finish iterator; unit tests for iterator

postgres/database.go

@@ -200,20 +200,20 @@ func (d *Database) NewBatch() ethdb.Batch {
 // NewIterator creates a binary-alphabetical iterator over the entire keyspace
 // contained within the key-value database.
 func (d *Database) NewIterator() ethdb.Iterator {
-	return NewIterator([]byte{}, []byte{}, d.db)
+	return NewIterator(nil, nil, d.db)
 }
 
 // NewIteratorWithStart creates a binary-alphabetical iterator over a subset of
 // database content starting at a particular initial key (or after, if it does
 // not exist).
 func (d *Database) NewIteratorWithStart(start []byte) ethdb.Iterator {
-	return NewIterator(start, []byte{}, d.db)
+	return NewIterator(start, nil, d.db)
 }
 
 // NewIteratorWithPrefix creates a binary-alphabetical iterator over a subset
 // of database content with a particular key prefix.
 func (d *Database) NewIteratorWithPrefix(prefix []byte) ethdb.Iterator {
-	return NewIterator([]byte{}, prefix, d.db)
+	return NewIterator(nil, prefix, d.db)
 }
 
 // Close satisfies the io.Closer interface

postgres/iterator.go

@@ -19,15 +19,17 @@ package pgipfsethdb
 import (
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/jmoiron/sqlx"
-	"github.com/sirupsen/logrus"
 )
 
 const (
-	nextPgStr = `SELECT key, data FROM public.blocks
+	initPgStr = `SELECT eth_key, data FROM public.blocks
+				INNER JOIN eth.key_preimages ON (ipfs_key = key)
+				WHERE eth_key = $1`
+	nextPgStr = `SELECT eth_key, data FROM public.blocks
 				INNER JOIN eth.key_preimages ON (ipfs_key = key)
 				WHERE eth_key > $1
 				ORDER BY eth_key LIMIT 1`
-	nextPgStrWithPrefix = `SELECT key, data FROM public.blocks
+	nextPgStrWithPrefix = `SELECT eth_key, data FROM public.blocks
 				INNER JOIN eth.key_preimages ON (ipfs_key = key)
 				WHERE eth_key > $1 AND prefix = $2 
 				ORDER BY eth_key LIMIT 1`
@@ -43,6 +45,7 @@ type Iterator struct {
 	db                               *sqlx.DB
 	currentKey, prefix, currentValue []byte
 	err                              error
+	init                             bool
 }
 
 // NewIterator returns an ethdb.Iterator interface for PG-IPFS
@@ -51,6 +54,7 @@ func NewIterator(start, prefix []byte, db *sqlx.DB) ethdb.Iterator {
 		db:         db,
 		prefix:     prefix,
 		currentKey: start,
+		init:       start != nil,
 	}
 }
 
@@ -59,21 +63,24 @@ func NewIterator(start, prefix []byte, db *sqlx.DB) ethdb.Iterator {
 // It returns whether the iterator is exhausted
 func (i *Iterator) Next() bool {
 	next := new(nextModel)
-	if i.prefix != nil {
+	if i.init {
-		if err := i.db.Get(next, nextPgStrWithPrefix, i.currentKey, i.prefix); err != nil {
+		i.init = false
-			logrus.Errorf("iterator.Next() error: %v", err)
+		if err := i.db.Get(next, initPgStr, i.currentKey); err != nil {
-			i.currentKey, i.currentValue = nil, nil
+			i.currentKey, i.currentValue, i.err = nil, nil, err
+			return false
+		}
+	} else if i.prefix != nil {
+		if err := i.db.Get(next, nextPgStrWithPrefix, i.currentKey, i.prefix); err != nil {
+			i.currentKey, i.currentValue, i.err = nil, nil, err
+			return false
+		}
+	} else {
+		if err := i.db.Get(next, nextPgStr, i.currentKey); err != nil {
+			i.currentKey, i.currentValue, i.err = nil, nil, err
 			return false
 		}
-		i.currentKey, i.currentValue = next.Key, next.Value
-		return true
 	}
-	if err := i.db.Get(next, nextPgStr, i.currentKey); err != nil {
+	i.currentKey, i.currentValue, i.err = next.Key, next.Value, nil
-		logrus.Errorf("iterator.Next() error: %v", err)
-		i.currentKey, i.currentValue = nil, nil
-		return false
-	}
-	i.currentKey, i.currentValue = next.Key, next.Value
 	return true
 }
 
@@ -104,5 +111,5 @@ func (i *Iterator) Value() []byte {
 // Release releases associated resources
 // Release should always succeed and can be called multiple times without causing error
 func (i *Iterator) Release() {
-	i.db.Close()
+	i.db, i.currentKey, i.currentValue, i.err, i.prefix = nil, nil, nil, nil, nil
 }

postgres/iterator_test.go

@@ -0,0 +1,513 @@
+// VulcanizeDB
+// Copyright © 2020 Vulcanize
+
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package pgipfsethdb_test
+
+import (
+	"database/sql"
+
+	"github.com/ethereum/go-ethereum/ethdb"
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+
+	"github.com/vulcanize/ipfs-ethdb/postgres"
+)
+
+var (
+	iterator            ethdb.Iterator
+	testPrefix          = []byte("testPrefix")
+	testEthKey1         = []byte{'\x01'}
+	testEthKey2         = []byte{'\x01', '\x01'}
+	testEthKey3         = []byte{'\x01', '\x02'}
+	testEthKey4         = []byte{'\x01', '\x0e'}
+	testEthKey5         = []byte{'\x01', '\x02', '\x01'}
+	testEthKey6         = []byte{'\x01', '\x0e', '\x01'}
+	prefixedTestEthKey1 = append(append(testPrefix, pgipfsethdb.KeyDelineation...), testEthKey1...)
+	prefixedTestEthKey2 = append(append(testPrefix, pgipfsethdb.KeyDelineation...), testEthKey2...)
+	prefixedTestEthKey3 = append(append(testPrefix, pgipfsethdb.KeyDelineation...), testEthKey3...)
+	prefixedTestEthKey4 = append(append(testPrefix, pgipfsethdb.KeyDelineation...), testEthKey4...)
+	prefixedTestEthKey5 = append(append(testPrefix, pgipfsethdb.KeyDelineation...), testEthKey5...)
+	prefixedTestEthKey6 = append(append(testPrefix, pgipfsethdb.KeyDelineation...), testEthKey6...)
+	mockValue1          = []byte{1}
+	mockValue2          = []byte{2}
+	mockValue3          = []byte{3}
+	mockValue4          = []byte{4}
+	mockValue5          = []byte{5}
+	mockValue6          = []byte{6}
+)
+
+var _ = Describe("Iterator", func() {
+	BeforeEach(func() {
+		db, err = pgipfsethdb.TestDB()
+		Expect(err).ToNot(HaveOccurred())
+		database = pgipfsethdb.NewDatabase(db)
+		// non-prefixed entries
+		err = database.Put(testEthKey1, mockValue1)
+		Expect(err).ToNot(HaveOccurred())
+		err = database.Put(testEthKey2, mockValue2)
+		Expect(err).ToNot(HaveOccurred())
+		err = database.Put(testEthKey3, mockValue3)
+		Expect(err).ToNot(HaveOccurred())
+		err = database.Put(testEthKey4, mockValue4)
+		Expect(err).ToNot(HaveOccurred())
+		err = database.Put(testEthKey5, mockValue5)
+		Expect(err).ToNot(HaveOccurred())
+		err = database.Put(testEthKey6, mockValue6)
+		Expect(err).ToNot(HaveOccurred())
+		// prefixed entries
+		err = database.Put(prefixedTestEthKey1, mockValue1)
+		Expect(err).ToNot(HaveOccurred())
+		err = database.Put(prefixedTestEthKey2, mockValue2)
+		Expect(err).ToNot(HaveOccurred())
+		err = database.Put(prefixedTestEthKey3, mockValue3)
+		Expect(err).ToNot(HaveOccurred())
+		err = database.Put(prefixedTestEthKey4, mockValue4)
+		Expect(err).ToNot(HaveOccurred())
+		err = database.Put(prefixedTestEthKey5, mockValue5)
+		Expect(err).ToNot(HaveOccurred())
+		err = database.Put(prefixedTestEthKey6, mockValue6)
+		Expect(err).ToNot(HaveOccurred())
+	})
+	AfterEach(func() {
+		err = pgipfsethdb.ResetTestDB(db)
+		Expect(err).ToNot(HaveOccurred())
+	})
+
+	Describe("NewIterator", func() {
+		It("iterates over the entire key-set (prefixed or not)", func() {
+			iterator = database.NewIterator()
+			Expect(iterator.Value()).To(BeNil())
+			Expect(iterator.Key()).To(BeNil())
+			Expect(iterator.Error()).To(BeNil())
+
+			more := iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(testEthKey1))
+			Expect(iterator.Value()).To(Equal(mockValue1))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(testEthKey2))
+			Expect(iterator.Value()).To(Equal(mockValue2))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(testEthKey3))
+			Expect(iterator.Value()).To(Equal(mockValue3))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(testEthKey5))
+			Expect(iterator.Value()).To(Equal(mockValue5))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(testEthKey4))
+			Expect(iterator.Value()).To(Equal(mockValue4))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(testEthKey6))
+			Expect(iterator.Value()).To(Equal(mockValue6))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(prefixedTestEthKey1))
+			Expect(iterator.Value()).To(Equal(mockValue1))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(prefixedTestEthKey2))
+			Expect(iterator.Value()).To(Equal(mockValue2))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(prefixedTestEthKey3))
+			Expect(iterator.Value()).To(Equal(mockValue3))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(prefixedTestEthKey5))
+			Expect(iterator.Value()).To(Equal(mockValue5))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(prefixedTestEthKey4))
+			Expect(iterator.Value()).To(Equal(mockValue4))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(prefixedTestEthKey6))
+			Expect(iterator.Value()).To(Equal(mockValue6))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).ToNot(BeTrue())
+			Expect(iterator.Value()).To(BeNil())
+			Expect(iterator.Key()).To(BeNil())
+			Expect(iterator.Error()).To(Equal(sql.ErrNoRows))
+		})
+	})
+
+	Describe("NewIteratorWithPrefix", func() {
+		It("iterates over all db entries that have the provided prefix", func() {
+			iterator = database.NewIteratorWithPrefix(testPrefix)
+			Expect(iterator.Value()).To(BeNil())
+			Expect(iterator.Key()).To(BeNil())
+			Expect(iterator.Error()).To(BeNil())
+
+			more := iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(prefixedTestEthKey1))
+			Expect(iterator.Value()).To(Equal(mockValue1))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(prefixedTestEthKey2))
+			Expect(iterator.Value()).To(Equal(mockValue2))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(prefixedTestEthKey3))
+			Expect(iterator.Value()).To(Equal(mockValue3))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(prefixedTestEthKey5))
+			Expect(iterator.Value()).To(Equal(mockValue5))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(prefixedTestEthKey4))
+			Expect(iterator.Value()).To(Equal(mockValue4))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(prefixedTestEthKey6))
+			Expect(iterator.Value()).To(Equal(mockValue6))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).ToNot(BeTrue())
+			Expect(iterator.Value()).To(BeNil())
+			Expect(iterator.Key()).To(BeNil())
+			Expect(iterator.Error()).To(Equal(sql.ErrNoRows))
+		})
+
+		It("behaves as no prefix is provided if prefix is nil", func() {
+			iterator = database.NewIteratorWithPrefix(nil)
+			Expect(iterator.Value()).To(BeNil())
+			Expect(iterator.Key()).To(BeNil())
+			Expect(iterator.Error()).To(BeNil())
+
+			more := iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(testEthKey1))
+			Expect(iterator.Value()).To(Equal(mockValue1))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(testEthKey2))
+			Expect(iterator.Value()).To(Equal(mockValue2))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(testEthKey3))
+			Expect(iterator.Value()).To(Equal(mockValue3))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(testEthKey5))
+			Expect(iterator.Value()).To(Equal(mockValue5))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(testEthKey4))
+			Expect(iterator.Value()).To(Equal(mockValue4))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(testEthKey6))
+			Expect(iterator.Value()).To(Equal(mockValue6))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(prefixedTestEthKey1))
+			Expect(iterator.Value()).To(Equal(mockValue1))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(prefixedTestEthKey2))
+			Expect(iterator.Value()).To(Equal(mockValue2))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(prefixedTestEthKey3))
+			Expect(iterator.Value()).To(Equal(mockValue3))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(prefixedTestEthKey5))
+			Expect(iterator.Value()).To(Equal(mockValue5))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(prefixedTestEthKey4))
+			Expect(iterator.Value()).To(Equal(mockValue4))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(prefixedTestEthKey6))
+			Expect(iterator.Value()).To(Equal(mockValue6))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).ToNot(BeTrue())
+			Expect(iterator.Value()).To(BeNil())
+			Expect(iterator.Key()).To(BeNil())
+			Expect(iterator.Error()).To(Equal(sql.ErrNoRows))
+		})
+
+		It("considers empty but non-nil []byte a valid prefix, which precludes iteration over any other prefixed keys", func() {
+			iterator = database.NewIteratorWithPrefix([]byte{})
+			Expect(iterator.Value()).To(BeNil())
+			Expect(iterator.Key()).To(BeNil())
+			Expect(iterator.Error()).To(BeNil())
+
+			more := iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(testEthKey1))
+			Expect(iterator.Value()).To(Equal(mockValue1))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(testEthKey2))
+			Expect(iterator.Value()).To(Equal(mockValue2))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(testEthKey3))
+			Expect(iterator.Value()).To(Equal(mockValue3))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(testEthKey5))
+			Expect(iterator.Value()).To(Equal(mockValue5))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(testEthKey4))
+			Expect(iterator.Value()).To(Equal(mockValue4))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(testEthKey6))
+			Expect(iterator.Value()).To(Equal(mockValue6))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).ToNot(BeTrue())
+			Expect(iterator.Value()).To(BeNil())
+			Expect(iterator.Key()).To(BeNil())
+			Expect(iterator.Error()).To(Equal(sql.ErrNoRows))
+		})
+	})
+
+	Describe("NewIteratorWithStart", func() {
+		It("iterates over the entire key-set (prefixed or not) starting with at the provided path", func() {
+			iterator = database.NewIteratorWithStart(testEthKey2)
+			Expect(iterator.Value()).To(BeNil())
+			Expect(iterator.Key()).To(Equal(testEthKey2))
+			Expect(iterator.Error()).To(BeNil())
+
+			more := iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(testEthKey2))
+			Expect(iterator.Value()).To(Equal(mockValue2))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(testEthKey3))
+			Expect(iterator.Value()).To(Equal(mockValue3))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(testEthKey5))
+			Expect(iterator.Value()).To(Equal(mockValue5))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(testEthKey4))
+			Expect(iterator.Value()).To(Equal(mockValue4))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(testEthKey6))
+			Expect(iterator.Value()).To(Equal(mockValue6))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(prefixedTestEthKey1))
+			Expect(iterator.Value()).To(Equal(mockValue1))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(prefixedTestEthKey2))
+			Expect(iterator.Value()).To(Equal(mockValue2))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(prefixedTestEthKey3))
+			Expect(iterator.Value()).To(Equal(mockValue3))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(prefixedTestEthKey5))
+			Expect(iterator.Value()).To(Equal(mockValue5))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(prefixedTestEthKey4))
+			Expect(iterator.Value()).To(Equal(mockValue4))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(prefixedTestEthKey6))
+			Expect(iterator.Value()).To(Equal(mockValue6))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).ToNot(BeTrue())
+			Expect(iterator.Value()).To(BeNil())
+			Expect(iterator.Key()).To(BeNil())
+			Expect(iterator.Error()).To(Equal(sql.ErrNoRows))
+		})
+
+		It("iterates over the entire key-set (prefixed or not) starting with at the provided path", func() {
+			iterator = database.NewIteratorWithStart(prefixedTestEthKey3)
+			Expect(iterator.Value()).To(BeNil())
+			Expect(iterator.Key()).To(Equal(prefixedTestEthKey3))
+			Expect(iterator.Error()).To(BeNil())
+
+			more := iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(prefixedTestEthKey3))
+			Expect(iterator.Value()).To(Equal(mockValue3))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(prefixedTestEthKey5))
+			Expect(iterator.Value()).To(Equal(mockValue5))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(prefixedTestEthKey4))
+			Expect(iterator.Value()).To(Equal(mockValue4))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(prefixedTestEthKey6))
+			Expect(iterator.Value()).To(Equal(mockValue6))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).ToNot(BeTrue())
+			Expect(iterator.Value()).To(BeNil())
+			Expect(iterator.Key()).To(BeNil())
+			Expect(iterator.Error()).To(Equal(sql.ErrNoRows))
+		})
+	})
+
+	Describe("Release", func() {
+		It("releases resources associated with the Iterator", func() {
+			iterator = database.NewIteratorWithStart(testEthKey2)
+			Expect(iterator.Value()).To(BeNil())
+			Expect(iterator.Key()).To(Equal(testEthKey2))
+			Expect(iterator.Error()).To(BeNil())
+
+			more := iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(testEthKey2))
+			Expect(iterator.Value()).To(Equal(mockValue2))
+			Expect(iterator.Error()).To(BeNil())
+
+			iterator.Release()
+			iterator.Release() // check that we don't panic if called multiple times
+
+			Expect(iterator.Value()).To(BeNil())
+			Expect(iterator.Key()).To(BeNil())
+			Expect(iterator.Error()).To(BeNil())
+			Expect(func() { iterator.Next() }).To(Panic()) // check that we panic if we try to use released iterator
+
+			// We can still create a new iterator from the same backing db
+			iterator = database.NewIteratorWithStart(testEthKey2)
+			Expect(iterator.Value()).To(BeNil())
+			Expect(iterator.Key()).To(Equal(testEthKey2))
+			Expect(iterator.Error()).To(BeNil())
+
+			more = iterator.Next()
+			Expect(more).To(BeTrue())
+			Expect(iterator.Key()).To(Equal(testEthKey2))
+			Expect(iterator.Value()).To(Equal(mockValue2))
+			Expect(iterator.Error()).To(BeNil())
+		})
+	})
+})