Hi all,
Looking at the syntax for aggregate expressions in the docs, it seems the
first three forms could perhaps be merged since the ALL and DISTINCT
keywords are effectively optional.
Currently:
aggregate_name (expression [ , ... ] [ order_by_clause ] ) [ FILTER ( WHERE
filter_clause ) ]
aggregate_name (ALL expression [ , ... ] [ order_by_clause ] ) [ FILTER (
WHERE filter_clause ) ]
aggregate_name (DISTINCT expression [ , ... ] [ order_by_clause ] ) [
FILTER ( WHERE filter_clause ) ]
Proposed:
aggregate_name ( [ ALL | DISTINCT ] expression [ , ... ] [ order_by_clause
] ) [ FILTER ( WHERE filter_clause ) ]
I've also found a precedent for this on the SELECT statement page:
[ { UNION | INTERSECT | EXCEPT } [ ALL | DISTINCT ] select ]
Patch attached with the proposed change.
Opinions?
Thom
diff --git a/doc/src/sgml/syntax.sgml b/doc/src/sgml/syntax.sgml
index 4b81b08..4f8a43b 100644
--- a/doc/src/sgml/syntax.sgml
+++ b/doc/src/sgml/syntax.sgml
@@ -1574,9 +1574,7 @@ sqrt(2)
syntax of an aggregate expression is one of the following:
<synopsis>
-<replaceable>aggregate_name</replaceable> (<replaceable>expression</replaceable> [ , ... ] [ <replaceable>order_by_clause</replaceable> ] ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ]
-<replaceable>aggregate_name</replaceable> (ALL <replaceable>expression</replaceable> [ , ... ] [ <replaceable>order_by_clause</replaceable> ] ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ]
-<replaceable>aggregate_name</replaceable> (DISTINCT <replaceable>expression</replaceable> [ , ... ] [ <replaceable>order_by_clause</replaceable> ] ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ]
+<replaceable>aggregate_name</replaceable> ( [ ALL | DISTINCT ] <replaceable>expression</replaceable> [ , ... ] [ <replaceable>order_by_clause</replaceable> ] ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ]
<replaceable>aggregate_name</replaceable> ( * ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ]
<replaceable>aggregate_name</replaceable> ( [ <replaceable>expression</replaceable> [ , ... ] ] ) WITHIN GROUP ( <replaceable>order_by_clause</replaceable> ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ]
</synopsis>
@@ -1591,14 +1589,12 @@ sqrt(2)
</para>
<para>
- The first form of aggregate expression invokes the aggregate
- once for each input row.
- The second form is the same as the first, since
- <literal>ALL</literal> is the default.
- The third form invokes the aggregate once for each distinct value
- of the expression (or distinct set of values, for multiple expressions)
- found in the input rows.
- The fourth form invokes the aggregate once for each input row; since no
+ The first form of aggregate expression with the <literal>ALL</literal>
+ keyword (the default) invokes the aggregate once for each input row.
+ Specifying <literal>DISTINCT</literal> invokes the aggregate once for
+ each distinct value of the expression (or distinct set of values, for
+ multiple expressions) found in the input rows.
+ The second form invokes the aggregate once for each input row; since no
particular input value is specified, it is generally only useful
for the <function>count(*)</function> aggregate function.
The last form is used with <firstterm>ordered-set</> aggregate
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