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Remove the single-argument form of string_agg(). It added nothing much in

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functionality, while creating an ambiguity in usage with ORDER BY that at
least two people have already gotten seriously confused by.  Also, add an
opr_sanity test to check that we don't in future violate the newly minted
policy of not having built-in aggregates with the same name and different
numbers of parameters.  Per discussion of a complaint from Thom Brown.
This commit is contained in:
Tom Lane
2010-08-05 18:21:19 +00:00
parent fd1843ff89
commit b0c451e145
11 changed files with 85 additions and 77 deletions
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12
doc/src/sgml/func.sgml
View File

@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.523 2010/08/05 04:21:53 petere Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.524 2010/08/05 18:21:17 tgl Exp $ -->
<chapter id="functions">
<title>Functions and Operators</title>
@ -9782,7 +9782,7 @@ SELECT NULLIF(value, '(none)') ...
<thead>
<row>
<entry>Function</entry>
<entry>Argument Type</entry>
<entry>Argument Type(s)</entry>
<entry>Return Type</entry>
<entry>Description</entry>
</row>
@ -9952,17 +9952,17 @@ SELECT NULLIF(value, '(none)') ...
<primary>string_agg</primary>
</indexterm>
<function>
string_agg(<replaceable class="parameter">expression</replaceable>
[, <replaceable class="parameter">delimiter</replaceable> ] )
string_agg(<replaceable class="parameter">expression</replaceable>,
<replaceable class="parameter">delimiter</replaceable>)
</function>
</entry>
<entry>
<type>text</type>
<type>text</type>, <type>text</type>
</entry>
<entry>
<type>text</type>
</entry>
<entry>input values concatenated into a string, optionally with delimiters</entry>
<entry>input values concatenated into a string, separated by delimiter</entry>
</row>
<row>

11
doc/src/sgml/syntax.sgml
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@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/syntax.sgml,v 1.149 2010/08/04 15:27:57 tgl Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/syntax.sgml,v 1.150 2010/08/05 18:21:17 tgl Exp $ -->
<chapter id="sql-syntax">
<title>SQL Syntax</title>
@ -1583,16 +1583,17 @@ SELECT array_agg(a ORDER BY b DESC) FROM table;
<para>
When dealing with multiple-argument aggregate functions, note that the
<literal>ORDER BY</> clause goes after all the aggregate arguments.
For example, this:
For example, write this:
<programlisting>
SELECT string_agg(a, ',' ORDER BY a) FROM table;
</programlisting>
not this:
<programlisting>
SELECT string_agg(a ORDER BY a, ',') FROM table; -- not what you want
SELECT string_agg(a ORDER BY a, ',') FROM table; -- incorrect
</programlisting>
The latter syntax will be accepted, but <literal>','</> will be
treated as a (useless) sort key.
The latter is syntactically valid, but it represents a call of a
single-argument aggregate function with two <literal>ORDER BY</> keys
(the second one being rather useless since it's a constant).
</para>
<para>