![]() At the same time, this property of triggers strongly couples the auditing logic to the business operation.For audit triggers, among other things this means that data mutations and their audit trail are committed as an atomic unit. One of the main selling points of triggers is that they are executed as part of the normal transaction logic in the database, hence they benefit from the usual atomicity and consistency guarantees of relational databases.Both approaches have their own advantages and disadvantages, and one should try to understand the differences before making up their mind. pgaudit) instead of using triggers to create change records. Debezium) often tail the Write-Ahead-Log or use extensions (e.g. Write-Ahead-Log / Logical Decoding / ExtensionsĮxisting solutions for CDC on top of a PostgreSQL database (e.g. Attempting to modify an audited table without prior insertion into the transactions table will result in an error. The entry in the transactions table must be created before any changes.This gives the developer a "natural" way to group related changes into events (more on events later). All changes created within a database transaction automatically and implicitly belong to the same record in the transactions table, even if they're created separately and agnostic of each other in the application logic.This leads to the following interesting properties: #Carbonite migrate manualConsistency is ensure by a manual lookup in the trigger procedure. Together these references ensure that, not only relates each changes record to a single transactions record, but records in these tables have been inserted within the same database transaction. Additionally, the ansaction_xact_id field is set to pg_current_xact_id().Consistency with the transactions table is guaranteed by a foreign key constraint. This is your regular foreign key column, enough to relate a changes record with exactly one transactions record. The ansaction_id (referencing transactions.id) field is filled with the "current value" of the related sequence.Each row in the changes table is associated to a single row in the transactions table, referencing both these identifiers. While id is an ordinary, autoincrementing integer primary key, the xact_id is set to pg_current_xact_id(), PostgreSQL's internal transaction identifier. Within your application logic, you can insert a row into this table after you begin a database transaction, and record arbitrary metadata for it.Īpart from the metadata, the transactions table houses two identifier columns: id and xact_id. These settings customize the procedure's behaviour, for instance, they may exclude certain table columns from being captured.īesides the changes table, storing information about individual database statements (or rather, their impact on the data), Carbonite's transactions table stores information on database transactions. The procedure fetches its own per-table settings from another table called triggers. This procedure captures the new or updated data within the changes table automatically. On each such table a trigger is installed (after INSERT, UPDATE, and DELETE statements - TRUNCATE is not supported, see below) which calls a procedure stored within the database. No configuration of PostgreSQL database neededĬarbonite keeps a central changes table where all mutations of participating tables are recorded.Based on Ecto and Postgrex with no further dependencies.Optional processing & purging logic following the Outbox pattern.Clear query interfaces to the audit trail.Customizable audit metadata (per transaction).Guaranteed consistency based on triggers, foreign-key constraints, and ACID.Convenient installation using migration functions.On top of its database layer, Carbonite provides an API allowing developers to effortlessly retrieve, process, and purge the audit trails within the Elixir application. The metadata record is associated to the table change records by a constraint. Any mutation on a participating table requires the developer first to record the operation metadata within the same database transaction. It is centered around the idea that the database transaction is the natural auditing unit of data mutation. It uses triggers to automatically record all changes applied to a database table in order to guarantee a complete audit trail of the contained data. Carbonite makes it easy to create audit trails for tables in a PostgreSQL database and integrate them into an Elixir application.Ĭarbonite implements the Change-Data-Capture pattern on top of a PostgreSQL database. ![]()
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