I have checked similar threats but not match exactly that I am trying to do.
I have two identical tables:
t_data: we will have the data of the last two months. There will be a job for delete data older than two months.
t_data_historical: we will have all data.
I want to do: If an INSERT is done into t_data, I want to "clone" the same query to t_data_historical.
I have seen that can be done with triggers but there is something that I don't understand: in the trigger definition I need to know the columns and values and I don't want to care about the INSERT query (I trust of the client that to do the query), I only clone it.
If you know that the history table will have the same definition, and the name is always constructed that way, you can
EXECUTE format('INSERT INTO %I.%I VALUES (($1).*)',
TG_TABLE_SCHEMA,
TG_TABLE_NAME || '_historical')
USING NEW;
in your trigger function.
That will work for all tables, and you don't need to know the actual columns.
Laurenz,
I created the trigger like:
CREATE OR REPLACE FUNCTION copy2historical() RETURNS trigger AS
$BODY$
BEGIN
EXECUTE format('INSERT INTO %I.%I VALUES (($1).*)', TG_TABLE_SCHEMA, TG_TABLE_NAME || '_historical')
USING NEW;
END;
RETURN NULL;
$BODY$
LANGUAGE plpgsql VOLATILE
COST 100;
CREATE TRIGGER copy2historical_tg
AFTER INSERT
ON t_data
FOR EACH ROW
EXECUTE PROCEDURE copy2historical();
thanks for your help.
Related
I have a problem I am stuck on for some time now. So I wanted to reach out for a little help.
I have 2 tables which are holding the same data: transactions and transactions2.
I want to write a Trigger that is triggering every time a new row is added to transactions and insert it into transaction2 in PLSQL.
First I simply duplicated the table with
CREATE TABLE transactions2 (SELECT * FROM transactions WHERE 1=1);
I think I found out how to insert
CREATE OR REPLACE FUNCTION copyRow RETURNS TRIGGER AS $$
DECLARE
BEGIN
INSERT INTO transaction2
VALUES transaction;
END;
I think the syntax with this is also wrong, but how do I say, that the Trigger should start as soon as a new Insert into the first table is made?
Can anyone help me with this?
Thanks
Bobby
The correct syntax for an INSERT is INSERT (<column list>) VALUES (<values list>). The INSERT syntax isn't different in a function compared to "outside". So your trigger function should look something like:
CREATE OR REPLACE FUNCTION t2t2_f ()
RETURNS TRIGGER
AS
$$
BEGIN
INSERT INTO transactions2
(column_1,
...,
column_n)
VALUES (NEW.column_1,
...,
NEW.column_n);
RETURN NEW;
END;
$$
LANGUAGE plpgsql;
Replace the column_is with the actual column names of your table. NEW is a pseudo record with which you can access the values of the new row.
To create the trigger itself use something like:
CREATE TRIGGER t2t2_t
AFTER INSERT
ON transactions
FOR EACH ROW
EXECUTE PROCEDURE t2t2_f();
You may want to use another timing, e.g. BEFORE instead of AFTER.
That should give you something to start with. Please consider studying the comprehensive PostgreSQL Manual for further and more detailed information.
Need help to create a generic trigger to log all tables.
i have table named "system" and need to log it.
the log table name system_audit is created with all columns of "system" table along with additional three columns named
modified_dt,modified_by and modified_type.
modified_dt will be current_timestamp
modified_by will be the user
and modified_type specifies whether its insert,update or delete.(Need to capture new data for insert/update and old for delete)
How to write a function to capture the above said data. Also it needs to be dynamics, so that i can use it across all the tables in my schema
Note: All audit tables contains the modified_dt,modified_by and modified_type as mandatory.
I got a couple of codes from the net, but it is not working, I was working on with oracle before, and new to postgres, not sure on how to code it properly.Please help
I have managed to create a generic function and its working fine.Thanks for the help.
create or replace function audit.fn__audit()
returns trigger as
$func$
declare
col_name text:='';
audit_table_name text := TG_TABLE_NAME || '_audit';
begin
if TG_OP = 'UPDATE' or TG_OP = 'INSERT' THEN
EXECUTE format('INSERT INTO audit.%1$I SELECT ($1).*,current_timestamp,user,'''||TG_OP||'''',audit_table_name) using NEW;
else
EXECUTE format('INSERT INTO audit.%1$I SELECT ($1).*,current_timestamp,user,'''||TG_OP||'''',audit_table_name) using old;
end if;
return new;
END $func$
LANGUAGE plpgsql VOLATILE;
I have 2 tables hourly and daily and my aim is to calculate average of values from hourly table and save it to daily table. I have written a trigger function like this -
CREATE OR REPLACE FUNCTION public.calculate_daily_avg()
RETURNS trigger AS
$BODY$
DECLARE chrly CURSOR for
SELECT device, date(datum) datum, avg(cpu_util) cpu_util
FROM chourly WHERE date(datum) = current_date group by device, date(datum);
BEGIN
FOR chrly_rec IN chrly
LOOP
insert into cdaily (device, datum, cpu_util)
values (chrly_rec.device, chrly_rec.datum, chrly_rec.cpu_util)
on conflict (device, datum) do update set
device=chrly_rec.device, datum=chrly_rec.datum, cpu_util=chrly_rec.cpu_util;
return NEW;
END LOOP;
EXCEPTION
WHEN NO_DATA_FOUND THEN
RAISE NOTICE 'NO DATA IN chourly FOR %', current_date;
END;
$BODY$
LANGUAGE plpgsql VOLATILE
COST 100;
ALTER FUNCTION public.calculate_daily_avg()
OWNER TO postgres;
and a trigger on hourly table like this -
CREATE TRIGGER calculate_daily_avg_trg
BEFORE INSERT OR UPDATE
ON public.chourly
FOR EACH ROW
EXECUTE PROCEDURE public.calculate_daily_avg();
But when I try to insert or update about 3000 records in the hourly table only 3 or 4 devices are inserted and not 3000. (also in trigger I have already tried AFTER INSERT OR UPDATE but even that gives the same result) What I am doing wrong here? Please suggest any better way to write the trigger if you feel I have written it wrongly. Thanks!
I don't suggest using TRIGGER for calculation when INSERT. Try different approach using function execute by cron hourly or daily.
WHY?
Because everytime you INSERT one row. the postgres will always do aggregate function AVG() and LOOPING for insert (based on your flow).
That mean another INSERT statement will waiting until Previous INSERT commited that will suffer your database performance for highly INSERT Transaction. If somehow you manage to BREAK the rule (maybe from configuration) you will get inconsistent data like what happened to you right now.
I'm trying to call a function from a trigger function and don't understand what control structure to use. Here's the situation:
I have 3 tables (table1, table2, table3) and two functions (Fct1 and Fct2).
Fct1 is a trigger function triggered after an insert in table1 and which makes insert in table2:
CREATE OR REPLACE FUNCTION Fct1()
RETURNS TRIGGER AS
$BODY$
BEGIN
TRUNCATE "table2";
INSERT INTO "table2"
SELECT ... FROM "table1";
RETURN NEW;
END;
$BODY$
LANGUAGE plpgsql VOLATILE
The trigger is:
CREATE TRIGGER trig_fct1
AFTER INSERT
ON table1
FOR EACH ROW
WHEN ((pg_trigger_depth() < 1))
EXECUTE PROCEDURE Fct1();
If I do after that a SELECT "Fct2"(); everything works fine, but if I add in Fct1 a PERFORM "Fct2"(); , like this:
CREATE OR REPLACE FUNCTION Fct1()
RETURNS TRIGGER AS
$BODY$
BEGIN
TRUNCATE "table2";
INSERT INTO "table2"
SELECT ... FROM "table1";
TRUNCATE "table3";
PERFORM "Fct2"(); -- will insert into table3
RETURN NEW;
END;
$BODY$
LANGUAGE plpgsql VOLATILE
It takes much more time to run (I never waited for the end, it's too long).
Fct2 looks like this
CREATE OR REPLACE FUNCTION "Fct2"()
RETURNS void AS
$BODY$
BEGIN
INSERT INTO "table3" ...;
RETURN;
END;
$BODY$
LANGUAGE plpgsql VOLATILE
So, there is something I don't understand and I think it is related to these 'RETURNs' which are not clear to me. I have tried different 'solutions' but I always got errors mentioning some 'return' mismatches. Any suggestions ?
I'm using PostgreSQL 9.6
To capture long running SQL statements from functions in the log, you can use auto_explain with auto_explain.log_nested_statements set to on. But if the query doesn't even finish, that won't help a lot.
My bet is that you are blocked by a database lock. Set log_lock_waits to on and see if something is reported in the log. You should also query pg_locks to see if there are locks requested but not granted.
I have a table called assignments. I would like to be able to read/write to all the columns in this table using either assignments.column or homework.column, how can I do this?
I know this is not something you would normally do. I need to be able to do this to provide backwards compatibility for a short period of time.
We have an iOS app that currently does direct postgresql queries against the DB. We're updating all of our apps to use an API. In the process of building the API the developer decided to change the name of the tables because we (foolishly) thought we didn't need backwards compatibility.
Now, V1.0 and the API both need to be able to write to this table so I don't have to do some voodoo later to transfer/combine data later...
We're using Ruby on Rails for the API.
With Postgres 9.3 the following should be enough:
CREATE VIEW homework AS SELECT * FROM assignments;
It works because simple views are automatically updatable (see docs).
In Postgres 9.3 or later, a simple VIEW is "updatable" automatically. The manual:
Simple views are automatically updatable: the system will allow
INSERT, UPDATE and DELETE statements to be used on the view in
the same way as on a regular table. A view is automatically updatable
if it satisfies all of the following conditions:
The view must have exactly one entry in its FROM list, which must be a table or another updatable view.
The view definition must not contain WITH, DISTINCT, GROUP BY, HAVING, LIMIT, or OFFSET clauses at the top level.
The view definition must not contain set operations (UNION, INTERSECT or EXCEPT) at the top level.
The view's select list must not contain any aggregates, window functions or set-returning functions.
If one of these conditions is not met (or for the now outdated Postgres 9.2 or older), a manual setup may do the job.
Building on your work in progress:
Trigger function
CREATE OR REPLACE FUNCTION trg_ia_insupdel()
RETURNS trigger
LANGUAGE plpgsql AS
$func$
DECLARE
_tbl CONSTANT regclass := 'iassignments_assignments';
_cols text;
_vals text;
BEGIN
CASE TG_OP
WHEN 'INSERT' THEN
INSERT INTO iassignments_assignments
VALUES (NEW.*);
RETURN NEW;
WHEN 'UPDATE' THEN
SELECT INTO _cols, _vals
string_agg(quote_ident(attname), ', ') -- incl. pk col!
, string_agg('n.' || quote_ident(attname), ', ')
FROM pg_attribute
WHERE attrelid = _tbl -- _tbl converted to oid automatically
AND attnum > 0 -- no system columns
AND NOT attisdropped; -- no dropped (dead) columns
EXECUTE format('
UPDATE %s t
SET (%s) = (%s)
FROM (SELECT ($1).*) n
WHERE t.published_assignment_id
= ($2).published_assignment_id' -- match to OLD value of pk
, _tbl, _cols, _vals) -- _tbl converted to text automatically
USING NEW, OLD;
RETURN NEW;
WHEN 'DELETE' THEN
DELETE FROM iassignments_assignments
WHERE published_assignment_id = OLD.published_assignment_id;
RETURN OLD;
END CASE;
RETURN NULL; -- control should never reach this
END
$func$;
Trigger
CREATE TRIGGER insupbef
INSTEAD OF INSERT OR UPDATE OR DELETE ON assignments_published
FOR EACH ROW EXECUTE PROCEDURE trg_ia_insupdel();
Notes
assignments_published must be a VIEW, an INSTEAD OF trigger is only allowed for views.
Dynamic SQL (in the UPDATE section) is not strictly necessary, only to cover future changes to the table layout automatically. The names of table and PK are still hard coded.
Simpler and probably cheaper without sub-block (like you had).
Using (SELECT ($1).*) instead of the shorter VALUES ($1.*) to preserve column names.
My naming convention: I prepend trg_ for trigger functions, followed by an abbreviation indicating the target table and finally one or more of the the tokens ins, up and del for INSERT, UPDATE and DELETE respectively. The name of the trigger is a copy of the function name, stripped of the first two parts. This is purely a matter of convention and taste but has proven useful for me since the names tell the purpose and are still short.
More explanation in the related answer that has already been mentioned:
Update multiple columns in a trigger function in plpgsql
This is where I am with the trigger functions so far, any feedback would be greatly appreciated. It's a combination of http://vibhorkumar.wordpress.com/2011/10/28/instead-of-trigger/ and Update multiple columns in a trigger function in plpgsql
Table: iassignments_assignments
Columns:
published_assignment_id
name
filepath
filename
link
teacher
due date
description
published
classrooms
View: assignments_published - SELECT * FROM iassignments_assignments
Trigger Function for assignments_published
CREATE OR REPLACE FUNCTION assignments_published_trigger_func()
RETURNS TRIGGER
LANGUAGE plpgsql
AS $function$
BEGIN
IF TG_OP = 'INSERT' THEN
EXECUTE format('INSERT INTO %s SELECT ($1).*', 'iassignments_assignments')
USING NEW;
RETURN NEW;
ELSIF TG_OP = 'UPDATE' THEN
DECLARE
tbl = 'iassignments_assignments';
cols text;
vals text;
BEGIN
SELECT INTO cols, vals
string_agg(quote_ident(attname), ', ')
,string_agg('x.' || quote_ident(attname), ', ')
FROM pg_attribute
WHERE attrelid = tbl
AND NOT attisdropped -- no dropped (dead) columns
AND attnum > 0; -- no system columns
EXECUTE format('
UPDATE %s t
SET (%s) = (%s)
FROM (SELECT ($1).*) x
WHERE t.published_assignment_id = ($2).published_assignment_id'
, tbl, cols, vals)
USING NEW, OLD;
RETURN NEW;
END
ELSIF TG_OP = 'DELETE' THEN
DELETE FROM iassignments_assignments WHERE published_assignment_id=OLD.published_assignment_id;
RETURN NULL;
END IF;
RETURN NEW;
END;
$function$;
Trigger
CREATE TRIGGER assignments_published_trigger
INSTEAD OF INSERT OR UPDATE OR DELETE ON
assignments_published FOR EACH ROW EXECUTE PROCEDURE assignments_published_trigger_func();
Table: iassignments_classes
Columns:
class_assignment_id
guid
assignment_published_id
View: assignments_class - SELECT * FROM assignments_classes
Trigger Function for assignments_class
**I'll create this function once I have received feedback on the other and know it's create, so I (hopefully) need very little changes to this function.
Trigger
CREATE TRIGGER assignments_class_trigger
INSTEAD OF INSERT OR UPDATE OR DELETE ON
assignments_class FOR EACH ROW EXECUTE PROCEDURE assignments_class_trigger_func();