kvdb: add postgres

kvdb/postgres/readwrite_cursor.go

@@ -0,0 +1,220 @@
+// +build kvdb_postgres
+
+package postgres
+
+import (
+	"database/sql"
+
+	"github.com/btcsuite/btcwallet/walletdb"
+)
+
+// readWriteCursor holds a reference to the cursors bucket, the value
+// prefix and the current key used while iterating.
+type readWriteCursor struct {
+	bucket *readWriteBucket
+
+	// currKey holds the current key of the cursor.
+	currKey []byte
+}
+
+func newReadWriteCursor(b *readWriteBucket) *readWriteCursor {
+	return &readWriteCursor{
+		bucket: b,
+	}
+}
+
+// First positions the cursor at the first key/value pair and returns
+// the pair.
+func (c *readWriteCursor) First() ([]byte, []byte) {
+	var (
+		key   []byte
+		value []byte
+	)
+	err := c.bucket.tx.QueryRow(
+		"SELECT key, value FROM "+c.bucket.table+" WHERE "+
+			parentSelector(c.bucket.id)+
+			" ORDER BY key LIMIT 1",
+	).Scan(&key, &value)
+
+	switch {
+	case err == sql.ErrNoRows:
+		return nil, nil
+
+	case err != nil:
+		panic(err)
+	}
+
+	// Copy current key to prevent modification by the caller.
+	c.currKey = make([]byte, len(key))
+	copy(c.currKey, key)
+
+	return key, value
+}
+
+// Last positions the cursor at the last key/value pair and returns the
+// pair.
+func (c *readWriteCursor) Last() ([]byte, []byte) {
+	var (
+		key   []byte
+		value []byte
+	)
+	err := c.bucket.tx.QueryRow(
+		"SELECT key, value FROM "+c.bucket.table+" WHERE "+
+			parentSelector(c.bucket.id)+
+			" ORDER BY key DESC LIMIT 1",
+	).Scan(&key, &value)
+
+	switch {
+	case err == sql.ErrNoRows:
+		return nil, nil
+
+	case err != nil:
+		panic(err)
+	}
+
+	// Copy current key to prevent modification by the caller.
+	c.currKey = make([]byte, len(key))
+	copy(c.currKey, key)
+
+	return key, value
+}
+
+// Next moves the cursor one key/value pair forward and returns the new
+// pair.
+func (c *readWriteCursor) Next() ([]byte, []byte) {
+	var (
+		key   []byte
+		value []byte
+	)
+	err := c.bucket.tx.QueryRow(
+		"SELECT key, value FROM "+c.bucket.table+" WHERE "+
+			parentSelector(c.bucket.id)+
+			" AND key>$1 ORDER BY key LIMIT 1",
+		c.currKey,
+	).Scan(&key, &value)
+
+	switch {
+	case err == sql.ErrNoRows:
+		return nil, nil
+
+	case err != nil:
+		panic(err)
+	}
+
+	// Copy current key to prevent modification by the caller.
+	c.currKey = make([]byte, len(key))
+	copy(c.currKey, key)
+
+	return key, value
+}
+
+// Prev moves the cursor one key/value pair backward and returns the new
+// pair.
+func (c *readWriteCursor) Prev() ([]byte, []byte) {
+	var (
+		key   []byte
+		value []byte
+	)
+	err := c.bucket.tx.QueryRow(
+		"SELECT key, value FROM "+c.bucket.table+" WHERE "+
+			parentSelector(c.bucket.id)+
+			" AND key<$1 ORDER BY key DESC LIMIT 1",
+		c.currKey,
+	).Scan(&key, &value)
+
+	switch {
+	case err == sql.ErrNoRows:
+		return nil, nil
+
+	case err != nil:
+		panic(err)
+	}
+
+	// Copy current key to prevent modification by the caller.
+	c.currKey = make([]byte, len(key))
+	copy(c.currKey, key)
+
+	return key, value
+}
+
+// Seek positions the cursor at the passed seek key.  If the key does
+// not exist, the cursor is moved to the next key after seek.  Returns
+// the new pair.
+func (c *readWriteCursor) Seek(seek []byte) ([]byte, []byte) {
+	// Convert nil to empty slice, otherwise sql mapping won't be correct
+	// and no keys are found.
+	if seek == nil {
+		seek = []byte{}
+	}
+
+	var (
+		key   []byte
+		value []byte
+	)
+	err := c.bucket.tx.QueryRow(
+		"SELECT key, value FROM "+c.bucket.table+" WHERE "+
+			parentSelector(c.bucket.id)+
+			" AND key>=$1 ORDER BY key LIMIT 1",
+		seek,
+	).Scan(&key, &value)
+
+	switch {
+	case err == sql.ErrNoRows:
+		return nil, nil
+
+	case err != nil:
+		panic(err)
+	}
+
+	// Copy current key to prevent modification by the caller.
+	c.currKey = make([]byte, len(key))
+	copy(c.currKey, key)
+
+	return key, value
+}
+
+// Delete removes the current key/value pair the cursor is at without
+// invalidating the cursor.  Returns ErrIncompatibleValue if attempted
+// when the cursor points to a nested bucket.
+func (c *readWriteCursor) Delete() error {
+	// Get first record at or after cursor.
+	var key []byte
+	err := c.bucket.tx.QueryRow(
+		"SELECT key FROM "+c.bucket.table+" WHERE "+
+			parentSelector(c.bucket.id)+
+			" AND key>=$1 ORDER BY key LIMIT 1",
+		c.currKey,
+	).Scan(&key)
+
+	switch {
+	case err == sql.ErrNoRows:
+		return nil
+
+	case err != nil:
+		panic(err)
+	}
+
+	// Delete record.
+	result, err := c.bucket.tx.Exec(
+		"DELETE FROM "+c.bucket.table+" WHERE "+
+			parentSelector(c.bucket.id)+
+			" AND key=$1 AND value IS NOT NULL",
+		key,
+	)
+	if err != nil {
+		panic(err)
+	}
+
+	rows, err := result.RowsAffected()
+	if err != nil {
+		return err
+	}
+
+	// The key exists but nothing has been deleted. This means that the key
+	// must have been a bucket key.
+	if rows != 1 {
+		return walletdb.ErrIncompatibleValue
+	}
+
+	return err
+}