0001-Generate-column-names-for-subquery-expressions-inste.patch

From 9f987efacfe2cd2af82722775127605e690df976 Mon Sep 17 00:00:00 2001
From: Marti Raudsepp <marti@juffo.org>
Date: Tue, 6 Sep 2011 21:17:54 +0300
Subject: [PATCH] Generate column names for subquery expressions instead of
 "?column?"

Previously these select expressions didn't have column names:
  select (SELECT colname FROM tab) => colname
  select (SELECT 1 AS foo) => foo
  select exists(SELECT 1) => exists
  select array(SELECT 1) => array

This change makes the subquery column name take precedence over "weak"
column names. Previously these two would return "int4" and "case", now
they return "foo":
  select (select 1 foo)::int
  select case when true then 1 else (select 1 as foo) end
---
 src/backend/parser/parse_target.c        |   33 ++++++++++++++++++++++++++++++
 src/test/regress/expected/aggregates.out |    6 ++--
 src/test/regress/expected/subselect.out  |   12 +++++-----
 src/test/regress/expected/with.out       |    4 +-
 4 files changed, 44 insertions(+), 11 deletions(-)

diff --git a/src/backend/parser/parse_target.c b/src/backend/parser/parse_target.c
index 9d4e580..685233c 100644
--- a/src/backend/parser/parse_target.c
+++ b/src/backend/parser/parse_target.c
@@ -1585,6 +1585,39 @@ FigureColnameInternal(Node *node, char **name)
 				return FigureColnameInternal(ind->arg, name);
 			}
 			break;
+		case T_SubLink:
+			switch (((SubLink *) node)->subLinkType)
+			{
+				case EXISTS_SUBLINK:
+					*name = "exists";
+					return 2;
+				case ARRAY_SUBLINK:
+					*name = "array";
+					return 2;
+				case EXPR_SUBLINK:
+					/* Get column name from the subquery's target list */
+					{
+						SubLink	   *sublink = (SubLink *) node;
+						Query	   *query = (Query *) sublink->subselect;
+						/* EXPR_SUBLINK always has a single target */
+						TargetEntry *te = (TargetEntry *) linitial(query->targetList);
+
+						/* Subqueries have already been transformed */
+						if(te->resname)
+						{
+							*name = te->resname;
+							return 2;
+						}
+					}
+					break;
+				/* As with other operator-like nodes, these don't really have names */
+				case ALL_SUBLINK:
+				case ANY_SUBLINK:
+				case ROWCOMPARE_SUBLINK:
+				case CTE_SUBLINK:
+					break;
+			}
+			break;
 		case T_FuncCall:
 			*name = strVal(llast(((FuncCall *) node)->funcname));
 			return 2;
diff --git a/src/test/regress/expected/aggregates.out b/src/test/regress/expected/aggregates.out
index 4861006..69926f7 100644
--- a/src/test/regress/expected/aggregates.out
+++ b/src/test/regress/expected/aggregates.out
@@ -300,9 +300,9 @@ LINE 4:                where sum(distinct a.four + b.four) = b.four)...
 select
   (select max((select i.unique2 from tenk1 i where i.unique1 = o.unique1)))
 from tenk1 o;
- ?column? 
-----------
-     9999
+ max  
+------
+ 9999
 (1 row)
 
 --
diff --git a/src/test/regress/expected/subselect.out b/src/test/regress/expected/subselect.out
index e638f0a..4ea8211 100644
--- a/src/test/regress/expected/subselect.out
+++ b/src/test/regress/expected/subselect.out
@@ -490,20 +490,20 @@ select view_a from view_a;
 (1 row)
 
 select (select view_a) from view_a;
- ?column? 
-----------
+ view_a 
+--------
  (42)
 (1 row)
 
 select (select (select view_a)) from view_a;
- ?column? 
-----------
+ view_a 
+--------
  (42)
 (1 row)
 
 select (select (a.*)::text) from view_a a;
- ?column? 
-----------
+  a   
+------
  (42)
 (1 row)
 
diff --git a/src/test/regress/expected/with.out b/src/test/regress/expected/with.out
index a1b0899..c4b0456 100644
--- a/src/test/regress/expected/with.out
+++ b/src/test/regress/expected/with.out
@@ -1065,7 +1065,7 @@ with cte(foo) as ( select 42 ) select * from ((select foo from cte)) q;
 select ( with cte(foo) as ( values(f1) )
          select (select foo from cte) )
 from int4_tbl;
-  ?column?   
+     foo     
 -------------
            0
       123456
@@ -1077,7 +1077,7 @@ from int4_tbl;
 select ( with cte(foo) as ( values(f1) )
           values((select foo from cte)) )
 from int4_tbl;
-  ?column?   
+   column1   
 -------------
            0
       123456
-- 
1.7.6.1