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Throw error if a <window definition> references a window that already has a

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frame clause, as appears to be required by the fine print in the SQL spec.
Per discussion with Pavel, not doing so risks user confusion.
This commit is contained in:
Tom Lane
2008-12-31 23:42:56 +00:00
parent eb273743ed
commit df0ea5a1cd
3 changed files with 29 additions and 14 deletions
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19
doc/src/sgml/syntax.sgml
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@@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/syntax.sgml,v 1.128 2008/12/31 00:08:35 tgl Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/syntax.sgml,v 1.129 2008/12/31 23:42:56 tgl Exp $ -->
<chapter id="sql-syntax">
<title>SQL Syntax</title>
@@ -1588,12 +1588,12 @@ sqrt(2)
where <replaceable class="parameter">window_definition</replaceable>
has the syntax
<synopsis>
[ <replaceable class="parameter">window_name</replaceable> ]
[ <replaceable class="parameter">existing_window_name</replaceable> ]
[ PARTITION BY <replaceable class="parameter">expression</replaceable> [, ...] ]
[ ORDER BY <replaceable class="parameter">expression</replaceable> [ ASC | DESC | USING <replaceable class="parameter">operator</replaceable> ] [ NULLS { FIRST | LAST } ] [, ...] ]
[ <replaceable class="parameter">framing_clause</replaceable> ]
[ <replaceable class="parameter">frame_clause</replaceable> ]
</synopsis>
and the optional <replaceable class="parameter">framing_clause</replaceable>
and the optional <replaceable class="parameter">frame_clause</replaceable>
can be one of
<synopsis>
RANGE UNBOUNDED PRECEDING
@@ -1614,7 +1614,8 @@ ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING
Named window specifications are usually referenced with just
<literal>OVER</> <replaceable>window_name</replaceable>, but it is
also possible to write a window name inside the parentheses and then
optionally override its ordering clause and/or framing clause.
optionally supply an ordering clause and/or frame clause (the referenced
window must lack these clauses, if they are supplied here).
This latter syntax follows the same rules as modifying an existing
window name within the <literal>WINDOW</literal> clause; see the
<xref linkend="sql-select" endterm="sql-select-title"> reference
@@ -1622,6 +1623,9 @@ ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING
</para>
<para>
The <replaceable class="parameter">frame_clause</replaceable> specifies
the set of rows constituting the <firstterm>window frame</>, for those
window functions that act on the frame instead of the whole partition.
The default framing option is <literal>RANGE UNBOUNDED PRECEDING</>,
which is the same as <literal>RANGE BETWEEN UNBOUNDED PRECEDING AND
CURRENT ROW</>; it selects rows up through the current row's last
@@ -1639,8 +1643,9 @@ ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING
<para>
The built-in window functions are described in <xref
linkend="functions-window-table">. Also, any built-in or
user-defined aggregate function can be used as a window function.
linkend="functions-window-table">. Other window functions can be added by
the user. Also, any built-in or user-defined aggregate function can be
used as a window function.
</para>
<para>