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This patch implements holdable cursors, following the proposal

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(materialization into a tuple store) discussed on pgsql-hackers earlier.
I've updated the documentation and the regression tests.

Notes on the implementation:

- I needed to change the tuple store API slightly -- it assumes that it
won't be used to hold data across transaction boundaries, so the temp
files that it uses for on-disk storage are automatically reclaimed at
end-of-transaction. I added a flag to tuplestore_begin_heap() to control
this behavior. Is changing the tuple store API in this fashion OK?

- in order to store executor results in a tuple store, I added a new
CommandDest. This works well for the most part, with one exception: the
current DestFunction API doesn't provide enough information to allow the
Executor to store results into an arbitrary tuple store (where the
particular tuple store to use is chosen by the call site of
ExecutorRun). To workaround this, I've temporarily hacked up a solution
that works, but is not ideal: since the receiveTuple DestFunction is
passed the portal name, we can use that to lookup the Portal data
structure for the cursor and then use that to get at the tuple store the
Portal is using. This unnecessarily ties the Portal code with the
tupleReceiver code, but it works...

The proper fix for this is probably to change the DestFunction API --
Tom suggested passing the full QueryDesc to the receiveTuple function.
In that case, callers of ExecutorRun could "subclass" QueryDesc to add
any additional fields that their particular CommandDest needed to get
access to. This approach would work, but I'd like to think about it for
a little bit longer before deciding which route to go. In the mean time,
the code works fine, so I don't think a fix is urgent.

- (semi-related) I added a NO SCROLL keyword to DECLARE CURSOR, and
adjusted the behavior of SCROLL in accordance with the discussion on
-hackers.

- (unrelated) Cleaned up some SGML markup in sql.sgml, copy.sgml

Neil Conway
This commit is contained in:
Bruce Momjian
2003-03-27 16:51:29 +00:00
parent 7638087882
commit 54f7338fa1
35 changed files with 850 additions and 314 deletions
Download Patch File Download Diff File Expand all files Collapse all files

112
src/test/regress/expected/portals.out
View File

@@ -1,30 +1,30 @@
--
-- PORTALS
-- Cursor regression tests
--
BEGIN;
DECLARE foo1 CURSOR FOR SELECT * FROM tenk1;
DECLARE foo2 CURSOR FOR SELECT * FROM tenk2;
DECLARE foo3 CURSOR FOR SELECT * FROM tenk1;
DECLARE foo4 CURSOR FOR SELECT * FROM tenk2;
DECLARE foo5 CURSOR FOR SELECT * FROM tenk1;
DECLARE foo6 CURSOR FOR SELECT * FROM tenk2;
DECLARE foo7 CURSOR FOR SELECT * FROM tenk1;
DECLARE foo8 CURSOR FOR SELECT * FROM tenk2;
DECLARE foo9 CURSOR FOR SELECT * FROM tenk1;
DECLARE foo10 CURSOR FOR SELECT * FROM tenk2;
DECLARE foo11 CURSOR FOR SELECT * FROM tenk1;
DECLARE foo12 CURSOR FOR SELECT * FROM tenk2;
DECLARE foo13 CURSOR FOR SELECT * FROM tenk1;
DECLARE foo14 CURSOR FOR SELECT * FROM tenk2;
DECLARE foo15 CURSOR FOR SELECT * FROM tenk1;
DECLARE foo16 CURSOR FOR SELECT * FROM tenk2;
DECLARE foo17 CURSOR FOR SELECT * FROM tenk1;
DECLARE foo18 CURSOR FOR SELECT * FROM tenk2;
DECLARE foo19 CURSOR FOR SELECT * FROM tenk1;
DECLARE foo20 CURSOR FOR SELECT * FROM tenk2;
DECLARE foo21 CURSOR FOR SELECT * FROM tenk1;
DECLARE foo22 CURSOR FOR SELECT * FROM tenk2;
DECLARE foo23 CURSOR FOR SELECT * FROM tenk1;
DECLARE foo1 SCROLL CURSOR FOR SELECT * FROM tenk1;
DECLARE foo2 SCROLL CURSOR FOR SELECT * FROM tenk2;
DECLARE foo3 SCROLL CURSOR FOR SELECT * FROM tenk1;
DECLARE foo4 SCROLL CURSOR FOR SELECT * FROM tenk2;
DECLARE foo5 SCROLL CURSOR FOR SELECT * FROM tenk1;
DECLARE foo6 SCROLL CURSOR FOR SELECT * FROM tenk2;
DECLARE foo7 SCROLL CURSOR FOR SELECT * FROM tenk1;
DECLARE foo8 SCROLL CURSOR FOR SELECT * FROM tenk2;
DECLARE foo9 SCROLL CURSOR FOR SELECT * FROM tenk1;
DECLARE foo10 SCROLL CURSOR FOR SELECT * FROM tenk2;
DECLARE foo11 SCROLL CURSOR FOR SELECT * FROM tenk1;
DECLARE foo12 SCROLL CURSOR FOR SELECT * FROM tenk2;
DECLARE foo13 SCROLL CURSOR FOR SELECT * FROM tenk1;
DECLARE foo14 SCROLL CURSOR FOR SELECT * FROM tenk2;
DECLARE foo15 SCROLL CURSOR FOR SELECT * FROM tenk1;
DECLARE foo16 SCROLL CURSOR FOR SELECT * FROM tenk2;
DECLARE foo17 SCROLL CURSOR FOR SELECT * FROM tenk1;
DECLARE foo18 SCROLL CURSOR FOR SELECT * FROM tenk2;
DECLARE foo19 SCROLL CURSOR FOR SELECT * FROM tenk1;
DECLARE foo20 SCROLL CURSOR FOR SELECT * FROM tenk2;
DECLARE foo21 SCROLL CURSOR FOR SELECT * FROM tenk1;
DECLARE foo22 SCROLL CURSOR FOR SELECT * FROM tenk2;
DECLARE foo23 SCROLL CURSOR FOR SELECT * FROM tenk1;
FETCH 1 in foo1;
unique1 | unique2 | two | four | ten | twenty | hundred | thousand | twothousand | fivethous | tenthous | odd | even | stringu1 | stringu2 | string4
---------+---------+-----+------+-----+--------+---------+----------+-------------+-----------+----------+-----+------+----------+----------+---------
@@ -675,4 +675,66 @@ CLOSE foo9;
CLOSE foo10;
CLOSE foo11;
CLOSE foo12;
end;
-- is there a reason why we don't close the rest of the open cursors?
END;
--
-- NO SCROLL disallows backward fetching
--
BEGIN;
DECLARE foo24 NO SCROLL CURSOR FOR SELECT * FROM tenk1;
FETCH 1 FROM foo24;
unique1 | unique2 | two | four | ten | twenty | hundred | thousand | twothousand | fivethous | tenthous | odd | even | stringu1 | stringu2 | string4
---------+---------+-----+------+-----+--------+---------+----------+-------------+-----------+----------+-----+------+----------+----------+---------
8800 | 0 | 0 | 0 | 0 | 0 | 0 | 800 | 800 | 3800 | 8800 | 0 | 1 | MAAAAA | AAAAAA | AAAAxx
(1 row)
FETCH BACKWARD 1 FROM foo24; -- should fail
ERROR: Cursor can only scan forward
Declare it with SCROLL option to enable backward scan
END;
--
-- Cursors outside transaction blocks
--
BEGIN;
DECLARE foo25 SCROLL CURSOR WITH HOLD FOR SELECT * FROM tenk2;
FETCH FROM foo25;
unique1 | unique2 | two | four | ten | twenty | hundred | thousand | twothousand | fivethous | tenthous | odd | even | stringu1 | stringu2 | string4
---------+---------+-----+------+-----+--------+---------+----------+-------------+-----------+----------+-----+------+----------+----------+---------
8800 | 0 | 0 | 0 | 0 | 0 | 0 | 800 | 800 | 3800 | 8800 | 0 | 1 | MAAAAA | AAAAAA | AAAAxx
(1 row)
FETCH FROM foo25;
unique1 | unique2 | two | four | ten | twenty | hundred | thousand | twothousand | fivethous | tenthous | odd | even | stringu1 | stringu2 | string4
---------+---------+-----+------+-----+--------+---------+----------+-------------+-----------+----------+-----+------+----------+----------+---------
1891 | 1 | 1 | 3 | 1 | 11 | 91 | 891 | 1891 | 1891 | 1891 | 182 | 183 | TUAAAA | BAAAAA | HHHHxx
(1 row)
COMMIT;
FETCH FROM foo25;
unique1 | unique2 | two | four | ten | twenty | hundred | thousand | twothousand | fivethous | tenthous | odd | even | stringu1 | stringu2 | string4
---------+---------+-----+------+-----+--------+---------+----------+-------------+-----------+----------+-----+------+----------+----------+---------
3420 | 2 | 0 | 0 | 0 | 0 | 20 | 420 | 1420 | 3420 | 3420 | 40 | 41 | OBAAAA | CAAAAA | OOOOxx
(1 row)
FETCH BACKWARD FROM foo25;
unique1 | unique2 | two | four | ten | twenty | hundred | thousand | twothousand | fivethous | tenthous | odd | even | stringu1 | stringu2 | string4
---------+---------+-----+------+-----+--------+---------+----------+-------------+-----------+----------+-----+------+----------+----------+---------
1891 | 1 | 1 | 3 | 1 | 11 | 91 | 891 | 1891 | 1891 | 1891 | 182 | 183 | TUAAAA | BAAAAA | HHHHxx
(1 row)
FETCH ABSOLUTE -1 FROM foo25;
unique1 | unique2 | two | four | ten | twenty | hundred | thousand | twothousand | fivethous | tenthous | odd | even | stringu1 | stringu2 | string4
---------+---------+-----+------+-----+--------+---------+----------+-------------+-----------+----------+-----+------+----------+----------+---------
2968 | 9999 | 0 | 0 | 8 | 8 | 68 | 968 | 968 | 2968 | 2968 | 136 | 137 | EKAAAA | PUOAAA | VVVVxx
(1 row)
CLOSE foo25;
--
-- ROLLBACK should close holdable cursors
--
BEGIN;
DECLARE foo26 CURSOR WITH HOLD FOR SELECT * FROM tenk1;
ROLLBACK;
-- should fail
FETCH FROM foo26;
WARNING: PerformPortalFetch: portal "foo26" not found

100
src/test/regress/sql/portals.sql
View File

@@ -1,54 +1,54 @@
--
-- PORTALS
-- Cursor regression tests
--
BEGIN;
DECLARE foo1 CURSOR FOR SELECT * FROM tenk1;
DECLARE foo1 SCROLL CURSOR FOR SELECT * FROM tenk1;
DECLARE foo2 CURSOR FOR SELECT * FROM tenk2;
DECLARE foo2 SCROLL CURSOR FOR SELECT * FROM tenk2;
DECLARE foo3 CURSOR FOR SELECT * FROM tenk1;
DECLARE foo3 SCROLL CURSOR FOR SELECT * FROM tenk1;
DECLARE foo4 CURSOR FOR SELECT * FROM tenk2;
DECLARE foo4 SCROLL CURSOR FOR SELECT * FROM tenk2;
DECLARE foo5 CURSOR FOR SELECT * FROM tenk1;
DECLARE foo5 SCROLL CURSOR FOR SELECT * FROM tenk1;
DECLARE foo6 CURSOR FOR SELECT * FROM tenk2;
DECLARE foo6 SCROLL CURSOR FOR SELECT * FROM tenk2;
DECLARE foo7 CURSOR FOR SELECT * FROM tenk1;
DECLARE foo7 SCROLL CURSOR FOR SELECT * FROM tenk1;
DECLARE foo8 CURSOR FOR SELECT * FROM tenk2;
DECLARE foo8 SCROLL CURSOR FOR SELECT * FROM tenk2;
DECLARE foo9 CURSOR FOR SELECT * FROM tenk1;
DECLARE foo9 SCROLL CURSOR FOR SELECT * FROM tenk1;
DECLARE foo10 CURSOR FOR SELECT * FROM tenk2;
DECLARE foo10 SCROLL CURSOR FOR SELECT * FROM tenk2;
DECLARE foo11 CURSOR FOR SELECT * FROM tenk1;
DECLARE foo11 SCROLL CURSOR FOR SELECT * FROM tenk1;
DECLARE foo12 CURSOR FOR SELECT * FROM tenk2;
DECLARE foo12 SCROLL CURSOR FOR SELECT * FROM tenk2;
DECLARE foo13 CURSOR FOR SELECT * FROM tenk1;
DECLARE foo13 SCROLL CURSOR FOR SELECT * FROM tenk1;
DECLARE foo14 CURSOR FOR SELECT * FROM tenk2;
DECLARE foo14 SCROLL CURSOR FOR SELECT * FROM tenk2;
DECLARE foo15 CURSOR FOR SELECT * FROM tenk1;
DECLARE foo15 SCROLL CURSOR FOR SELECT * FROM tenk1;
DECLARE foo16 CURSOR FOR SELECT * FROM tenk2;
DECLARE foo16 SCROLL CURSOR FOR SELECT * FROM tenk2;
DECLARE foo17 CURSOR FOR SELECT * FROM tenk1;
DECLARE foo17 SCROLL CURSOR FOR SELECT * FROM tenk1;
DECLARE foo18 CURSOR FOR SELECT * FROM tenk2;
DECLARE foo18 SCROLL CURSOR FOR SELECT * FROM tenk2;
DECLARE foo19 CURSOR FOR SELECT * FROM tenk1;
DECLARE foo19 SCROLL CURSOR FOR SELECT * FROM tenk1;
DECLARE foo20 CURSOR FOR SELECT * FROM tenk2;
DECLARE foo20 SCROLL CURSOR FOR SELECT * FROM tenk2;
DECLARE foo21 CURSOR FOR SELECT * FROM tenk1;
DECLARE foo21 SCROLL CURSOR FOR SELECT * FROM tenk1;
DECLARE foo22 CURSOR FOR SELECT * FROM tenk2;
DECLARE foo22 SCROLL CURSOR FOR SELECT * FROM tenk2;
DECLARE foo23 CURSOR FOR SELECT * FROM tenk1;
DECLARE foo23 SCROLL CURSOR FOR SELECT * FROM tenk1;
FETCH 1 in foo1;
@@ -166,5 +166,55 @@ CLOSE foo11;
CLOSE foo12;
end;
-- is there a reason why we don't close the rest of the open cursors?
END;
--
-- NO SCROLL disallows backward fetching
--
BEGIN;
DECLARE foo24 NO SCROLL CURSOR FOR SELECT * FROM tenk1;
FETCH 1 FROM foo24;
FETCH BACKWARD 1 FROM foo24; -- should fail
END;
--
-- Cursors outside transaction blocks
--
BEGIN;
DECLARE foo25 SCROLL CURSOR WITH HOLD FOR SELECT * FROM tenk2;
FETCH FROM foo25;
FETCH FROM foo25;
COMMIT;
FETCH FROM foo25;
FETCH BACKWARD FROM foo25;
FETCH ABSOLUTE -1 FROM foo25;
CLOSE foo25;
--
-- ROLLBACK should close holdable cursors
--
BEGIN;
DECLARE foo26 CURSOR WITH HOLD FOR SELECT * FROM tenk1;
ROLLBACK;
-- should fail
FETCH FROM foo26;