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Bug #664: Strange cursor behaviour with particular database schema

From: pgsql-bugs(at)postgresql(dot)org
To: pgsql-bugs(at)postgresql(dot)org
Subject: Bug #664: Strange cursor behaviour with particular database schema
Date: 2002-05-11 21:08:25
Message-ID: 20020511210825.8CC25475864@postgresql.org (view raw or flat)
Thread:
Lists: pgsql-bugs
Geert-Jan Van den Bogaerde (gvdbogae(at)vub(dot)ac(dot)be) reports a bug with a severity of 2
The lower the number the more severe it is.

Short Description
Strange cursor behaviour with particular database schema

Long Description

With the (stripped-down) database schema attached in the example code, i get the following result on the interative console (psql):

template1=> begin work;
BEGIN
template1=> declare foo cursor for select * from nodes_view where node_id in (select id from nodes where parent in (2));
DECLARE
template1=> fetch 1 from foo;
 resource_id |     resource_creationDate     |   resource_modificationDate   | node_id | node_parent | node_name
-------------+-------------------------------+-------------------------------+---------+-------------+-----------
           4 | 2002-05-11 23:00:24.344979+02 | 2002-05-11 23:00:24.344979+02 |       4 |           2 | foo4
(1 row)

template1=> move -1 from foo;
MOVE 0
template1=> fetch 1 from foo;
 resource_id | resource_creationDate | resource_modificationDate | node_id | node_parent | node_name
-------------+-----------------------+---------------------------+---------+-------------+-----------
(0 rows)

template1=>

Which even though the SQL query is less than optimal seems to me to be a bug. The query works fine, the only weirdness seems to occur after a MOVE on the cursor. It only seems to occur with this rather particular database schema. I ran accross this because some of my SQL is auto-generated from some scripts and thus not always very well optimized.


Sample Code

CREATE TABLE "resources" (
        "id" integer DEFAULT nextval('resourceSequence'::text) NOT NULL,
        "creationDate" timestamp with time zone DEFAULT ('now'::text)::timestamp(6) with time zone NOT
NULL,
        "modificationDate" timestamp with time zone DEFAULT ('now'::text)::timestamp(6) with time zone
NOT NULL,
        Constraint "resources_id_pk" Primary Key ("id")
);

CREATE TABLE "nodes" (
        "id" integer NOT NULL,
        "parent" integer,
        "name" character varying(250) NOT NULL,
        Constraint "nodes_id_pk" Primary Key ("id")
);

CREATE VIEW "resources_view" as SELECT resources.id AS resource_id, resources."creationDate" AS "resour
ce_creationDate", resources."modificationDate" AS "resource_modificationDate" FROM resources;

CREATE VIEW "nodes_view" as SELECT resources_view.resource_id, resources_view."resource_creationDate",
resources_view."resource_modificationDate", nodes.id AS node_id, nodes.parent AS node_parent, nodes.nam
e AS node_name FROM (nodes LEFT JOIN resources_view ON ((resources_view.resource_id = nodes.id)));

INSERT INTO resources (id) VALUES (1);
INSERT INTO resources (id) VALUES (2);
INSERT INTO resources (id) VALUES (3);
INSERT INTO resources (id) VALUES (4);
INSERT INTO resources (id) VALUES (5);

INSERT INTO nodes (id, parent, name) VALUES (1, NULL, 'foo1');
INSERT INTO nodes (id, parent, name) VALUES (2, 1, 'foo2');
INSERT INTO nodes (id, parent, name) VALUES (3, 1, 'foo3');
INSERT INTO nodes (id, parent, name) VALUES (4, 2, 'foo4');
INSERT INTO nodes (id, parent, name) VALUES (5, 2, 'foo5');


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Next:From: pgsql-bugsDate: 2002-05-11 21:13:39
Subject: Bug #665: MORE INFO Re: "Strange cursor behaviour with a particular database schema"
Previous:From: fereydoun hormozdiariDate: 2002-05-11 07:20:03
Subject: bug........HELP

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