Bitcoin: levelDB : How key/value pairs work for datadir/blocks/index/

Here’s a detailed explanation of how the key-value pairs work for LevelDB in Bitcoin data storage:

Understanding Key-Value Pairs in LevelDB

LevelDB is a database that allows you to store large amounts of data using key-value pairs. In the context of Bitcoin, we’ll focus on storing blocks and transactions. The datadir parameter specifies the directory where LevelDB will store the Bitcoin data.

Key-Value Pair Format

In LevelDB, each key-value pair consists of a single string. The string is divided into two parts:

• Key

  : A unique string that identifies the key-value pair.

• Value: The actual value stored in the database.

The format of each key-value pair is as follows:

key=value

Example Raw Key and Value

Let’s take a look at an example raw key and value:

Raw Key: "blockhash"

             ^ ^

       |  |

       v Bitcoin Block Hash


Value: "0a5b7cd1234567890ab12345abcdef"

In this example, the raw_key is the string "blockhash", and the value is a hexadecimal string representing the Bitcoin block hash.

How ​​Key-Value Pairs Work in LevelDB

Now that we understand how key-value pairs work in LevelDB, let’s dive into how it stores blocks and transactions. Here’s a step-by-step explanation:

• Creating a New Database: When you create a new database using leveldb init, LevelDB creates a new directory for the Bitcoin data.

• Adding a Block: To store a block, you need to add a key-value pair to the database with the following format:

"blockhash=0a5b7cd1234567890ab12345abcdef"

The raw_key is set to "blockhash", and the value is a hexadecimal string representing the Bitcoin block hash.

• Indexing: LevelDB uses an index (or index) to store blocks. The index contains a mapping of raw keys to their corresponding values ​​in the database. To store a block, you need to add its index entry using the same key-value pair format:

"index=0a5b7cd1234567890ab12345abcdef"

The raw_key is set to "index" and the value is a hexadecimal string representing the Bitcoin index.

• Cache: LevelDB also uses caching to improve performance. When you update a block or transaction, LevelDB can use its index to quickly find the corresponding value in the database.

Example Raw Keys and Values ​​for Blocks

Here are some examples of raw keys and values ​​for blocks:

block1=0a5b7cd1234567890ab12345abcdef

block2=0a1b2c3d4e5f6g7h8i9j10k11l12m13n14o15p16q17r18s19t20u21v22w23x24y25z26

Key-Value Pair Format for Transactions

In LevelDB, each key-value pair can also represent a transaction. Here’s an example of how it works:

transactionid=0a5b7cd1234567890ab12345abcdef

transactiontype=1

transactiondata=with...

The raw_key is set to "transactionid", and the value is a hexadecimal string representing the transaction ID.

• Indexing Transactions

  

  : LevelDB uses an index (or index) to store transactions. The index contains a mapping of raw keys to their corresponding values ​​in the database.

In conclusion, LevelDB provides a flexible and efficient way to store Bitcoin data using key-value pairs. By understanding how key-value pairs work in LevelDB, you can effectively manage your Bitcoin data and perform various operations on it.