Postgresql 8.4 update query syntax error in plpgsql function - postgresql

Question

I am using PostgreSQL 8.4 and creating a plpgsql function. In the body of this function I have a query to update records.
...
UPDATE device_syncfiles SET
state_code = 1, updated_at = NOW() at time zone 'UTC'
WHERE
((state_code = 2 AND EXTRACT(EPOCH FROM (NOW() at time zone 'UTC' - updated_at::timestamp without time zone)) > 3600) OR
(state_code = 3 AND EXTRACT(EPOCH FROM (NOW() at time zone 'UTC' - updated_at::timestamp without time zone)) > 3600));
...
When I load this function into database, a syntax error turns out
ERROR: syntax error at or near "$1"
LINE 1: UPDATE device_syncfiles SET $1 = 1, $2 = NOW() at time z...
^
QUERY: UPDATE device_syncfiles SET $1 = 1, $2 = NOW() at time zone 'UTC' WHERE (( $1 = 2 AND EXTRACT(EPOCH FROM (NOW() at time zone 'UTC' - $2 ::timestamp without time zone)) > $3 ) OR ( $1 = 3 AND EXTRACT(EPOCH FROM (NOW() at time zone 'UTC' - $2 ::timestamp without time zone)) > $4 ))
CONTEXT: SQL statement in PL/PgSQL function "syncfile_get" near line 19
I cannot find any problem with this query. What's wrong here?
UPDATE: (missing information)
Table: device_syncfiles
id PK integer auto inc
user_id integer FK
file_name character varying(255) NOT NULL,
state_code integer NOT NULL FK,
md5 character varying(255) NOT NULL,
msg character varying(255),
created_at timestamp without time zone,
updated_at timestamp without time zone
Function: syncfile_get()
CREATE OR REPLACE FUNCTION syncfile_get()
RETURNS TABLE(id integer, user_id integer, file_name character varying, state_code integer, md5 character varying, created_at timestamp without time zone, updated_at timestamp without time zone) AS
$BODY$
DECLARE
_device_syncfile_id integer;
_download_timeout integer;
_processing_timeout integer;
BEGIN
-- GET all timeout info
SELECT state_timeout INTO _download_timeout FROM device_syncfile_states
WHERE state_name = 'downloading';
SELECT state_timeout INTO _processing_timeout FROM device_syncfile_states
WHERE state_name = 'processing';
-- GET syncfile id
_device_syncfile_id = NULL;
-- Reset timed out file to idel state
UPDATE device_syncfiles SET
state_code = 1, updated_at = NOW() at time zone 'UTC'
WHERE
((state_code = 2 AND EXTRACT(EPOCH FROM (NOW() at time zone 'UTC' - updated_at::timestamp without time zone)) > _download_timeout) OR
(state_code = 3 AND EXTRACT(EPOCH FROM (NOW() at time zone 'UTC' - updated_at::timestamp without time zone)) > _processing_timeout));
-- GET the id of one idel/timed out file => result could be a integer or NULL
SELECT device_syncfiles.id INTO _device_syncfile_id FROM device_syncfiles
WHERE
device_syncfiles.state_code = 1 OR
(device_syncfiles.state_code = 2 AND EXTRACT(EPOCH FROM (NOW() at time zone 'UTC' - device_syncfiles.updated_at::timestamp without time zone)) > _download_timeout) OR
(device_syncfiles.state_code = 3 AND EXTRACT(EPOCH FROM (NOW() at time zone 'UTC' - device_syncfiles.updated_at::timestamp without time zone)) > _processing_timeout)
LIMIT 1;
-- WHEN NULL skip state update and return empty set of record
-- Otherwise return the set of record with the id found in last step
IF _device_syncfile_id IS NOT NULL THEN
PERFORM syncfile_update(_device_syncfile_id, 2, NULL);
END IF;
RETURN QUERY SELECT
device_syncfiles.id,
device_syncfiles.user_id ,
device_syncfiles.file_name ,
device_syncfiles.state_code ,
device_syncfiles.md5 ,
device_syncfiles.created_at ,
device_syncfiles.updated_at
FROM device_syncfiles WHERE device_syncfiles.id = _device_syncfile_id;
END;
$BODY$
LANGUAGE plpgsql VOLATILE

Answer 1

Many problems.
0.
I am using Postgresql 8.4
Postgres 8.4 reached EOL in July 2014. Consider upgrading to a current version. Urgently.
1.
Your question does not disclose the complete function (at least header and footer) nor any table definition and some sample data to help us help you.
I have to make assumptions, and my educated guess is that you have a function parameter named state_code, which conflicts with the identical column name. In three places. Basics:
Postgresql - INSERT RETURNING INTO ambiguous column reference
How to return result of a SELECT inside a function in PostgreSQL?
You must be aware the all fields declared in a RETURNS TABLE clause are effectively OUT parameters as well. (As stated in the first sentence of the first link.) So your Q update confirmed my assumptions.
2.
Your error message reports the first of those instances here:
UPDATE device_syncfiles SET
state_code = 1 ...
That's a consequence of 0.. You are tripping over your long dead and forgotten version of Postgres, where the superficial syntax check at function creation time used to detect a naming conflict between target columns of UPDATE statements and function parameters. Which is silly and was later removed: those target columns cannot conflict with function parameters on principal.
Your error reproduced in Postgres 8.4: dbfiddle here
The same does not happen in Postgres 9.4: dbfiddle here
To fix, best rename the function parameter to avoid conflicts. Related:
Postgres function returning a row as JSON value
3.
There are two more instances:
WHERE
((state_code = 2 AND EXTRACT(EPOCH FROM (NOW() at time zone 'UTC' - updated_at::timestamp without time zone)) > 3600) OR
(state_code = 3 AND EXTRACT(EPOCH FROM (NOW() at time zone 'UTC' - updated_at::timestamp without time zone)) > 3600));
Would need a fix in any version. Postgres cannot tell whether to resolve to the function parameter or the table column. Best table-qualify all columns to avoid any possible conflicts with parameter names a priori. (Except for UPDATE target columns, which do not need nor allow table qualification.)
4.
That's still lipstick on a pig. Improve the query like this:
UPDATE device_syncfiles d
SET state_code = 1
, updated_at = NOW() AT TIME ZONE 'UTC'
WHERE d.state_code IN (2, 3)
AND d.updated_at < (now() - interval '1 hour') AT TIME ZONE 'UTC';
Shorter, faster, can use an index on updated_at.
5.
Finally consider using timestamp with time zone instead of timestamp without time zone to begin with:
Ignoring timezones altogether in Rails and PostgreSQL