I am using Microsoft Access as a front-end to my PostgreSQL database. My workflow is pretty simple:
Create a linked table using the ODBC driver
Build a form using form wizard for data entry
Inserting data works really well if i submit the data directly on the table or using the form. However, i can update the data that was submitted directly to the table, but i cannot update the data submitted through the form as i get a write.conflict error.
I checked many previous answers and one of the issues was to do with the timestamp precision. This helped with updating the data submitted directly on the table as it didn't work before.
Now i just need to resolve updating data that was submitted using the form. I tried using Me.Dirty as follows:
Private Sub Form_Dirty(Cancel As Integer)
Me.Dirty = False
End Sub
That didn't work for me unfortunately. It really does look like something to do with the form as entering data using the table works perfectly. Is it how the form saves the data? How can i get it off editing mode? I really don't know and i tried various things.
I would really appreciate a hand on this as i have been on it for days and i can't resolve it.
Thank you.
Here is a simplified version of the code i used to create my table. I just have more VARCHAR and numeric columns in the table i am using.
I also created a logs table that would update if any changes are made to the main table. This logs table is populate via a trigger as shown in the code.
CREATE TABLE table_1 (
id INT PRIMARY KEY DEFAULT to_char(now(), 'YYMMDDHH24MI') :: INT,
column_1 VARCHAR(50),
column_2 VARCHAR(100),
column_3 BOOLEAN,
last_updated timestamp(0));
CREATE TABLE logs_table
(like table_1 EXCLUDING CONSTRAINTS,
operation char(10) not null,
date_operated timestamp(0) default current_timestamp
);
create function logs_function()
returns trigger as $$
BEGIN
insert into logs_table (id, column_1, column_2, column_3, last_updated, operation)
values (old.id, old.column_1, old.column_2, old.column_3, old.last_updated, TG_OP);
IF TG_OP = 'UPDATE'
THEN
new.last_updated := current_timestamp;
RETURN NEW;
ELSIF TG_OP = 'DELETE'
THEN
RETURN OLD;
END IF;
end;
$$ LANGUAGE plpgsql;
CREATE TRIGGER logs_trigger
BEFORE UPDATE OR DELETE ON table_1
FOR EACH ROW EXECUTE PROCEDURE logs_function();
Related
I am trying to set up triggers for insert and update events for the master table of some partition tables in PostgreSQL. Each time an insertion is made into the master table, the insert trigger event will redirect it into the correct partition table. Consequently, I will need to return NULL from this function call, since I don't want the master table to be populated as well. If the master table receives an update event, it will update a timestamp before making the change in the table. The problem is that the update trigger is never fired. I am using PostgreSQL version 9.6.
I have tried to combine the trigger functions into one, and merged the called trigger procedures into one as well, but the results are the same. The update trigger is only triggered if I return NEW from the insertion trigger function (which populates the master table), or if I comment out the insertion trigger function altogether.
DROP SCHEMA IF EXISTS test CASCADE;
CREATE SCHEMA test;
SET SCHEMA 'test';
CREATE TYPE test_type AS ENUM ('unit', 'performance');
CREATE TABLE test (
type test_type NOT NULL,
score INTEGER NOT NULL CHECK (score > 0),
id SERIAL PRIMARY KEY,
updated_at TIMESTAMP DEFAULT current_timestamp
);
CREATE TABLE performance_test (
CHECK (type = 'performance')
) INHERITS (test);
CREATE FUNCTION insert_test()
RETURNS trigger AS
$$
BEGIN
INSERT INTO performance_test VALUES (NEW.*);
RETURN NULL;
END;
$$ LANGUAGE plpgsql;
CREATE FUNCTION update_timestamp()
RETURNS trigger AS
$$
BEGIN
RAISE NOTICE 'This is never reached.';
UPDATE performance_test
SET updated_at = current_timestamp
WHERE id = NEW.id;
RETURN NULL;
END;
$$ LANGUAGE plpgsql;
CREATE TRIGGER test_insertion BEFORE INSERT ON test
FOR EACH ROW EXECUTE PROCEDURE insert_test();
CREATE TRIGGER test_update BEFORE UPDATE ON test
FOR EACH ROW EXECUTE PROCEDURE update_timestamp();
---------------------------------------------------------------------------
INSERT INTO test VALUES ('performance', 10);
SELECT * FROM performance_test;
UPDATE test SET score = 20 WHERE id = 1;
SELECT * FROM performance_test;
I am not sure if it is possible to achieve what I want with this method, so I'm reaching out here for any advice. Thanks in advance!
/ Hampus
Row triggers must be defined on individual partitions, not the partitioned table. See https://www.postgresql.org/docs/10/ddl-partitioning.html#DDL-PARTITIONING-DECLARATIVE-LIMITATIONS
I don't know why the documentation for 9.6 doesn't mention this
working update trigger:
CREATE FUNCTION update_timestamp()
RETURNS trigger AS
$$
BEGIN
NEW.updated_at = now();
RETURN NEW;
END;
$$ LANGUAGE plpgsql;
CREATE TRIGGER test_update BEFORE UPDATE ON performance_test
FOR EACH ROW EXECUTE PROCEDURE update_timestamp();
if you do UPDATE test SET score = 30, updated_at=DEFAULT; or UPDATE test SET score = 30, updated_at=current_timestamp; you might not need the update trigger.
Partitioning is not a free lunch because it has non-obvious effects on both behavior and performance, as you noticed by the trigger not behaving as you expected. If you make a mistake it can easily lead to failing queries and even bad data.
If you are really sure you need it you should make sure you understand it in detail and otherwise I'd recommend you to avoid it, most issues with slow queries can be solved by making sure the table statistics is up to date, using the right indexes, optimizing queries, changing Postgres configuration or adding more hardware.
So I´m fairly new to Postgresql and started working with it by testing out some stuff with pgadmin4 on Postgres9.6.
The problem:
I have a table: test(id, text)
In this table I have 10 rows of data.
Now I want to import a CSV which has 12 rows to update the test table. Some text changed for the first 10 rows AND I want to insert the 2 additional rows from the CSV.
I know that you can truncate all the data from a table and just import everything again from the CSV, but that´s not a nice way to do this. I want to Update my existing data & Insert the new data with one query.
I already found a function which should solve this by using a temporary table. This updates the existing rows correct, but the 2 additional rows do not get inserted
CREATE OR REPLACE FUNCTION upsert_test(integer,varchar) RETURNS VOID AS $$
DECLARE
BEGIN
UPDATE test
SET id = tmp_table.id,
text = tmp_table.text
FROM tmp_table
WHERE test.id = tmp_table.id;
IF NOT FOUND THEN
INSERT INTO test(id,text) values
(tmp_table.id,tmp_table.text);
END IF;
END;
$$ Language 'plpgsql';
DO $$ BEGIN
PERFORM upsert_test(id,text) FROM test;
END $$;
So what do I need to change to also get the insert to work?
Assuming you have a primary or unique constraint on the id column you can do this with a single statement, no function required:
insert into test (id, text)
select id, text
from tmp_table
on conflict (id)
do update set text = excluded.text;
I am new to PostgreSQL and found a trigger which serves my purpose completely except for one little thing. The trigger is quite generic and runs across different tables and logs different field changes. I found here.
What I now need to do is test for a specific field which changes as the tables change on which the trigger fires. I thought of using substr as all the column will have the same name format e.g. XXX_cust_no but the XXX can change to 2 or 4 characters. I need to log the value in theXXX_cust_no field with every record that is written to the history_ / audit table. Using a bunch of IF / ELSE statements to accomplish this is not something I would like to do.
The trigger as it now works logs the table_name, column_name, old_value, new_value. I however need to log the XXX_cust_no of the record that was changed as well.
Basically you need dynamic SQL for dynamic column names. format helps to format the DML command. Pass values from NEW and OLD with the USING clause.
Given these tables:
CREATE TABLE tbl (
t_id serial PRIMARY KEY
,abc_cust_no text
);
CREATE TABLE log (
id int
,table_name text
,column_name text
,old_value text
,new_value text
);
It could work like this:
CREATE OR REPLACE FUNCTION trg_demo()
RETURNS TRIGGER AS
$func$
BEGIN
EXECUTE format('
INSERT INTO log(id, table_name, column_name, old_value, new_value)
SELECT ($2).t_id
, $3
, $4
,($1).%1$I
,($2).%1$I', TG_ARGV[0])
USING OLD, NEW, TG_RELNAME, TG_ARGV[0];
RETURN NEW;
END
$func$ LANGUAGE plpgsql;
CREATE TRIGGER demo
BEFORE UPDATE ON tbl
FOR EACH ROW EXECUTE PROCEDURE trg_demo('abc_cust_no'); -- col name here.
SQL Fiddle.
Related answer on dba.SE:
How to access NEW or OLD field given only the field's name?
List of special variables visible in plpgsql trigger functions in the manual.
I've created the following table:
CREATE TABLE updates
(
"table" text,
last_update timestamp without time zone
)
I want to update it whenever any table is updated, the problem is I don't know how, could someone please help me turn this pseudocode into a trigger?
this = current table on whitch operation is performed
ON ALTER,INSERT,DELETE {
IF (SELECT COUNT(*) FROM updates where table = this) = 1
THEN
UPDATE updates SET last_update = timeofday()::timestamp WHERE `table`=this
ELSE
INSERT INTO updates VALUES (this,timeofday()::timestamp);
}
You need a trigger function that is called whenever one of your tables is "updated", assuming that you mean that an INSERT, UPDATE, or DELETE is successfully executed. That trigger function would look like this:
CREATE FUNCTION log_update() RETURNS trigger AS $$
BEGIN
UPDATE updates SET last_update = now() WHERE "table" = TG_TABLE_NAME;
IF NOT FOUND THEN
INSERT INTO updates VALUES (TG_TABLE_NAME, now());
END IF;
IF (TG_OP = 'DELETE') THEN
RETURN OLD;
ELSE
RETURN NEW;
END IF;
END; $$ LANGUAGE PLPGSQL;
Every table that has to be logged this way needs to have a trigger associated with it like this:
CREATE TRIGGER ZZZ_mytable_log_updates
AFTER INSERT OR UPDATE OR DELETE ON mytable
FOR EACH ROW EXECUTE PROCEDURE log_update();
A few comments:
Trigger functions are created with PL/PgSQL; see chapter 40 in the documentation. Trigger functions come with some automatic parameters such as TG_TABLE_NAME.
Don't use reserved words ("table" in your case) as column names. Actually, in this case you are better off using the oid of the table, with the associated TG_RELID automatic parameter. It takes up less storage, it is faster, and it avoids confusion between tables with the same name in different schemas of your database. You can use the pg_tables system catalog table to look up the table name from the oid.
You must return the proper value depending on the operation, or the operation may fail. INSERT and UPDATE operations need to have NEW returned; DELETE needs to have OLD returned.
The name of the trigger starts with "ZZZ" to make sure that it fires after any other triggers on the same table have succeeded (they are fired in alphabetical order). If a prior trigger fails, this trigger function will not be called, which is the proper behaviour because the insert, update or delete will not take place either.
I am writing a trigger in plpgsql for Postgres 9.1. I need to be able to capture the column names that were issued in the SET clause of an UPDATE so I can record the specified action in an audit table. The examples in the Postgres documentation are simple and inadequate for my needs. I have searched the internet for days and I am unable to find any other examples that try to achieve what I want to do here.
I am on a tight schedule to resolve this soon. I don't know Tcl so pl/Tcl is out of the question for me at this point. pl/Perl may work but I don't know where to start with it. Also I wanted to find a way to accomplish this in pl/pgsql if at all possible for portability and maintenance. If someone can recommend a pl/Perl solution to this I would be grateful.
Here is the table structure of the target table that will be audited:
Note: There are many other columns in the record table but I have not listed them here in order to keep things simple. But the trigger should be able to record changes to any of the columns in the row.
CREATE TABLE record (
record_id integer NOT NULL PRIMARY KEY,
lastname text,
frstname text,
dob date,
created timestamp default NOW(),
created_by integer,
inactive boolean default false
);
create sequence record_record_id_seq;
alter table record alter record_id set default nextval('record_record_id_seq');
Here is my audit table:
CREATE TABLE record_audit (
id integer NOT NULL PRIMARY KEY,
operation char(1) NOT NULL, -- U, I or D
source_column text,
source_id integer,
old_value text,
new_value text,
created_date timestamp default now(),
created_by integer
);
create sequence record_audit_id_seq;
alter table record_audit alter id set default nextval('record_audit_id_seq');
My goal is to record INSERTS and UPDATES to the record table in the record_audit table that will detail not only what the target record_id was (source_id) that was updated and what column was updated (source_column), but also the old_value and the new_value of the column.
I understand that the column values will have to be CAST() to a type of text. I believe I can access the old_value and new_value by accessing NEW and OLD but I am having difficulty figuring out how to obtain the column names used in the SET clause of the UPDATE query. I need the trigger to add a new record to the record_audit table for every column specified in the SET clause. Note, there are not DELETE actions as records are simply UPDATED to inactive = 't' (and thus recorded in the audit table)
Here is my trigger so far (obviously incomplete). Please forgive me, I am learning pl/pgsql as I go.
-- Trigger function for record_audit table
CREATE OR REPLACE FUNCTION audit_record() RETURNS TRIGER AS $$
DECLARE
insert_table text;
ref_col text; --how to get the referenced column name??
BEGIN
--
-- Create a new row in record_audit depending on the operation (TG_OP)
--
IF (TG_OP = 'INSERT') THEN
-- old_value and new_value are meaningless for INSERTs. Just record the new ID.
INSERT INTO record_audit
(operation,source_id,created_by)
VALUES
('I', NEW.record_id, NEW.created_by);
ELSIF (TG_OP = 'UPDATE') THEN
FOR i in 1 .. TG_ARGV[0] LOOP
ref_col := TG_ARGV[i].column; -- I know .column doesn't exist but what to use?
INSERT INTO record_audit
(operation, source_column, source_id, old_value, new_value, created_by)
VALUES
('U', ref_col, NEW.record_id, OLD.ref_col, NEW.ref_col, NEW.created_by);
END LOOP;
END IF;
RETURN NULL; -- result is ignored anyway since this is an AFTER trigger
END;
$$ LANGUAGE plpgsql;
CREATE TRIGGER record_audit_trig
AFTER INSERT OR UPDATE on record
FOR EACH ROW EXECUTE PROCEDURE audit_record();
Thanks for reading this long and winding question!
you cannot to get this information - not in PL level - probably it is possible in C.
Good enough solution is based on changed fields in records NEW and OLD. You can get list of fields from system tables ~ are related to table that is joined to trigger.