#Postgresql insert conflict update#
#Postgresql insert conflict code#

#Postgresql insert conflict code#

Naturally this doesn’t cover the Ecto side, and I don’t have a good environment for demonstrating from Elixir right now but I did take a quick look at the source code and I’m pretty sure the on_conflict: construct creates an upsert query similar to my test query. PostgreSQL generating apparent data changes without actually doing anything (a no-op) wouldn’t be desirable if you were needing logic that included the transaction details… since our “upsert” query happened within the context of a transaction it makes sense that anything PostgreSQL tells us it did would have to also reflect the effective transaction id. And if we think about it, this makes sense. Note that we’re not filtering the table and we only have one row which is identical in the id and text_value user columns.Īs we can see, even though the record would appear to have not changed to a user it’s in fact a new record (all PostgreSQL updates can be thought of as a DELETE/INSERT combination). Now let’s query the table again, and again with the system columns. For example, table 'reports' has 3 columns, so far I have the following: INSERT INTO reports (col2, col3) VALUES (1, 2) ON CONFLICT ON CONSTRAINT customindex DO SELECT FROM reports WHERE col11 AND col22 For those who will ask, customindex was created using: CREATE UNIQUE INDEX customindex ON reports (col2) INCLUDE (col3) The.

#Postgresql insert conflict update#

ON CONFLICT (id) DO UPDATE SET id = excluded.id, text_value = excluded.text_value Again, we’ll do this in a transaction so we can capture some of the transaction details. ON CONFLICT in a way that’s similar to what I believe the Ecto query to produce. With no options, uses ON CONFLICT DO NOTHING.

Now that we have a row and understand the system perspective of that row, let’s do an INSERT. Handle uniqueness violations when inserting, by updating the conflicting row, using ON CONFLICT. To use the upsert feature in PostgreSQL, you use the INSERT ON CONFLICT statement as follows: INSERT INTO tablename (columnlist) VALUES (valuelist) ON CONFLICT target action PostgreSQL added the ON CONFLICT target action clause to the INSERT statement to support the upsert feature.

> SELECT xmin, ctid, id, text_value FROM demo

Let’s query the table, but we’ll include the system columns xmin (The identity (transaction ID) of the inserting transaction for this row version.) and ctid (The physical location of the row version within its table.).

> INSERT INTO demo (text_value) VALUES ('demo') RETURNING *

Insert a single row into the table We’ll do this in a transaction block so we can query the transaction id as well.

The usage and requirements for all these. In PostgreSQL, an insert statement can contain several clauses, such as simple insert with the values to be put into a table, an insert with the ON CONFLICT DO NOTHING clause, or an insert with the ON CONFLICT DO UPDATE SET clause. Id integer PRIMARY KEY GENERATED BY DEFAULT AS IDENTITY, Understanding the differences between INSERT and INSERT.ON CONFLICT. DO UPDATE is not a no-op.ġ27.0.0.1(from musebms).postgres.scb.5432 Values( 'jon', to run sql query: duplicate key value violates unique constraint 'users_username_key”īut, let’s say we wanted our users to be able to update their email, but not their username.So from the PostgreSQL side, it can be demonstrated that ON CONFLICT. So if we try to insert a new user: insert into users(username, email)īut try to insert that user again, and we have a BIG problem! insert into users(username, email)

Your insert statement needs to include something that is unique, otherwise, Postgres will just keep creating new rows - not idempotent! One important thing to note here, is that both username and email are unique. Id uuid default uuid_generate_v4() primary key, Let’s create a new table for users: create table if not exists users ( Thankfully, PostgreSQL makes it super easy to turn any insert statement into an upsert, using the on conflict condition.

It allows us to write idempotent statements - can be executed multiple times without breaking everything! - and improve the convenience and resilience of our code. The upsert action is a combination of insert and update. INSERT conforms to the SQL standard, except that the RETURNING clause is a PostgreSQL extension, as is the ability to use WITH with INSERT, and the ability to specify an alternative action with ON CONFLICT.