How can I get result by using “execute ‘delete from table1'" - postgresql

when I use execute command to run a sql cmd, I want to get the result of it.
As we know, I can get total counts by variable sc when I use :
execute 'select * from table" into sc;
But How can I get result by using:
execute 'delete from table1'"?
when I use INTO, it turns out
ERROR: "INTO used with a command that cannot return data"

execute 'WITH row_deleted AS (DELETE FROM table1 RETURNING *) SELECT count(*) FROM row_deleted' into c;
You can use it inside a plsql funtion as following:
--Drop the table and the functin if it exist:
DROP TABLE IF EXISTS table1;
DROP FUNCTION if exists _deleted_rows();
--Create the table for the example:
CREATE TABLE table1
(
row_id serial NOT NULL,
col1 character varying,
CONSTRAINT table1_pkey PRIMARY KEY (row_id)
);
--Insert some rows:
insert into table1 (col1) values ('test1');
insert into table1 (col1) values ('test2');
insert into table1 (col1) values ('test3');
--Ctreate the function that count the number of deleted rows of the table: table1
CREATE OR REPLACE FUNCTION _deleted_rows()
RETURNS character varying AS
$BODY$declare
nbr_deleted integer;
begin
execute 'WITH row_deleted AS (DELETE FROM table1 RETURNING *) SELECT count(*) FROM row_deleted' into nbr_deleted;
return (nbr_deleted);
end;$BODY$
LANGUAGE plpgsql VOLATILE;
Test that function (got problem building shema on sqlfidlle):
select * from _deleted_rows();
_deleted_rows
---------------
3
(1 ligne)
Execute command
DELETE command

It's a little unclear to me what you are trying to do, but you should be able use "RETURNING". Here I am just returning the rows that were deleted:
CREATE TEMP TABLE foo(id int, description text);
INSERT INTO foo VALUES
(1, 'HELLO'),
(2, 'WORLD');
DELETE FROM foo returning *;
+----+-------------+
| id | description |
+----+-------------+
| 1 | HELLO |
| 2 | WORLD |
+----+-------------+
(2 rows)
Also, if you need them moved "into" a table (for example), you could do something like:
DROP TABLE IF EXISTS foo;
DROP TABLE IF EXISTS deleted_foo;
CREATE TEMP TABLE foo(id int, description text);
INSERT INTO foo VALUES
(1, 'HELLO'),
(2, 'WORLD');
CREATE TEMP TABLE deleted_foo(id int, description text);
WITH x AS (DELETE FROM foo RETURNING *)
INSERT INTO deleted_foo
SELECT * FROM x;
SELECT * FROM deleted_foo;
+----+-------------+
| id | description |
+----+-------------+
| 1 | HELLO |
| 2 | WORLD |
+----+-------------+
(2 rows)
Assuming that you are doing this from inside a plpgsql function, you could also use the ROW_COUNT variable. For example:
GET DIAGNOSTICS integer_var = ROW_COUNT;
This would give you the number of rows that were deleted.

Related

PostgreSQL and temp table triggers

I am looking for the best practice to define triggers and sequences on temporary tables with PostgreSQL.
When creating a temp table, PostgreSQL automatically creates a temporary schema with the name "pg_temp_nnn" (alias: "pg_temp")
It appears that one can create user functions and objects in this temporary schema.
I wonder if this is really valid SQL for PostgreSQL or just working by accident?
Tested with various PostgreSQL versions from 10 to 14.
Note: Triggers created on temp tables automatically land in the temp schema because the trigger inherits the schema of its table.
Tx!
CREATE TEMP TABLE tt1 (pk INTEGER NOT NULL, name VARCHAR(50));
CREATE SEQUENCE pg_temp.tt1_seq START 1;
CREATE FUNCTION pg_temp.tt1_srl() RETURNS TRIGGER AS
'DECLARE ls BIGINT;
BEGIN
SELECT INTO ls nextval(''pg_temp.tt1_seq'');
IF new.pk ISNULL OR new.pk=0 THEN
new.pk:=ls;
ELSE
IF new.pk>=ls THEN
PERFORM setval(''pg_temp.tt1_seq'',new.pk);
END IF;
END IF;
RETURN new;
END;'
LANGUAGE 'plpgsql';
CREATE TRIGGER tt1_srlt BEFORE INSERT ON tt1 FOR EACH ROW EXECUTE PROCEDURE pg_temp.tt1_srl();
INSERT INTO tt1 (name) VALUES ('aaaa');
SELECT 'Insert #1:', currval('pg_temp.tt1_seq');
INSERT INTO tt1 VALUES (0,'bbbb');
SELECT 'Insert #2:', currval('pg_temp.tt1_seq');
INSERT INTO tt1 VALUES (100,'cccc');
SELECT 'Insert #3:', currval('pg_temp.tt1_seq');
INSERT INTO tt1 (name) VALUES ('dddd');
SELECT 'Insert #4:', currval('pg_temp.tt1_seq');
SELECT * FROM tt1 ORDER BY pk;
Output:
CREATE TABLE
CREATE SEQUENCE
CREATE FUNCTION
CREATE TRIGGER
INSERT 0 1
?column? | currval
------------+---------
Insert #1: | 1
(1 row)
INSERT 0 1
?column? | currval
------------+---------
Insert #2: | 2
(1 row)
INSERT 0 1
?column? | currval
------------+---------
Insert #3: | 100
(1 row)
INSERT 0 1
?column? | currval
------------+---------
Insert #4: | 101
(1 row)
pk | name
-----+------
1 | aaaa
2 | bbbb
100 | cccc
101 | dddd
(4 rows)
Yes, that works and is supported.
Creating objects in schema pg_temp creates temporary objects that will be removed when the session ends. CREATE TEMP TABLE x (...) is the same as CREATE TABLE pg_temp.x (...).

fetch data from two different tables in single function postresql

I want to write function to get data from two different tables
My code:
create function
return table(a integer,b integer,c integer,k integer,l integer,m integer);
if(x=1) then
select a,b,c from mst_1
else
select k,l,m from mst_2
end IF;
end;
the problem is that two tables posses different columns, I'm getting error.
I replicated a case similar to yours, and it's just a matter of using the correct sintax.
If you have two tables like test and test_other like in my case
create table test (id serial, name varchar, surname varchar);
insert into test values(1,'Carlo', 'Rossi');
insert into test values(2,'Giovanni', 'Galli');
create table test_other (id_other serial, name_other varchar, surname_other varchar);
insert into test_other values(1,'Beppe', 'Bianchi');
insert into test_other values(2,'Salmo', 'Verdi');
you now want a function that returns the 3 columns from test if an input parameter is 1, the 3 columns from test_other otherwise.
Your function will look like the following
create or replace function case_return(x integer)
returns table(id integer,value_1 varchar, value_2 varchar)
language plpgsql
as
$$
begin
if(x=1) then
return query select test.id,test.name,test.surname from test;
else
return query select test_other.id_other, test_other.name_other, test_other.surname_other from test_other;
end IF;
end;
$$
;
The function always returns the columns id, value_1 and value_2 as per definition even if your source columns are different
defaultdb=> select * from case_return(0); id | value_1 | value_2
----+---------+---------
1 | Beppe | Bianchi
2 | Salmo | Verdi
(2 rows)
defaultdb=> select * from case_return(1); id | value_1 | value_2
----+----------+---------
1 | Carlo | Rossi
2 | Giovanni | Galli
(2 rows)

Create function in postgresql to update column values from a table with preferred values and aliases

I want to create a function that will update a column of type varchar to a preferred string that is referenced in the column of another table to help me clean this column more iteratively.
CREATE TABLE big_table (
mn_uid NUMERIC PRIMARY KEY,
user_name VARCHAR
);
INSERT INTO big_table VALUES
(1, 'DAVE'),
(2, 'Dave'),
(3, 'david'),
(4, 'Jak'),
(5, 'jack'),
(6, 'Jack'),
(7, 'Grant');
CREATE TABLE nameKey_table (
nk_uid NUMERIC PRIMARY KEY,
correct VARCHAR,
wrong VARCHAR
);
INSERT INTO nameKey_table VALUES
(1, 'David', 'Dave_DAVE_dave_DAVID_david'),
(2, 'Jack', 'JACK_jack_Jak_jak');
I want to perform the following procedure:
UPDATE big_table
SET user_name = (SELECT correct
FROM nameKey_table
WHERE wrong
LIKE '%DAVE%')
WHERE user_name = 'DAVE';
but looped over each user_name in big_table so that I have a function that can do something like this:
UPDATE big_table SET user_name = corrected_name_fn();
Here is my attempt to do something like this but I can't seem to get it to work:
CREATE FUNCTION corrected_name_fn() RETURNS VARCHAR AS $$
DECLARE entry RECORD;
DECLARE correct_name VARCHAR;
BEGIN
FOR entry IN SELECT DISTINCT user_name FROM big_table LOOP
EXECUTE 'SELECT correct
FROM nameKey_table
WHERE wrong
LIKE ''%$1%'''
INTO correct_name
USING entry;
RETURN correct_name;
END LOOP;
END;
$$ LANGUAGE plpgsql;
I want the final output in big_table to be:
| mn_uid | user_name |
| 1 | 'David' |
| 2 | 'David' |
| 3 | 'David' |
| 4 | 'Jack' |
| 5 | 'Jack' |
| 6 | 'Jack' |
| 7 | 'Grant' |
I realize rows 6 and 7 provide two unique cases that I want to build into the function with IF ELSE statements.
If user_name is in nameKey_table.correct, go to next
If user_name is not in nameKey_table.correct or does not match a string in nameKey_table.wrong, leave as is.
Thanks for any help on this!!
It sounds like you want a trigger on the table. Here is my suggestion:
CREATE OR REPLACE FUNCTION tf_fix_name() RETURNS TRIGGER AS
$$
DECLARE
corrected_name TEXT;
BEGIN
SELECT correct INTO corrected_name FROM nameKey_table WHERE expression ~* NEW.user_name;
IF FOUND THEN
NEW.user_name := corrected_name;
END IF;
RETURN NEW;
END;
$$
LANGUAGE plpgsql;
CREATE TEMP TABLE big_table (
mn_uid INT PRIMARY KEY,
user_name TEXT NOT NULL
);
CREATE TRIGGER trigger_fix_name
BEFORE INSERT
ON big_table
FOR EACH ROW
EXECUTE PROCEDURE tf_fix_name();
CREATE TEMP TABLE nameKey_table (
nk_uid INT PRIMARY KEY,
correct TEXT NOT NULL,
expression TEXT NOT NULL
);
INSERT INTO nameKey_table VALUES
(1, 'David', '(dave|david)'),
(2, 'Jack', '(jack|jak)');
INSERT INTO big_table VALUES
(1, 'DAVE'),
(2, 'Dave'),
(3, 'david'),
(4, 'Jak'),
(5, 'jack'),
(6, 'Jack'),
(7, 'Grant');
SELECT * FROM big_table;
+--------+-----------+
| mn_uid | user_name |
+--------+-----------+
| 1 | David |
| 2 | David |
| 3 | David |
| 4 | Jack |
| 5 | Jack |
| 6 | Jack |
| 7 | Grant |
+--------+-----------+
(7 rows)
Note: I think you can do what you want a lot easier with a case insensitive regular expression. And I also changed your primary keys to INTs. Not sure why they are numerics, but it doesn't really change the solutions. My solution was developed and tested on PostgreSQL 9.6.
You don't need a function; you can just update one table from the contents of another table:
UPDATE big_table dst
SET user_name = src.correct
FROM nameKey_table src
WHERE src.wrong LIKE '%' || dst.user_name || '%'
AND dst.user_name <> src.correct -- avoid idempotent updates
;
And if you need performance, dont rely on the LIKE operator, it cannot use indexes for leading %. Instead, use a lookup-table with one entry per row:
CREATE TABLE bad_spell (
correct VARCHAR,
wrong VARCHAR PRIMARY KEY -- This will cause an unique index to be created.
);
INSERT INTO bad_spell VALUES
('David', 'Dave')
,('David', 'DAVE')
,('David', 'dave')
,('David', 'DAVID')
,('David', 'david')
,('Jack', 'JACK')
,('Jack', 'jack')
,('Jack', 'Jak')
,('Jack', 'jak')
;
-- This indexes could be temporary
CREATE INDEX ON big_table(user_name);
-- EXPLAIN
UPDATE big_table dst
SET user_name = src.correct
FROM bad_spell src
WHERE dst.user_name = src.wrong
AND dst.user_name <> src.correct -- avoid idempotent updates
;
SELECT* FROM big_table
;

Postgres 10: do rows automatically move between partitions?

Assuming I have a parent table with child partitions that are created based on the value of a field.
If the value of that field changes, is there a way to have Postgres automatically move the row into the appropriate partition?
For example:
create table my_table(name text)
partition by list (left(name, 1));
create table my_table_a
partition of my_table
for values in ('a');
create table my_table_b
partition of my_table
for values in ('b');
In this case, if I change the value of name in a row from aaa to bbb, how can I get it to automatically move that row into my_table_b.
When I tried to do that, (i.e. update my_table set name = 'bbb' where name = 'aaa';), I get the following error:
ERROR: new row for relation "my_table_a" violates partition constraint
https://git.postgresql.org/gitweb/?p=postgresql.git;a=commitdiff;h=f0e44751d7175fa3394da2c8f85e3ceb3cdbfe63
it doesn't handle updates that cross partition boundaries.
thus you need to create one yourself... here's your set:
t=# insert into my_table select 'abc';
INSERT 0 1
t=# insert into my_table select 'bcd';
INSERT 0 1
t=# select tableoid::regclass,* from my_table;
tableoid | name
------------+------
my_table_a | abc
my_table_b | bcd
(2 rows)
here's rule and fn():
t=# create or replace function puf(_j json,_o text) returns void as $$
begin
raise info '%',': '||left(_j->>'name',1);
execute format('insert into %I select * from json_populate_record(null::my_table, %L)','my_table_'||left(_j->>'name',1), _j);
execute format('delete from %I where name = %L','my_table_'||left(_o,1), _o);
end;
$$language plpgsql;
CREATE FUNCTION
t=# create rule psr AS ON update to my_table do instead select puf(row_to_json(n),OLD.name) from (select NEW.*) n;
CREATE RULE
here's update:
t=# update my_table set name = 'bbb' where name = 'abc';
INFO: : b
puf
-----
(1 row)
UPDATE 0
checking result:
t=# select tableoid::regclass,* from my_table;
tableoid | name
------------+------
my_table_b | bcd
my_table_b | bbb
(2 rows)
once again:
t=# update my_table set name = 'a1' where name = 'bcd';
INFO: : a
puf
-----
(1 row)
UPDATE 0
t=# select tableoid::regclass,* from my_table;
tableoid | name
------------+------
my_table_a | a1
my_table_b | bbb
(2 rows)
Of course using json to pass NEW record looks ugly. And it is ugly indeed. But I did not have time to study the new PARTITION feature of 10, so don't know the elegant way to do this task. Hopefully I could give the generic idea of how you can possible solve the problem and you will produce a better neat code.
update
its probablygood idea to limit such rule to ON update to my_table where left(NEW.name,1) <> left(OLD.name,1) do instead, to release the heavy manipulations need

insert for each element in jsonb array with 'instead of' trigger on a view

I'm using a view to report related rows as an array. It would be convenient to also insert those rows with a instead of insert trigger on the view. The rows to insert will need to construct a json object with keys from a related table.
My current incomplete implementation needs where task in JSONB_ARRAY. I don't know if that is possible.
in addition to a visit table with primary id colum vid, I have
task table to pull from.
| task | sections |
+--------+-------------------------+
|task_A | ["section1","section2"] |
|task_B | ["part1", "part2" ] |
and a visit_task table to populate
| vid | task | measures |
+-----+--------+------------------------------------------------+
| 1 | task_C | ["level1": "value added later","level2": null] |
| 1 | task_E | ["q1": null,"q2": null] |
want:
insert into vt_view (vid,tasks) values (1,'["task_A","task_B"]::jsonb)
to actually do:
insert into visit_task (vid,task,measures)
values (1,'task_A','{"section1": null, "section2": null}'::jsonb);
insert into visit_task (vid,task,measures)
values (1,'task_B','{"part1": null, "part2": null}'::jsonb);
current incomplete trigger solution excerpt:
insert into visit_task from
select
NEW.vid as vid,
NEW.task as task,
-- *MAGIC* to create json object; measures list becomes object with null vals
row_to_json(_) from (select json_object(t.measures, 'null')) as measures
-- /MAGIC
from task t
-- *MAGIC* where we only grab the tasks within the array NEW.tasks
where t.task in (select * from NEW.tasks)
-- /MAGIC
Unfortunately, the server doesn't know what to do with/in the MAGIC flags. Neither do I.
To make the task easier create an auxiliary function to expand sections to desired format:
create or replace function expand_sections(jsonb)
returns jsonb language sql as $$
select jsonb_object_agg(e, null)
from jsonb_array_elements_text($1) e
$$;
-- test the function:
select task, expand_sections(sections)
from task;
task | expand_sections
--------+--------------------------------------
task_A | {"section1": null, "section2": null}
task_B | {"part1": null, "part2": null}
(2 rows)
Use the function in the trigger function:
create or replace function trigger_instead_on_vt_view()
returns trigger language plpgsql as $$
begin
insert into visit_task
select vid, task, expand_sections(sections)
from (
select new.vid, task
from jsonb_array_elements_text(new.tasks) task
) sub
join task using(task);
return null;
end $$;
create trigger trigger_instead_on_vt_view
instead of insert on vt_view
for each row execute procedure trigger_instead_on_vt_view();
insert into vt_view (vid,tasks) values (1,'["task_A","task_B"]'::jsonb);
select * from visit_task;
vid | task | measures
-----+--------+--------------------------------------
1 | task_A | {"section1": null, "section2": null}
1 | task_B | {"part1": null, "part2": null}
(2 rows)
If you do not want to create the auxiliary function, use this variant:
create or replace function trigger_instead_on_vt_view()
returns trigger language plpgsql as $$
begin
insert into visit_task
select vid, task, measures
from (
select new.vid, task
from jsonb_array_elements_text(new.tasks) task
) s
join (
select task, jsonb_object_agg(e, null) measures
from task, jsonb_array_elements_text(sections) e
group by 1
) t
using (task);
return null;
end $$;