I have a name of table or view in PostgreSQL database and need to delete in in single pgSQL command. How can i afford it?
I was able to select form system table to find out if there any table with such a name but stuck with procedural part:
SELECT count(*) FROM pg_tables where tablename='user_statistics';
DROP TABLE user_statistics;
DROP VIEW user_statistics;
complete syntax:
DROP TABLE
DROP VIEW
And if you want a complete function, i tried something like this:
CREATE OR REPLACE FUNCTION delete_table_or_view(objectName varchar) RETURNS integer AS $$
DECLARE
isTable integer;
isView integer;
BEGIN
SELECT INTO isTable count(*) FROM pg_tables where tablename=objectName;
SELECT INTO isView count(*) FROM pg_views where viewname=objectName;
IF isTable = 1 THEN
execute 'DROP TABLE ' || objectName;
RETURN 1;
END IF;
IF isView = 1 THEN
execute 'DROP VIEW ' || objectName;
RETURN 2;
END IF;
RETURN 0;
END;
$$ LANGUAGE plpgsql;
Consider using DROP TABLE IF EXISTS and DROP VIEW IF EXISTS. That way you won't get an error message if it fails, just a notice.
Related
I'm trying to create a function on PostgreSQL, and I have some problem to use a local variable. Here's my code :
DECLARE query RECORD;
DECLARE schema_name TEXT;
BEGIN
FOR query IN SELECT * FROM context WHERE created_at + make_interval(days => duration) <= CURRENT_TIMESTAMP LOOP
SELECT lower(quote_ident(query.title)) INTO schema_name;
DROP SCHEMA schema_name CASCADE;
DELETE FROM context WHERE id = query.id;
END LOOP;
RETURN 1;
END;
$$ LANGUAGE plpgsql;
The select and delete queries work fine, and I've made a test returning the value of schema_name variable, and it's OK.
My problem is with this line :
DROP SCHEMA schema_name CASCADE;
I get an error as "the schema 'schema_name' doesn't exist".
I'd really appreciate any ideas for how to use this variable to do the drop query.
You need dynamic SQL for this:
DECLARE
query RECORD;
BEGIN
FOR query IN SELECT id, lower(title) as title
FROM context
WHERE created_at + make_interval(days => duration) <= CURRENT_TIMESTAMP
LOOP
execute format('DROP SCHEMA %I CASCADE', query.title);
DELETE FROM context WHERE id = query.id;
END LOOP;
RETURN 1;
END;
$$ LANGUAGE plpgsql;
I also removed the unnecessary SELECT statement to make the title lower case, this is better done in the query directly.
Also: variable assignment is faster with := then with select, so:
schema_name := lower(quote_ident(query.title));
would be better if the variable was needed.
I have a few db tables.
I want write universtal postgres function on copy rows to history tables
I have tables:
table1
table1_h
table2
table2_h
I wrote function (with help stackoverflow)
CREATE OR REPLACE FUNCTION copy_history_f() RETURNS TRIGGER AS
$BODY$
DECLARE
tablename_h text:= TG_TABLE_NAME || '_h';
BEGIN
EXECUTE 'INSERT INTO ' || quote_ident(TG_TABLE_SCHEMA) || '.' || quote_ident(tablename_h) || ' VALUES (' || OLD.* ||')';
RETURN NULL;
END;
$BODY$
LANGUAGE plpgsql VOLATILE;
And functions was create, but after update is error.
ERROR: syntax error at or near ","
ROW 1: ...RT INTO table1_h VALUES ((12,,,0,,"Anto...
I know where is error in this insert but I don't know how I repair that.
Structure tables table1 and table1_h are identical but table1_h has one more column (id_h)
Can you help me, how I have create psql function?
Thnak you.
drop table if exists t;
drop table if exists t_h;
drop function if exists ftg();
create table t(i serial, x numeric);
insert into t(x) values(1.1),(2.2);
create table t_h(i int, x numeric);
create function ftg() returns trigger language plpgsql as $ftg$
declare
tablename_h text:= TG_TABLE_NAME || '_h';
begin
execute format($q$ insert into %I.%I select $1.*; $q$, TG_TABLE_SCHEMA, tablename_h) using old;
return null;
end $ftg$;
create trigger tg_t after delete on t for each row execute procedure ftg();
delete from t where i = 1;
select * from t_h;
dbfiddle
Update It solves your problem, but I think that you want to have a bit more info in your history tables. It will be more complex a bit:
drop table if exists t;
drop table if exists t_h;
drop function if exists ftg();
create table t(i serial, x numeric);
insert into t(x) values(1.1),(2.2);
create table t_h(
hi serial, -- just ID
hd timestamp, -- timestamp
hu text, -- user who made changes
ha text, -- action
i int, x numeric
);
create function ftg() returns trigger language plpgsql as $ftg$
declare
tablename_h text:= TG_TABLE_NAME || '_h';
begin
execute format(
$q$
insert into %I.%I
select
nextval(%L || '_hi_seq'),
clock_timestamp(),
current_user,
%L,
$1.*
$q$, TG_TABLE_SCHEMA, tablename_h, tablename_h, TG_OP) using old;
return null;
end $ftg$;
create trigger tg_t after delete or update on t for each row execute procedure ftg();
update t set x = x * 2;
update t set x = x * 2 where i = 2;
delete from t where i = 1;
select * from t_h;
dbfiddle
I assume you are inserting the 'old' values from table1 into table1_h.
The additional column is your problem. When you using an insert without naming columns you must use a matching number and type for the insert.
You must use column referencing.
eg.
Insert into table1_h(column1, column2, column3)
values (a,b,c)
Consider a default value for the additional column in table table1_h.
I'm new to plpgsql. I'm sure there is some really simple way to do this, but for some reason I'm having a lot of trouble trying to figure out how to do this.
I'm simply trying to loop through the list of existing tables and execute
CREATE TABLE z_existing_table_name AS SELECT * FROM existing_table_name WITH DATA
So far, I have this:
CREATE OR REPLACE FUNCTION create_backup_row()
RETURNS RECORD
AS $$
DECLARE
row RECORD;
BEGIN
FOR row IN SELECT * FROM information_schema.tables WHERE table_catalog = 'my_db' and table_schema = 'public'
LOOP
EXECUTE 'CREATE TABLE z_' || t.table_name || ' as ' || t.table_name
END LOOP;
END;
$$ LANGUAGE plpgsql;
It would be an added bonus if I can make this function re-runnable. Something like drop table if exist then create table ...
#Steven, use below procedure,
-- Function: create_backup_row()
-- DROP FUNCTION create_backup_row();
CREATE OR REPLACE FUNCTION create_backup_row()
RETURNS integer AS
$BODY$
DECLARE
v_table text;
BEGIN
FOR v_table IN
SELECT table_name
FROM information_schema.tables
WHERE table_catalog = 'my_db'
AND table_schema = 'public'
AND table_name not ilike '%z_%' -- to skip the table with z_ when we rerun it.
LOOP
EXECUTE ' DROP TABLE IF EXISTS z_' || v_table ;
EXECUTE 'CREATE TABLE z_' || v_table || ' as SELECT * FROM ' || v_table ;
END LOOP;
return 1;
END;
$BODY$
LANGUAGE plpgsql VOLATILE
COST 100;
ALTER FUNCTION create_backup_row()
OWNER TO postgres;
For some fancy database maintenance for my developer database I'd like to be able to use queries to generate commands to alter the database. The thing is: I'm a complete greenhorn to PostgreSQL. I've made my attempt but have failed colorfully.
So in the end, I would like to have a table with a single column and each row would be a command (or group of commands, depending on the case) that I would think would look something like this...
DO $$
DECLARE
command_entry RECORD;
BEGIN
FOR command_entry IN SELECT * FROM list_of_commands
LOOP
EXECUTE command_entry;
END LOOP;
END;
$$;
Where the table list_of_commands could be populated with something like the following (which in this example would remove all tables from the public schema)...
CREATE TEMP TABLE list_of_commands AS
SELECT 'drop table if exists "' || tablename || '" cascade;'
FROM pg_tables
WHERE schemaname = 'public';
However, with this I get the following error...
ERROR: syntax error at or near ""drop table if exists ""dummy_table"" cascade;""
LINE 1: ("drop table if exists ""dummy_table"" cascade;")
I assume this is a matter of escaping characters, but I'm not entirely sure how to fit that into either A) the population of the table or B) the execution of each row. Does anyone know what I could do to achieve the desired result?
The command_entry variable is of type record while the EXECUTE command expects a string. What is apparently happening is that PostgreSQL turns the record into a double-quoted string, but that messes up your command. Also, your temp table does not use a column name, making things a bit awkward to work with (the column name becomes ?column?), so change both as follows:
CREATE TEMP TABLE list_of_commands AS
SELECT 'drop table if exists public.' || quote_ident(tablename) || ' cascade' AS cmd
FROM pg_tables
WHERE schemaname = 'public';
DO $$
DECLARE
command_entry varchar;
BEGIN
FOR command_entry IN SELECT cmd FROM list_of_commands
LOOP
EXECUTE command_entry;
END LOOP;
END;
$$;
But seeing that you do all of this at session level (temp table, anonymous code block), why not write a stored procedure that performs all of this housekeeping when you are ready to do spring cleaning?
CREATE FUNCTION cleanup() RETURNS void AS $$
BEGIN
FOR tbl IN SELECT tablename FROM pg_tables WHERE schemaname = 'public'
LOOP
EXECUTE 'DROP TABLE IF EXISTS ' || quote_ident(tbl) || ' CASCADE';
END LOOP;
-- More housekeeping jobs
END;
$$ LANGUAGE plpgsql;
This saves a lot of typing: SELECT cleanup();. Any other housekeeping jobs you have you simply add to the stored procedure.
I had trouble with Patrick's answers, so here is an updated version for postgreSQL 10.
CREATE FUNCTION droptables(sn varchar) RETURNS void AS $$
DECLARE
tbl varchar;
BEGIN
FOR tbl IN SELECT tablename FROM pg_tables WHERE schemaname = sn
LOOP
EXECUTE 'DROP TABLE IF EXISTS ' || quote_ident(tbl) || ' CASCADE';
END LOOP;
END;
$$ LANGUAGE plpgsql;
And then "SELECT droptables('public');".
I have the following script to dynamically create views into a PostgreSQL database.
CREATE OR REPLACE FUNCTION cs_refresh_mviews() RETURNS integer AS $$
DECLARE
mviews RECORD;
query text;
park_name text;
ppstatements int;
BEGIN
RAISE NOTICE 'Creating views...';
FOR mviews IN SELECT name FROM "Canadian_Parks" LOOP
park_name := mviews.name;
RAISE NOTICE 'Creating or replace view %s...', mviews.name;
query := 'CREATE OR REPLACE VIEW %_view AS
SELECT * from "Canadian_Parks" where name=''%'';
ALTER TABLE %_view OWNER TO postgres', park_name, park_name, park_name;
-- RAISE NOTICE query;
EXECUTE query;
END LOOP;
RAISE NOTICE 'Done refreshing materialized views.';
RETURN 1;
END;
$$ LANGUAGE plpgsql;
I have confirmed integrity of the string, such as
CREATE OR REPLACE VIEW Saguenay_St__Lawrence_view AS
SELECT * from "Canadian_Parks" where name='Saguenay_St__Lawrence';
ALTER TABLE Saguenay_St__Lawrence_view OWNER TO postgres
assigned to the query variable by manually submitting this to the database and getting a successful response.
However, if I attempt to execute the function using
SELECT cs_refresh_mviews();
the followig error is displayed:
ERROR: query "SELECT 'CREATE OR REPLACE VIEW %_view AS SELECT * from "Canadian_Parks" where name=''%''; ALTER TABLE %_view OWNER TO postgres', park_name, park_name, park_name" returned 4 columns
CONTEXT: PL/pgSQL function "cs_refresh_mviews" line 32 at assignment
********** Error **********
ERROR: query "SELECT 'CREATE OR REPLACE VIEW %_view AS SELECT * from "Canadian_Parks" where name=''%''; ALTER TABLE %_view OWNER TO postgres', park_name, park_name, park_name" returned 4 columns
SQL state: 42601
Context: PL/pgSQL function "cs_refresh_mviews" line 32 at assignment
Why has this been converted to a SELECT statement, instead of a pure CREATE?
You setup is pretty twisted. Why would you save part of the name of a view in a composite type of a table instead of saving it in a plain text column?
Anyhow, it could work like this:
Setup matching question:
CREATE SCHEMA x; -- demo in test schema
SET search_path = x;
CREATE TYPE mviews AS (id int, name text); -- composite type used in table
CREATE TABLE "Canadian_Parks" (name mviews);
INSERT INTO "Canadian_Parks"(name) VALUES
('(1,"canadian")')
,('(2,"islandic")'); -- composite types, seriously?
SELECT name, (name).* from "Canadian_Parks";
CREATE OR REPLACE FUNCTION cs_refresh_mviews()
RETURNS int LANGUAGE plpgsql SET search_path = x AS -- search_path for test
$func$
DECLARE
_parkname text;
BEGIN
FOR _parkname IN SELECT (name).name FROM "Canadian_Parks" LOOP
EXECUTE format('
CREATE OR REPLACE VIEW %1$I AS
SELECT * FROM "Canadian_Parks" WHERE (name).name = %2$L;
ALTER TABLE %1$I OWNER TO postgres'
, _parkname || '_view', _parkname);
END LOOP;
RETURN 1;
END
$func$;
SELECT cs_refresh_mviews();
DROP SCHEMA x CASCADE; -- clean up
Major points
As you are executing text with execute, you need to safeguard against SQL injection. I use the format() function for identifiers and the literal
I use the syntax SELECT (name).name to cope with your weird setup and extract the name we need right away.
Similarly, the VIEW needs to read WHERE (name).name = .. to work in this setup.
I removed a lot of noise that is irrelevant to the question.
It's also probably pointless to have the function RETURN 1. Just define the function with RETURNS void. I kept it, though, to match the question.
Untangled setup
How it probably should be:
CREATE SCHEMA x;
SET search_path = x;
CREATE TABLE canadian_parks (id serial primary key, name text);
INSERT INTO canadian_parks(name) VALUES ('canadian'), ('islandic');
SELECT * from canadian_parks;
CREATE OR REPLACE FUNCTION cs_refresh_mviews()
RETURNS void LANGUAGE plpgsql SET search_path = x AS
$func$
DECLARE
parkname text;
BEGIN
FOR parkname IN SELECT name FROM canadian_parks LOOP
EXECUTE format('
CREATE OR REPLACE VIEW %1$I AS
SELECT * FROM canadian_parks WHERE name = %2$L;
ALTER TABLE %1$I OWNER TO postgres'
, parkname || '_view', parkname);
END LOOP;
END
$func$;
SELECT cs_refresh_mviews();
DROP SCHEMA x CASCADE;
You've misunderstood usage of commas in assignment expression.
It turns query to array (RECORD) instead of scalar.
Use concatenation:
park_name := quote_ident(mviews.name||'_view');
query := 'CREATE OR REPLACE VIEW '||park_name||' AS SELECT * from "Canadian_Parks" where name='||quote_literal(mviews.name)||'; ALTER TABLE '||park_name||' OWNER TO postgres';