80 lines
1.8 KiB
Go
80 lines
1.8 KiB
Go
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package memdb
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import (
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"sync"
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"github.com/hashicorp/go-immutable-radix"
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)
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// MemDB is an in-memory database. It provides a table abstraction,
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// which is used to store objects (rows) with multiple indexes based
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// on values. The database makes use of immutable radix trees to provide
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// transactions and MVCC.
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type MemDB struct {
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schema *DBSchema
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root *iradix.Tree
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// There can only be a single writter at once
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writer sync.Mutex
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}
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// NewMemDB creates a new MemDB with the given schema
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func NewMemDB(schema *DBSchema) (*MemDB, error) {
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// Validate the schema
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if err := schema.Validate(); err != nil {
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return nil, err
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}
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// Create the MemDB
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db := &MemDB{
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schema: schema,
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root: iradix.New(),
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}
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if err := db.initialize(); err != nil {
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return nil, err
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}
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return db, nil
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}
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// Txn is used to start a new transaction, in either read or write mode.
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// There can only be a single concurrent writer, but any number of readers.
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func (db *MemDB) Txn(write bool) *Txn {
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if write {
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db.writer.Lock()
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}
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txn := &Txn{
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db: db,
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write: write,
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rootTxn: db.root.Txn(),
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}
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return txn
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}
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// Snapshot is used to capture a point-in-time snapshot
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// of the database that will not be affected by any write
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// operations to the existing DB.
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func (db *MemDB) Snapshot() *MemDB {
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clone := &MemDB{
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schema: db.schema,
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root: db.root,
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}
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return clone
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}
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// initialize is used to setup the DB for use after creation
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func (db *MemDB) initialize() error {
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for tName, tableSchema := range db.schema.Tables {
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for iName, _ := range tableSchema.Indexes {
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index := iradix.New()
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path := indexPath(tName, iName)
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db.root, _, _ = db.root.Insert(path, index)
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}
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}
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return nil
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}
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// indexPath returns the path from the root to the given table index
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func indexPath(table, index string) []byte {
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return []byte(table + "." + index)
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}
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