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Add docs and regression test about sorting the output of a recursive query in

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depth-first search order.  Upon close reading of SQL:2008, it seems that the
spec's SEARCH DEPTH FIRST and SEARCH BREADTH FIRST options do not actually
guarantee any particular result order: what they do is provide a constructed
column that the user can then sort on in the outer query.  So this is actually
just as much functionality ...
This commit is contained in:
Tom Lane
2008-10-14 00:41:35 +00:00
parent 1f238e569a
commit 06224652f2
3 changed files with 61 additions and 2 deletions
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38
src/test/regress/expected/with.out
View File

@ -499,6 +499,44 @@ select * from search_graph;
2 | 3 | arc 2 -> 3 | {"(1,4)","(4,5)","(5,1)","(1,2)","(2,3)"} | f
(25 rows)
-- ordering by the path column has same effect as SEARCH DEPTH FIRST
with recursive search_graph(f, t, label, path, cycle) as (
select *, array[row(g.f, g.t)], false from graph g
union all
select g.*, path || row(g.f, g.t), row(g.f, g.t) = any(path)
from graph g, search_graph sg
where g.f = sg.t and not cycle
)
select * from search_graph order by path;
f | t | label | path | cycle
---+---+------------+-------------------------------------------+-------
1 | 2 | arc 1 -> 2 | {"(1,2)"} | f
2 | 3 | arc 2 -> 3 | {"(1,2)","(2,3)"} | f
1 | 3 | arc 1 -> 3 | {"(1,3)"} | f
1 | 4 | arc 1 -> 4 | {"(1,4)"} | f
4 | 5 | arc 4 -> 5 | {"(1,4)","(4,5)"} | f
5 | 1 | arc 5 -> 1 | {"(1,4)","(4,5)","(5,1)"} | f
1 | 2 | arc 1 -> 2 | {"(1,4)","(4,5)","(5,1)","(1,2)"} | f
2 | 3 | arc 2 -> 3 | {"(1,4)","(4,5)","(5,1)","(1,2)","(2,3)"} | f
1 | 3 | arc 1 -> 3 | {"(1,4)","(4,5)","(5,1)","(1,3)"} | f
1 | 4 | arc 1 -> 4 | {"(1,4)","(4,5)","(5,1)","(1,4)"} | t
2 | 3 | arc 2 -> 3 | {"(2,3)"} | f
4 | 5 | arc 4 -> 5 | {"(4,5)"} | f
5 | 1 | arc 5 -> 1 | {"(4,5)","(5,1)"} | f
1 | 2 | arc 1 -> 2 | {"(4,5)","(5,1)","(1,2)"} | f
2 | 3 | arc 2 -> 3 | {"(4,5)","(5,1)","(1,2)","(2,3)"} | f
1 | 3 | arc 1 -> 3 | {"(4,5)","(5,1)","(1,3)"} | f
1 | 4 | arc 1 -> 4 | {"(4,5)","(5,1)","(1,4)"} | f
4 | 5 | arc 4 -> 5 | {"(4,5)","(5,1)","(1,4)","(4,5)"} | t
5 | 1 | arc 5 -> 1 | {"(5,1)"} | f
1 | 2 | arc 1 -> 2 | {"(5,1)","(1,2)"} | f
2 | 3 | arc 2 -> 3 | {"(5,1)","(1,2)","(2,3)"} | f
1 | 3 | arc 1 -> 3 | {"(5,1)","(1,3)"} | f
1 | 4 | arc 1 -> 4 | {"(5,1)","(1,4)"} | f
4 | 5 | arc 4 -> 5 | {"(5,1)","(1,4)","(4,5)"} | f
5 | 1 | arc 5 -> 1 | {"(5,1)","(1,4)","(4,5)","(5,1)"} | t
(25 rows)
--
-- test multiple WITH queries
--

10
src/test/regress/sql/with.sql
View File

@ -272,6 +272,16 @@ with recursive search_graph(f, t, label, path, cycle) as (
)
select * from search_graph;
-- ordering by the path column has same effect as SEARCH DEPTH FIRST
with recursive search_graph(f, t, label, path, cycle) as (
select *, array[row(g.f, g.t)], false from graph g
union all
select g.*, path || row(g.f, g.t), row(g.f, g.t) = any(path)
from graph g, search_graph sg
where g.f = sg.t and not cycle
)
select * from search_graph order by path;
--
-- test multiple WITH queries
--