Remove Prev from Iterator

db/c_level_db.go

@@ -202,13 +202,6 @@ func (c cLevelDBIterator) Next() {
 	c.itr.Next()
 }
 
-func (c cLevelDBIterator) Prev() {
-	if !c.itr.Valid() {
-		panic("cLevelDBIterator Prev() called when invalid")
-	}
-	c.itr.Prev()
-}
-
 func (c cLevelDBIterator) Release() {
 	c.itr.Close()
 }

db/cache_db_test.go

@@ -1,83 +0,0 @@
-package db
-
-import (
-	"testing"
-
-	"github.com/stretchr/testify/require"
-)
-
-func bz(s string) []byte { return []byte(s) }
-
-func TestCacheDB(t *testing.T) {
-	mem := NewMemDB()
-	cdb := mem.CacheDB()
-
-	require.Empty(t, cdb.Get(bz("key1")), "Expected `key1` to be empty")
-
-	mem.Set(bz("key1"), bz("value1"))
-	cdb.Set(bz("key1"), bz("value1"))
-	require.Equal(t, bz("value1"), cdb.Get(bz("key1")))
-
-	cdb.Set(bz("key1"), bz("value2"))
-	require.Equal(t, bz("value2"), cdb.Get(bz("key1")))
-	require.Equal(t, bz("value1"), mem.Get(bz("key1")))
-
-	cdb.Write()
-	require.Equal(t, bz("value2"), mem.Get(bz("key1")))
-
-	require.Panics(t, func() { cdb.Write() }, "Expected second cdb.Write() to fail")
-
-	cdb = mem.CacheDB()
-	cdb.Delete(bz("key1"))
-	require.Empty(t, cdb.Get(bz("key1")))
-	require.Equal(t, mem.Get(bz("key1")), bz("value2"))
-
-	cdb.Write()
-	require.Empty(t, cdb.Get(bz("key1")), "Expected `key1` to be empty")
-	require.Empty(t, mem.Get(bz("key1")), "Expected `key1` to be empty")
-}
-
-func TestCacheDBWriteLock(t *testing.T) {
-	mem := NewMemDB()
-	cdb := mem.CacheDB()
-	require.NotPanics(t, func() { cdb.Write() })
-	require.Panics(t, func() { cdb.Write() })
-	cdb = mem.CacheDB()
-	require.NotPanics(t, func() { cdb.Write() })
-	require.Panics(t, func() { cdb.Write() })
-}
-
-func TestCacheDBWriteLockNested(t *testing.T) {
-	mem := NewMemDB()
-	cdb := mem.CacheDB()
-	cdb2 := cdb.CacheDB()
-	require.NotPanics(t, func() { cdb2.Write() })
-	require.Panics(t, func() { cdb2.Write() })
-	cdb2 = cdb.CacheDB()
-	require.NotPanics(t, func() { cdb2.Write() })
-	require.Panics(t, func() { cdb2.Write() })
-}
-
-func TestCacheDBNested(t *testing.T) {
-	mem := NewMemDB()
-	cdb := mem.CacheDB()
-	cdb.Set(bz("key1"), bz("value1"))
-
-	require.Empty(t, mem.Get(bz("key1")))
-	require.Equal(t, bz("value1"), cdb.Get(bz("key1")))
-	cdb2 := cdb.CacheDB()
-	require.Equal(t, bz("value1"), cdb2.Get(bz("key1")))
-
-	cdb2.Set(bz("key1"), bz("VALUE2"))
-	require.Equal(t, []byte(nil), mem.Get(bz("key1")))
-	require.Equal(t, bz("value1"), cdb.Get(bz("key1")))
-	require.Equal(t, bz("VALUE2"), cdb2.Get(bz("key1")))
-
-	cdb2.Write()
-	require.Equal(t, []byte(nil), mem.Get(bz("key1")))
-	require.Equal(t, bz("VALUE2"), cdb.Get(bz("key1")))
-
-	cdb.Write()
-	require.Equal(t, bz("VALUE2"), mem.Get(bz("key1")))
-
-}

db/common_test.go

@@ -23,16 +23,6 @@ func checkNextPanics(t *testing.T, itr Iterator) {
 	assert.Panics(t, func() { itr.Next() }, "checkNextPanics expected panic but didn't")
 }
 
-func checkPrevPanics(t *testing.T, itr Iterator) {
-	assert.Panics(t, func() { itr.Prev() }, "checkPrevPanics expected panic but didn't")
-}
-
-func checkPrev(t *testing.T, itr Iterator, expected bool) {
-	itr.Prev()
-	valid := itr.Valid()
-	assert.Equal(t, expected, valid)
-}
-
 func checkItem(t *testing.T, itr Iterator, key []byte, value []byte) {
 	k, v := itr.Key(), itr.Value()
 	assert.Exactly(t, key, k)
@@ -44,7 +34,6 @@ func checkInvalid(t *testing.T, itr Iterator) {
 	checkKeyPanics(t, itr)
 	checkValuePanics(t, itr)
 	checkNextPanics(t, itr)
-	checkPrevPanics(t, itr)
 }
 
 func checkKeyPanics(t *testing.T, itr Iterator) {
@@ -67,7 +56,7 @@ func TestDBIteratorSingleKey(t *testing.T) {
 		t.Run(fmt.Sprintf("Backend %s", backend), func(t *testing.T) {
 			db := newTempDB(t, backend)
 			db.SetSync(bz("1"), bz("value_1"))
-			itr := db.Iterator()
+			itr := db.Iterator(BeginningKey(), EndingKey())
 
 			checkValid(t, itr, true)
 			checkNext(t, itr, false)
@@ -88,15 +77,12 @@ func TestDBIteratorTwoKeys(t *testing.T) {
 			db.SetSync(bz("2"), bz("value_1"))
 
 			{ // Fail by calling Next too much
-				itr := db.Iterator()
+				itr := db.Iterator(BeginningKey(), EndingKey())
 				checkValid(t, itr, true)
 
 				for i := 0; i < 10; i++ {
 					checkNext(t, itr, true)
 					checkValid(t, itr, true)
-
-					checkPrev(t, itr, true)
-					checkValid(t, itr, true)
 				}
 
 				checkNext(t, itr, true)
@@ -110,27 +96,6 @@ func TestDBIteratorTwoKeys(t *testing.T) {
 				// Once invalid...
 				checkInvalid(t, itr)
 			}
-
-			{ // Fail by calling Prev too much
-				itr := db.Iterator()
-				checkValid(t, itr, true)
-
-				for i := 0; i < 10; i++ {
-					checkNext(t, itr, true)
-					checkValid(t, itr, true)
-
-					checkPrev(t, itr, true)
-					checkValid(t, itr, true)
-				}
-
-				checkPrev(t, itr, false)
-				checkValid(t, itr, false)
-
-				checkPrevPanics(t, itr)
-
-				// Once invalid...
-				checkInvalid(t, itr)
-			}
 		})
 	}
 }
@@ -139,32 +104,30 @@ func TestDBIteratorEmpty(t *testing.T) {
 	for backend, _ := range backends {
 		t.Run(fmt.Sprintf("Backend %s", backend), func(t *testing.T) {
 			db := newTempDB(t, backend)
-			itr := db.Iterator()
+			itr := db.Iterator(BeginningKey(), EndingKey())
 
 			checkInvalid(t, itr)
 		})
 	}
 }
 
-func TestDBIteratorEmptySeek(t *testing.T) {
+func TestDBIteratorEmptyBeginAfter(t *testing.T) {
 	for backend, _ := range backends {
 		t.Run(fmt.Sprintf("Backend %s", backend), func(t *testing.T) {
 			db := newTempDB(t, backend)
-			itr := db.Iterator()
+			itr := db.Iterator(bz("1"), EndingKey())
-			itr.Seek(bz("1"))
 
 			checkInvalid(t, itr)
 		})
 	}
 }
 
-func TestDBIteratorBadSeek(t *testing.T) {
+func TestDBIteratorNonemptyBeginAfter(t *testing.T) {
 	for backend, _ := range backends {
 		t.Run(fmt.Sprintf("Backend %s", backend), func(t *testing.T) {
 			db := newTempDB(t, backend)
 			db.SetSync(bz("1"), bz("value_1"))
-			itr := db.Iterator()
+			itr := db.Iterator(bz("2"), EndingKey())
-			itr.Seek(bz("2"))
 
 			checkInvalid(t, itr)
 		})

db/mem_db_test.go

@@ -19,7 +19,7 @@ func TestMemDbIterator(t *testing.T) {
 		db.Set(k, value)
 	}
 
-	iter := db.Iterator()
+	iter := db.Iterator(BeginningKey(), EndingKey())
 	i := 0
 	for ; iter.Valid(); iter.Next() {
 		assert.Equal(t, db.Get(iter.Key()), iter.Value(), "values dont match for key")

db/types.go

@@ -90,17 +90,11 @@ type Iterator interface {
 	Valid() bool
 
 	// Next moves the iterator to the next sequential key in the database, as
-	// defined by the Comparator in the ReadOptions used to create this Iterator.
+	// defined by order of iteration.
 	//
 	// If Valid returns false, this method will panic.
 	Next()
 
-	// Prev moves the iterator to the previous sequential key in the database, as
-	// defined by the Comparator in the ReadOptions used to create this Iterator.
-	//
-	// If Valid returns false, this method will panic.
-	Prev()
-
 	// Key returns the key of the cursor.
 	//
 	// If Valid returns false, this method will panic.
@@ -120,3 +114,8 @@ type Iterator interface {
 	// Release deallocates the given Iterator.
 	Release()
 }
+
+// For testing convenience.
+func bz(s string) []byte {
+	return []byte(s)
+}

db/util_test.go

@@ -66,7 +66,6 @@ func TestPrefixIteratorMatches1N(t *testing.T) {
 			db.SetSync(bz("a/1"), bz("value_1"))
 			db.SetSync(bz("a/3"), bz("value_3"))
 			itr := IteratePrefix(db, []byte("a/"))
-			itr.Seek(bz("a/1"))
 
 			checkValid(t, itr, true)
 			checkItem(t, itr, bz("a/1"), bz("value_1"))
@@ -82,32 +81,6 @@ func TestPrefixIteratorMatches1N(t *testing.T) {
 	}
 }
 
-// Search for a/1, fail by too much Prev()
-func TestPrefixIteratorMatches1P(t *testing.T) {
-	for backend, _ := range backends {
-		t.Run(fmt.Sprintf("Prefix w/ backend %s", backend), func(t *testing.T) {
-			db := newTempDB(t, backend)
-			db.SetSync(bz("a/1"), bz("value_1"))
-			db.SetSync(bz("a/3"), bz("value_3"))
-			itr := IteratePrefix(db, []byte("a/"))
-			itr.Seek(bz("a/1"))
-
-			checkValid(t, itr, true)
-			checkItem(t, itr, bz("a/1"), bz("value_1"))
-			checkNext(t, itr, true)
-			checkItem(t, itr, bz("a/3"), bz("value_3"))
-			checkPrev(t, itr, true)
-			checkItem(t, itr, bz("a/1"), bz("value_1"))
-
-			// Bad!
-			checkPrev(t, itr, false)
-
-			// Once invalid...
-			checkInvalid(t, itr)
-		})
-	}
-}
-
 // Search for a/2, fail by too much Next()
 func TestPrefixIteratorMatches2N(t *testing.T) {
 	for backend, _ := range backends {
@@ -116,13 +89,11 @@ func TestPrefixIteratorMatches2N(t *testing.T) {
 			db.SetSync(bz("a/1"), bz("value_1"))
 			db.SetSync(bz("a/3"), bz("value_3"))
 			itr := IteratePrefix(db, []byte("a/"))
-			itr.Seek(bz("a/2"))
 
 			checkValid(t, itr, true)
-			checkItem(t, itr, bz("a/3"), bz("value_3"))
-			checkPrev(t, itr, true)
 			checkItem(t, itr, bz("a/1"), bz("value_1"))
 			checkNext(t, itr, true)
+			checkValid(t, itr, true)
 			checkItem(t, itr, bz("a/3"), bz("value_3"))
 
 			// Bad!
@@ -134,30 +105,6 @@ func TestPrefixIteratorMatches2N(t *testing.T) {
 	}
 }
 
-// Search for a/2, fail by too much Prev()
-func TestPrefixIteratorMatches2P(t *testing.T) {
-	for backend, _ := range backends {
-		t.Run(fmt.Sprintf("Prefix w/ backend %s", backend), func(t *testing.T) {
-			db := newTempDB(t, backend)
-			db.SetSync(bz("a/1"), bz("value_1"))
-			db.SetSync(bz("a/3"), bz("value_3"))
-			itr := IteratePrefix(db, []byte("a/"))
-			itr.Seek(bz("a/2"))
-
-			checkValid(t, itr, true)
-			checkItem(t, itr, bz("a/3"), bz("value_3"))
-			checkPrev(t, itr, true)
-			checkItem(t, itr, bz("a/1"), bz("value_1"))
-
-			// Bad!
-			checkPrev(t, itr, false)
-
-			// Once invalid...
-			checkInvalid(t, itr)
-		})
-	}
-}
-
 // Search for a/3, fail by too much Next()
 func TestPrefixIteratorMatches3N(t *testing.T) {
 	for backend, _ := range backends {
@@ -166,11 +113,8 @@ func TestPrefixIteratorMatches3N(t *testing.T) {
 			db.SetSync(bz("a/1"), bz("value_1"))
 			db.SetSync(bz("a/3"), bz("value_3"))
 			itr := IteratePrefix(db, []byte("a/"))
-			itr.Seek(bz("a/3"))
 
 			checkValid(t, itr, true)
-			checkItem(t, itr, bz("a/3"), bz("value_3"))
-			checkPrev(t, itr, true)
 			checkItem(t, itr, bz("a/1"), bz("value_1"))
 			checkNext(t, itr, true)
 			checkItem(t, itr, bz("a/3"), bz("value_3"))
@@ -183,27 +127,3 @@ func TestPrefixIteratorMatches3N(t *testing.T) {
 		})
 	}
 }
-
-// Search for a/3, fail by too much Prev()
-func TestPrefixIteratorMatches3P(t *testing.T) {
-	for backend, _ := range backends {
-		t.Run(fmt.Sprintf("Prefix w/ backend %s", backend), func(t *testing.T) {
-			db := newTempDB(t, backend)
-			db.SetSync(bz("a/1"), bz("value_1"))
-			db.SetSync(bz("a/3"), bz("value_3"))
-			itr := IteratePrefix(db, []byte("a/"))
-			itr.Seek(bz("a/3"))
-
-			checkValid(t, itr, true)
-			checkItem(t, itr, bz("a/3"), bz("value_3"))
-			checkPrev(t, itr, true)
-			checkItem(t, itr, bz("a/1"), bz("value_1"))
-
-			// Bad!
-			checkPrev(t, itr, false)
-
-			// Once invalid...
-			checkInvalid(t, itr)
-		})
-	}
-}