Merge mutations during apply mutations step if possible

[eincs]

Haeinsa applies mutations of transaction to rows on commit phase. If transaction contains several mutations for certain row, Haeinsa applies mutations step by step with checkAndPut and checkAndDelete operation. We can optimize this step.

Let's assume that certain transaction should applies following mutations to certain row:

• put(row, col1, value1)
• put(row, col2, value2)
• delete(row, col1)
• put(row, col3, value3)
• put(row, col4, value4)
• delete(row, col3)
• put(row, col5, value5)

Here is comparison of how Haeinsa works on current version and optimized version:

AS-IS Haeinsa	TO-BE Haeinsa
checkAndPut(row, [{col1, value1}, {col2, value2}, {lock, newLock}) checkAndDelete(row, [col1]) checkAndPut(row, [{col3, value3}, {col4, value4}]) checkAndDelete(row, [col3]) checkAndPut(row, [{col5, value5}], {lock, newLock})	checkAndPut(row, [{col2, value2}, {lock, newLock}]) checkAndDelete(row, [col1, col3]) checkAndPut(row, [{col1, value4}, {col2, value5}, {lock, newLock}])

Series of operations above have the same result but TO-BE has small number of operations which means faster. I didn't mention deleteFamily operation on the example, but this should be consider too.

Note that this optimization is effective on complicate transaction. With this merging mutation algorithm, we can achieve faster execution of complicate transaction.

[ewmkkpe]

Good idea!

[eincs]

I close this issue since #49 merged.