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Support ORDER BY within aggregate function calls, at long last providing a

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non-kluge method for controlling the order in which values are fed to an
aggregate function.  At the same time eliminate the old implementation
restriction that DISTINCT was only supported for single-argument aggregates.

Possibly release-notable behavioral change: formerly, agg(DISTINCT x)
dropped null values of x unconditionally.  Now, it does so only if the
agg transition function is strict; otherwise nulls are treated as DISTINCT
normally would, ie, you get one copy.

Andrew Gierth, reviewed by Hitoshi Harada
This commit is contained in:
Tom Lane
2009-12-15 17:57:48 +00:00
parent 6a6efb9640
commit 34d26872ed
31 changed files with 1184 additions and 248 deletions
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8
src/include/nodes/parsenodes.h
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@@ -13,7 +13,7 @@
* Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/nodes/parsenodes.h,v 1.418 2009/12/11 03:34:56 itagaki Exp $
* $PostgreSQL: pgsql/src/include/nodes/parsenodes.h,v 1.419 2009/12/15 17:57:47 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -264,9 +264,10 @@ typedef struct TypeCast
/*
* FuncCall - a function or aggregate invocation
*
* agg_order (if not NIL) indicates we saw 'foo(... ORDER BY ...)'.
* agg_star indicates we saw a 'foo(*)' construct, while agg_distinct
* indicates we saw 'foo(DISTINCT ...)'. In either case, the construct
* *must* be an aggregate call. Otherwise, it might be either an
* indicates we saw 'foo(DISTINCT ...)'. In any of these cases, the
* construct *must* be an aggregate call. Otherwise, it might be either an
* aggregate or some other kind of function. However, if OVER is present
* it had better be an aggregate or window function.
*/
@@ -275,6 +276,7 @@ typedef struct FuncCall
NodeTag type;
List *funcname; /* qualified name of function */
List *args; /* the arguments (list of exprs) */
List *agg_order; /* ORDER BY (list of SortBy) */
bool agg_star; /* argument was really '*' */
bool agg_distinct; /* arguments were labeled DISTINCT */
bool func_variadic; /* last argument was labeled VARIADIC */