Question

Unique partial indexes in PostgreSQL

I have a table (table_a) with columns: id, column_b, column_c, column_d, and archived. The id column is the primary key. The combination of column_b and column_c should be unique when archived = 0. If archived = 1, there are no restrictions, and duplicate records are allowed. This table is being inserted into and updated by multiple instances in our microservice architecture.

In the code, before inserting a record, it checks whether a record already exists for the given column_b and column_c values. If it exists, it will update the record. However, sometimes while one instance is inserting a record, another instance tries to insert another record with the same column_b and column_c values, resulting in duplicate records.

To prevent this, I added the following unique partial index:

CREATE UNIQUE INDEX unique_column_b_column_c ON table_a (column_b, column_c) WHERE archived = 0;

I also modified the existing insert query. This change works fine in Development environment, but I need to identify any potential issues that might arise from using database constraints and adding unique partial indexes with PostgreSQL. Additionally, I am unsure about the performance impact.

Old query:

INSERT INTO table_a (
    column_b, column_c, column_d
)
VALUES (2, 2, 2)
RETURNING column_b;

New query:

INSERT INTO table_a (
    column_b, column_c, column_d
)
VALUES (2, 2, 2)
ON CONFLICT (column_b, column_c) WHERE archived = 0 DO UPDATE SET
    column_b = EXCLUDED.column_b,
    column_c = EXCLUDED.column_c,
    column_d = EXCLUDED.column_d,
RETURNING column_b;

I need to identify any potential issues that might arise from using database constraints and adding unique partial indexes with PostgreSQL. Additionally, I need to know performance impact.

2 48 2

1 Jan 1970