87 lines
2.9 KiB
Go
87 lines
2.9 KiB
Go
/*
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* Copyright 2017 Dgraph Labs, Inc. and Contributors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package badger
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// ManagedDB allows end users to manage the transactions themselves. Transaction
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// start and commit timestamps are set by end-user.
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//
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// This is only useful for databases built on top of Badger (like Dgraph), and
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// can be ignored by most users.
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//
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// WARNING: This is an experimental feature and may be changed significantly in
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// a future release. So please proceed with caution.
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type ManagedDB struct {
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*DB
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}
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// OpenManaged returns a new ManagedDB, which allows more control over setting
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// transaction timestamps.
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//
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// This is only useful for databases built on top of Badger (like Dgraph), and
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// can be ignored by most users.
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func OpenManaged(opts Options) (*ManagedDB, error) {
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opts.managedTxns = true
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db, err := Open(opts)
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if err != nil {
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return nil, err
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}
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return &ManagedDB{db}, nil
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}
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// NewTransaction overrides DB.NewTransaction() and panics when invoked. Use
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// NewTransactionAt() instead.
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func (db *ManagedDB) NewTransaction(update bool) {
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panic("Cannot use NewTransaction() for ManagedDB. Use NewTransactionAt() instead.")
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}
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// NewTransactionAt follows the same logic as DB.NewTransaction(), but uses the
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// provided read timestamp.
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//
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// This is only useful for databases built on top of Badger (like Dgraph), and
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// can be ignored by most users.
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func (db *ManagedDB) NewTransactionAt(readTs uint64, update bool) *Txn {
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txn := db.DB.NewTransaction(update)
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txn.readTs = readTs
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return txn
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}
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// CommitAt commits the transaction, following the same logic as Commit(), but
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// at the given commit timestamp. This will panic if not used with ManagedDB.
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//
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// This is only useful for databases built on top of Badger (like Dgraph), and
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// can be ignored by most users.
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func (txn *Txn) CommitAt(commitTs uint64, callback func(error)) error {
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if !txn.db.opt.managedTxns {
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return ErrManagedTxn
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}
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txn.commitTs = commitTs
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return txn.Commit(callback)
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}
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// PurgeVersionsBelow will delete all versions of a key below the specified version
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func (db *ManagedDB) PurgeVersionsBelow(key []byte, ts uint64) error {
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txn := db.NewTransactionAt(ts, false)
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defer txn.Discard()
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return db.purgeVersionsBelow(txn, key, ts)
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}
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// GetSequence is not supported on ManagedDB. Calling this would result
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// in a panic.
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func (db *ManagedDB) GetSequence(_ []byte, _ uint64) (*Sequence, error) {
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panic("Cannot use GetSequence for ManagedDB.")
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}
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