Record returned from function has columns concatenated
I have a table which stores account changes over time. I need to join that up with two other tables to create some records for a particular day, if those records don't already exist.
To make things easier (I hope), I've encapsulated the query that returns the correct historical data into a function that takes in an account id, and the day.
If I execute "Select * account_servicetier_for_day(20424, '2014-08-12')"
, I get the expected result (all the data returned from the function in separate columns). If I use the function within another query, I get all the columns joined into one:
("2014-08-12 14:20:37",hollenbeck,691,12129,20424,69.95,"2Mb/1Mb 20GB Limit",2048,1024,20.000)
I'm using "PostgreSQL 9.2.4 on x86_64-slackware-linux-gnu, compiled by gcc (GCC) 4.7.1, 64-bit".
Query:
Select
'2014-08-12' As day, 0 As inbytes, 0 As outbytes, acct.username, acct.accountid, acct.userid,
account_servicetier_for_day(acct.accountid, '2014-08-12')
From account_tab acct
Where acct.isdsl = 1
And acct.dslservicetypeid Is Not Null
And acct.accountid Not In (Select accountid From dailyaccounting_tab Where Day = '2014-08-12')
Order By acct.username
Function:
CREATE OR REPLACE FUNCTION account_servicetier_for_day(_accountid integer, _day timestamp without time zone) RETURNS setof account_dsl_history_info AS
$BODY$
DECLARE _accountingrow record;
BEGIN
Return Query
Select * From account_dsl_history_info
Where accountid = _accountid And timestamp <= _day + interval '1 day - 1 millisecond'
Order By timestamp Desc
Limit 1;
END;
$BODY$ LANGUAGE plpgsql;
Generally, to decompose rows returned from a function and get individual columns:
SELECT * FROM account_servicetier_for_day(20424, '2014-08-12');
As for the query:
Postgres 9.3 or newer
Cleaner with JOIN LATERAL
:
SELECT '2014-08-12' AS day, 0 AS inbytes, 0 AS outbytes
, a.username, a.accountid, a.userid
, f.* -- but avoid duplicate column names!
FROM account_tab a
, account_servicetier_for_day(a.accountid, '2014-08-12') f -- <-- HERE
WHERE a.isdsl = 1
AND a.dslservicetypeid IS NOT NULL
AND NOT EXISTS (
SELECT FROM dailyaccounting_tab
WHERE day = '2014-08-12'
AND accountid = a.accountid
)
ORDER BY a.username;
The LATERAL
keyword is implicit here, functions can always refer earlier FROM
items. The manual:
LATERAL
can also precede a function-callFROM
item, but in this case it is a noise word, because the function expression can refer to earlierFROM
items in any case.
Related:
- Insert multiple rows in one table based on number in another table
Short notation with a comma in the FROM
list is (mostly) equivalent to a CROSS JOIN LATERAL
(same as [INNER] JOIN LATERAL ... ON TRUE
) and thus removes rows from the result where the function call returns no row. To retain such rows, use LEFT JOIN LATERAL ... ON TRUE
:
...
FROM account_tab a
LEFT JOIN LATERAL account_servicetier_for_day(a.accountid, '2014-08-12') f ON TRUE
...
Also, don't use NOT IN (subquery)
when you can avoid it. It's the slowest and most tricky of several ways to do that:
- Select rows which are not present in other table
I suggest NOT EXISTS
instead.
Postgres 9.2 or older
You can call a set-returning function in the SELECT
list (which is a Postgres extension of standard SQL). For performance reasons, this is best done in a subquery. Decompose the (well-known!) row type in the outer query to avoid repeated evaluation of the function:
SELECT '2014-08-12' AS day, 0 AS inbytes, 0 AS outbytes
, a.username, a.accountid, a.userid
, (a.rec).* -- but be wary of duplicate column names!
FROM (
SELECT *, account_servicetier_for_day(a.accountid, '2014-08-12') AS rec
FROM account_tab a
WHERE a.isdsl = 1
AND a.dslservicetypeid Is Not Null
AND NOT EXISTS (
SELECT FROM dailyaccounting_tab
WHERE day = '2014-08-12'
AND accountid = a.accountid
)
) a
ORDER BY a.username;
Related answer by Craig Ringer with an explanation, why it's better not to decompose on the same query level:
- How to avoid multiple function evals with the (func()).* syntax in an SQL query?
Postgres 10 removed some oddities in the behavior of set-returning functions in the SELECT
:
- What is the expected behaviour for multiple set-returning functions in SELECT clause?
Use the function in the from
clause
Select
'2014-08-12' As day,
0 As inbytes,
0 As outbytes,
acct.username,
acct.accountid,
acct.userid,
asfd.*
From
account_tab acct
cross join lateral
account_servicetier_for_day(acct.accountid, '2014-08-12') asfd
Where acct.isdsl = 1
And acct.dslservicetypeid Is Not Null
And acct.accountid Not In (Select accountid From dailyaccounting_tab Where Day = '2014-08-12')
Order By acct.username