refactor: optimizing dropoutEnrollment command

[ashshidiq23]

Benchmark Comparison

Metric	Before Optimization	After Optimization	Improvement
Execution Time	1376.9 sec (22.95 min)	58.8 sec (~1 min)	23.4× faster (-95.7%)
Memory Usage	626 MiB	30 MiB	20.9× lower (-95.2%)

Before:

After:

Optimization Process

Identifying Bottlenecks

Initially, the dropout process fetched all enrollments into memory (->get()), then iterating one by one to check conditions and update records.
This approach has resulted in:

• Load too much data into memory at once.
• Performed excessive queries, making the process inefficient.
• Updated enrollments individually, increasing query overhead.

Optimization Strategies

To improve performance, I implemented the following optimizations:

1. Joining Tables and Filter Data in SQL
   Moved filtering logic using the database query using LEFT JOIN with NULL checks to avoids unnecessary PHP-level processing.

2. Batch Processing with chunkById
   Instead of loading all data into memory, I used chunkById(), reduced memory consumption and improving efficiency.

3. Bulk Updates & Inserts
   Used whereIn('id', $ids)->update() to update enrollments in bulk rather than by foreach every data.

4. Inserted activity logs using Activity::insert($activities), reducing query execution time.

5. Moving now() calls to variable $now to avoid repeated call and improving updated_at date consistency in every batch

6. Garbage Collection (gc_collect_cycles())
   Forced garbage collection after each batch to free up memory.