Migrations are a way to make database changes or updates, like creating or dropping tables, as well as updating a table with new columns with constraints via generated scripts. We can build these scripts via the command line using knex command line tool.
To learn more about migrations, check out this article on the different types of database migrations!
| Latency Comparison Numbers (~2012) | |
| ---------------------------------- | |
| L1 cache reference 0.5 ns | |
| Branch mispredict 5 ns | |
| L2 cache reference 7 ns 14x L1 cache | |
| Mutex lock/unlock 25 ns | |
| Main memory reference 100 ns 20x L2 cache, 200x L1 cache | |
| Compress 1K bytes with Zippy 3,000 ns 3 us | |
| Send 1K bytes over 1 Gbps network 10,000 ns 10 us | |
| Read 4K randomly from SSD* 150,000 ns 150 us ~1GB/sec SSD |
| def merge(left, right): | |
| if not len(left) or not len(right): | |
| return left or right | |
| result = [] | |
| i, j = 0, 0 | |
| while (len(result) < len(left) + len(right)): | |
| if left[i] < right[j]: | |
| result.append(left[i]) | |
| i+= 1 |