I have a query similar to this:
SELECT COALESCE(
(SELECT jsonb_agg(s) FROM ((SELECT column FROM my_table)) AS s),
'[]'::jsonb
);
which returns all rows in json format:
[
{
"column": 1,
},
{
"column": 2
}
]
And if there are no rows, it returns a empty array instead of null.
I want to re-use this, but it would quickly become a mess to type out the whole thing everywhere. That's why I trying to create this as_json function:
-- DOESNT WORK
CREATE FUNCTION as_json(query ???)
RETURNS jsonb
LANGUAGE sql
AS $$
SELECT COALESCE((SELECT jsonb_agg(s) FROM query AS s), '[]'::jsonb);
$$;
If I could make it work, using it would be as simple as
as_json(SELECT column FROM my_table)
Can I achieve something like that in postgresql?
It's actually quite easy to write something similar to query_to_xml()
create or replace function query_to_jsonb(p_query text, p_include_nulls boolean default false)
returns jsonb
as
$$
declare
l_result jsonb;
l_sql text;
begin
if p_include_nulls then
l_sql := 'select jsonb_agg(to_jsonb(dt)) from ('||p_query||') as dt';
else
l_sql := 'select jsonb_agg(jsonb_strip_nulls(to_jsonb(dt))) from ('||p_query||') as dt';
end if;
execute l_sql
into l_result;
return coalesce(l_result, '{}');
end;
$$
language plpgsql;
Then you can return the result of a query (string) as a JSON value, e.g.
select query_to_jsonb('SELECT column FROM my_table');
To remove NULL values from the result, use:
select query_to_jsonb('select col1, col2 from some_table', true);
Related
When performing a loop on a table in which a value has ", I get those quotes doubled such as:
initial input: 'test AND "test"'
output in the loop: 'test AND ""test""'
How to reproduce:
CREATE TABLE roles(
id int,
criteria VARCHAR (255)
);
INSERT INTO roles (id, criteria) VALUES (1, 'test AND "test"');
CREATE OR REPLACE FUNCTION test_quote()
RETURNS VARCHAR
LANGUAGE plpgsql
AS $$
DECLARE
sample varchar;
rec record;
BEGIN
FOR rec IN
SELECT * FROM roles
LOOP
sample:= rec;
END LOOP;
RETURN sample;
END
$$;
SELECT * FROM test_quote();
Expected result: (1,"test AND "test"")
Actual result: (1,"test AND ""test""")
Does anyone have an idea how to get the expected behaviour here?
Found it, indeed, the issue is from the conversion from record to varchar.
I can directly pass the column from the rec like:
sample:= rec.criteria;
(I didn't know that we could do that)
So, that gives:
CREATE TABLE roles(
id int,
criteria VARCHAR (255)
);
INSERT INTO roles (id, criteria) VALUES (1, 'test AND "test"');
CREATE OR REPLACE FUNCTION test_quote()
RETURNS VARCHAR
LANGUAGE plpgsql
AS $$
DECLARE
sample varchar;
rec record;
BEGIN
FOR rec IN
SELECT * FROM roles
LOOP
sample := rec.criteria;
END LOOP;
RETURN sample;
END
$$;
SELECT * FROM test_quote();
Thx guys!
I have the function in which I have prepared dynamic query, which I want print in output window before executing it.
Note: In the following example I have just add simple select statement to understand the requirement.
Sample tables:
create table t1
(
col1 int,
col2 text
);
insert into t1 values(1,'Table T1');
insert into t1 values(2,'Table T1');
create table t2
(
col1 int,
col2 text
);
insert into t2 values(1,'Table T2');
insert into t2 values(2,'Table T2');
Function:
create or replace function fn_testing(tbl_Name text)
returns table(col1 int,col2 text) as
$$
begin
return query execute 'select col1,col2 from '||tbl_name||'';
end;
$$
language plpgsql;
Function call:
select * from fn_testing('t2');
I want to print following in message window with result set too in result window:
select col1,col2 from t1;
You can use RAISE NOTICE for messages.
CREATE OR REPLACE FUNCTION fn_testing
(_tbl_name name)
RETURNS TABLE
(col1 integer,
col2 text)
AS
$$
DECLARE
_query text;
BEGIN
_query := format('SELECT col1, col2 FROM %I;', _tbl_name);
RAISE NOTICE '%', _query;
RETURN QUERY EXECUTE _query;
END;
$$
LANGUAGE plpgsql;
Note: There's a special type, name, for identifiers. And to prevent SQL injection or errors you should make sure the dynamic identifiers are properly quoted. You can use format() with %I for that.
I have some function on PostgreSQL 9.6 returning a cursor (refcursor):
CREATE OR REPLACE FUNCTION public.test_returning_cursor()
RETURNS refcursor
IMMUTABLE
LANGUAGE plpgsql
AS $$
DECLARE
_ref refcursor = 'test_returning_cursor_ref1';
BEGIN
OPEN _ref FOR
SELECT 'a' :: text AS col1
UNION
SELECT 'b'
UNION
SELECT 'c';
RETURN _ref;
END
$$;
I need to write another function in which a temp table is created and all data from this refcursor are inserted to it. But INSERT INTO ... FETCH ALL FROM ... seems to be impossible. Such function can't be compiled:
CREATE OR REPLACE FUNCTION public.test_insert_from_cursor()
RETURNS table(col1 text)
IMMUTABLE
LANGUAGE plpgsql
AS $$
BEGIN
CREATE TEMP TABLE _temptable (
col1 text
) ON COMMIT DROP;
INSERT INTO _temptable (col1)
FETCH ALL FROM "test_returning_cursor_ref1";
RETURN QUERY
SELECT col1
FROM _temptable;
END
$$;
I know that I can use:
FOR _rec IN
FETCH ALL FROM "test_returning_cursor_ref1"
LOOP
INSERT INTO ...
END LOOP;
But is there better way?
Unfortunately, INSERT and SELECT don't have access to cursors as a whole.
To avoid expensive single-row INSERT, you could have intermediary functions with RETURNS TABLE and return the cursor as table with RETURN QUERY. See:
Return a query from a function?
CREATE OR REPLACE FUNCTION f_cursor1_to_tbl()
RETURNS TABLE (col1 text) AS
$func$
BEGIN
-- MOVE BACKWARD ALL FROM test_returning_cursor_ref1; -- optional, see below
RETURN QUERY
FETCH ALL FROM test_returning_cursor_ref1;
END
$func$ LANGUAGE plpgsql; -- not IMMUTABLE
Then create the temporary table(s) directly like:
CREATE TEMP TABLE t1 ON COMMIT DROP
AS SELECT * FROM f_cursor1_to_tbl();
See:
Creating temporary tables in SQL
Still not very elegant, but much faster than single-row INSERT.
Note: Since the source is a cursor only the first call succeeds. Executing the function a second time would return an empty set. You would need a cursor with the SCROLL option and move to the start for repeated calls.
This function does INSERT INTO from refcursor. It is universal for all the tables. The only requirement is that all columns of table corresponds to columns of refcursor by types and order (not necessary by names).
to_json() does the trick to convert any primitive data types to string with double-quotes "", which are later replaced with ''.
CREATE OR REPLACE FUNCTION public.insert_into_from_refcursor(_table_name text, _ref refcursor)
RETURNS void
LANGUAGE plpgsql
AS $$
DECLARE
_sql text;
_sql_val text = '';
_row record;
_hasvalues boolean = FALSE;
BEGIN
LOOP --for each row
FETCH _ref INTO _row;
EXIT WHEN NOT found; --there are no rows more
_hasvalues = TRUE;
SELECT _sql_val || '
(' ||
STRING_AGG(val.value :: text, ',') ||
'),'
INTO _sql_val
FROM JSON_EACH(TO_JSON(_row)) val;
END LOOP;
_sql_val = REPLACE(_sql_val, '"', '''');
_sql_val = TRIM(TRAILING ',' FROM _sql_val);
_sql = '
INSERT INTO ' || _table_name || '
VALUES ' || _sql_val;
--RAISE NOTICE 'insert_into_from_refcursor(): SQL is: %', _sql;
IF _hasvalues THEN --to avoid error when trying to insert 0 values
EXECUTE (_sql);
END IF;
END;
$$;
Usage:
CREATE TABLE public.table1 (...);
PERFORM my_func_opening_refcursor();
PERFORM public.insert_into_from_refcursor('public.table1', 'name_of_refcursor_portal'::refcursor);
where my_func_opening_refcursor() contains
DECLARE
_ref refcursor = 'name_of_refcursor_portal';
OPEN _ref FOR
SELECT ...;
I am trying to create procedure which selects data, processes and returns them, but I am struggling how to define array variable for multiple columns.
This works:
CREATE OR REPLACE FUNCTION testing_array_return()
RETURNS TABLE(id BIGINT) AS
$body$
DECLARE
l_rows BIGINT[];
BEGIN
-- select data using for update etc
l_rows := ARRAY(
SELECT 1 AS id
UNION
SELECT 2 AS id
);
-- do some stuff
-- return previously selected data
RETURN QUERY
SELECT *
FROM UNNEST(l_rows);
END;
$body$
LANGUAGE 'plpgsql'
But I want to do this for 2 or more columns without using composite type or rowtype:
CREATE OR REPLACE FUNCTION testing_array_return()
RETURNS TABLE(id BIGINT, text VARCHAR2) AS
$body$
DECLARE
l_rows -- what should I put here?
BEGIN
-- select data using for update etc
l_rows := ARRAY(
SELECT 1 AS id, 'test' AS text
UNION
SELECT 2 AS id, 'test2' AS text
);
-- do some stuff
-- return previously selected data
RETURN QUERY
SELECT *
FROM UNNEST(l_rows);
END;
$body$
LANGUAGE 'plpgsql'
In oracle I could define record type and then table type of it, but I can't find how to do this in postgres. Maybe using wrong keywords when searching...
edit: this is how I would do this in Oracle (without returning).
DECLARE
TYPE t_row IS RECORD(
id NUMBER
,text VARCHAR2(10));
TYPE t_tbl IS TABLE OF t_row;
l_rows t_tbl := t_tbl(); --how to do this in postgres?
BEGIN
SELECT *
BULK COLLECT
INTO l_rows
FROM (SELECT 1 AS id
,'test' AS text
FROM dual
UNION ALL
SELECT 2 AS id
,'test' AS text
FROM dual);
END;
Anything similiar in postgres? Like record but for array.
You would do the same in Postgres:
Create the record type:
create type footype as (id bigint, text_ varchar);
Then use an array of that type in your function:
CREATE OR REPLACE FUNCTION testing_array_return()
RETURNS TABLE(id BIGINT, text VARCHAR) AS
$body$
DECLARE
l_rows footype[];
BEGIN
-- select data using for update etc
l_rows := ARRAY(
SELECT (1, 'test')
UNION
SELECT (2, 'test2')
);
-- do some stuff
-- return previously selected data
RETURN QUERY
SELECT *
FROM UNNEST(l_rows);
END;
$body$
LANGUAGE plpgsql;
Online example: http://rextester.com/UMRZFO54266
The expression (1, 'test') creates a single value of record type. As that is assigned to a typed variable, there is no need to alias the columns (and in fact you can't do that anyway).
Unrelated, but: the language name is an identifier. Do not put that in single quotes.
Note that text is also a keyword in Postgres because it's a data type. You shouldn't use it as a column name
I have a function returning table, which accumulates output of multiple calls to another function returning table. I would like to perform final query on built table before returning result. Currently I implemented this as two functions, one accumulating and one performing final query, which is ugly:
CREATE OR REPLACE FUNCTION func_accu(LOCATION_ID INTEGER, SCHEMA_CUSTOMER TEXT)
RETURNS TABLE("networkid" integer, "count" bigint) AS $$
DECLARE
GATEWAY_ID integer;
BEGIN
FOR GATEWAY_ID IN
execute format(
'SELECT id FROM %1$I.gateway WHERE location_id=%2$L'
, SCHEMA_CUSTOMER, LOCATION_ID)
LOOP
RETURN QUERY execute format(
'SELECT * FROM get_available_networks_gw(%1$L, %2$L)'
, GATEWAY_ID, SCHEMA_CUSTOMER);
END LOOP;
END;
$$ LANGUAGE plpgsql;
CREATE OR REPLACE FUNCTION func_query(LOCATION_ID INTEGER, SCHEMA_CUSTOMER TEXT)
RETURNS TABLE("networkid" integer, "count" bigint) AS $$
DECLARE
BEGIN
RETURN QUERY execute format('
SELECT networkid, max(count) FROM func_accu(%2$L, %1$L) GROUP BY networkid;'
, SCHEMA_CUSTOMER, LOCATION_ID);
END;
$$ LANGUAGE plpgsql;
How can this be done in single function, elegantly?
Both functions simplified and merged, also supplying value parameters in the USING clause:
CREATE OR REPLACE FUNCTION pg_temp.func_accu(_location_id integer, schema_customer text)
RETURNS TABLE(networkid integer, count bigint) AS
$func$
BEGIN
RETURN QUERY EXECUTE format('
SELECT f.networkid, max(f.ct)
FROM %I.gateway g
, get_available_networks_gw(g.id, $1) f(networkid, ct)
WHERE g.location_id = $2
GROUP BY 1'
, _schema_customer)
USING _schema_customer, _location_id;
END
$func$ LANGUAGE plpgsql;
Call:
SELECT * FROM func_accu(123, 'my_schema');
Related:
Dynamically access column value in record
I am using alias names for the columns returned by the function (f(networkid, ct)) to be sure because you did not disclose the return type of get_available_networks_gw(). You can use the column names of the return type directly.
The comma (,) in the FROM clause is short syntax for CROSS JOIN LATERAL .... Requires Postgres 9.3 or later.
What is the difference between LATERAL and a subquery in PostgreSQL?
Or you could run this query instead of the function:
SELECT f.networkid, max(f.ct)
FROM myschema.gateway g, get_available_networks_gw(g.id, 'my_schema') f(networkid, ct)
WHERE g.location_id = $2
GROUP BY 1;