diff --git a/CHANGELOG.md b/CHANGELOG.md
index f3b48f3145..a981779636 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -54,6 +54,7 @@ GRDB adheres to [Semantic Versioning](https://semver.org/).
 - [#443](https://github.com/groue/GRDB.swift/pull/443): In place record update
 - [#444](https://github.com/groue/GRDB.swift/pull/444): Combine Value Observations
 - [#451](https://github.com/groue/GRDB.swift/pull/451): ValueObservation.compactMap
+- [#452](https://github.com/groue/GRDB.swift/pull/452): ValueObservation.mapReducer
 - [#445](https://github.com/groue/GRDB.swift/pull/445): Quality of service and target dispatch queue
 - ValueObservation methods which used to accept a variadic list of observed regions now also accept an array.
 - ValueReducer, the protocol that fuels ValueObservation, is flagged [**:fire: EXPERIMENTAL**](README.md#what-are-experimental-features). It will remain so until more experience has been acquired.
@@ -111,7 +112,11 @@ GRDB adheres to [Semantic Versioning](https://semver.org/).
 +    func compactMap<T>(_ transform: @escaping (Reducer.Value) -> T?)
 +        -> ValueObservation<CompactMapValueReducer<Reducer, T>>
 +}
- 
+
++extension ValueObservation {
++    func mapReducer<R>(_ transform: @escaping (Database, Reducer) throws -> R)
++        -> ValueObservation<R>
++}
  
  struct Configuration {
 +    var qos: DispatchQoS
diff --git a/GRDB.xcodeproj/project.pbxproj b/GRDB.xcodeproj/project.pbxproj
index 64db67dbc2..ca19ec9f61 100755
--- a/GRDB.xcodeproj/project.pbxproj
+++ b/GRDB.xcodeproj/project.pbxproj
@@ -211,6 +211,9 @@
 		564CE4E721B2E06800652B19 /* ValueObservationCompactMapTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 564CE4E521B2E06700652B19 /* ValueObservationCompactMapTests.swift */; };
 		564CE4E921B2E06F00652B19 /* ValueObservationMapTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 564CE4E821B2E06F00652B19 /* ValueObservationMapTests.swift */; };
 		564CE4EA21B2E06F00652B19 /* ValueObservationMapTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 564CE4E821B2E06F00652B19 /* ValueObservationMapTests.swift */; };
+		564CE52021B3129A00652B19 /* ValueObservation+MapReducer.swift in Sources */ = {isa = PBXBuildFile; fileRef = 564CE51F21B3129900652B19 /* ValueObservation+MapReducer.swift */; };
+		564CE52121B3129A00652B19 /* ValueObservation+MapReducer.swift in Sources */ = {isa = PBXBuildFile; fileRef = 564CE51F21B3129900652B19 /* ValueObservation+MapReducer.swift */; };
+		564CE52221B3129A00652B19 /* ValueObservation+MapReducer.swift in Sources */ = {isa = PBXBuildFile; fileRef = 564CE51F21B3129900652B19 /* ValueObservation+MapReducer.swift */; };
 		564E73DF203D50B9000C443C /* JoinSupportTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 564E73DE203D50B9000C443C /* JoinSupportTests.swift */; };
 		564E73E0203D50B9000C443C /* JoinSupportTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 564E73DE203D50B9000C443C /* JoinSupportTests.swift */; };
 		564F9C1E1F069B4E00877A00 /* DatabaseAggregateTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 564F9C1D1F069B4E00877A00 /* DatabaseAggregateTests.swift */; };
@@ -974,6 +977,7 @@
 		564CE4D521B2DEB500652B19 /* ValueObservation+CompactMap.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = "ValueObservation+CompactMap.swift"; sourceTree = "<group>"; };
 		564CE4E521B2E06700652B19 /* ValueObservationCompactMapTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = ValueObservationCompactMapTests.swift; sourceTree = "<group>"; };
 		564CE4E821B2E06F00652B19 /* ValueObservationMapTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = ValueObservationMapTests.swift; sourceTree = "<group>"; };
+		564CE51F21B3129900652B19 /* ValueObservation+MapReducer.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = "ValueObservation+MapReducer.swift"; sourceTree = "<group>"; };
 		564E73DE203D50B9000C443C /* JoinSupportTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = JoinSupportTests.swift; sourceTree = "<group>"; };
 		564F9C1D1F069B4E00877A00 /* DatabaseAggregateTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = DatabaseAggregateTests.swift; sourceTree = "<group>"; };
 		564F9C2C1F075DD200877A00 /* DatabaseFunction.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = DatabaseFunction.swift; sourceTree = "<group>"; };
@@ -1403,6 +1407,7 @@
 				5613ED4F21A95C6D00DC7A68 /* ValueObservation+DatabaseValueConvertible.swift */,
 				5613ED4B21A95C4300DC7A68 /* ValueObservation+FetchableRecord.swift */,
 				5613ED3421A95A5C00DC7A68 /* ValueObservation+Map.swift */,
+				564CE51F21B3129900652B19 /* ValueObservation+MapReducer.swift */,
 				5613ED4721A95C1200DC7A68 /* ValueObservation+Row.swift */,
 				564CE43021AA901800652B19 /* ValueObserver.swift */,
 				5613ED4321A95B2C00DC7A68 /* ValueReducer.swift */,
@@ -2508,6 +2513,7 @@
 				565490C51D5AE236005622CB /* SerializedDatabase.swift in Sources */,
 				56F3E7691E67F8C100BF0F01 /* Fixits-0.101.1.swift in Sources */,
 				5698AC7E1DA37DCB0056AF8C /* VirtualTableModule.swift in Sources */,
+				564CE52221B3129A00652B19 /* ValueObservation+MapReducer.swift in Sources */,
 				5653EB1A20944C7C00F46237 /* ForeignKey.swift in Sources */,
 				5698AC3D1D9E5A590056AF8C /* FTS3Pattern.swift in Sources */,
 				563EF45D2163309F007DAACD /* Inflections.swift in Sources */,
@@ -2658,6 +2664,7 @@
 				56D51D031EA789FA0074638A /* FetchableRecord+TableRecord.swift in Sources */,
 				5653EB1620944C7C00F46237 /* AssociationQuery.swift in Sources */,
 				560D924C1C672C4B00F4F92B /* TableRecord.swift in Sources */,
+				564CE52121B3129A00652B19 /* ValueObservation+MapReducer.swift in Sources */,
 				5653EC132098738B00F46237 /* SQLGenerationContext.swift in Sources */,
 				5657AB121D10899D006283EF /* URL.swift in Sources */,
 				5616AAF2207CD45E00AC3664 /* RequestProtocols.swift in Sources */,
@@ -3118,6 +3125,7 @@
 				566B91131FA4C3F50012D5B0 /* DatabaseCollation.swift in Sources */,
 				5605F1591C672E4000235C62 /* CGFloat.swift in Sources */,
 				5674A7031F307FCD0095F066 /* DatabaseValueConvertible+ReferenceConvertible.swift in Sources */,
+				564CE52021B3129A00652B19 /* ValueObservation+MapReducer.swift in Sources */,
 				5659F4A01EA8D997004A4992 /* Result.swift in Sources */,
 				5605F1631C672E4000235C62 /* Date.swift in Sources */,
 				5605F1711C672E4000235C62 /* DatabaseValueConvertible+RawRepresentable.swift in Sources */,
diff --git a/GRDB/ValueObservation/ValueObservation+Combine.swift b/GRDB/ValueObservation/ValueObservation+Combine.swift
index 64979a307b..da06efc207 100644
--- a/GRDB/ValueObservation/ValueObservation+Combine.swift
+++ b/GRDB/ValueObservation/ValueObservation+Combine.swift
@@ -12,7 +12,7 @@ extension ValueObservation where Reducer == Void {
                 tracking: { try DatabaseRegion.union(
                     o1.observedRegion($0),
                     o2.observedRegion($0)) },
-                reducer: { try ValueReducers.combine(
+                reducer: { try _combine(
                     o1.makeReducer($0),
                     o2.makeReducer($0)) })
     }
@@ -32,7 +32,7 @@ extension ValueObservation where Reducer == Void {
                     o1.observedRegion($0),
                     o2.observedRegion($0),
                     o3.observedRegion($0)) },
-                reducer: { try ValueReducers.combine(
+                reducer: { try _combine(
                     o1.makeReducer($0),
                     o2.makeReducer($0),
                     o3.makeReducer($0)) })
@@ -55,7 +55,7 @@ extension ValueObservation where Reducer == Void {
                     o2.observedRegion($0),
                     o3.observedRegion($0),
                     o4.observedRegion($0)) },
-                reducer: { try ValueReducers.combine(
+                reducer: { try _combine(
                     o1.makeReducer($0),
                     o2.makeReducer($0),
                     o3.makeReducer($0),
@@ -81,7 +81,7 @@ extension ValueObservation where Reducer == Void {
                     o3.observedRegion($0),
                     o4.observedRegion($0),
                     o5.observedRegion($0)) },
-                reducer: { try ValueReducers.combine(
+                reducer: { try _combine(
                     o1.makeReducer($0),
                     o2.makeReducer($0),
                     o3.makeReducer($0),
@@ -90,186 +90,184 @@ extension ValueObservation where Reducer == Void {
     }
 }
 
-extension ValueReducers {
-    static func combine<R1: ValueReducer, R2: ValueReducer>(
-        _ r1: R1,
-        _ r2: R2)
-        -> AnyValueReducer<
-        (R1.Fetched, R2.Fetched),
-        (R1.Value, R2.Value)>
-    {
-        var r1 = r1
-        var r2 = r2
-        var prev1: R1.Value?
-        var prev2: R2.Value?
-        func fetch(db: Database) throws -> (R1.Fetched, R2.Fetched) {
-            return try (
-                r1.fetch(db),
-                r2.fetch(db))
+private func _combine<R1: ValueReducer, R2: ValueReducer>(
+    _ r1: R1,
+    _ r2: R2)
+    -> AnyValueReducer<
+    (R1.Fetched, R2.Fetched),
+    (R1.Value, R2.Value)>
+{
+    var r1 = r1
+    var r2 = r2
+    var prev1: R1.Value?
+    var prev2: R2.Value?
+    func fetch(db: Database) throws -> (R1.Fetched, R2.Fetched) {
+        return try (
+            r1.fetch(db),
+            r2.fetch(db))
+    }
+    func value(tuple: (R1.Fetched, R2.Fetched)) -> (R1.Value, R2.Value)? {
+        let v1 = r1.value(tuple.0)
+        let v2 = r2.value(tuple.1)
+        defer {
+            if let v1 = v1 { prev1 = v1 }
+            if let v2 = v2 { prev2 = v2 }
         }
-        func value(tuple: (R1.Fetched, R2.Fetched)) -> (R1.Value, R2.Value)? {
-            let v1 = r1.value(tuple.0)
-            let v2 = r2.value(tuple.1)
-            defer {
-                if let v1 = v1 { prev1 = v1 }
-                if let v2 = v2 { prev2 = v2 }
-            }
-            if  v1 != nil || v2 != nil,
-                let c1 = v1 ?? prev1,
-                let c2 = v2 ?? prev2
-            {
-                return (c1, c2)
-            } else {
-                return nil
-            }
+        if  v1 != nil || v2 != nil,
+            let c1 = v1 ?? prev1,
+            let c2 = v2 ?? prev2
+        {
+            return (c1, c2)
+        } else {
+            return nil
         }
-        return AnyValueReducer(fetch: fetch, value: value)
     }
-    
-    static func combine<R1: ValueReducer, R2: ValueReducer, R3: ValueReducer>(
-        _ r1: R1,
-        _ r2: R2,
-        _ r3: R3)
-        -> AnyValueReducer<
-        (R1.Fetched, R2.Fetched, R3.Fetched),
-        (R1.Value, R2.Value, R3.Value)>
-    {
-        var r1 = r1
-        var r2 = r2
-        var r3 = r3
-        var prev1: R1.Value?
-        var prev2: R2.Value?
-        var prev3: R3.Value?
-        func fetch(db: Database) throws -> (R1.Fetched, R2.Fetched, R3.Fetched) {
-            return try (
-                r1.fetch(db),
-                r2.fetch(db),
-                r3.fetch(db))
+    return AnyValueReducer(fetch: fetch, value: value)
+}
+
+private func _combine<R1: ValueReducer, R2: ValueReducer, R3: ValueReducer>(
+    _ r1: R1,
+    _ r2: R2,
+    _ r3: R3)
+    -> AnyValueReducer<
+    (R1.Fetched, R2.Fetched, R3.Fetched),
+    (R1.Value, R2.Value, R3.Value)>
+{
+    var r1 = r1
+    var r2 = r2
+    var r3 = r3
+    var prev1: R1.Value?
+    var prev2: R2.Value?
+    var prev3: R3.Value?
+    func fetch(db: Database) throws -> (R1.Fetched, R2.Fetched, R3.Fetched) {
+        return try (
+            r1.fetch(db),
+            r2.fetch(db),
+            r3.fetch(db))
+    }
+    func value(tuple: (R1.Fetched, R2.Fetched, R3.Fetched)) -> (R1.Value, R2.Value, R3.Value)? {
+        let v1 = r1.value(tuple.0)
+        let v2 = r2.value(tuple.1)
+        let v3 = r3.value(tuple.2)
+        defer {
+            if let v1 = v1 { prev1 = v1 }
+            if let v2 = v2 { prev2 = v2 }
+            if let v3 = v3 { prev3 = v3 }
         }
-        func value(tuple: (R1.Fetched, R2.Fetched, R3.Fetched)) -> (R1.Value, R2.Value, R3.Value)? {
-            let v1 = r1.value(tuple.0)
-            let v2 = r2.value(tuple.1)
-            let v3 = r3.value(tuple.2)
-            defer {
-                if let v1 = v1 { prev1 = v1 }
-                if let v2 = v2 { prev2 = v2 }
-                if let v3 = v3 { prev3 = v3 }
-            }
-            if  v1 != nil || v2 != nil || v3 != nil,
-                let c1 = v1 ?? prev1,
-                let c2 = v2 ?? prev2,
-                let c3 = v3 ?? prev3
-            {
-                return (c1, c2, c3)
-            } else {
-                return nil
-            }
+        if  v1 != nil || v2 != nil || v3 != nil,
+            let c1 = v1 ?? prev1,
+            let c2 = v2 ?? prev2,
+            let c3 = v3 ?? prev3
+        {
+            return (c1, c2, c3)
+        } else {
+            return nil
         }
-        return AnyValueReducer(fetch: fetch, value: value)
     }
-    
-    static func combine<R1: ValueReducer, R2: ValueReducer, R3: ValueReducer, R4: ValueReducer>(
-        _ r1: R1,
-        _ r2: R2,
-        _ r3: R3,
-        _ r4: R4)
-        -> AnyValueReducer<
-        (R1.Fetched, R2.Fetched, R3.Fetched, R4.Fetched),
-        (R1.Value, R2.Value, R3.Value, R4.Value)>
-    {
-        var r1 = r1
-        var r2 = r2
-        var r3 = r3
-        var r4 = r4
-        var prev1: R1.Value?
-        var prev2: R2.Value?
-        var prev3: R3.Value?
-        var prev4: R4.Value?
-        func fetch(db: Database) throws -> (R1.Fetched, R2.Fetched, R3.Fetched, R4.Fetched) {
-            return try (
-                r1.fetch(db),
-                r2.fetch(db),
-                r3.fetch(db),
-                r4.fetch(db))
+    return AnyValueReducer(fetch: fetch, value: value)
+}
+
+private func _combine<R1: ValueReducer, R2: ValueReducer, R3: ValueReducer, R4: ValueReducer>(
+    _ r1: R1,
+    _ r2: R2,
+    _ r3: R3,
+    _ r4: R4)
+    -> AnyValueReducer<
+    (R1.Fetched, R2.Fetched, R3.Fetched, R4.Fetched),
+    (R1.Value, R2.Value, R3.Value, R4.Value)>
+{
+    var r1 = r1
+    var r2 = r2
+    var r3 = r3
+    var r4 = r4
+    var prev1: R1.Value?
+    var prev2: R2.Value?
+    var prev3: R3.Value?
+    var prev4: R4.Value?
+    func fetch(db: Database) throws -> (R1.Fetched, R2.Fetched, R3.Fetched, R4.Fetched) {
+        return try (
+            r1.fetch(db),
+            r2.fetch(db),
+            r3.fetch(db),
+            r4.fetch(db))
+    }
+    func value(tuple: (R1.Fetched, R2.Fetched, R3.Fetched, R4.Fetched)) -> (R1.Value, R2.Value, R3.Value, R4.Value)? {
+        let v1 = r1.value(tuple.0)
+        let v2 = r2.value(tuple.1)
+        let v3 = r3.value(tuple.2)
+        let v4 = r4.value(tuple.3)
+        defer {
+            if let v1 = v1 { prev1 = v1 }
+            if let v2 = v2 { prev2 = v2 }
+            if let v3 = v3 { prev3 = v3 }
+            if let v4 = v4 { prev4 = v4 }
         }
-        func value(tuple: (R1.Fetched, R2.Fetched, R3.Fetched, R4.Fetched)) -> (R1.Value, R2.Value, R3.Value, R4.Value)? {
-            let v1 = r1.value(tuple.0)
-            let v2 = r2.value(tuple.1)
-            let v3 = r3.value(tuple.2)
-            let v4 = r4.value(tuple.3)
-            defer {
-                if let v1 = v1 { prev1 = v1 }
-                if let v2 = v2 { prev2 = v2 }
-                if let v3 = v3 { prev3 = v3 }
-                if let v4 = v4 { prev4 = v4 }
-            }
-            if  v1 != nil || v2 != nil || v3 != nil || v4 != nil,
-                let c1 = v1 ?? prev1,
-                let c2 = v2 ?? prev2,
-                let c3 = v3 ?? prev3,
-                let c4 = v4 ?? prev4
-            {
-                return (c1, c2, c3, c4)
-            } else {
-                return nil
-            }
+        if  v1 != nil || v2 != nil || v3 != nil || v4 != nil,
+            let c1 = v1 ?? prev1,
+            let c2 = v2 ?? prev2,
+            let c3 = v3 ?? prev3,
+            let c4 = v4 ?? prev4
+        {
+            return (c1, c2, c3, c4)
+        } else {
+            return nil
         }
-        return AnyValueReducer(fetch: fetch, value: value)
     }
-    
-    static func combine<R1: ValueReducer, R2: ValueReducer, R3: ValueReducer, R4: ValueReducer, R5: ValueReducer>(
-        _ r1: R1,
-        _ r2: R2,
-        _ r3: R3,
-        _ r4: R4,
-        _ r5: R5)
-        -> AnyValueReducer<
-        (R1.Fetched, R2.Fetched, R3.Fetched, R4.Fetched, R5.Fetched),
-        (R1.Value, R2.Value, R3.Value, R4.Value, R5.Value)>
-    {
-        var r1 = r1
-        var r2 = r2
-        var r3 = r3
-        var r4 = r4
-        var r5 = r5
-        var prev1: R1.Value?
-        var prev2: R2.Value?
-        var prev3: R3.Value?
-        var prev4: R4.Value?
-        var prev5: R5.Value?
-        func fetch(db: Database) throws -> (R1.Fetched, R2.Fetched, R3.Fetched, R4.Fetched, R5.Fetched) {
-            return try (
-                r1.fetch(db),
-                r2.fetch(db),
-                r3.fetch(db),
-                r4.fetch(db),
-                r5.fetch(db))
+    return AnyValueReducer(fetch: fetch, value: value)
+}
+
+private func _combine<R1: ValueReducer, R2: ValueReducer, R3: ValueReducer, R4: ValueReducer, R5: ValueReducer>(
+    _ r1: R1,
+    _ r2: R2,
+    _ r3: R3,
+    _ r4: R4,
+    _ r5: R5)
+    -> AnyValueReducer<
+    (R1.Fetched, R2.Fetched, R3.Fetched, R4.Fetched, R5.Fetched),
+    (R1.Value, R2.Value, R3.Value, R4.Value, R5.Value)>
+{
+    var r1 = r1
+    var r2 = r2
+    var r3 = r3
+    var r4 = r4
+    var r5 = r5
+    var prev1: R1.Value?
+    var prev2: R2.Value?
+    var prev3: R3.Value?
+    var prev4: R4.Value?
+    var prev5: R5.Value?
+    func fetch(db: Database) throws -> (R1.Fetched, R2.Fetched, R3.Fetched, R4.Fetched, R5.Fetched) {
+        return try (
+            r1.fetch(db),
+            r2.fetch(db),
+            r3.fetch(db),
+            r4.fetch(db),
+            r5.fetch(db))
+    }
+    func value(tuple: (R1.Fetched, R2.Fetched, R3.Fetched, R4.Fetched, R5.Fetched)) -> (R1.Value, R2.Value, R3.Value, R4.Value, R5.Value)? {
+        let v1 = r1.value(tuple.0)
+        let v2 = r2.value(tuple.1)
+        let v3 = r3.value(tuple.2)
+        let v4 = r4.value(tuple.3)
+        let v5 = r5.value(tuple.4)
+        defer {
+            if let v1 = v1 { prev1 = v1 }
+            if let v2 = v2 { prev2 = v2 }
+            if let v3 = v3 { prev3 = v3 }
+            if let v4 = v4 { prev4 = v4 }
+            if let v5 = v5 { prev5 = v5 }
         }
-        func value(tuple: (R1.Fetched, R2.Fetched, R3.Fetched, R4.Fetched, R5.Fetched)) -> (R1.Value, R2.Value, R3.Value, R4.Value, R5.Value)? {
-            let v1 = r1.value(tuple.0)
-            let v2 = r2.value(tuple.1)
-            let v3 = r3.value(tuple.2)
-            let v4 = r4.value(tuple.3)
-            let v5 = r5.value(tuple.4)
-            defer {
-                if let v1 = v1 { prev1 = v1 }
-                if let v2 = v2 { prev2 = v2 }
-                if let v3 = v3 { prev3 = v3 }
-                if let v4 = v4 { prev4 = v4 }
-                if let v5 = v5 { prev5 = v5 }
-            }
-            if  v1 != nil || v2 != nil || v3 != nil || v4 != nil || v5 != nil,
-                let c1 = v1 ?? prev1,
-                let c2 = v2 ?? prev2,
-                let c3 = v3 ?? prev3,
-                let c4 = v4 ?? prev4,
-                let c5 = v5 ?? prev5
-            {
-                return (c1, c2, c3, c4, c5)
-            } else {
-                return nil
-            }
+        if  v1 != nil || v2 != nil || v3 != nil || v4 != nil || v5 != nil,
+            let c1 = v1 ?? prev1,
+            let c2 = v2 ?? prev2,
+            let c3 = v3 ?? prev3,
+            let c4 = v4 ?? prev4,
+            let c5 = v5 ?? prev5
+        {
+            return (c1, c2, c3, c4, c5)
+        } else {
+            return nil
         }
-        return AnyValueReducer(fetch: fetch, value: value)
     }
+    return AnyValueReducer(fetch: fetch, value: value)
 }
diff --git a/GRDB/ValueObservation/ValueObservation+CompactMap.swift b/GRDB/ValueObservation/ValueObservation+CompactMap.swift
index 66edf990e5..5778b5ab5c 100644
--- a/GRDB/ValueObservation/ValueObservation+CompactMap.swift
+++ b/GRDB/ValueObservation/ValueObservation+CompactMap.swift
@@ -5,18 +5,13 @@ extension ValueObservation where Reducer: ValueReducer {
     public func compactMap<T>(_ transform: @escaping (Reducer.Value) -> T?)
         -> ValueObservation<CompactMapValueReducer<Reducer, T>>
     {
-        let makeReducer = self.makeReducer
-        var observation = ValueObservation<CompactMapValueReducer<Reducer, T>>(
-            tracking: observedRegion,
-            reducer: { db in try makeReducer(db).compactMap(transform) })
-        observation.extent = extent
-        observation.scheduling = scheduling
-        observation.requiresWriteAccess = requiresWriteAccess
-        return observation
+        return mapReducer { $1.compactMap(transform) }
     }
 }
 
 extension ValueReducer {
+    /// [**Experimental**](http://github.com/groue/GRDB.swift#what-are-experimental-features)
+    ///
     /// Returns a reducer which outputs the non-nil results of calling the given
     /// transformation which each element emitted by this reducer.
     public func compactMap<T>(_ transform: @escaping (Value) -> T?) -> CompactMapValueReducer<Self, T> {
@@ -24,6 +19,8 @@ extension ValueReducer {
     }
 }
 
+/// [**Experimental**](http://github.com/groue/GRDB.swift#what-are-experimental-features)
+///
 /// See ValueReducer.compactMap(_:)
 ///
 /// :nodoc:
diff --git a/GRDB/ValueObservation/ValueObservation+Count.swift b/GRDB/ValueObservation/ValueObservation+Count.swift
index f455db68f5..fec32c8627 100644
--- a/GRDB/ValueObservation/ValueObservation+Count.swift
+++ b/GRDB/ValueObservation/ValueObservation+Count.swift
@@ -26,7 +26,7 @@ extension ValueObservation where Reducer == Void {
     /// - parameter request: the observed request.
     /// - returns: a ValueObservation.
     public static func trackingCount<Request: FetchRequest>(_ request: Request)
-        -> ValueObservation<ValueReducers.Distinct<Int>>
+        -> ValueObservation<DistinctValueReducer<Int>>
     {
         return ValueObservation.tracking(request, fetchDistinct: request.fetchCount)
     }
diff --git a/GRDB/ValueObservation/ValueObservation+DatabaseValueConvertible.swift b/GRDB/ValueObservation/ValueObservation+DatabaseValueConvertible.swift
index f92572f05e..c32634532e 100644
--- a/GRDB/ValueObservation/ValueObservation+DatabaseValueConvertible.swift
+++ b/GRDB/ValueObservation/ValueObservation+DatabaseValueConvertible.swift
@@ -27,12 +27,12 @@ extension ValueObservation where Reducer == Void {
     /// - parameter request: the observed request.
     /// - returns: a ValueObservation.
     public static func trackingAll<Request: FetchRequest>(_ request: Request)
-        -> ValueObservation<ValueReducers.Values<Request.RowDecoder>>
+        -> ValueObservation<DatabaseValuesReducer<Request>>
         where Request.RowDecoder: DatabaseValueConvertible
     {
-        return ValueObservation<ValueReducers.Values<Request.RowDecoder>>.tracking(
-            request,
-            reducer: { _ in ValueReducers.Values { try DatabaseValue.fetchAll($0, request) } })
+        return ValueObservation<DatabaseValuesReducer<Request>>.tracking(request, reducer: { _ in
+            DatabaseValuesReducer(request: request) }
+        )
     }
     
     /// Creates a ValueObservation which observes *request*, and notifies a
@@ -59,12 +59,11 @@ extension ValueObservation where Reducer == Void {
     /// - parameter request: the observed request.
     /// - returns: a ValueObservation.
     public static func trackingOne<Request: FetchRequest>(_ request: Request)
-        -> ValueObservation<ValueReducers.Value<Request.RowDecoder>>
+        -> ValueObservation<DatabaseValueReducer<Request>>
         where Request.RowDecoder: DatabaseValueConvertible
     {
-        return ValueObservation<ValueReducers.Value<Request.RowDecoder>>.tracking(
-            request,
-            reducer: { _ in ValueReducers.Value { try DatabaseValue.fetchOne($0, request) } })
+        return ValueObservation<DatabaseValueReducer<Request>>.tracking(request, reducer: { _ in DatabaseValueReducer(request: request)
+        })
     }
     
     /// Creates a ValueObservation which observes *request*, and notifies
@@ -92,108 +91,120 @@ extension ValueObservation where Reducer == Void {
     /// - parameter request: the observed request.
     /// - returns: a ValueObservation.
     public static func trackingAll<Request: FetchRequest>(_ request: Request)
-        -> ValueObservation<ValueReducers.OptionalValues<Request.RowDecoder._Wrapped>>
+        -> ValueObservation<OptionalDatabaseValuesReducer<Request>>
         where Request.RowDecoder: _OptionalProtocol,
         Request.RowDecoder._Wrapped: DatabaseValueConvertible
     {
-        return ValueObservation<ValueReducers.OptionalValues<Request.RowDecoder._Wrapped>>.tracking(
-            request,
-            reducer: { _ in ValueReducers.OptionalValues { try DatabaseValue.fetchAll($0, request) } })
+        return ValueObservation<OptionalDatabaseValuesReducer<Request>>.tracking(request, reducer: { _ in
+            OptionalDatabaseValuesReducer(request: request)
+        })
     }
 }
 
-extension ValueReducers {
-    /// A reducer which outputs arrays of values, filtering out consecutive
-    /// identical database values.
-    public struct Values<T: DatabaseValueConvertible>: ValueReducer {
-        private let _fetch: (Database) throws -> [DatabaseValue]
-        private var previousDbValues: [DatabaseValue]?
-        
-        init(_ fetch: @escaping (Database) throws -> [DatabaseValue]) {
-            self._fetch = fetch
-        }
-        
-        /// :nodoc:
-        public func fetch(_ db: Database) throws -> [DatabaseValue] {
-            return try _fetch(db)
+/// [**Experimental**](http://github.com/groue/GRDB.swift#what-are-experimental-features)
+///
+/// A reducer which outputs arrays of values, filtering out consecutive
+/// identical database values.
+///
+/// :nodoc:
+public struct DatabaseValuesReducer<Request: FetchRequest>: ValueReducer
+    where Request.RowDecoder: DatabaseValueConvertible
+{
+    public let request: Request
+    private var previousDbValues: [DatabaseValue]?
+    
+    init(request: Request) {
+        self.request = request
+    }
+    
+    public func fetch(_ db: Database) throws -> [DatabaseValue] {
+        return try DatabaseValue.fetchAll(db, request)
+    }
+    
+    public mutating func value(_ dbValues: [DatabaseValue]) -> [Request.RowDecoder]? {
+        if let previousDbValues = previousDbValues, previousDbValues == dbValues {
+            // Don't notify consecutive identical dbValue arrays
+            return nil
         }
-        
-        /// :nodoc:
-        public mutating func value(_ dbValues: [DatabaseValue]) -> [T]? {
-            if let previousDbValues = previousDbValues, previousDbValues == dbValues {
-                // Don't notify consecutive identical dbValue arrays
-                return nil
-            }
-            self.previousDbValues = dbValues
-            return dbValues.map {
-                T.decode(from: $0, conversionContext: nil)
-            }
+        self.previousDbValues = dbValues
+        return dbValues.map {
+            Request.RowDecoder.decode(from: $0, conversionContext: nil)
         }
     }
+}
+
+/// [**Experimental**](http://github.com/groue/GRDB.swift#what-are-experimental-features)
+///
+/// A reducer which outputs optional values, filtering out consecutive
+/// identical database values.
+///
+/// :nodoc:
+public struct DatabaseValueReducer<Request: FetchRequest>: ValueReducer
+    where Request.RowDecoder: DatabaseValueConvertible
+{
+    public let request: Request
+    private var previousDbValue: DatabaseValue??
+    private var previousValueWasNil = false
     
-    /// A reducer which outputs optional values, filtering out consecutive
-    /// identical database values.
-    public struct Value<T: DatabaseValueConvertible>: ValueReducer {
-        private let _fetch: (Database) throws -> DatabaseValue?
-        private var previousDbValue: DatabaseValue??
-        private var previousValueWasNil = false
-        
-        init(_ fetch: @escaping (Database) throws -> DatabaseValue?) {
-            self._fetch = fetch
-        }
-        
-        /// :nodoc:
-        public func fetch(_ db: Database) throws -> DatabaseValue? {
-            return try _fetch(db)
+    init(request: Request) {
+        self.request = request
+    }
+    
+    public func fetch(_ db: Database) throws -> DatabaseValue? {
+        return try DatabaseValue.fetchOne(db, request)
+    }
+    
+    public mutating func value(_ dbValue: DatabaseValue?) -> Request.RowDecoder?? {
+        if let previousDbValue = previousDbValue, previousDbValue == dbValue {
+            // Don't notify consecutive identical dbValue
+            return nil
         }
-        
-        /// :nodoc:
-        public mutating func value(_ dbValue: DatabaseValue?) -> T?? {
-            if let previousDbValue = previousDbValue, previousDbValue == dbValue {
-                // Don't notify consecutive identical dbValue
-                return nil
-            }
-            self.previousDbValue = dbValue
-            if let dbValue = dbValue,
-                let value = T.decodeIfPresent(from: dbValue, conversionContext: nil)
-            {
-                previousValueWasNil = false
-                return .some(value)
-            } else if previousValueWasNil {
-                // Don't notify consecutive nil values
-                return nil
-            } else {
-                previousValueWasNil = true
-                return .some(nil)
-            }
+        self.previousDbValue = dbValue
+        if let dbValue = dbValue,
+            let value = Request.RowDecoder.decodeIfPresent(from: dbValue, conversionContext: nil)
+        {
+            previousValueWasNil = false
+            return .some(value)
+        } else if previousValueWasNil {
+            // Don't notify consecutive nil values
+            return nil
+        } else {
+            previousValueWasNil = true
+            return .some(nil)
         }
     }
+}
+
+/// [**Experimental**](http://github.com/groue/GRDB.swift#what-are-experimental-features)
+///
+/// A reducer which outputs arrays of optional values, filtering out consecutive
+/// identical database values.
+///
+/// :nodoc:
+public struct OptionalDatabaseValuesReducer<Request: FetchRequest>: ValueReducer
+    where
+    Request.RowDecoder: _OptionalProtocol,
+    Request.RowDecoder._Wrapped: DatabaseValueConvertible
+{
+    public let request: Request
+    private var previousDbValues: [DatabaseValue]?
+    
+    init(request: Request) {
+        self.request = request
+    }
     
-    /// A reducer which outputs arrays of optional values, filtering out consecutive
-    /// identical database values.
-    public struct OptionalValues<T: DatabaseValueConvertible>: ValueReducer {
-        private let _fetch: (Database) throws -> [DatabaseValue]
-        private var previousDbValues: [DatabaseValue]?
-        
-        init(_ fetch: @escaping (Database) throws -> [DatabaseValue]) {
-            self._fetch = fetch
-        }
-        
-        /// :nodoc:
-        public func fetch(_ db: Database) throws -> [DatabaseValue] {
-            return try _fetch(db)
+    public func fetch(_ db: Database) throws -> [DatabaseValue] {
+        return try DatabaseValue.fetchAll(db, request)
+    }
+    
+    public mutating func value(_ dbValues: [DatabaseValue]) -> [Request.RowDecoder._Wrapped?]? {
+        if let previousDbValues = previousDbValues, previousDbValues == dbValues {
+            // Don't notify consecutive identical dbValue arrays
+            return nil
         }
-        
-        /// :nodoc:
-        public mutating func value(_ dbValues: [DatabaseValue]) -> [T?]? {
-            if let previousDbValues = previousDbValues, previousDbValues == dbValues {
-                // Don't notify consecutive identical dbValue arrays
-                return nil
-            }
-            self.previousDbValues = dbValues
-            return dbValues.map {
-                T.decodeIfPresent(from: $0, conversionContext: nil)
-            }
+        self.previousDbValues = dbValues
+        return dbValues.map {
+            Request.RowDecoder._Wrapped.decodeIfPresent(from: $0, conversionContext: nil)
         }
     }
 }
diff --git a/GRDB/ValueObservation/ValueObservation+FetchableRecord.swift b/GRDB/ValueObservation/ValueObservation+FetchableRecord.swift
index 6b30f1ce11..1f18722fd8 100644
--- a/GRDB/ValueObservation/ValueObservation+FetchableRecord.swift
+++ b/GRDB/ValueObservation/ValueObservation+FetchableRecord.swift
@@ -1,5 +1,5 @@
 extension ValueObservation where Reducer == Void {
-
+    
     // MARK: - FetchableRecord Observation
     
     /// Creates a ValueObservation which observes *request*, and notifies
@@ -27,12 +27,12 @@ extension ValueObservation where Reducer == Void {
     /// - parameter request: the observed request.
     /// - returns: a ValueObservation.
     public static func trackingAll<Request: FetchRequest>(_ request: Request)
-        -> ValueObservation<ValueReducers.Records<Request.RowDecoder>>
+        -> ValueObservation<FetchableRecordsReducer<Request>>
         where Request.RowDecoder: FetchableRecord
     {
-        return ValueObservation<ValueReducers.Records<Request.RowDecoder>>.tracking(
-            request,
-            reducer: { _ in ValueReducers.Records { try Row.fetchAll($0, request) } })
+        return ValueObservation<FetchableRecordsReducer<Request>>.tracking(request, reducer: { _ in
+            FetchableRecordsReducer(request: request)
+        })
     }
     
     /// Creates a ValueObservation which observes *request*, and notifies a
@@ -59,65 +59,71 @@ extension ValueObservation where Reducer == Void {
     /// - parameter request: the observed request.
     /// - returns: a ValueObservation.
     public static func trackingOne<Request: FetchRequest>(_ request: Request) ->
-        ValueObservation<ValueReducers.Record<Request.RowDecoder>>
+        ValueObservation<FetchableRecordReducer<Request>>
         where Request.RowDecoder: FetchableRecord
     {
-        return ValueObservation<ValueReducers.Record<Request.RowDecoder>>.tracking(
-            request,
-            reducer: { _ in ValueReducers.Record { try Row.fetchOne($0, request) } })
+        return ValueObservation<FetchableRecordReducer<Request>>.tracking(request, reducer: { _ in
+            FetchableRecordReducer(request: request)
+        })
     }
 }
 
-extension ValueReducers {
-    /// A reducer which outputs arrays of records, filtering out consecutive
-    /// identical database rows.
-    public struct Records<Record: FetchableRecord>: ValueReducer {
-        private let _fetch: (Database) throws -> [Row]
-        private var previousRows: [Row]?
-        
-        init(_ fetch: @escaping (Database) throws -> [Row]) {
-            self._fetch = fetch
-        }
-        
-        /// :nodoc:
-        public func fetch(_ db: Database) throws -> [Row] {
-            return try _fetch(db)
-        }
-        
-        /// :nodoc:
-        public mutating func value(_ rows: [Row]) -> [Record]? {
-            if let previousRows = previousRows, previousRows == rows {
-                // Don't notify consecutive identical row arrays
-                return nil
-            }
-            self.previousRows = rows
-            return rows.map(Record.init(row:))
-        }
+/// [**Experimental**](http://github.com/groue/GRDB.swift#what-are-experimental-features)
+///
+/// A reducer which outputs arrays of records, filtering out consecutive
+/// identical database rows.
+///
+/// :nodoc:
+public struct FetchableRecordsReducer<Request: FetchRequest>: ValueReducer
+    where Request.RowDecoder: FetchableRecord
+{
+    public let request: Request
+    private var previousRows: [Row]?
+    
+    init(request: Request) {
+        self.request = request
     }
     
-    /// A reducer which outputs optional records, filtering out consecutive
-    /// identical database rows.
-    public struct Record<Record: FetchableRecord>: ValueReducer {
-        private let _fetch: (Database) throws -> Row?
-        private var previousRow: Row??
-        
-        init(_ fetch: @escaping (Database) throws -> Row?) {
-            self._fetch = fetch
-        }
-        
-        /// :nodoc:
-        public func fetch(_ db: Database) throws -> Row? {
-            return try _fetch(db)
+    public func fetch(_ db: Database) throws -> [Row] {
+        return try Row.fetchAll(db, request)
+    }
+    
+    public mutating func value(_ rows: [Row]) -> [Request.RowDecoder]? {
+        if let previousRows = previousRows, previousRows == rows {
+            // Don't notify consecutive identical row arrays
+            return nil
         }
-        
-        /// :nodoc:
-        public mutating func value(_ row: Row?) -> Record?? {
-            if let previousRow = previousRow, previousRow == row {
-                // Don't notify consecutive identical rows
-                return nil
-            }
-            self.previousRow = row
-            return .some(row.map(Record.init(row:)))
+        self.previousRows = rows
+        return rows.map(Request.RowDecoder.init(row:))
+    }
+}
+
+/// [**Experimental**](http://github.com/groue/GRDB.swift#what-are-experimental-features)
+///
+/// A reducer which outputs optional records, filtering out consecutive
+/// identical database rows.
+///
+/// :nodoc:
+public struct FetchableRecordReducer<Request: FetchRequest>: ValueReducer
+    where Request.RowDecoder: FetchableRecord
+{
+    public let request: Request
+    private var previousRow: Row??
+    
+    init(request: Request) {
+        self.request = request
+    }
+    
+    public func fetch(_ db: Database) throws -> Row? {
+        return try Row.fetchOne(db, request)
+    }
+    
+    public mutating func value(_ row: Row?) -> Request.RowDecoder?? {
+        if let previousRow = previousRow, previousRow == row {
+            // Don't notify consecutive identical rows
+            return nil
         }
+        self.previousRow = row
+        return .some(row.map(Request.RowDecoder.init(row:)))
     }
 }
diff --git a/GRDB/ValueObservation/ValueObservation+Map.swift b/GRDB/ValueObservation/ValueObservation+Map.swift
index c9e510b7e2..cefd648b51 100644
--- a/GRDB/ValueObservation/ValueObservation+Map.swift
+++ b/GRDB/ValueObservation/ValueObservation+Map.swift
@@ -5,18 +5,13 @@ extension ValueObservation where Reducer: ValueReducer {
     public func map<T>(_ transform: @escaping (Reducer.Value) -> T)
         -> ValueObservation<MapValueReducer<Reducer, T>>
     {
-        let makeReducer = self.makeReducer
-        var observation = ValueObservation<MapValueReducer<Reducer, T>>(
-            tracking: observedRegion,
-            reducer: { db in try makeReducer(db).map(transform) })
-        observation.extent = extent
-        observation.scheduling = scheduling
-        observation.requiresWriteAccess = requiresWriteAccess
-        return observation
+        return mapReducer { $1.map(transform) }
     }
 }
 
 extension ValueReducer {
+    /// [**Experimental**](http://github.com/groue/GRDB.swift#what-are-experimental-features)
+    ///
     /// Returns a reducer which outputs the results of calling the given
     /// transformation which each element emitted by this reducer.
     public func map<T>(_ transform: @escaping (Value) -> T) -> MapValueReducer<Self, T> {
@@ -24,6 +19,8 @@ extension ValueReducer {
     }
 }
 
+/// [**Experimental**](http://github.com/groue/GRDB.swift#what-are-experimental-features)
+///
 /// A ValueReducer whose values consist of those in a Base ValueReducer passed
 /// through a transform function.
 ///
diff --git a/GRDB/ValueObservation/ValueObservation+MapReducer.swift b/GRDB/ValueObservation/ValueObservation+MapReducer.swift
new file mode 100644
index 0000000000..baea470b8c
--- /dev/null
+++ b/GRDB/ValueObservation/ValueObservation+MapReducer.swift
@@ -0,0 +1,15 @@
+extension ValueObservation {
+    /// [**Experimental**](http://github.com/groue/GRDB.swift#what-are-experimental-features)
+    ///
+    /// Returns a ValueObservation with a transformed reducer.
+    public func mapReducer<R>(_ transform: @escaping (Database, Reducer) throws -> R) -> ValueObservation<R> {
+        let makeReducer = self.makeReducer
+        var observation = ValueObservation<R>(
+            tracking: observedRegion,
+            reducer: { db in try transform(db, makeReducer(db)) })
+        observation.extent = extent
+        observation.scheduling = scheduling
+        observation.requiresWriteAccess = requiresWriteAccess
+        return observation
+    }
+}
diff --git a/GRDB/ValueObservation/ValueObservation+Row.swift b/GRDB/ValueObservation/ValueObservation+Row.swift
index 35dee402fe..e041f2e066 100644
--- a/GRDB/ValueObservation/ValueObservation+Row.swift
+++ b/GRDB/ValueObservation/ValueObservation+Row.swift
@@ -26,10 +26,12 @@ extension ValueObservation where Reducer == Void {
     /// - parameter request: the observed request.
     /// - returns: a ValueObservation.
     public static func trackingAll<Request: FetchRequest>(_ request: Request)
-        -> ValueObservation<ValueReducers.Distinct<[Row]>>
+        -> ValueObservation<RowsReducer<Request>>
         where Request.RowDecoder == Row
     {
-        return ValueObservation.tracking(request, fetchDistinct: request.fetchAll)
+        return ValueObservation<RowsReducer<Request>>.tracking(request, reducer: { _ in
+            RowsReducer(request: request)
+        })
     }
     
     /// Creates a ValueObservation which observes *request*, and notifies a
@@ -56,9 +58,71 @@ extension ValueObservation where Reducer == Void {
     /// - parameter request: the observed request.
     /// - returns: a ValueObservation.
     public static func trackingOne<Request: FetchRequest>(_ request: Request)
-        -> ValueObservation<ValueReducers.Distinct<Row?>>
+        -> ValueObservation<RowReducer<Request>>
         where Request.RowDecoder == Row
     {
-        return ValueObservation.tracking(request, fetchDistinct: request.fetchOne)
+        return ValueObservation<RowReducer<Request>>.tracking(request, reducer: { _ in
+            RowReducer(request: request)
+        })
+    }
+}
+
+/// [**Experimental**](http://github.com/groue/GRDB.swift#what-are-experimental-features)
+///
+/// A reducer which outputs arrays of database rows, filtering out
+/// consecutive identical arrays.
+///
+/// :nodoc:
+public struct RowsReducer<Request: FetchRequest>: ValueReducer
+    where Request.RowDecoder == Row
+{
+    public let request: Request
+    private var previousRows: [Row]?
+    
+    init(request: Request) {
+        self.request = request
+    }
+    
+    public func fetch(_ db: Database) throws -> [Row] {
+        return try request.fetchAll(db)
+    }
+    
+    public mutating func value(_ rows: [Row]) -> [Row]? {
+        if let previousRows = previousRows, previousRows == rows {
+            // Don't notify consecutive identical row arrays
+            return nil
+        }
+        self.previousRows = rows
+        return rows
+    }
+}
+
+/// [**Experimental**](http://github.com/groue/GRDB.swift#what-are-experimental-features)
+///
+/// A reducer which outputs optional records, filtering out consecutive
+/// identical database rows.
+///
+/// :nodoc:
+public struct RowReducer<Request: FetchRequest>: ValueReducer
+    where Request.RowDecoder == Row
+{
+    public let request: Request
+    private var previousRow: Row??
+    
+    init(request: Request) {
+        self.request = request
+    }
+    
+    public func fetch(_ db: Database) throws -> Row? {
+        return try request.fetchOne(db)
+    }
+    
+    public mutating func value(_ row: Row?) -> Row?? {
+        if let previousRow = previousRow, previousRow == row {
+            // Don't notify consecutive identical rows
+            return nil
+        }
+        self.previousRow = row
+        return row
     }
 }
diff --git a/GRDB/ValueObservation/ValueObservation.swift b/GRDB/ValueObservation/ValueObservation.swift
index e6727c8a92..73a40a4832 100644
--- a/GRDB/ValueObservation/ValueObservation.swift
+++ b/GRDB/ValueObservation/ValueObservation.swift
@@ -326,7 +326,7 @@ extension ValueObservation where Reducer == Void {
     public static func tracking<Value>(
         _ regions: DatabaseRegionConvertible...,
         fetch: @escaping (Database) throws -> Value)
-        -> ValueObservation<ValueReducers.Raw<Value>>
+        -> ValueObservation<RawValueReducer<Value>>
     {
         return ValueObservation.tracking(regions, fetch: fetch)
     }
@@ -359,11 +359,11 @@ extension ValueObservation where Reducer == Void {
     public static func tracking<Value>(
         _ regions: [DatabaseRegionConvertible],
         fetch: @escaping (Database) throws -> Value)
-        -> ValueObservation<ValueReducers.Raw<Value>>
+        -> ValueObservation<RawValueReducer<Value>>
     {
-        return ValueObservation<ValueReducers.Raw<Value>>(
+        return ValueObservation<RawValueReducer<Value>>(
             tracking: DatabaseRegion.union(regions),
-            reducer: { _ in ValueReducers.Raw(fetch) })
+            reducer: { _ in RawValueReducer(fetch) })
     }
     
     /// Creates a ValueObservation which observes *regions*, and notifies the
@@ -395,7 +395,7 @@ extension ValueObservation where Reducer == Void {
     public static func tracking<Value>(
         _ regions: DatabaseRegionConvertible...,
         fetchDistinct fetch: @escaping (Database) throws -> Value)
-        -> ValueObservation<ValueReducers.Distinct<Value>>
+        -> ValueObservation<DistinctValueReducer<Value>>
         where Value: Equatable
     {
         return ValueObservation.tracking(regions, fetchDistinct: fetch)
@@ -430,11 +430,11 @@ extension ValueObservation where Reducer == Void {
     public static func tracking<Value>(
         _ regions: [DatabaseRegionConvertible],
         fetchDistinct fetch: @escaping (Database) throws -> Value)
-        -> ValueObservation<ValueReducers.Distinct<Value>>
+        -> ValueObservation<DistinctValueReducer<Value>>
         where Value: Equatable
     {
-        return ValueObservation<ValueReducers.Distinct<Value>>(
+        return ValueObservation<DistinctValueReducer<Value>>(
             tracking: DatabaseRegion.union(regions),
-            reducer: { _ in ValueReducers.Distinct(fetch) })
+            reducer: { _ in DistinctValueReducer(fetch) })
     }
 }
diff --git a/GRDB/ValueObservation/ValueReducer.swift b/GRDB/ValueObservation/ValueReducer.swift
index b2fcc9b12b..6828451de8 100644
--- a/GRDB/ValueObservation/ValueReducer.swift
+++ b/GRDB/ValueObservation/ValueReducer.swift
@@ -70,49 +70,49 @@ public struct AnyValueReducer<Fetched, Value>: ValueReducer {
 }
 
 /// [**Experimental**](http://github.com/groue/GRDB.swift#what-are-experimental-features)
-public enum ValueReducers {
-    /// A reducer which outputs raw database values, without any processing.
-    public struct Raw<Value>: ValueReducer {
-        private let _fetch: (Database) throws -> Value
-        
-        init(_ fetch: @escaping (Database) throws -> Value) {
-            self._fetch = fetch
-        }
-        
-        /// :nodoc:
-        public func fetch(_ db: Database) throws -> Value {
-            return try _fetch(db)
-        }
-        
-        /// :nodoc:
-        public func value(_ fetched: Value) -> Value? {
-            return fetched
-        }
+///
+/// A reducer which outputs raw values.
+///
+/// :nodoc:
+public struct RawValueReducer<Value>: ValueReducer {
+    private let _fetch: (Database) throws -> Value
+    
+    public init(_ fetch: @escaping (Database) throws -> Value) {
+        self._fetch = fetch
     }
     
-    /// A reducer which outputs raw database values, filtering out consecutive
-    /// values that are equal.
-    public struct Distinct<Value: Equatable>: ValueReducer {
-        private let _fetch: (Database) throws -> Value
-        private var previousValue: Value??
-        
-        init(_ fetch: @escaping (Database) throws -> Value) {
-            self._fetch = fetch
-        }
-        
-        /// :nodoc:
-        public func fetch(_ db: Database) throws -> Value {
-            return try _fetch(db)
-        }
-        
-        /// :nodoc:
-        public mutating func value(_ value: Value) -> Value? {
-            if let previousValue = previousValue, previousValue == value {
-                // Don't notify consecutive identical values
-                return nil
-            }
-            self.previousValue = value
-            return value
+    public func fetch(_ db: Database) throws -> Value {
+        return try _fetch(db)
+    }
+    
+    public func value(_ fetched: Value) -> Value? {
+        return fetched
+    }
+}
+
+/// [**Experimental**](http://github.com/groue/GRDB.swift#what-are-experimental-features)
+///
+/// A reducer which filters out consecutive values that are equal.
+///
+/// :nodoc:
+public struct DistinctValueReducer<Value: Equatable>: ValueReducer {
+    private let _fetch: (Database) throws -> Value
+    private var previousValue: Value??
+    
+    public init(_ fetch: @escaping (Database) throws -> Value) {
+        self._fetch = fetch
+    }
+    
+    public func fetch(_ db: Database) throws -> Value {
+        return try _fetch(db)
+    }
+    
+    public mutating func value(_ value: Value) -> Value? {
+        if let previousValue = previousValue, previousValue == value {
+            // Don't notify consecutive identical values
+            return nil
         }
+        self.previousValue = value
+        return value
     }
 }
diff --git a/GRDBCipher.xcodeproj/project.pbxproj b/GRDBCipher.xcodeproj/project.pbxproj
index a1843a183b..b218fa0cbe 100755
--- a/GRDBCipher.xcodeproj/project.pbxproj
+++ b/GRDBCipher.xcodeproj/project.pbxproj
@@ -272,6 +272,8 @@
 		564CE4F221B2E08A00652B19 /* ValueObservationMapTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 564CE4F021B2E08A00652B19 /* ValueObservationMapTests.swift */; };
 		564CE4F321B2E08A00652B19 /* ValueObservationMapTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 564CE4F021B2E08A00652B19 /* ValueObservationMapTests.swift */; };
 		564CE4F421B2E08A00652B19 /* ValueObservationMapTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 564CE4F021B2E08A00652B19 /* ValueObservationMapTests.swift */; };
+		564CE52621B312B500652B19 /* ValueObservation+MapReducer.swift in Sources */ = {isa = PBXBuildFile; fileRef = 564CE51A21B3128400652B19 /* ValueObservation+MapReducer.swift */; };
+		564CE52721B312B700652B19 /* ValueObservation+MapReducer.swift in Sources */ = {isa = PBXBuildFile; fileRef = 564CE51A21B3128400652B19 /* ValueObservation+MapReducer.swift */; };
 		564E73EF203DA2A2000C443C /* JoinSupportTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 564E73EB203DA29B000C443C /* JoinSupportTests.swift */; };
 		564E73F0203DA2A3000C443C /* JoinSupportTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 564E73EB203DA29B000C443C /* JoinSupportTests.swift */; };
 		564E73F1203DA2A3000C443C /* JoinSupportTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 564E73EB203DA29B000C443C /* JoinSupportTests.swift */; };
@@ -1087,6 +1089,7 @@
 		564CE4DC21B2DEF700652B19 /* ValueObservation+CompactMap.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = "ValueObservation+CompactMap.swift"; sourceTree = "<group>"; };
 		564CE4EB21B2E08200652B19 /* ValueObservationCompactMapTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = ValueObservationCompactMapTests.swift; sourceTree = "<group>"; };
 		564CE4F021B2E08A00652B19 /* ValueObservationMapTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = ValueObservationMapTests.swift; sourceTree = "<group>"; };
+		564CE51A21B3128400652B19 /* ValueObservation+MapReducer.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = "ValueObservation+MapReducer.swift"; sourceTree = "<group>"; };
 		564E73EB203DA29B000C443C /* JoinSupportTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = JoinSupportTests.swift; sourceTree = "<group>"; };
 		564F9C1D1F069B4E00877A00 /* DatabaseAggregateTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = DatabaseAggregateTests.swift; sourceTree = "<group>"; };
 		564F9C2C1F075DD200877A00 /* DatabaseFunction.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = DatabaseFunction.swift; sourceTree = "<group>"; };
@@ -1486,6 +1489,7 @@
 				5613ED7821A95E8400DC7A68 /* ValueObservation+DatabaseValueConvertible.swift */,
 				5613ED7721A95E8400DC7A68 /* ValueObservation+FetchableRecord.swift */,
 				5613ED7521A95E8400DC7A68 /* ValueObservation+Map.swift */,
+				564CE51A21B3128400652B19 /* ValueObservation+MapReducer.swift */,
 				5613ED7621A95E8400DC7A68 /* ValueObservation+Row.swift */,
 				564CE43F21AA957000652B19 /* ValueObserver.swift */,
 				5613ED7921A95E8400DC7A68 /* ValueReducer.swift */,
@@ -2331,6 +2335,7 @@
 				560FC51F1CB003810014AA8E /* CGFloat.swift in Sources */,
 				5674A7091F307FCD0095F066 /* DatabaseValueConvertible+ReferenceConvertible.swift in Sources */,
 				5653EC17209873A400F46237 /* SQLExpression+QueryInterface.swift in Sources */,
+				564CE52621B312B500652B19 /* ValueObservation+MapReducer.swift in Sources */,
 				5659F4A11EA8D997004A4992 /* Result.swift in Sources */,
 				560FC5201CB003810014AA8E /* Date.swift in Sources */,
 				560FC5221CB003810014AA8E /* DatabaseValueConvertible+RawRepresentable.swift in Sources */,
@@ -2814,6 +2819,7 @@
 				56AFC9F31CB1A8BB00F48B96 /* Database.swift in Sources */,
 				5674A7061F307FCD0095F066 /* DatabaseValueConvertible+ReferenceConvertible.swift in Sources */,
 				5653EC18209873A400F46237 /* SQLExpression+QueryInterface.swift in Sources */,
+				564CE52721B312B700652B19 /* ValueObservation+MapReducer.swift in Sources */,
 				5659F4A41EA8D997004A4992 /* Result.swift in Sources */,
 				56AFC9F41CB1A8BB00F48B96 /* CGFloat.swift in Sources */,
 				56AFC9F51CB1A8BB00F48B96 /* Date.swift in Sources */,
diff --git a/GRDBCustom.xcodeproj/project.pbxproj b/GRDBCustom.xcodeproj/project.pbxproj
index 9bfc3b181d..3efd7d6390 100755
--- a/GRDBCustom.xcodeproj/project.pbxproj
+++ b/GRDBCustom.xcodeproj/project.pbxproj
@@ -103,6 +103,8 @@
 		564CE4E121B2E04500652B19 /* ValueObservationCompactMapTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 564CE4DF21B2E04500652B19 /* ValueObservationCompactMapTests.swift */; };
 		564CE4E321B2E05400652B19 /* ValueObservationMapTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 564CE4E221B2E05400652B19 /* ValueObservationMapTests.swift */; };
 		564CE4E421B2E05400652B19 /* ValueObservationMapTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 564CE4E221B2E05400652B19 /* ValueObservationMapTests.swift */; };
+		564CE52421B312AD00652B19 /* ValueObservation+MapReducer.swift in Sources */ = {isa = PBXBuildFile; fileRef = 564CE52321B312AC00652B19 /* ValueObservation+MapReducer.swift */; };
+		564CE52521B312AD00652B19 /* ValueObservation+MapReducer.swift in Sources */ = {isa = PBXBuildFile; fileRef = 564CE52321B312AC00652B19 /* ValueObservation+MapReducer.swift */; };
 		564E73F3203DA2AC000C443C /* JoinSupportTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 564E73E7203DA278000C443C /* JoinSupportTests.swift */; };
 		564E73F4203DA2AD000C443C /* JoinSupportTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 564E73E7203DA278000C443C /* JoinSupportTests.swift */; };
 		564F9C211F069B4E00877A00 /* DatabaseAggregateTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 564F9C1D1F069B4E00877A00 /* DatabaseAggregateTests.swift */; };
@@ -724,6 +726,7 @@
 		564CE4D921B2DEEB00652B19 /* ValueObservation+CompactMap.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = "ValueObservation+CompactMap.swift"; sourceTree = "<group>"; };
 		564CE4DF21B2E04500652B19 /* ValueObservationCompactMapTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = ValueObservationCompactMapTests.swift; sourceTree = "<group>"; };
 		564CE4E221B2E05400652B19 /* ValueObservationMapTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = ValueObservationMapTests.swift; sourceTree = "<group>"; };
+		564CE52321B312AC00652B19 /* ValueObservation+MapReducer.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = "ValueObservation+MapReducer.swift"; sourceTree = "<group>"; };
 		564E73E7203DA278000C443C /* JoinSupportTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = JoinSupportTests.swift; sourceTree = "<group>"; };
 		564F9C1D1F069B4E00877A00 /* DatabaseAggregateTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = DatabaseAggregateTests.swift; sourceTree = "<group>"; };
 		564F9C2C1F075DD200877A00 /* DatabaseFunction.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = DatabaseFunction.swift; sourceTree = "<group>"; };
@@ -1089,6 +1092,7 @@
 				5613ED5E21A95E6100DC7A68 /* ValueObservation+DatabaseValueConvertible.swift */,
 				5613ED5D21A95E6100DC7A68 /* ValueObservation+FetchableRecord.swift */,
 				5613ED5B21A95E6100DC7A68 /* ValueObservation+Map.swift */,
+				564CE52321B312AC00652B19 /* ValueObservation+MapReducer.swift */,
 				5613ED5C21A95E6100DC7A68 /* ValueObservation+Row.swift */,
 				564CE43B21AA955B00652B19 /* ValueObserver.swift */,
 				5613ED5F21A95E6100DC7A68 /* ValueReducer.swift */,
@@ -1970,6 +1974,7 @@
 				F3BA80181CFB2876003DC1BA /* SerializedDatabase.swift in Sources */,
 				5674A7051F307FCD0095F066 /* DatabaseValueConvertible+ReferenceConvertible.swift in Sources */,
 				5659F4A51EA8D997004A4992 /* Result.swift in Sources */,
+				564CE52521B312AD00652B19 /* ValueObservation+MapReducer.swift in Sources */,
 				F3BA800D1CFB2871003DC1BA /* DatabasePool.swift in Sources */,
 				F3BA800B1CFB286D003DC1BA /* Database.swift in Sources */,
 				F3BA80341CFB28A4003DC1BA /* Record.swift in Sources */,
@@ -2274,6 +2279,7 @@
 				F3BA80741CFB2E55003DC1BA /* SerializedDatabase.swift in Sources */,
 				5674A7041F307FCD0095F066 /* DatabaseValueConvertible+ReferenceConvertible.swift in Sources */,
 				5659F4A21EA8D997004A4992 /* Result.swift in Sources */,
+				564CE52421B312AD00652B19 /* ValueObservation+MapReducer.swift in Sources */,
 				F3BA80691CFB2E55003DC1BA /* DatabasePool.swift in Sources */,
 				F3BA80671CFB2E55003DC1BA /* Database.swift in Sources */,
 				F3BA80901CFB2E7A003DC1BA /* Record.swift in Sources */,
diff --git a/Tests/GRDBTests/ValueObservationDatabaseValueConvertibleTests.swift b/Tests/GRDBTests/ValueObservationDatabaseValueConvertibleTests.swift
index 50edc1864a..bc996d8582 100644
--- a/Tests/GRDBTests/ValueObservationDatabaseValueConvertibleTests.swift
+++ b/Tests/GRDBTests/ValueObservationDatabaseValueConvertibleTests.swift
@@ -174,8 +174,8 @@ class ValueObservationDatabaseValueConvertibleTests: GRDBTestCase {
             results.append(names)
             notificationExpectation.fulfill()
         }
-        let valueObserver = transactionObserver as! ValueObserver<ValueReducers.Values<Name>>
-        XCTAssertEqual(valueObserver.region.description, "t(id,name)")
+        let valueObserver = transactionObserver as! ValueObserver<DatabaseValuesReducer<SQLRequest<Name>>>
+        XCTAssertEqual(valueObserver.region.description, "t(id,name)") // view is not tracked
         
         // Test view observation
         try dbQueue.inDatabase { db in