do
$$
declare
f record;
begin
for f in SELECT DISTINCT station_code FROM rainfall LIMIT 3
loop
EXECUTE format('SELECT * FROM rainfall WHERE station_code=''%I''', f.station_code);
RAISE NOTICE '%',f.station_code;
end loop;
end;
$$
Hi i'm trying to print out the execute statement for each f.station_code. It doesn't return any output but doesn't throw error. The raise notice however returns
NOTICE: MALUDAM
NOTICE: IGAN
NOTICE: LUBOKANTU
DO
Query returned successfully in 4 secs 4 msec.
Appreciate any help given.
A do block can not return a result.
But I don't see any reason to use PL/pgSQL, a loop or even dynamic SQL for this:
A single query like the following will do what you want:
SELECT *
FROM rainfall
WHERE station_code IN (SELECT station_code FROM rainfall LIMIT 3);
(The IN with a LIMIT on the same table makes zero sense to me though)
Related
I need to fetch data as 100 of records batches from a PostgresSQL table. I have tried the following function,
CREATE OR REPLACE FUNCTION fetch_compare_prices(n integer)
RETURNS SETOF varchar AS $$
DECLARE
curs CURSOR FOR SELECT * FROM compareprices LIMIT n;
row RECORD;
BEGIN
open curs;
LOOP
FETCH FROM curs INTO row;
EXIT WHEN NOT FOUND;
return next row.deal_id;
END LOOP;
END; $$ LANGUAGE plpgsql;
I ran this query to get results from the above function.select fetch_compare_prices(100); But this gives me only same 100 records always. Is there a way to fetch 100 records as batches using a cursor.
also with this return next row.deal_id; statement I can only return just the deal_id but no other columns. Is there a way to get all the columns/row?
Also, It should work like when I run select fetch_compare_prices(100); this for the 1st time, it should return first 100 rows, when I run it 2nd time, it should give rows from 100 to 200(next 100). What's the correct usage of cursor to do this?
I have a long and complex plpgsql function that creates a bunch of temporary tables nested within a while statement to get the optimal result. When the condition has been met I insert the result into an existing table, the function is far to long to post here but this is an example:
CREATE OR REPLACE FUNCTION public.test_function(id_input integer, val_input numeric)
RETURNS VOID AS
$BODY$
DECLARE
id_input numeric = $1;
val_input numeric = $2;
BEGIN
WHILE test_val < 0
LOOP
CREATE TEMP TABLE temp_table AS
SELECT a.existing_val - val_input AS new_val
FROM existing_table a
WHERE a.id = id_input;
test_val := (SELECT new_val FROM temp_table);
val_input := val_input + 1;
END LOOP;
INSERT INTO output_table (id, new_val)
SELECT a.id, a.new_val
FROM temp_table a;
END;
$BODY$
LANGUAGE plpgsql;
The function works if I call it like this SELECT test_function(1, 1000) However I would like run this function on a table with 60,000+ rows, like this:
SELECT test_function(a.id, a.val_input)
FROM data_table a;
It works when I use a subset of the data_table, say 1000 rows. However when I run it on the full table (60,000+ rows) I get the following error "AbortTransaction while in COMMIT state". After some reading I found out COMMITS, so in my case the inserts do not occur until the function has finished running which takes about 4 hours. So does anyone know what is going on?
As a workaround I tried nesting the function in a DO statement so the inserts are committed straight away:
DO
$do$
DECLARE
r data_table%rowtype;
BEGIN
FOR r IN
SELECT * FROM data_table
LOOP
SELECT public.test_function(r.id, r.val_input);
END LOOP;
END
$do$;
However then I get the following error "ERROR: query has no destination for result data", which I guess means I need to rewrite the function to use PERFORM instead of SELECT. However I have not had any luck with this as yet.
Any ideas?
Since you are not interested in the function result, you should use
PERFORM public.test_function(r.id, r.val_input);
instead of
SELECT public.test_function(r.id, r.val_input);
The latter syntax would only work if you add INTO some_variable as a destination for the query result.
Thank you all for your suggestions. I ended up using Jim Jones's suggestion and converting the function to a procedure which allowed me to use COMMIT after I did the INSERT. I also followed Jeremy's suggestion and moved from temp tables to CTE's. This solved the problem for me.
I have a view that returns 'bad' rows. I would like a procedure to raise an exception if the view returns any records. I will call this from an external program. How can this be implemented? Pseudo code follows:
create procedure pr_bad_records_check()
language sql
as
$$
if
select count(*) from vw_my_bad_records > 0
then
raise error 'some bad rows were found, run select * from vw_my_bad_records for details'
end if
$$;
I know there is an accepted answer, but let me show you another approach.
You won't need to declare any variables since you can use the special variable FOUND.
Also, would be better to add a LIMIT clause to your select, since one row is enough to throw the exception:
CREATE OR REPLACE FUNCTION pr_bad_records_check() RETURNS void AS $$
BEGIN
PERFORM * FROM vw_my_bad_records LIMIT 1;
IF FOUND THEN
RAISE EXCEPTION 'some bad rows were found, run select * from vw_my_bad_records for details';
END IF;
END;
$$ LANGUAGE plpgsql;
PLpgSQL allows to use SQL queries inside a expressions. So your task can to have a easy, readable and fast solution:
CREATE OR REPLACE FUNCTION pr_bad_records_check()
RETURNS void AS $$
BEGIN
IF EXISTS(SELECT * FROM vw_my_bad_records) THEN
RAISE EXCEPTION
USING MESSAGE='some bad rows were found',
HINT='Run select * from vw_my_bad_records for details.';
END IF;
END;
$$ LANGUAGE plpgsql;
I have a table with series of months with cumulative activity e.g.
month | activity
Jan-15 | 20
Feb-15 | 22
I also have a series of thresholds in another table e.g. 50, 100, 200. I need to get the date when the threshold is reached i.e. activity >= threshold.
The way I thought of doing this is to have a pgsql function that reads in the thresholds table, iterates over that cursor and reads in the months table to a cursor, then iterating over those rows working out the month where the threshold is reached. For performance reasons, rather than selecting all rows in the months table each time, I would then go back to the first row in the cursor and re-iterate over with the new value from the thresholds table.
Is this a sensible way to approach the problem? This is what I have so far - I am getting a
ERROR: cursor "curs" already in use error.
CREATE OR REPLACE FUNCTION schema.function()
RETURNS SETOF schema.row_type AS
$BODY$
DECLARE
rec RECORD;
rectimeline RECORD;
notification_threshold int;
notification_text text;
notification_date date;
output_rec schema.row_type;
curs SCROLL CURSOR FOR select * from schema.another_function_returning_set(); -- this is months table
curs2 CURSOR FOR select * from schema.notifications_table;
BEGIN
OPEN curs;
FOR rec IN curs2 LOOP
notification_threshold := rec.threshold;
LOOP
FETCH curs INTO rectimeline; -- this line seems to be the problem - not sure why cursor is closing
IF notification_threshold >= rectimeline.activity_total THEN
notification_text := rec.housing_notification_text;
notification_date := rectimeline.active_date;
SELECT notification_text, notification_date INTO output_rec.notification_text, output_rec.notification_date;
MOVE FIRST from curs;
RETURN NEXT output_rec;
END IF;
END LOOP;
END LOOP;
RETURN;
END;
$BODY$
LANGUAGE plpgsql VOLATILE
select distinct on (t.threshold) *
from
thresholds t
inner join
months m on t.threshold < m.activity
order by t.threshold desc, m.month
I have a function that is used as an INSERT trigger. This function deletes rows that would conflict with [the serial number in] the row being inserted. It works beautifully, so I'd really rather not debate the merits of the concept.
DECLARE
re1 feeds_item.shareurl%TYPE;
BEGIN
SELECT regexp_replace(NEW.shareurl, '/[^/]+(-[0-9]+\.html)$','/[^/]+\\1') INTO re1;
RAISE NOTICE 'DELETEing rows from feeds_item where shareurl ~ ''%''', re1;
DELETE FROM feeds_item where shareurl ~ re1;
RETURN NEW;
END;
I would like to add to the NOTICE an indication of how many rows are affected (aka: deleted). How can I do that (using LANGUAGE 'plpgsql')?
UPDATE:
Base on some excellent guidance from "Chicken in the kitchen", I have changed it to this:
DECLARE
re1 feeds_item.shareurl%TYPE;
num_rows int;
BEGIN
SELECT regexp_replace(NEW.shareurl, '/[^/]+(-[0-9]+\.html)$','/[^/]+\\1') INTO re1;
DELETE FROM feeds_item where shareurl ~ re1;
IF FOUND THEN
GET DIAGNOSTICS num_rows = ROW_COUNT;
RAISE NOTICE 'DELETEd % row(s) from feeds_item where shareurl ~ ''%''', num_rows, re1;
END IF;
RETURN NEW;
END;
For a very robust solution, that is part of PostgreSQL SQL and not just plpgsql you could also do the following:
with a as (DELETE FROM feeds_item WHERE shareurl ~ re1 returning 1)
select count(*) from a;
You can actually get lots more information such as:
with a as (delete from sales returning amount)
select sum(amount) from a;
to see totals, in this way you could get any aggregate and even group and filter it.
In Oracle PL/SQL, the system variable to store the number of deleted / inserted / updated rows is:
SQL%ROWCOUNT
After a DELETE / INSERT / UPDATE statement, and BEFORE COMMITTING, you can store SQL%ROWCOUNT in a variable of type NUMBER. Remember that COMMIT or ROLLBACK reset to ZERO the value of SQL%ROWCOUNT, so you have to copy the SQL%ROWCOUNT value in a variable BEFORE COMMIT or ROLLBACK.
Example:
BEGIN
DECLARE
affected_rows NUMBER DEFAULT 0;
BEGIN
DELETE FROM feeds_item
WHERE shareurl = re1;
affected_rows := SQL%ROWCOUNT;
DBMS_OUTPUT.
put_line (
'This DELETE would affect '
|| affected_rows
|| ' records in FEEDS_ITEM table.');
ROLLBACK;
END;
END;
I have found also this interesting SOLUTION (source: http://markmail.org/message/grqap2pncqd6w3sp )
On 4/7/07, Karthikeyan Sundaram wrote:
Hi,
I am using 8.1.0 postgres and trying to write a plpgsql block. In that I am inserting a row. I want to check to see if the row has been
inserted or not.
In oracle we can say like this
begin
insert into table_a values (1);
if sql%rowcount > 0
then
dbms.output.put_line('rows inserted');
else
dbms.output.put_line('rows not inserted');
end if; end;
Is there something equal to sql%rowcount in postgres? Please help.
Regards skarthi
Maybe:
http://www.postgresql.org/docs/8.2/static/plpgsql-statements.html#PLPGSQL-STATEMENTS-SQL-ONEROW
Click on the link above, you'll see this content:
37.6.6. Obtaining the Result Status There are several ways to determine the effect of a command. The first method is to use the GET
DIAGNOSTICS command, which has the form:
GET DIAGNOSTICS variable = item [ , ... ];This command allows
retrieval of system status indicators. Each item is a key word
identifying a state value to be assigned to the specified variable
(which should be of the right data type to receive it). The currently
available status items are ROW_COUNT, the number of rows processed by
the last SQL command sent down to the SQL engine, and RESULT_OID, the
OID of the last row inserted by the most recent SQL command. Note that
RESULT_OID is only useful after an INSERT command into a table
containing OIDs.
An example:
GET DIAGNOSTICS integer_var = ROW_COUNT; The second method to
determine the effects of a command is to check the special variable
named FOUND, which is of type boolean. FOUND starts out false within
each PL/pgSQL function call. It is set by each of the following types
of statements:
A SELECT INTO statement sets FOUND true if a row is assigned, false if
no row is returned.
A PERFORM statement sets FOUND true if it produces (and discards) a
row, false if no row is produced.
UPDATE, INSERT, and DELETE statements set FOUND true if at least one
row is affected, false if no row is affected.
A FETCH statement sets FOUND true if it returns a row, false if no row
is returned.
A FOR statement sets FOUND true if it iterates one or more times, else
false. This applies to all three variants of the FOR statement
(integer FOR loops, record-set FOR loops, and dynamic record-set FOR
loops). FOUND is set this way when the FOR loop exits; inside the
execution of the loop, FOUND is not modified by the FOR statement,
although it may be changed by the execution of other statements within
the loop body.
FOUND is a local variable within each PL/pgSQL function; any changes
to it affect only the current function.
I would to share my code (I had this idea from Roelof Rossouw):
CREATE OR REPLACE FUNCTION my_schema.sp_delete_mytable(_id integer)
RETURNS integer AS
$BODY$
DECLARE
AFFECTEDROWS integer;
BEGIN
WITH a AS (DELETE FROM mytable WHERE id = _id RETURNING 1)
SELECT count(*) INTO AFFECTEDROWS FROM a;
IF AFFECTEDROWS = 1 THEN
RETURN 1;
ELSE
RETURN 0;
END IF;
EXCEPTION WHEN OTHERS THEN
RETURN 0;
END;
$BODY$
LANGUAGE plpgsql VOLATILE
COST 100;