Efficient Ways Of Tracking Graph Database Changes Using Postgresql.
Tags: database, postgres, sql, graphdatabase
Published: 2023-11-08 21:20:14

**Introduction**
In this article we are going to describe what it's like tracking graph changes especially in postgresql and describing the best and most efficient techniques of tracking graph changes.

Graph databases are powerful tools for representing and querying complex relationships between data points. Efficiently tracking changes in a graph database is crucial for auditing, debugging, and maintaining data integrity

We will start off by listing some of the graph databases that are support by postgresql so as to  get a clear understanding on what we can and cannot implement on these graph databases in terms of tracking changes that happen in the graphs.
Some of the most notable graph database that are  supported under postgresql include:

- Apache Age.
- Citus.
- Arangodb.
- Graphelion.
- HyperGraphDB.

In PostgreSQL, achieving this efficiently requires a combination of triggers, versioning tables, and custom functions. We'll explore some of the efficient techniques  for tracking graph changes in PostgreSQL.

The following are techniques that can be used to efficiently track changes in graphs in postgresql and they include:

1.Change Data capture
2.Versioning
3.Query Logging


**1.Change Data Capture**
This mechanism enables you to capture and record modifications made to your graph data. This involves identifying the specific changes, such as inserts, updates, or deletes, and storing them in a separate log or table. CDC tools can then be used to process and analyze these change events, providing insights into how the graph is evolving over time.
There are different ways to implement Change Data capture in postgresql and they include:

Trigger-based approach: Utilize database triggers to capture changes to graph elements (nodes and edges) and propagate those changes to a separate CDC stream or table.

Log-based approach: Monitor the database's transaction logs to identify changes made to graph elements and extract the relevant information for CDC purposes.

Replication approach: Employ replication mechanisms to replicate graph data to a secondary database, enabling CDC by capturing changes in the replicated data.

sample example of cdc(change data capture) using the trigger approach:

```

CREATE FUNCTION node_insert_trigger()
RETURNS TRIGGER AS $$
BEGIN
    INSERT INTO cdc_nodes (node_id, node_label, node_properties, timestamp)
    VALUES (NEW.node_id, NEW.node_label, NEW.node_properties, CURRENT_TIMESTAMP);
    RETURN NEW;
END;
$$ LANGUAGE plpgsql;
```
The trigger function above captures the INSERT operation on nodes, extracting the node ID, label, properties, and timestamp, and storing them in the cdc_nodes table as shown above.

**2. Versioning**
Versioning involves creating separate copies of graph data at different points in time. This allows you to revert to previous versions if necessary and track the evolution of the graph over time. You can implement versioning using PostgreSQL's built-in temporal features or by creating your own versioning schema.

Leveraging PostgreSQL's temporal data management capabilities, particularly the CITUS extension, enables versioning by tracking changes to graph entities and their relationships over time. This approach involves creating temporal tables that store historical versions of nodes and edges, along with their corresponding timestamps.


**Query Logging**
Query logging is a valuable technique for tracking changes made to a graph database, providing insights into data modifications, identifying potential errors, and facilitating data recovery. In PostgreSQL, query logging can be implemented using various methods, including:

PostgreSQL's Built-in Logging Mechanisms: PostgreSQL offers built-in logging capabilities, such as `log_statement` and `log_min_duration_statement`, which can be configured to record query information.

sample example of how query logging can be implemented using `log_statements`:

Use the log_statement parameter: 
This parameter can be set to all to log all queries, or to a specific level of detail, such as statement or plans.

```
SET log_statement = 'all';
```


**Conclusion**
In conclusion there are many ways of tracking graph database changes in postgresql.The choice of technique depends on the specific requirements of the application, including the frequency of changes, the need for real-time updates, and the desired level of granularity in change tracking. Careful consideration of performance, scalability, and complexity is essential when selecting and implementing the most suitable approach.