About the QueryBuilder

The QueryBuilder lets you query your AiiDA database independently of the backend used under the hood. Before starting to write a query, it helps to:

• know what you want to query for. In database-speek, you need to tell the backend what to project. For example, you might be interested in the label of a calculation and the pks of all its outputs.

• know the relationships between entities you are interested in. Nodes of an AiiDA graph (vertices) are connected with links (edges). A Node can be either input or output of another Node, but also an ancestor or a descendant.

• know how you want to filter the result.

Once you are clear about what you want and how you can get it, the QueryBuilder will build an SQL-query for you.

There are two ways of using the QueryBuilder:

1. In the appender method, you construct your query step by step using QueryBuilder.append()

2. In the queryhelp approach, you construct a dictionary first and pass it to the QueryBuilder

Both APIs provide the same functionality - the appender method may be more suitable for everyday use in the verdi shell, while the queryhelp method can be useful in scripting.