On 22.05.20 14:32, Peter Eisentraut wrote:
As an improvement over the spec, I think the vast majority of people
will be using simple true/false values. Can we make that optional?
CYCLE f, t SET is_cycle USING path
would be the same as
CYCLE f, t SET is_cycle TO true DEFAULT false USING path
I was also considering that. It would be an easy change to make.
This change has been accepted into the SQL:202x draft. Here is a patch
for it.
From 55c9050b4ec413e9b1b9eb9296196fc9c1957c8c Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <pe...@eisentraut.org>
Date: Mon, 22 Feb 2021 09:36:49 +0100
Subject: [PATCH] Enhanced cycle mark values
Per SQL:202x draft, in the CYCLE clause of a recursive query, the
cycle mark values can be of type boolean and can be omitted, in which
case they default to TRUE and FALSE.
---
doc/src/sgml/queries.sgml | 5 +-
doc/src/sgml/ref/select.sgml | 8 +-
src/backend/parser/gram.y | 11 +++
src/backend/utils/adt/ruleutils.c | 19 ++++-
src/test/regress/expected/with.out | 117 ++++++++++++++++++++++-------
src/test/regress/sql/with.sql | 30 +++++---
6 files changed, 143 insertions(+), 47 deletions(-)
diff --git a/doc/src/sgml/queries.sgml b/doc/src/sgml/queries.sgml
index 4741506eb5..bc0b3cc9fe 100644
--- a/doc/src/sgml/queries.sgml
+++ b/doc/src/sgml/queries.sgml
@@ -2349,14 +2349,13 @@ <title>Cycle Detection</title>
SELECT g.id, g.link, g.data, sg.depth + 1
FROM graph g, search_graph sg
WHERE g.id = sg.link
-) <emphasis>CYCLE id SET is_cycle TO true DEFAULT false USING path</emphasis>
+) <emphasis>CYCLE id SET is_cycle USING path</emphasis>
SELECT * FROM search_graph;
</programlisting>
and it will be internally rewritten to the above form. The
<literal>CYCLE</literal> clause specifies first the list of columns to
track for cycle detection, then a column name that will show whether a
- cycle has been detected, then two values to use in that column for the yes
- and no cases, and finally the name of another column that will track the
+ cycle has been detected, and finally the name of another column that will
track the
path. The cycle and path columns will implicitly be added to the output
rows of the CTE.
</para>
diff --git a/doc/src/sgml/ref/select.sgml b/doc/src/sgml/ref/select.sgml
index eb8b524951..ab91105599 100644
--- a/doc/src/sgml/ref/select.sgml
+++ b/doc/src/sgml/ref/select.sgml
@@ -74,7 +74,7 @@
<replaceable class="parameter">with_query_name</replaceable> [ (
<replaceable class="parameter">column_name</replaceable> [, ...] ) ] AS [ [ NOT
] MATERIALIZED ] ( <replaceable class="parameter">select</replaceable> |
<replaceable class="parameter">values</replaceable> | <replaceable
class="parameter">insert</replaceable> | <replaceable
class="parameter">update</replaceable> | <replaceable
class="parameter">delete</replaceable> )
[ SEARCH { BREADTH | DEPTH } FIRST BY
<replaceable>column_name</replaceable> [, ...] SET
<replaceable>search_seq_col_name</replaceable> ]
- [ CYCLE <replaceable>column_name</replaceable> [, ...] SET
<replaceable>cycle_mark_col_name</replaceable> TO
<replaceable>cycle_mark_value</replaceable> DEFAULT
<replaceable>cycle_mark_default</replaceable> USING
<replaceable>cycle_path_col_name</replaceable> ]
+ [ CYCLE <replaceable>column_name</replaceable> [, ...] SET
<replaceable>cycle_mark_col_name</replaceable> [ TO
<replaceable>cycle_mark_value</replaceable> DEFAULT
<replaceable>cycle_mark_default</replaceable> ] USING
<replaceable>cycle_path_col_name</replaceable> ]
TABLE [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ]
</synopsis>
@@ -302,8 +302,10 @@ <title><literal>WITH</literal> Clause</title>
been detected. <replaceable>cycle_mark_value</replaceable> and
<replaceable>cycle_mark_default</replaceable> must be constants and they
must be coercible to a common data type, and the data type must have an
- inequality operator. (The SQL standard requires that they be character
- strings, but PostgreSQL does not require that.) Furthermore, a column
+ inequality operator. (The SQL standard requires that they be Boolean
+ constants or character strings, but PostgreSQL does not require that.) By
+ default, <literal>TRUE</literal> and <literal>FALSE</literal> (of type
+ <type>boolean</type>) are used. Furthermore, a column
named <replaceable>cycle_path_col_name</replaceable> will be added to the
result column list of the <literal>WITH</literal> query. This column is
used internally for tracking visited rows. See <xref
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index dd72a9fc3c..652be0b96d 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -11442,6 +11442,17 @@ opt_cycle_clause:
n->location = @1;
$$ = (Node *) n;
}
+ | CYCLE columnList SET ColId USING ColId
+ {
+ CTECycleClause *n = makeNode(CTECycleClause);
+ n->cycle_col_list = $2;
+ n->cycle_mark_column = $4;
+ n->cycle_mark_value = makeBoolAConst(true, -1);
+ n->cycle_mark_default = makeBoolAConst(false,
-1);
+ n->cycle_path_column = $6;
+ n->location = @1;
+ $$ = (Node *) n;
+ }
| /*EMPTY*/
{
$$ = NULL;
diff --git a/src/backend/utils/adt/ruleutils.c
b/src/backend/utils/adt/ruleutils.c
index 4a9244f4f6..879288c139 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -5208,10 +5208,21 @@ get_with_clause(Query *query, deparse_context *context)
}
appendStringInfo(buf, " SET %s",
quote_identifier(cte->cycle_clause->cycle_mark_column));
- appendStringInfoString(buf, " TO ");
- get_rule_expr(cte->cycle_clause->cycle_mark_value,
context, false);
- appendStringInfoString(buf, " DEFAULT ");
- get_rule_expr(cte->cycle_clause->cycle_mark_default,
context, false);
+
+ {
+ Const *cmv = castNode(Const,
cte->cycle_clause->cycle_mark_value);
+ Const *cmd = castNode(Const,
cte->cycle_clause->cycle_mark_default);
+
+ if (!(cmv->consttype == BOOLOID &&
!cmv->constisnull && DatumGetBool(cmv->constvalue) == true &&
+ cmd->consttype == BOOLOID &&
!cmd->constisnull && DatumGetBool(cmd->constvalue) == false))
+ {
+ appendStringInfoString(buf, " TO ");
+
get_rule_expr(cte->cycle_clause->cycle_mark_value, context, false);
+ appendStringInfoString(buf, " DEFAULT
");
+
get_rule_expr(cte->cycle_clause->cycle_mark_default, context, false);
+ }
+ }
+
appendStringInfo(buf, " USING %s",
quote_identifier(cte->cycle_clause->cycle_path_column));
}
diff --git a/src/test/regress/expected/with.out
b/src/test/regress/expected/with.out
index c519a61c4f..1394302f3b 100644
--- a/src/test/regress/expected/with.out
+++ b/src/test/regress/expected/with.out
@@ -892,7 +892,7 @@ with recursive search_graph(f, t, label) as (
select g.*
from graph g, search_graph sg
where g.f = sg.t
-) cycle f, t set is_cycle to true default false using path
+) cycle f, t set is_cycle using path
select * from search_graph;
f | t | label | is_cycle | path
---+---+------------+----------+-------------------------------------------
@@ -1012,7 +1012,7 @@ with recursive a as (
select 1 as b
union all
select * from a
-) cycle b set c to true default false using p
+) cycle b set c using p
select * from a;
b | c | p
---+---+-----------
@@ -1028,7 +1028,7 @@ with recursive search_graph(f, t, label) as (
from graph g, search_graph sg
where g.f = sg.t
) search depth first by f, t set seq
- cycle f, t set is_cycle to true default false using path
+ cycle f, t set is_cycle using path
select * from search_graph;
f | t | label | seq | is_cycle |
path
---+---+------------+-------------------------------------------+----------+-------------------------------------------
@@ -1066,7 +1066,7 @@ with recursive search_graph(f, t, label) as (
from graph g, search_graph sg
where g.f = sg.t
) search breadth first by f, t set seq
- cycle f, t set is_cycle to true default false using path
+ cycle f, t set is_cycle using path
select * from search_graph;
f | t | label | seq | is_cycle | path
---+---+------------+---------+----------+-------------------------------------------
@@ -1104,10 +1104,10 @@ with recursive search_graph(f, t, label) as (
select g.*
from graph g, search_graph sg
where g.f = sg.t
-) cycle foo, tar set is_cycle to true default false using path
+) cycle foo, tar set is_cycle using path
select * from search_graph;
ERROR: cycle column "foo" not in WITH query column list
-LINE 7: ) cycle foo, tar set is_cycle to true default false using pa...
+LINE 7: ) cycle foo, tar set is_cycle using path
^
with recursive search_graph(f, t, label) as (
select * from graph g
@@ -1198,38 +1198,99 @@ ERROR: search_sequence column name and cycle path
column name are the same
LINE 7: ) search depth first by f, t set foo
^
-- test ruleutils and view expansion
-create temp view v_cycle as
+create temp view v_cycle1 as
with recursive search_graph(f, t, label) as (
select * from graph g
union all
select g.*
from graph g, search_graph sg
where g.f = sg.t
-) cycle f, t set is_cycle to true default false using path
+) cycle f, t set is_cycle using path
select f, t, label from search_graph;
-select pg_get_viewdef('v_cycle');
- pg_get_viewdef
---------------------------------------------------------------------
- WITH RECURSIVE search_graph(f, t, label) AS ( +
- SELECT g.f, +
- g.t, +
- g.label +
- FROM graph g +
- UNION ALL +
- SELECT g.f, +
- g.t, +
- g.label +
- FROM graph g, +
- search_graph sg +
- WHERE (g.f = sg.t) +
- ) CYCLE f, t SET is_cycle TO true DEFAULT false USING path+
- SELECT search_graph.f, +
- search_graph.t, +
- search_graph.label +
+create temp view v_cycle2 as
+with recursive search_graph(f, t, label) as (
+ select * from graph g
+ union all
+ select g.*
+ from graph g, search_graph sg
+ where g.f = sg.t
+) cycle f, t set is_cycle to 'Y' default 'N' using path
+select f, t, label from search_graph;
+select pg_get_viewdef('v_cycle1');
+ pg_get_viewdef
+------------------------------------------------
+ WITH RECURSIVE search_graph(f, t, label) AS (+
+ SELECT g.f, +
+ g.t, +
+ g.label +
+ FROM graph g +
+ UNION ALL +
+ SELECT g.f, +
+ g.t, +
+ g.label +
+ FROM graph g, +
+ search_graph sg +
+ WHERE (g.f = sg.t) +
+ ) CYCLE f, t SET is_cycle USING path +
+ SELECT search_graph.f, +
+ search_graph.t, +
+ search_graph.label +
FROM search_graph;
(1 row)
-select * from v_cycle;
+select pg_get_viewdef('v_cycle2');
+ pg_get_viewdef
+-----------------------------------------------------------------------------
+ WITH RECURSIVE search_graph(f, t, label) AS ( +
+ SELECT g.f, +
+ g.t, +
+ g.label +
+ FROM graph g +
+ UNION ALL +
+ SELECT g.f, +
+ g.t, +
+ g.label +
+ FROM graph g, +
+ search_graph sg +
+ WHERE (g.f = sg.t) +
+ ) CYCLE f, t SET is_cycle TO 'Y'::text DEFAULT 'N'::text USING path+
+ SELECT search_graph.f, +
+ search_graph.t, +
+ search_graph.label +
+ FROM search_graph;
+(1 row)
+
+select * from v_cycle1;
+ f | t | label
+---+---+------------
+ 1 | 2 | arc 1 -> 2
+ 1 | 3 | arc 1 -> 3
+ 2 | 3 | arc 2 -> 3
+ 1 | 4 | arc 1 -> 4
+ 4 | 5 | arc 4 -> 5
+ 5 | 1 | arc 5 -> 1
+ 1 | 2 | arc 1 -> 2
+ 1 | 3 | arc 1 -> 3
+ 1 | 4 | arc 1 -> 4
+ 2 | 3 | arc 2 -> 3
+ 4 | 5 | arc 4 -> 5
+ 5 | 1 | arc 5 -> 1
+ 1 | 2 | arc 1 -> 2
+ 1 | 3 | arc 1 -> 3
+ 1 | 4 | arc 1 -> 4
+ 2 | 3 | arc 2 -> 3
+ 4 | 5 | arc 4 -> 5
+ 5 | 1 | arc 5 -> 1
+ 1 | 2 | arc 1 -> 2
+ 1 | 3 | arc 1 -> 3
+ 1 | 4 | arc 1 -> 4
+ 2 | 3 | arc 2 -> 3
+ 4 | 5 | arc 4 -> 5
+ 5 | 1 | arc 5 -> 1
+ 2 | 3 | arc 2 -> 3
+(25 rows)
+
+select * from v_cycle2;
f | t | label
---+---+------------
1 | 2 | arc 1 -> 2
diff --git a/src/test/regress/sql/with.sql b/src/test/regress/sql/with.sql
index f4ba0d8e39..359bfd456f 100644
--- a/src/test/regress/sql/with.sql
+++ b/src/test/regress/sql/with.sql
@@ -465,7 +465,7 @@ CREATE TEMPORARY TABLE tree(
select g.*
from graph g, search_graph sg
where g.f = sg.t
-) cycle f, t set is_cycle to true default false using path
+) cycle f, t set is_cycle using path
select * from search_graph;
with recursive search_graph(f, t, label) as (
@@ -501,7 +501,7 @@ CREATE TEMPORARY TABLE tree(
select 1 as b
union all
select * from a
-) cycle b set c to true default false using p
+) cycle b set c using p
select * from a;
-- search+cycle
@@ -512,7 +512,7 @@ CREATE TEMPORARY TABLE tree(
from graph g, search_graph sg
where g.f = sg.t
) search depth first by f, t set seq
- cycle f, t set is_cycle to true default false using path
+ cycle f, t set is_cycle using path
select * from search_graph;
with recursive search_graph(f, t, label) as (
@@ -522,7 +522,7 @@ CREATE TEMPORARY TABLE tree(
from graph g, search_graph sg
where g.f = sg.t
) search breadth first by f, t set seq
- cycle f, t set is_cycle to true default false using path
+ cycle f, t set is_cycle using path
select * from search_graph;
-- various syntax errors
@@ -532,7 +532,7 @@ CREATE TEMPORARY TABLE tree(
select g.*
from graph g, search_graph sg
where g.f = sg.t
-) cycle foo, tar set is_cycle to true default false using path
+) cycle foo, tar set is_cycle using path
select * from search_graph;
with recursive search_graph(f, t, label) as (
@@ -610,19 +610,31 @@ CREATE TEMPORARY TABLE tree(
select * from search_graph;
-- test ruleutils and view expansion
-create temp view v_cycle as
+create temp view v_cycle1 as
with recursive search_graph(f, t, label) as (
select * from graph g
union all
select g.*
from graph g, search_graph sg
where g.f = sg.t
-) cycle f, t set is_cycle to true default false using path
+) cycle f, t set is_cycle using path
+select f, t, label from search_graph;
+
+create temp view v_cycle2 as
+with recursive search_graph(f, t, label) as (
+ select * from graph g
+ union all
+ select g.*
+ from graph g, search_graph sg
+ where g.f = sg.t
+) cycle f, t set is_cycle to 'Y' default 'N' using path
select f, t, label from search_graph;
-select pg_get_viewdef('v_cycle');
+select pg_get_viewdef('v_cycle1');
+select pg_get_viewdef('v_cycle2');
-select * from v_cycle;
+select * from v_cycle1;
+select * from v_cycle2;
--
-- test multiple WITH queries
--
2.30.1
