I'm using a function in my Postgres and with this function, I want to delete a record using table and id and store the record as a JSON.
As you can imagine, I'm getting the table name as a parameter, but at that point, I don't know the name of the fields inside of my table. And I have:
create or replace function deletetable(_table text, _id int)
returns json as
$func$
declare
res json;
begin
execute format('SELECT json_to_recordset(::json) FROM ' || _table || ' WHERE id ' || id) into res;
-- HERE ONCE I GET THE RECORD AS JSON I HAVE TO INSERT IT IN MY TABLE
return res;
end
$func$ language plpgsql;
Well, my specific question is, how can I retrieve that information?
With my current function I get:
SELECT json_to_recordset(::json) FROM table
First create a log table:
create table logtable (
id serial primary key,
del_tname text not null,
del_ts timestamptz not null default now(),
del_rec jsonb
);
Your function should then look like this:
create or replace function deletetable(_table text, _id int)
returns jsonb as
$$
declare
res jsonb;
begin
execute format('with d as (delete from %I where id = %s returning *) '
'insert into logtable (del_tname, del_rec) '
'select %L, to_jsonb(d) from d returning del_rec',
_table, _id, _table) into res;
return res;
end
$$ language plpgsql;
Executing a select * from deletetable('tablename', 14); will delete your row, log it to logtable, and return the jsonb of the row.
Related
I have been working on creating a store procedure that will select data from a table, do some modification to that data, and then I need to insert that modified data into the same table. Take an example my table name is student. My procedure looks like below:
create or replace procedure student_create(p_code varchar)
language plpgsql
as $$
declare
v_student public.student;
begin
select * into v_student from student where code = p_code and is_latest_version is true;
raise notice 'Value: %', v_student;
v_student.id = uuid_generate_v4();
v_student.version_created_at = now();
v_student.version_updated_at = v_student.version_created_at;
raise notice 'Value: %', v_student;
INSERT INTO public.student VALUES(v_student);
end;$$
I am getting errors while calling this procedure:
ERROR: column "id" is of type uuid but expression is of type hotel
LINE 1: INSERT INTO public.hotel VALUES(v_hotel)
I know I can make insert statements like I can get each value from the variable and set it like
INSERT INTO public.student VALUES(v_student.id, v_student.code, v_student.name);
But I don't want to do that because it will become tightly coupled and later if I add another column into the table then I need to add that column into this procedure as well.
Does anyone have idea how can I insert the declared type variable directly into table.
There is no table type, there is only row composite type. Check manual 43.3.4. Row Types.
use row type.
create or replace procedure student_create(p_code text)
language plpgsql
as $$
declare
v_student public.student
begin
for v_student in select * from student where code = p_code and is_latest_version is true
loop
v_student.id = uuid_generate_v4();
v_student.version_created_at = now();
v_student.version_updated_at = v_student.version_created_at;
v_student.is_latest_version = true;
v_student.code = p_code;
INSERT INTO student VALUES(v_student.*);
end loop;
end;$$;
call it: call student_create('hello');
3. use update clause directly.
create or replace procedure student_create_1(p_code text)
language plpgsql as $$
BEGIN
with a as ( select uuid_generate_v4() as id ,
now() as version_created_at,
now() as version_updated_at,
p_code as "code" from student
where code = p_code and is_latest_version is true)
INSERT INTO student(id, version_created_at, version_updated_at, code)
select a.id, a.version_created_at,a.version_updated_at,a."code" from a;
end
$$;
call it: call student_create_1('hello');
fiddle code: here
I am currently working a stored procedure capable of detecting continuity on a specific set of entries..
The specific set of entries is extracted from a sql query
The function takes in two input parameter, first being the table that should be investigated, and the other being the list of ids which should be evaluated.
For every Id I need to investigate every row provided by the select statement.
DROP FUNCTION IF EXISTS GapAndOverlapDetection(table_name text, entity_ids bigint[]);
create or replace function GapAndOverlapDetection ( table_name text, enteity_ids bigint[] )
returns table ( entity_id bigint, valid tsrange, causes_overlap boolean, causes_gap boolean)
as $$
declare
x bigint;
var_r record;
begin
FOREACH x in array $2
loop
EXECUTE format('select entity_id, valid from' ||table_name|| '
where entity_id = '||x||'
and registration #> now()::timestamp
order by valid ASC') INTO result;
for var_r in result
loop
end loop;
end loop ;
end
$$ language plpgsql;
select * from GapAndOverlapDetection('temp_country_registration', '{1,2,3,4}')
I currently get an error in the for statement saying
ERROR: syntax error at or near "$1"
LINE 12: for var_r in select entity_id, valid from $1
You can iterate over the result of the dynamic query directly:
create or replace function gapandoverlapdetection ( table_name text, entity_ids bigint[])
returns table (entity_id bigint, valid tsrange, causes_overlap boolean, causes_gap boolean)
as $$
declare
var_r record;
begin
for var_r in EXECUTE format('select entity_id, valid
from %I
where entity_id = any($1)
and registration > now()::timestamp
order by valid ASC', table_name)
using entity_ids
loop
... do something with var_r
-- return a row for the result
-- this does not end the function
-- it just appends this row to the result
return query
select entity_id, true, false;
end loop;
end
$$ language plpgsql;
The %I injects an identifier into a string and the $1 inside the dynamic SQL is then populated through passing the argument with the using keyword
Firstly, decide whether you want to pass the table's name or oid. If you want to identify the table by name, then the parameter should be of text type and not regclass.
Secondly, if you want the table name to change between executions then you need to execute the SQL statement dynamically with the EXECUTE statement.
This stored function returns a query:
DROP FUNCTION IF EXISTS get_query (
ctl text, scm text, tbl text, seq text);
CREATE OR REPLACE FUNCTION get_query (
ctl text, scm text, tbl text, seq text)
RETURNS text
AS
$$
select concat('insert into ',$2,'.',$1, ' select nextval("',$4,'") as id, ',
string_agg(concat('NEW.', column_name), ', '), ', current_timestamp as audited_at;')
from information_schema.columns
where table_catalog = $1
and table_schema = $2
and table_name = $3
$$
LANGUAGE sql;
How do I PREPARE the query that this function returns.
I want insert a record in a table when a trigger is fired but I don't want to specify the list of columns to be inserted. The schema might keep changing. Hence, trying to use prepared statements.
This sample code illustrates how I mean the query string to be executed:
DROP FUNCTION IF EXISTS fn_name (store_temporary_query text);
CREATE OR REPLACE FUNCTION fn_name (store_temporary_query text)
RETURNS table (query text)
LANGUAGE plpgsql
AS
$$
begin
select 'select 1 as ID' into store_temporary_query;
return query (select store_temporary_query);
end;
$$
select fn_name('');
The above query gives the following output
fn_name
select 1 as ID
The desired result is the query
ID
1
EDIT #2
DROP FUNCTION IF EXISTS fn_name (store_temporary_query text);
CREATE OR REPLACE FUNCTION fn_name (store_temporary_query text)
RETURNS table (query text)
LANGUAGE plpgsql
AS
$$
begin
select 'select 1 as ID;' into store_temporary_query;
return query execute store_temporary_query;
end;
$$
select fn_name('');
This gets us here,
Error executing SQL statement. ERROR: syntax error at or near "select"
Position: 254 - Connection: Aurora Legacy: 794ms
You need EXECUTE to execute a query stored in a string:
RETURN QUERY EXECUTE store_temporary_query;
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 have dynamicly generated SELECT. I try to return result as SETOF RECORD. Sth like that:
CREATE FUNCTION test(column_name text) RETURNS SETOF RECORD AS $$
DECLARE
row RECORD;
BEGIN
FOR row IN EXECUTE 'SELECT ' || quote_ident(column_name) || ' FROM dates'
LOOP
RETURN NEXT row;
END LOOP;
RETURN;
END;
$$ LANGUAGE 'plpgsql';
When I try:
SELECT * FROM test('column1');
I get this:
ERROR: a column definition list is required for functions returning "record"
I know that column1 is integer type:
SELECT * FROM test('column1') f(a int);
result is correct, because I know that this is going to be Integer type.
When I try:
SELECT * FROM test('column1') f(a varchar);
I get error:
ERROR: wrong record type supplied in RETURN NEXT
DETAIL: Returned type integer does not match expected type character varying in column 1.
Now my question:
What to do to get rid of part of querty where I define types 'f(a int)'. It should by feasible because Postgres knowns what is returned type. I tried with IMMUTABLE options, but unsuccessfully.
You could cast the value to text inside the function, and declare that the function RETURNS SETOF text. You can also return the whole result set at once; no need to iterate explicitly.
CREATE TABLE dates (column1 int, column2 date);
INSERT INTO dates VALUES (1, date '2012-12-22'), (2, date '2013-01-01');
CREATE FUNCTION test(column_name text) RETURNS SETOF text AS $$
BEGIN
RETURN QUERY EXECUTE 'SELECT '
|| quote_ident(column_name) || '::text FROM dates';
END;
$$ LANGUAGE 'plpgsql';
Now SELECT test('column1'); yields:
test
------
1
2
(2 rows)
... and (with my locale settings) SELECT test('column2'); yields:
test
------------
2012-12-22
2013-01-01
(2 rows)
You need to specify OUT parameters corresponding to the columns you want to return.