Re: [HACKERS] [REVIEW] Generate column names for subquery expressions
Marti Raudsepp ma...@juffo.org writes: On Wed, Sep 14, 2011 at 05:26, Kyotaro HORIGUCHI horiguchi.kyot...@oss.ntt.co.jp wrote: This is a review for the patch `Generate column names for subquery expressions' (https://commitfest.postgresql.org/action/patch_view?id=632) Thanks for the review. :) Applied with minor adjustments. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] [REVIEW] Generate column names for subquery expressions
Hi, PS: When you send a review, you should add the author's email to the To: line to make sure they see it. I noticed your email only today because it was in a new thread and not addressed to me directly. Thanks for the advise. I will do so after this. Good catch, a new patch is attached. Apparently the results of this query have also changed in recent versions, but I didn't touch that. I've comfirmed that is fixed. I'll send this comitter review. -- Kyotaro Horiguchi NTT Open Source Software Center -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] [REVIEW] Generate column names for subquery expressions
On Wed, Sep 14, 2011 at 05:26, Kyotaro HORIGUCHI
horiguchi.kyot...@oss.ntt.co.jp wrote:
This is a review for the patch `Generate column names for
subquery expressions'
(https://commitfest.postgresql.org/action/patch_view?id=632)
Thanks for the review. :)
PS: When you send a review, you should add the author's email to the
To: line to make sure they see it. I noticed your email only today
because it was in a new thread and not addressed to me directly.
I think this patch needs no documentation, but it is needed to
edit the changed behaviors quoted in document. Maybe only one
change as far as I have seen.
http://www.postgresql.org/docs/9.0/static/sql-expressions.html
SELECT ARRAY(SELECT oid FROM pg_proc WHERE proname LIKE 'bytea%');
?column?
-
{2011,1954,1948,1952,1951,1244,1950,2005,1949,1953,2006,31}
Good catch, a new patch is attached. Apparently the results of this
query have also changed in recent versions, but I didn't touch that.
Regards,
Marti
From 0defe411697f84d26e6f23970d90c70cd057c298 Mon Sep 17 00:00:00 2001
From: Marti Raudsepp ma...@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
---
doc/src/sgml/syntax.sgml |2 +-
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 +-
5 files changed, 45 insertions(+), 12 deletions(-)
diff --git a/doc/src/sgml/syntax.sgml b/doc/src/sgml/syntax.sgml
index 9119b60..ab81f78 100644
--- a/doc/src/sgml/syntax.sgml
+++ b/doc/src/sgml/syntax.sgml
@@ -2109,7 +2109,7 @@ SELECT ARRAY[]::integer[];
bracketed) subquery. For example:
programlisting
SELECT ARRAY(SELECT oid FROM pg_proc WHERE proname LIKE 'bytea%');
- ?column?
+array
-
{2011,1954,1948,1952,1951,1244,1950,2005,1949,1953,2006,31}
(1 row)
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?
---
-
+ max
+--
+
(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)
[HACKERS] [REVIEW] Generate column names for subquery expressions
This is a review for the patch `Generate column names for
subquery expressions'
(https://commitfest.postgresql.org/action/patch_view?id=632)
Summary
Patch format is in context diff format.
This patch applies cleanly on HEAD and make check suceeded.
It seems have no problem to apply.
Documents is needed to modify.
Purpose and function of this patch
This patch intends to name a part of the columns in the outmost
SELECT caluse currently left unnamed - seen as `?column?' - and
fix `unnatural' naming - seen as `int4', `case'.
This patch figures column name after T_SubLink parse nodes
corresponding to EXISTS, ARRAY, and subquery in addition to
currently processed parse node types.
It seems reasonable that (ALL|ANY|ROWCOMPARE|CTE)_SUBLINK is left
unnnamed.
Patch application, regression test
The patch applies cleanly onto HEAD. make check yiels no error.
This patch adds no additional test case and it seems ok.
The coding style in this patch seems according to the convention.
Behavior changes
The behavior of column naming changes as following.
STATEMENTAFTER BEFORE
-
select (select 1 as foo) foo ?column?
select (exists (select 1)) exists ?column?
select (array (select 1 as x)) array ?column?
select (select 1 as aaa)::int aaa int4
select case when true then 1 else (select 1 as foo) end;
foo case
Aboves are same as described. But the following expression
returns somewhat confising outcome.
select case when true then (select 2 as bar) else (select 1 as foo) end;
foo
-
2
(1 row)
But this patch is not to blame for the behavior. The following is
seen for unpatched pg.
# create table foo (a int, b int, c int);
# insert into foo values (1, 100, -100), (0, 10, -10), (-1, 25, -25);
# select case when a 0 then b else c end from foo;
c
--
(snipped)
# select case a when -1 then c when 1 then a else b end from foo;
b
-
(snipped)
Nevertheless this behavior seems a bit unnatural, it is not the
issue for this patch.
Performance
This patch adds no extra load such as loops, recursive calls or
deep calls. Added code runs for exists(), array() and subquery
appear in the column list of select clause. So I think this patch
can put only negligible impact on performance.
Gleaning
This patch assumes node(subLinkType==EXPR_SUBLINK)-subselect is
not null, and it seems that gram.y(c) says the assumption is
correct.
I think this patch needs no documentation, but it is needed to
edit the changed behaviors quoted in document. Maybe only one
change as far as I have seen.
http://www.postgresql.org/docs/9.0/static/sql-expressions.html
4.2.11
..
SELECT ARRAY(SELECT oid FROM pg_proc WHERE proname LIKE 'bytea%');
?column?
-
{2011,1954,1948,1952,1951,1244,1950,2005,1949,1953,2006,31}
Sincerely,
--
Kyotaro Horiguchi
--
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