Apex cursors allow us to divide the processing of a SOQL query result into batches that can be handled within the context of a single transaction. Cursors allow us to work with large query result sets without returning the entire set. We can traverse a query result in batches, with the option to move forward and back in the result set.
Apex Cursors is an alternative to batch Apex and addresses some limitations. Cursors are powerful because they can be used in a series of queued Apex jobs.
Use Case for this Feature Implementation
My Bank gets a lot of loan applications daily. This application needs to be verified properly before the loan is sanctioned. The system will email all customers to reply with the required documents within the provided timeline.
Solution
We will create a queueable apex class to email customers whose document verification is pending. This apex class will use a new Apex Cursor to divide and fetch records.
How does the Cursor work?
When a database executes a SOQL query using getCursor() or Database.getCursorWithBinds(), a cursor is created. When the Cursor.fetch(integer position, integer count) method is called with an offset position and a count of records to fetch, the cursor returns the corresponding rows. The maximum number of rows allowed per cursor is 50 million, regardless of whether the operation is synchronous or asynchronous. Cursor.getNumRecords() returns the number of cursor rows returned from the SOQL query.
Summary
Apex Cursor can be used in Queuable apex to handle high-volume and high-resource processing jobs. It is particularly useful in handling large data sets efficiently, as it fetches the data in batches rather than loading all records into memory at once, thereby conserving resources and improving performance.
References:
Use Cursors for Expanded SOQL Query Result Support (Beta)
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