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a88ac5822c
This allows setting the meta field when you commit. This is a version change because the signature of Database commit changed in a non backwards compatible way. It now takes an optional third options object instead of an optional array.
104 lines
4.8 KiB
Go
104 lines
4.8 KiB
Go
// Copyright 2016 Attic Labs, Inc. All rights reserved.
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// Licensed under the Apache License, version 2.0:
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// http://www.apache.org/licenses/LICENSE-2.0
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// Package datas defines and implements the database layer used in Noms.
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package datas
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import (
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"io"
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"github.com/attic-labs/noms/go/chunks"
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"github.com/attic-labs/noms/go/hash"
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"github.com/attic-labs/noms/go/types"
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)
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// Database provides versioned storage for noms values. While Values can be
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// directly read and written from a Database, it is generally more appropriate
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// to read data by inspecting the Head of a Dataset and write new data by
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// updating the Head of a Dataset via Commit() or similar. Particularly, new
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// data is not guaranteed to be persistent until after a Commit (Delete,
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// SetHead, or FastForward) operation completes.
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// The Database API is stateful, meaning that calls to GetDataset() or
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// Datasets() occurring after a call to Commit() (et al) will represent the
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// result of the Commit().
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type Database interface {
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// To implement types.ValueWriter, Database implementations provide
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// WriteValue(). WriteValue() writes v to this Database, though v is not
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// guaranteed to be be persistent until after a subsequent Commit(). The
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// return value is the Ref of v.
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types.ValueReadWriter
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io.Closer
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// Datasets returns the root of the database which is a
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// Map<String, Ref<Commit>> where string is a datasetID.
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Datasets() types.Map
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// GetDataset returns a Dataset struct containing the current mapping of
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// datasetID in the above Datasets Map.
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GetDataset(datasetID string) Dataset
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// Commit updates the Commit that ds.ID() in this database points at. All
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// Values that have been written to this Database are guaranteed to be
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// persistent after Commit() returns.
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// The new Commit struct is constructed using v, opts.Parents, and
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// opts.Meta. If opts.Parents is the zero value (types.Set{}) then
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// the current head is used. If opts.Meta is the zero value
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// (types.Struct{}) then a fully initialized empty Struct is passed to
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// NewCommit.
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// The returned Dataset is always the newest snapshot, regardless of
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// success or failure, and Datasets() is updated to match backing storage
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// upon return as well. If the update cannot be performed, e.g., because
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// of a conflict, Commit returns an 'ErrMergeNeeded' error.
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Commit(ds Dataset, v types.Value, opts CommitOptions) (Dataset, error)
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// CommitValue updates the Commit that ds.ID() in this database points at.
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// All Values that have been written to this Database are guaranteed to be
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// persistent after Commit().
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// The new Commit struct is constructed using `v`, and the current Head of
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// `ds` as the lone Parent.
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// The returned Dataset is always the newest snapshot, regardless of
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// success or failure, and Datasets() is updated to match backing storage
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// upon return as well. If the update cannot be performed, e.g., because
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// of a conflict, Commit returns an 'ErrMergeNeeded' error.
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CommitValue(ds Dataset, v types.Value) (Dataset, error)
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// Delete removes the Dataset named ds.ID() from the map at the root of
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// the Database. The Dataset data is not necessarily cleaned up at this
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// time, but may be garbage collected in the future.
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// The returned Dataset is always the newest snapshot, regardless of
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// success or failure, and Datasets() is updated to match backing storage
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// upon return as well. If the update cannot be performed, e.g., because
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// of a conflict, Delete returns an 'ErrMergeNeeded' error.
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Delete(ds Dataset) (Dataset, error)
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// SetHead ignores any lineage constraints (e.g. the current Head being in
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// commit’s Parent set) and force-sets a mapping from datasetID: commit in
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// this database.
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// All Values that have been written to this Database are guaranteed to be
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// persistent after SetHead(). If the update cannot be performed, e.g.,
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// because another process moved the current Head out from under you,
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// error will be non-nil.
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// The newest snapshot of the Dataset is always returned, so the caller an
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// easily retry using the latest.
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// Regardless, Datasets() is updated to match backing storage upon return.
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SetHead(ds Dataset, newHeadRef types.Ref) (Dataset, error)
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// FastForward takes a types.Ref to a Commit object and makes it the new
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// Head of ds iff it is a descendant of the current Head. Intended to be
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// used e.g. after a call to Pull(). If the update cannot be performed,
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// e.g., because another process moved the current Head out from under
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// you, err will be non-nil.
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// The newest snapshot of the Dataset is always returned, so the caller
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// can easily retry using the latest.
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// Regardless, Datasets() is updated to match backing storage upon return.
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FastForward(ds Dataset, newHeadRef types.Ref) (Dataset, error)
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has(h hash.Hash) bool
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validatingBatchStore() types.BatchStore
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}
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func NewDatabase(cs chunks.ChunkStore) Database {
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return newLocalDatabase(cs)
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}
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