Write-Ahead Log Append

Problem

Append records to a write-ahead log with monotonic log sequence numbers.

existing is the current log of [lsn, key, value] entries. Each record in records is a [key, value] pair appended with the next LSN.

Return the full log after appending.

Hint

The LSN is one more than the number of entries already in the log.

case 1

in: [[],[["a",1],["b",2]]]

expected: [[1,"a",1],[2,"b",2]]

case 2

in: [[[1,"x",0]],[["y",5]]]

expected: [[1,"x",0],[2,"y",5]]

case 3

in: [[],[]]

expected: []

case 4

in: [[[1,"a",1],[2,"b",2]],[["c",3]]]

expected: [[1,"a",1],[2,"b",2],[3,"c",3]]

Starter codePython

def wal_append(existing, records):
    # Your code here
    pass

4 test cases · run your code against them in the editor