_ Here's how it works: Anybody can ask a question Anybody can answer The best answers are voted up and rise to the top up vote 5 down vote favorite 3 Ethereum clients (such as geth, eth, pyethapp, ethereumj, and ethereumH) download the Ethereum blockchain from their peers and then store a copy of it locally, presumably indexed within some sort of database for efficient lookup and retrieval.Other uses for databases within the clients may include storage of the state, tracking of peers, etc. Which databases are used by the respective clients, and for what reasons have they been selected?clients database up vote down vote Geth uses leveldb.Some of the reasons behind choosing it was: In process database (i.e.I don't need to run an additional software) Native implementation in Go (i.e.cross platform to everything Go supports) Key/value store (i.e.values are arbitrary binary blobs, no schema constraints) Modern data storage (i.e.

multiple layers on disk, organized in the background) Proven track record (i.e.many companies and other databases build on top) However, there are also limitations: Ethereum uses hashes exclusively for identifying anything.However, hashes are uniformly randomly distributed identifiers.Leveldb keeps keys organized "alphabetically" on disk, so accessing values associated with hashes is very expensive.This is mostly felt for the state trie, which is hundreds of thousands of nodes scattered and pointing all over the disk.bitcointalk miningHowever, without a specific database modelling the Ethereum trie by design, I don't see how this could be further optimized.earn bitcoin minecraftLeveldb was originally designed by Google to be a disk backed memory database.bitcoin aws

As long as most of it can fit into memory, it performs very well, but as more and more disk access is required, performance can degrade.Facebook's RocksDB tries to address some of these issues + multi threaded background compaction, but its still a fairly new thing and being in C makes portability hard.Your Answer Sign up or log in Sign up using Google Sign up using Email and Password Post as a guest Name Email discard By posting your answer, you agree to the privacy policy and terms of service.bitcoin paper wallet reviewBrowse other questions tagged clients database or ask your own question.dogecoin to bitcoin exchangeTo make your app work on Ethereum, you can use the web3 object provided by the web3.js library.comprar apartamento bitcoin

Under the hood it communicates to a local node through RPC calls.web3.js works with any Ethereum node, which exposes an RPC layer.web3 contains the eth object - web3.eth (for specifically Ethereum blockchain interactions) and the shh object - web3.shh (for Whisper interaction).Over time we'll introduce other objects for each of the other web3 protocols.Working examples can be found here.If you want to look at some more sophisticated examples using web3.js check out these useful app patterns.bitcoin bowl player giftsFirst you need to get web3.js into your project.ethereum gasThis can be done using the following methods: Then you need to create a web3 instance, setting a provider.bitcoin kostenlos kaufenTo make sure you don't overwrite the already set provider when in mist, check first if the web3 is available: After that you can use the API of the web3 object.

As this API is designed to work with a local RPC node, all its functions use synchronous HTTP requests by default.If you want to make an asynchronous request, you can pass an optional callback as the last parameter to most functions.All callbacks are using an error first callback style: Batch requests allow queuing up requests and processing them at once.Note Batch requests are not faster!In fact making many requests at once will in some cases be faster, as requests are processed asynchronous.Batch requests are mainly useful to ensure the serial processing of requests.You will always get a BigNumber object for number values as JavaScript is not able to handle big numbers correctly.Look at the following examples: web3.js depends on the BigNumber Library and adds it automatically.The next example wouldn't work as we have more than 20 floating points, therefore it is recommended to keep you balance always in wei and only transform it to other units when presenting to the user: The web3 object provides all methods.

String - The ethereum js api version.String - The client/node version.String - The network protocol version.String - The ethereum protocol version.String - The whisper protocol version.Should be called to check if a connection to a node exists Should be called to set provider.Will contain the current provider, if one is set.This can be used to check if mist etc. set already a provider.Object - The provider set or null; Should be called to reset state of web3.Resets everything except manager.String - The Keccak-256 SHA3 of the given data.Converts any value into HEX.String - The hex string of mixed.Converts a HEX string into a ASCII string.String - An ASCII string made from the given hexString.Converts any ASCII string to a HEX string.String - The converted HEX string.Converts a HEX string to its number representation.Number - The number representing the data hexString.Converts a number or number string to its HEX representation.String - The HEX string representing of the given number.

Converts a number of wei into the following ethereum units: String|BigNumber - Either a number string, or a BigNumber instance, depending on the given number parameter.Converts an ethereum unit into wei.Possible units are: String|BigNumber - Either a number string, or a BigNumber instance, depending on the given number parameter.Converts a given number into a BigNumber instance.See the note on BigNumber.BigNumber - A BigNumber instance representing the given value.Checks if the given string is an address.Boolean - false if it's not on a valid address format.Returns true if it's an all lowercase or all uppercase valid address.If it's a mixed case address, it checks using web3.isChecksumAddress().This property is read only and says whether the node is actively listening for network connections or not.Boolean - true if the client is actively listening for network connections, otherwise false.This property is read only and returns the number of connected peers.Number - The number of peers currently connected to the client.

Contains the ethereum blockchain related methods.This default address is used for the following methods (optionally you can overwrite it by specifying the from property): String, 20 Bytes - Any address you own, or where you have the private key for.String, 20 Bytes - The currently set default address.This default block is used for the following methods (optionally you can override it by passing the defaultBlock parameter): Default block parameters can be one of the following: Number|String - The default block number to use when querying a state.This property is read only and returns the either a sync object, when the node is syncing or false.Object|Boolean - A sync object as follows, when the node is currently syncing or false: This convenience function calls the callback everytime a sync starts, updates and stops.Object - a isSyncing object with the following methods: This property is read only and returns the coinbase address were the mining rewards go to.String - The coinbase address of the client.

This property is read only and says whether the node is mining or not.Boolean - true if the client is mining, otherwise false.This property is read only and returns the number of hashes per second that the node is mining with.Number - number of hashes per second.This property is read only and returns the current gas price.The gas price is determined by the x latest blocks median gas price.BigNumber - A BigNumber instance of the current gas price in wei.This property is read only and returns a list of accounts the node controls.Array - An array of addresses controlled by client.This property is read only and returns the current block number.Number - The number of the most recent block.(Not Implemented yet) Registers the given address to be included in web3.eth.accounts.This allows non-private-key owned accounts to be associated as an owned account (e.g., contract wallets).(Not Implemented yet) Unregisters a given address.Get the balance of an address at a given block.String - A BigNumber instance of the current balance for the given address in wei.

Get the storage at a specific position of an address.String - The value in storage at the given position.Get the code at a specific address.String - The data at given address addressHexString.Returns a block matching the block number or block hash.Object - The block object: Returns the number of transaction in a given block.Number - The number of transactions in the given block.Returns a blocks uncle by a given uncle index position.Object - the returned uncle.For a return value see web3.eth.getBlock().Note: An uncle doesn't contain individual transactions.Returns a transaction matching the given transaction hash.Object - A transaction object its hash transactionHash: Returns a transaction based on a block hash or number and the transactions index position.Object - A transaction object, see web3.eth.getTransaction: Returns the receipt of a transaction by transaction hash.Note That the receipt is not available for pending transactions.Object - A transaction receipt object, or null when no receipt was found: Get the numbers of transactions sent from this address.

Number - The number of transactions sent from the given address.Sends a transaction to the network.String - The 32 Bytes transaction hash as HEX string.If the transaction was a contract creation use web3.eth.getTransactionReceipt() to get the contract address, after the transaction was mined.Sends an already signed transaction./SilentCicero/ethereumjs-accounts String - The 32 Bytes transaction hash as HEX string.Signs data from a specific account.This account needs to be unlocked.String - The signed data.After the hex prefix, characters correspond to ECDSA values like this: Note that if you are using ecrecover, v will be either "00" or "01".As a result, in order to use this value, you will have to parse it to an integer and then add 27.This will result in either a 27 or a 28.Executes a message call transaction, which is directly executed in the VM of the node, but never mined into the blockchain.String - The returned data of the call, e.g.a codes functions return value.Executes a message call or transaction, which is directly executed in the VM of the node, but never mined into the blockchain and returns the amount of the gas used.

See web3.eth.sendTransaction, except that all properties are optional.Number - the used gas for the simulated call/transaction.Object - A filter object with the following methods: Note For event filter return values see Contract Events Creates a contract object for a solidity contract, which can be used to initiate contracts on an address.You can read more about events here.Object - A contract object, which can be initiated as follows: And then you can either initiate an existing contract on an address, or deploy the contract using the compiled byte code: The contract object exposes the contract's methods, which can be called using parameters and a transaction object.String - If its a call the result data, if its a send transaction a created contract address, or the transaction hash, see web3.eth.sendTransaction for details.You can use events like filters and they have the same methods, but you pass different objects to create the event filter.Object - An event object as follows: Will call the callback for all events which are created by this contract.

Object - See Contract Events for more.Gets a list of available compilers.Array - An array of strings of available compilers.Object - Contract and compiler info.String - The compiled LLL code as HEX string.String - The compiled serpent code as HEX string.This method should be called, when we want to store a string in the local leveldb database.Boolean - true if successfull, otherwise false.param is db name, second is the key, and third is the string value.This method should be called, when we want to get string from the local leveldb database.String - The stored value.param is db name and second is the key of string value.This method should be called, when we want to store binary data in HEX form in the local leveldb database.This method should be called, when we want to get a binary data in HEX form from the local leveldb database.String - The stored HEX value.param is db name and second is the key of value.This method should be called, when we want to post whisper message to the network.