92 lines
3.9 KiB
Go
92 lines
3.9 KiB
Go
// Copyright (c) 2015-2016 The btcsuite developers
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// Use of this source code is governed by an ISC
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// license that can be found in the LICENSE file.
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/*
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Package database provides a block and metadata storage database.
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Overview
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As of Feb 2016, there are over 400,000 blocks in the Bitcoin block chain and
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and over 112 million transactions (which turns out to be over 60GB of data).
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This package provides a database layer to store and retrieve this data in a
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simple and efficient manner.
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The default backend, ffldb, has a strong focus on speed, efficiency, and
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robustness. It makes use leveldb for the metadata, flat files for block
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storage, and strict checksums in key areas to ensure data integrity.
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A quick overview of the features database provides are as follows:
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- Key/value metadata store
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- Bitcoin block storage
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- Efficient retrieval of block headers and regions (transactions, scripts, etc)
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- Read-only and read-write transactions with both manual and managed modes
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- Nested buckets
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- Supports registration of backend databases
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- Comprehensive test coverage
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Database
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The main entry point is the DB interface. It exposes functionality for
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transactional-based access and storage of metadata and block data. It is
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obtained via the Create and Open functions which take a database type string
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that identifies the specific database driver (backend) to use as well as
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arguments specific to the specified driver.
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The interface provides facilities for obtaining transactions (the Tx interface)
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that are the basis of all database reads and writes. Unlike some database
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interfaces that support reading and writing without transactions, this interface
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requires transactions even when only reading or writing a single key.
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The Begin function provides an unmanaged transaction while the View and Update
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functions provide a managed transaction. These are described in more detail
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below.
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Transactions
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The Tx interface provides facilities for rolling back or committing changes that
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took place while the transaction was active. It also provides the root metadata
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bucket under which all keys, values, and nested buckets are stored. A
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transaction can either be read-only or read-write and managed or unmanaged.
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Managed versus Unmanaged Transactions
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A managed transaction is one where the caller provides a function to execute
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within the context of the transaction and the commit or rollback is handled
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automatically depending on whether or not the provided function returns an
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error. Attempting to manually call Rollback or Commit on the managed
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transaction will result in a panic.
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An unmanaged transaction, on the other hand, requires the caller to manually
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call Commit or Rollback when they are finished with it. Leaving transactions
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open for long periods of time can have several adverse effects, so it is
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recommended that managed transactions are used instead.
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Buckets
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The Bucket interface provides the ability to manipulate key/value pairs and
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nested buckets as well as iterate through them.
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The Get, Put, and Delete functions work with key/value pairs, while the Bucket,
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CreateBucket, CreateBucketIfNotExists, and DeleteBucket functions work with
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buckets. The ForEach function allows the caller to provide a function to be
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called with each key/value pair and nested bucket in the current bucket.
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Metadata Bucket
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As discussed above, all of the functions which are used to manipulate key/value
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pairs and nested buckets exist on the Bucket interface. The root metadata
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bucket is the upper-most bucket in which data is stored and is created at the
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same time as the database. Use the Metadata function on the Tx interface
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to retrieve it.
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Nested Buckets
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The CreateBucket and CreateBucketIfNotExists functions on the Bucket interface
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provide the ability to create an arbitrary number of nested buckets. It is
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a good idea to avoid a lot of buckets with little data in them as it could lead
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to poor page utilization depending on the specific driver in use.
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*/
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package database
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