> = { <literal>READ_ONLY</> | <literal>SHARABLE</> | <literal>READ_WRITE</> }</term>
<term><literal>FINALFUNC_MODIFY</literal> = { <literal>READ_ONLY</literal> | <literal>SHARABLE</literal> | <literal>READ_WRITE</literal> }</term>
<listitem>
<para>
This option specifies whether the final function is a pure function
that does not modify its arguments. <literal>READ_ONLY</> indicates
that does not modify its arguments. <literal>READ_ONLY</literal> indicates
it does not; the other two values indicate that it may change the
transition state value. See <xref linkend="sql-createaggregate-notes"
endterm="sql-createaggregate-notes-title"> below for more detail. The
default is <literal>READ_ONLY</>, except for ordered-set aggregates,
for which the default is <literal>READ_WRITE</>.
default is <literal>READ_ONLY</literal>, except for ordered-set aggregates,
for which the default is <literal>READ_WRITE</literal>.
</para>
</listitem>
</varlistentry>
@@ -482,11 +482,11 @@ SELECT col FROM tab ORDER BY col USING sortop LIMIT 1;
<para>
An aggregate function
whose <replaceable class="parameter">state_data_type</replaceable>
is <type>internal</> can participate in parallel aggregation only if it
is <type>internal</type> can participate in parallel aggregation only if it
has a <replaceable class="parameter">serialfunc</replaceable> function,
which must serialize the aggregate state into a <type>bytea</> value for
which must serialize the aggregate state into a <type>bytea</type> value for
transmission to another process. This function must take a single
argument of type <type>internal</> and return type <type>bytea</>. A
argument of type <type>internal</type> and return type <type>bytea</type>. A
corresponding <replaceable class="parameter">deserialfunc</replaceable>
is also required.
</para>
@@ -499,9 +499,9 @@ SELECT col FROM tab ORDER BY col USING sortop LIMIT 1;
<para>
Deserialize a previously serialized aggregate state back into
<replaceable class="parameter">state_data_type</replaceable>. This
function must take two arguments of types <type>bytea</>
and <type>internal</>, and produce a result of type <type>internal</>.
(Note: the second, <type>internal</> argument is unused, but is required
function must take two arguments of types <type>bytea</type>
and <type>internal</type>, and produce a result of type <type>internal</type>.
(Note: the second, <type>internal</type> argument is unused, but is required
for type safety reasons.)
</para>
</listitem>
@@ -526,8 +526,8 @@ SELECT col FROM tab ORDER BY col USING sortop LIMIT 1;
The name of the forward state transition function to be called for each
input row in moving-aggregate mode. This is exactly like the regular
transition function, except that its first argument and result are of
type <replaceable>mstate_data_type</>, which might be different
from <replaceable>state_data_type</>.
type <replaceable>mstate_data_type</replaceable>, which might be different
from <replaceable>state_data_type</replaceable>.
</para>
</listitem>
</varlistentry>
@@ -538,7 +538,7 @@ SELECT col FROM tab ORDER BY col USING sortop LIMIT 1;
<para>
The name of the inverse state transition function to be used in
moving-aggregate mode. This function has the same argument and
result types as <replaceable>msfunc</>, but it is used to remove
result types as <replaceable>msfunc</replaceable>, but it is used to remove
a value from the current aggregate state, rather than add a value to
it. The inverse transition function must have the same strictness
attribute as the forward state transition function.
@@ -562,7 +562,7 @@ SELECT col FROM tab ORDER BY col USING sortop LIMIT 1;
<para>
The approximate average size (in bytes) of the aggregate's state
value, when using moving-aggregate mode. This works the same as
<replaceable>state_data_size</>.
<replaceable>state_data_size</replaceable>.
</para>
</listitem>
</varlistentry>
@@ -573,22 +573,22 @@ SELECT col FROM tab ORDER BY col USING sortop LIMIT 1;
<para>
The name of the final function called to compute the aggregate's
result after all input rows have been traversed, when using
moving-aggregate mode. This works the same as <replaceable>ffunc</>,
moving-aggregate mode. This works the same as <replaceable>ffunc</replaceable>,
except that its first argument's type
is <replaceable>mstate_data_type</> and extra dummy arguments are
specified by writing <literal>MFINALFUNC_EXTRA</>.
The aggregate result type determined by <replaceable>mffunc</>
or <replaceable>mstate_data_type</> must match that determined by the
is <replaceable>mstate_data_type</replaceable> and extra dummy arguments are
specified by writing <literal>MFINALFUNC_EXTRA</literal>.
The aggregate result type determined by <replaceable>mffunc</replaceable>
or <replaceable>mstate_data_type</replaceable> must match that determined by the
aggregate's regular implementation.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>MFINALFUNC_MODIFY</> = { <literal>READ_ONLY</> | <literal>SHARABLE</> | <literal>READ_WRITE</> }</term>
<term><literal>MFINALFUNC_MODIFY</literal> = { <literal>READ_ONLY</literal> | <literal>SHARABLE</literal> | <literal>READ_WRITE</literal> }</term>
<listitem>
<para>
This option is like <literal>FINALFUNC_MODIFY</>, but it describes
This option is like <literal>FINALFUNC_MODIFY</literal>, but it describes
the behavior of the moving-aggregate final function.
</para>
</listitem>
@@ -599,7 +599,7 @@ SELECT col FROM tab ORDER BY col USING sortop LIMIT 1;
<listitem>
<para>
The initial setting for the state value, when using moving-aggregate
mode. This works the same as <replaceable>initial_condition</>.
mode. This works the same as <replaceable>initial_condition</replaceable>.
</para>
</listitem>
</varlistentry>
@@ -608,8 +608,8 @@ SELECT col FROM tab ORDER BY col USING sortop LIMIT 1;
<term><replaceable class="parameter">sort_operator</replaceable></term>
<listitem>
<para>
The associated sort operator for a <function>MIN</>- or
<function>MAX</>-like aggregate.
The associated sort operator for a <function>MIN</function>- or
<function>MAX</function>-like aggregate.
This is just an operator name (possibly schema-qualified).
The operator is assumed to have the same input data types as
the aggregate (which must be a single-argument normal aggregate).
@@ -618,14 +618,14 @@ SELECT col FROM tab ORDER BY col USING sortop LIMIT 1;
</varlistentry>
<varlistentry>
<term><literal>PARALLEL =</> { <literal>SAFE</> | <literal>RESTRICTED</> | <literal>UNSAFE</> }</term>
<term><literal>PARALLEL =</literal> { <literal>SAFE</literal> | <literal>RESTRICTED</literal> | <literal>UNSAFE</literal> }</term>
<listitem>
<para>
The meanings of <literal>PARALLEL SAFE</>, <literal>PARALLEL
RESTRICTED</>, and <literal>PARALLEL UNSAFE</> are the same as
The meanings of <literal>PARALLEL SAFE</literal>, <literal>PARALLEL
RESTRICTED</literal>, and <literal>PARALLEL UNSAFE</literal> are the same as
in <xref linkend="sql-createfunction">. An aggregate will not be
considered for parallelization if it is marked <literal>PARALLEL
UNSAFE</> (which is the default!) or <literal>PARALLEL RESTRICTED</>.
UNSAFE</literal> (which is the default!) or <literal>PARALLEL RESTRICTED</literal>.
Note that the parallel-safety markings of the aggregate's support
functions are not consulted by the planner, only the marking of the
aggregate itself.
@@ -640,7 +640,7 @@ SELECT col FROM tab ORDER BY col USING sortop LIMIT 1;
For ordered-set aggregates only, this flag specifies that the aggregate
arguments are to be processed according to the requirements for
hypothetical-set aggregates: that is, the last few direct arguments must
match the data types of the aggregated (<literal>WITHIN GROUP</>)
match the data types of the aggregated (<literal>WITHIN GROUP</literal>)
arguments. The <literal>HYPOTHETICAL</literal> flag has no effect on
run-time behavior, only on parse-time resolution of the data types and
collations of the aggregate's arguments.
@@ -660,7 +660,7 @@ SELECT col FROM tab ORDER BY col USING sortop LIMIT 1;
<para>
In parameters that specify support function names, you can write
a schema name if needed, for example <literal>SFUNC = public.sum</>.
a schema name if needed, for example <literal>SFUNC = public.sum</literal>.
Do not write argument types there, however &mdash; the argument types
of the support functions are determined from other parameters.
</para>
@@ -668,7 +668,7 @@ SELECT col FROM tab ORDER BY col USING sortop LIMIT 1;
<para>
Ordinarily, PostgreSQL functions are expected to be true functions that
do not modify their input values. However, an aggregate transition
function, <emphasis>when used in the context of an aggregate</>,
function, <emphasis>when used in the context of an aggregate</emphasis>,
is allowed to cheat and modify its transition-state argument in place.
This can provide substantial performance benefits compared to making
a fresh copy of the transition state each time.
@@ -678,26 +678,26 @@ SELECT col FROM tab ORDER BY col USING sortop LIMIT 1;
Likewise, while an aggregate final function is normally expected not to
modify its input values, sometimes it is impractical to avoid modifying
the transition-state argument. Such behavior must be declared using
the <literal>FINALFUNC_MODIFY</> parameter. The <literal>READ_WRITE</>
the <literal>FINALFUNC_MODIFY</literal> parameter. The <literal>READ_WRITE</literal>
value indicates that the final function modifies the transition state in
unspecified ways. This value prevents use of the aggregate as a window
function, and it also prevents merging of transition states for aggregate
calls that share the same input values and transition functions.
The <literal>SHARABLE</> value indicates that the transition function
The <literal>SHARABLE</literal> value indicates that the transition function
cannot be applied after the final function, but multiple final-function
calls can be performed on the ending transition state value. This value
prevents use of the aggregate as a window function, but it allows merging
of transition states. (That is, the optimization of interest here is not
applying the same final function repeatedly, but applying different final
functions to the same ending transition state value. This is allowed as
long as none of the final functions are marked <literal>READ_WRITE</>.)
long as none of the final functions are marked <literal>READ_WRITE</literal>.)
</para>
<para>
If an aggregate supports moving-aggregate mode, it will improve
calculation efficiency when the aggregate is used as a window function
for a window with moving frame start (that is, a frame start mode other
than <literal>UNBOUNDED PRECEDING</>). Conceptually, the forward
than <literal>UNBOUNDED PRECEDING</literal>). Conceptually, the forward
transition function adds input values to the aggregate's state when
they enter the window frame from the bottom, and the inverse transition
function removes them again when they leave the frame at the top. So,
@@ -738,20 +738,20 @@ SELECT col FROM tab ORDER BY col USING sortop LIMIT 1;
</para>
<para>
The syntax for ordered-set aggregates allows <literal>VARIADIC</>
The syntax for ordered-set aggregates allows <literal>VARIADIC</literal>
to be specified for both the last direct parameter and the last
aggregated (<literal>WITHIN GROUP</>) parameter. However, the
current implementation restricts use of <literal>VARIADIC</>
aggregated (<literal>WITHIN GROUP</literal>) parameter. However, the
current implementation restricts use of <literal>VARIADIC</literal>
in two ways. First, ordered-set aggregates can only use
<literal>VARIADIC "any"</>, not other variadic array types.
Second, if the last direct parameter is <literal>VARIADIC "any"</>,
<literal>VARIADIC "any"</literal>, not other variadic array types.
Second, if the last direct parameter is <literal>VARIADIC "any"</literal>,
then there can be only one aggregated parameter and it must also
be <literal>VARIADIC "any"</>. (In the representation used in the
be <literal>VARIADIC "any"</literal>. (In the representation used in the
system catalogs, these two parameters are merged into a single
<literal>VARIADIC "any"</> item, since <structname>pg_proc</> cannot
represent functions with more than one <literal>VARIADIC</> parameter.)
<literal>VARIADIC "any"</literal> item, since <structname>pg_proc</structname> cannot
represent functions with more than one <literal>VARIADIC</literal> parameter.)
If the aggregate is a hypothetical-set aggregate, the direct arguments
that match the <literal>VARIADIC "any"</> parameter are the hypothetical
that match the <literal>VARIADIC "any"</literal> parameter are the hypothetical
ones; any preceding parameters represent additional direct arguments
that are not constrained to match the aggregated arguments.
</para>
@@ -764,7 +764,7 @@ SELECT col FROM tab ORDER BY col USING sortop LIMIT 1;
<para>
Partial (including parallel) aggregation is currently not supported for
ordered-set aggregates. Also, it will never be used for aggregate calls
that include <literal>DISTINCT</> or <literal>ORDER BY</> clauses, since
that include <literal>DISTINCT</literal> or <literal>ORDER BY</literal> clauses, since
those semantics cannot be supported during partial aggregation.
</para>
</refsect1>