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kvdb: add postgres
This commit is contained in:
Joost Jager
412
kvdb/postgres/readwrite_bucket.go
Normal file
412
kvdb/postgres/readwrite_bucket.go
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@@ -0,0 +1,412 @@
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// +build kvdb_postgres
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package postgres
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import (
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"database/sql"
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"errors"
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"fmt"
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"github.com/btcsuite/btcwallet/walletdb"
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)
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// readWriteBucket stores the bucket id and the buckets transaction.
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type readWriteBucket struct {
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// id is used to identify the bucket. If id is null, it refers to the
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// root bucket.
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id *int64
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// tx holds the parent transaction.
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tx *readWriteTx
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table string
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}
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// newReadWriteBucket creates a new rw bucket with the passed transaction
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// and bucket id.
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func newReadWriteBucket(tx *readWriteTx, id *int64) *readWriteBucket {
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return &readWriteBucket{
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id: id,
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tx: tx,
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table: tx.db.table,
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}
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}
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// NestedReadBucket retrieves a nested read bucket with the given key.
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// Returns nil if the bucket does not exist.
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func (b *readWriteBucket) NestedReadBucket(key []byte) walletdb.ReadBucket {
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return b.NestedReadWriteBucket(key)
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}
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func parentSelector(id *int64) string {
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if id == nil {
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return "parent_id IS NULL"
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}
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return fmt.Sprintf("parent_id=%v", *id)
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}
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// ForEach invokes the passed function with every key/value pair in
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// the bucket. This includes nested buckets, in which case the value
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// is nil, but it does not include the key/value pairs within those
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// nested buckets.
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func (b *readWriteBucket) ForEach(cb func(k, v []byte) error) error {
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cursor := b.ReadWriteCursor()
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k, v := cursor.First()
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for k != nil {
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err := cb(k, v)
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if err != nil {
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return err
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}
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k, v = cursor.Next()
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}
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return nil
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}
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// Get returns the value for the given key. Returns nil if the key does
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// not exist in this bucket.
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func (b *readWriteBucket) Get(key []byte) []byte {
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// Return nil if the key is empty.
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if len(key) == 0 {
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return nil
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}
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var value *[]byte
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err := b.tx.QueryRow(
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"SELECT value FROM "+b.table+" WHERE "+parentSelector(b.id)+
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" AND key=$1", key,
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).Scan(&value)
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switch {
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case err == sql.ErrNoRows:
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return nil
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case err != nil:
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panic(err)
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}
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return *value
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}
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// ReadCursor returns a new read-only cursor for this bucket.
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func (b *readWriteBucket) ReadCursor() walletdb.ReadCursor {
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return newReadWriteCursor(b)
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}
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// NestedReadWriteBucket retrieves a nested bucket with the given key.
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// Returns nil if the bucket does not exist.
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func (b *readWriteBucket) NestedReadWriteBucket(
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key []byte) walletdb.ReadWriteBucket {
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if len(key) == 0 {
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return nil
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}
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var id int64
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err := b.tx.QueryRow(
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"SELECT id FROM "+b.table+" WHERE "+parentSelector(b.id)+
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" AND key=$1 AND value IS NULL", key,
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).Scan(&id)
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switch {
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case err == sql.ErrNoRows:
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return nil
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case err != nil:
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panic(err)
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}
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return newReadWriteBucket(b.tx, &id)
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}
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// CreateBucket creates and returns a new nested bucket with the given key.
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// Returns ErrBucketExists if the bucket already exists, ErrBucketNameRequired
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// if the key is empty, or ErrIncompatibleValue if the key value is otherwise
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// invalid for the particular database implementation. Other errors are
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// possible depending on the implementation.
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func (b *readWriteBucket) CreateBucket(key []byte) (
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walletdb.ReadWriteBucket, error) {
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if len(key) == 0 {
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return nil, walletdb.ErrBucketNameRequired
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}
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// Check to see if the bucket already exists.
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var (
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value *[]byte
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id int64
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)
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err := b.tx.QueryRow(
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"SELECT id,value FROM "+b.table+" WHERE "+parentSelector(b.id)+
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" AND key=$1", key,
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).Scan(&id, &value)
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switch {
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case err == sql.ErrNoRows:
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case err == nil && value == nil:
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return nil, walletdb.ErrBucketExists
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case err == nil && value != nil:
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return nil, walletdb.ErrIncompatibleValue
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case err != nil:
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return nil, err
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}
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// Bucket does not yet exist, so create it. Postgres will generate a
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// bucket id for the new bucket.
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err = b.tx.QueryRow(
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"INSERT INTO "+b.table+" (parent_id, key) "+
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"VALUES($1, $2) RETURNING id", b.id, key,
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).Scan(&id)
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if err != nil {
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return nil, err
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}
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return newReadWriteBucket(b.tx, &id), nil
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}
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// CreateBucketIfNotExists creates and returns a new nested bucket with
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// the given key if it does not already exist. Returns
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// ErrBucketNameRequired if the key is empty or ErrIncompatibleValue
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// if the key value is otherwise invalid for the particular database
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// backend. Other errors are possible depending on the implementation.
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func (b *readWriteBucket) CreateBucketIfNotExists(key []byte) (
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walletdb.ReadWriteBucket, error) {
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if len(key) == 0 {
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return nil, walletdb.ErrBucketNameRequired
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}
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// Check to see if the bucket already exists.
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var (
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value *[]byte
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id int64
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)
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err := b.tx.QueryRow(
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"SELECT id,value FROM "+b.table+" WHERE "+parentSelector(b.id)+
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" AND key=$1", key,
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).Scan(&id, &value)
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switch {
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// Bucket does not yet exist, so create it now. Postgres will generate a
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// bucket id for the new bucket.
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case err == sql.ErrNoRows:
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err = b.tx.QueryRow(
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"INSERT INTO "+b.table+" (parent_id, key) "+
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"VALUES($1, $2) RETURNING id", b.id, key).
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Scan(&id)
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if err != nil {
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return nil, err
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}
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case err == nil && value != nil:
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return nil, walletdb.ErrIncompatibleValue
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case err != nil:
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return nil, err
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}
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return newReadWriteBucket(b.tx, &id), nil
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}
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// DeleteNestedBucket deletes the nested bucket and its sub-buckets
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// pointed to by the passed key. All values in the bucket and sub-buckets
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// will be deleted as well.
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func (b *readWriteBucket) DeleteNestedBucket(key []byte) error {
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if len(key) == 0 {
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return walletdb.ErrIncompatibleValue
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}
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result, err := b.tx.Exec(
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"DELETE FROM "+b.table+" WHERE "+parentSelector(b.id)+
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" AND key=$1 AND value IS NULL",
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key,
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)
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if err != nil {
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return err
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}
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rows, err := result.RowsAffected()
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if err != nil {
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return err
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}
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if rows == 0 {
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return walletdb.ErrBucketNotFound
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}
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return nil
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}
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// Put updates the value for the passed key.
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// Returns ErrKeyRequired if te passed key is empty.
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func (b *readWriteBucket) Put(key, value []byte) error {
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if len(key) == 0 {
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return walletdb.ErrKeyRequired
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}
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// Prevent NULL being written for an empty value slice.
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if value == nil {
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value = []byte{}
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}
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var (
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result sql.Result
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err error
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)
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// We are putting a value in a bucket in this table. Try to insert the
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// key first. If the key already exists (ON CONFLICT), update the key.
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// Do not update a NULL value, because this indicates that the key
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// contains a sub-bucket. This case will be caught via RowsAffected
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// below.
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if b.id == nil {
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// ON CONFLICT requires the WHERE parent_id IS NULL hint to let
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// Postgres find the NULL-parent_id unique index (<table>_unp).
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result, err = b.tx.Exec(
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"INSERT INTO "+b.table+" (key, value) VALUES($1, $2) "+
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"ON CONFLICT (key) WHERE parent_id IS NULL "+
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"DO UPDATE SET value=$2 "+
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"WHERE "+b.table+".value IS NOT NULL",
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key, value,
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)
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} else {
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// ON CONFLICT requires the WHERE parent_id NOT IS NULL hint to
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// let Postgres find the non-NULL-parent_id unique index
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// (<table>_up).
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result, err = b.tx.Exec(
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"INSERT INTO "+b.table+" (key, value, parent_id) "+
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"VALUES($1, $2, $3) "+
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"ON CONFLICT (key, parent_id) "+
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"WHERE parent_id IS NOT NULL "+
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"DO UPDATE SET value=$2 "+
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"WHERE "+b.table+".value IS NOT NULL",
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key, value, b.id,
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)
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}
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if err != nil {
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return err
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}
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rows, err := result.RowsAffected()
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if err != nil {
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return err
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}
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if rows != 1 {
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return walletdb.ErrIncompatibleValue
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}
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return nil
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}
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// Delete deletes the key/value pointed to by the passed key.
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// Returns ErrKeyRequired if the passed key is empty.
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func (b *readWriteBucket) Delete(key []byte) error {
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if key == nil {
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return nil
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}
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if len(key) == 0 {
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return walletdb.ErrKeyRequired
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}
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// Check to see if a bucket with this key exists.
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var dummy int
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err := b.tx.QueryRow(
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"SELECT 1 FROM "+b.table+" WHERE "+parentSelector(b.id)+
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" AND key=$1 AND value IS NULL", key,
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).Scan(&dummy)
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switch {
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// No bucket exists, proceed to deletion of the key.
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case err == sql.ErrNoRows:
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case err != nil:
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return err
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// Bucket exists.
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default:
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return walletdb.ErrIncompatibleValue
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}
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_, err = b.tx.Exec(
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"DELETE FROM "+b.table+" WHERE key=$1 AND "+
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parentSelector(b.id)+" AND value IS NOT NULL",
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key,
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)
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if err != nil {
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return err
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}
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return nil
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}
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// ReadWriteCursor returns a new read-write cursor for this bucket.
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func (b *readWriteBucket) ReadWriteCursor() walletdb.ReadWriteCursor {
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return newReadWriteCursor(b)
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}
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// Tx returns the buckets transaction.
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func (b *readWriteBucket) Tx() walletdb.ReadWriteTx {
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return b.tx
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}
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// NextSequence returns an autoincrementing sequence number for this bucket.
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// Note that this is not a thread safe function and as such it must not be used
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// for synchronization.
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func (b *readWriteBucket) NextSequence() (uint64, error) {
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seq := b.Sequence() + 1
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return seq, b.SetSequence(seq)
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}
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// SetSequence updates the sequence number for the bucket.
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func (b *readWriteBucket) SetSequence(v uint64) error {
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if b.id == nil {
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panic("sequence not supported on top level bucket")
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}
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result, err := b.tx.Exec(
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"UPDATE "+b.table+" SET sequence=$2 WHERE id=$1",
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b.id, int64(v),
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)
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if err != nil {
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return err
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}
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rows, err := result.RowsAffected()
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if err != nil {
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return err
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}
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if rows != 1 {
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return errors.New("cannot set sequence")
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}
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return nil
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}
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// Sequence returns the current sequence number for this bucket without
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// incrementing it.
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func (b *readWriteBucket) Sequence() uint64 {
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if b.id == nil {
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panic("sequence not supported on top level bucket")
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}
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var seq int64
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err := b.tx.QueryRow(
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"SELECT sequence FROM "+b.table+" WHERE id=$1 "+
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"AND sequence IS NOT NULL",
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b.id,
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).Scan(&seq)
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switch {
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case err == sql.ErrNoRows:
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return 0
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case err != nil:
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panic(err)
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}
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return uint64(seq)
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}
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