From fa3014eefe4e00acd74ea20b8a3c3ee4208efb58 Mon Sep 17 00:00:00 2001
From: Facundo Medica <facundomedica@gmail.com>
Date: Tue, 14 Jun 2022 14:38:09 -0300
Subject: [PATCH 01/12] poc

---
 types/query/filtered_pagination.go | 116 +++++++++++++++++++++++++++++
 x/authz/keeper/grpc_query.go       |  34 +++------
 2 files changed, 125 insertions(+), 25 deletions(-)

diff --git a/types/query/filtered_pagination.go b/types/query/filtered_pagination.go
index 0f755c55e788..245c32cc70ac 100644
--- a/types/query/filtered_pagination.go
+++ b/types/query/filtered_pagination.go
@@ -4,6 +4,7 @@ import (
 	"fmt"
 
 	"github.com/cosmos/cosmos-sdk/store/types"
+	proto "github.com/gogo/protobuf/proto"
 )
 
 // FilteredPaginate does pagination of all the results in the PrefixStore based on the
@@ -114,3 +115,118 @@ func FilteredPaginate(
 
 	return res, nil
 }
+
+func GenericFilteredPaginated[V proto.Message](
+	prefixStore types.KVStore,
+	pageRequest *PageRequest,
+	onResult func(key []byte, value V) (V, error),
+) ([]V, *PageResponse, error) {
+	// if the PageRequest is nil, use default PageRequest
+	if pageRequest == nil {
+		pageRequest = &PageRequest{}
+	}
+
+	offset := pageRequest.Offset
+	key := pageRequest.Key
+	limit := pageRequest.Limit
+	countTotal := pageRequest.CountTotal
+	reverse := pageRequest.Reverse
+	results := []V{}
+
+	if offset > 0 && key != nil {
+		return nil, nil, fmt.Errorf("invalid request, either offset or key is expected, got both")
+	}
+
+	if limit == 0 {
+		limit = DefaultLimit
+
+		// count total results when the limit is zero/not supplied
+		countTotal = true
+	}
+
+	if len(key) != 0 {
+		iterator := getIterator(prefixStore, key, reverse)
+		defer iterator.Close()
+
+		var numHits uint64
+		var nextKey []byte
+
+		for ; iterator.Valid(); iterator.Next() {
+			if numHits == limit {
+				nextKey = iterator.Key()
+				break
+			}
+
+			if iterator.Error() != nil {
+				return nil, nil, iterator.Error()
+			}
+
+			var protoMsg *V
+			err := proto.Unmarshal(iterator.Value(), *protoMsg)
+			if err != nil {
+				return nil, nil, err
+			}
+
+			val, err := onResult(iterator.Key(), *protoMsg)
+			if err != nil {
+				return nil, nil, err
+			}
+
+			if protoMsg != nil {
+				results = append(results, val)
+				numHits++
+			}
+		}
+
+		return nil, &PageResponse{
+			NextKey: nextKey,
+		}, nil
+	}
+
+	iterator := getIterator(prefixStore, nil, reverse)
+	defer iterator.Close()
+
+	end := offset + limit
+
+	var numHits uint64
+	var nextKey []byte
+
+	for ; iterator.Valid(); iterator.Next() {
+		if iterator.Error() != nil {
+			return nil, nil, iterator.Error()
+		}
+
+		var protoMsg *V
+		err := proto.Unmarshal(iterator.Value(), *protoMsg)
+		if err != nil {
+			return nil, nil, err
+		}
+
+		val, err := onResult(iterator.Key(), *protoMsg)
+		if err != nil {
+			return nil, nil, err
+		}
+
+		if protoMsg != nil {
+			results = append(results, val)
+			numHits++
+		}
+
+		if numHits == end+1 {
+			if nextKey == nil {
+				nextKey = iterator.Key()
+			}
+
+			if !countTotal {
+				break
+			}
+		}
+	}
+
+	res := &PageResponse{NextKey: nextKey}
+	if countTotal {
+		res.Total = numHits
+	}
+
+	return results, res, nil
+}
diff --git a/x/authz/keeper/grpc_query.go b/x/authz/keeper/grpc_query.go
index 1156ac23521d..d7a86b26da21 100644
--- a/x/authz/keeper/grpc_query.go
+++ b/x/authz/keeper/grpc_query.go
@@ -6,8 +6,6 @@ import (
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/status"
 
-	proto "github.com/gogo/protobuf/proto"
-
 	"github.com/cosmos/cosmos-sdk/codec"
 	codectypes "github.com/cosmos/cosmos-sdk/codec/types"
 	"github.com/cosmos/cosmos-sdk/store/prefix"
@@ -64,34 +62,20 @@ func (k Keeper) Grants(c context.Context, req *authz.QueryGrantsRequest) (*authz
 	key := grantStoreKey(grantee, granter, "")
 	grantsStore := prefix.NewStore(store, key)
 
-	var authorizations []*authz.Grant
-	pageRes, err := query.FilteredPaginate(grantsStore, req.Pagination, func(key []byte, value []byte, accumulate bool) (bool, error) {
-		auth, err := unmarshalAuthorization(k.cdc, value)
+	authorizations, pageRes, err := query.GenericFilteredPaginated(grantsStore, req.Pagination, func(key []byte, value *authz.Grant) (*authz.Grant, error) {
+		auth, err := value.GetAuthorization()
 		if err != nil {
-			return false, err
+			return nil, err
 		}
 
-		auth1, err := auth.GetAuthorization()
+		authorizationAny, err := codectypes.NewAnyWithValue(auth)
 		if err != nil {
-			return false, err
-		}
-
-		if accumulate {
-			msg, ok := auth1.(proto.Message)
-			if !ok {
-				return false, status.Errorf(codes.Internal, "can't protomarshal %T", msg)
-			}
-
-			authorizationAny, err := codectypes.NewAnyWithValue(msg)
-			if err != nil {
-				return false, status.Errorf(codes.Internal, err.Error())
-			}
-			authorizations = append(authorizations, &authz.Grant{
-				Authorization: authorizationAny,
-				Expiration:    auth.Expiration,
-			})
+			return nil, status.Errorf(codes.Internal, err.Error())
 		}
-		return true, nil
+		return &authz.Grant{
+			Authorization: authorizationAny,
+			Expiration:    value.Expiration,
+		}, nil
 	})
 	if err != nil {
 		return nil, err

From cb28171529a679e023d9582d50ee03d9573ff9ee Mon Sep 17 00:00:00 2001
From: Facundo Medica <facundomedica@gmail.com>
Date: Tue, 14 Jun 2022 17:31:51 -0300
Subject: [PATCH 02/12] progress

---
 types/query/filtered_pagination.go | 32 +++++++-----
 x/authz/keeper/grpc_query.go       | 84 +++++++++++-------------------
 x/authz/keeper/grpc_query_test.go  |  3 +-
 3 files changed, 51 insertions(+), 68 deletions(-)

diff --git a/types/query/filtered_pagination.go b/types/query/filtered_pagination.go
index 245c32cc70ac..ca4668c20060 100644
--- a/types/query/filtered_pagination.go
+++ b/types/query/filtered_pagination.go
@@ -3,8 +3,8 @@ package query
 import (
 	"fmt"
 
+	"github.com/cosmos/cosmos-sdk/codec"
 	"github.com/cosmos/cosmos-sdk/store/types"
-	proto "github.com/gogo/protobuf/proto"
 )
 
 // FilteredPaginate does pagination of all the results in the PrefixStore based on the
@@ -116,11 +116,12 @@ func FilteredPaginate(
 	return res, nil
 }
 
-func GenericFilteredPaginated[V proto.Message](
+func GenericFilteredPaginate[V any, F codec.ProtoMarshaler](
+	cdc codec.BinaryCodec,
 	prefixStore types.KVStore,
 	pageRequest *PageRequest,
-	onResult func(key []byte, value V) (V, error),
-) ([]V, *PageResponse, error) {
+	onResult func(key []byte, value V) (F, error),
+) ([]F, *PageResponse, error) {
 	// if the PageRequest is nil, use default PageRequest
 	if pageRequest == nil {
 		pageRequest = &PageRequest{}
@@ -131,7 +132,7 @@ func GenericFilteredPaginated[V proto.Message](
 	limit := pageRequest.Limit
 	countTotal := pageRequest.CountTotal
 	reverse := pageRequest.Reverse
-	results := []V{}
+	results := []F{}
 
 	if offset > 0 && key != nil {
 		return nil, nil, fmt.Errorf("invalid request, either offset or key is expected, got both")
@@ -161,18 +162,18 @@ func GenericFilteredPaginated[V proto.Message](
 				return nil, nil, iterator.Error()
 			}
 
-			var protoMsg *V
-			err := proto.Unmarshal(iterator.Value(), *protoMsg)
+			protoMsg := any(new(V))
+			err := cdc.Unmarshal(iterator.Value(), protoMsg.(codec.ProtoMarshaler))
 			if err != nil {
 				return nil, nil, err
 			}
 
-			val, err := onResult(iterator.Key(), *protoMsg)
+			val, err := onResult(iterator.Key(), *(protoMsg.(*V)))
 			if err != nil {
 				return nil, nil, err
 			}
 
-			if protoMsg != nil {
+			if any(val) != nil {
 				results = append(results, val)
 				numHits++
 			}
@@ -196,19 +197,22 @@ func GenericFilteredPaginated[V proto.Message](
 			return nil, nil, iterator.Error()
 		}
 
-		var protoMsg *V
-		err := proto.Unmarshal(iterator.Value(), *protoMsg)
+		protoMsg := any(new(V))
+		err := cdc.Unmarshal(iterator.Value(), protoMsg.(codec.ProtoMarshaler))
 		if err != nil {
 			return nil, nil, err
 		}
 
-		val, err := onResult(iterator.Key(), *protoMsg)
+		val, err := onResult(iterator.Key(), *(protoMsg.(*V)))
 		if err != nil {
 			return nil, nil, err
 		}
 
-		if protoMsg != nil {
-			results = append(results, val)
+		if any(val) != nil {
+			// Previously this was the "accumulate" flag
+			if numHits >= offset && numHits < end {
+				results = append(results, val)
+			}
 			numHits++
 		}
 
diff --git a/x/authz/keeper/grpc_query.go b/x/authz/keeper/grpc_query.go
index d7a86b26da21..e1a54d6dd619 100644
--- a/x/authz/keeper/grpc_query.go
+++ b/x/authz/keeper/grpc_query.go
@@ -6,7 +6,6 @@ import (
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/status"
 
-	"github.com/cosmos/cosmos-sdk/codec"
 	codectypes "github.com/cosmos/cosmos-sdk/codec/types"
 	"github.com/cosmos/cosmos-sdk/store/prefix"
 	sdk "github.com/cosmos/cosmos-sdk/types"
@@ -62,19 +61,19 @@ func (k Keeper) Grants(c context.Context, req *authz.QueryGrantsRequest) (*authz
 	key := grantStoreKey(grantee, granter, "")
 	grantsStore := prefix.NewStore(store, key)
 
-	authorizations, pageRes, err := query.GenericFilteredPaginated(grantsStore, req.Pagination, func(key []byte, value *authz.Grant) (*authz.Grant, error) {
-		auth, err := value.GetAuthorization()
+	authorizations, pageRes, err := query.GenericFilteredPaginate(k.cdc, grantsStore, req.Pagination, func(key []byte, auth authz.Grant) (*authz.Grant, error) {
+		auth1, err := auth.GetAuthorization()
 		if err != nil {
 			return nil, err
 		}
 
-		authorizationAny, err := codectypes.NewAnyWithValue(auth)
+		authorizationAny, err := codectypes.NewAnyWithValue(auth1)
 		if err != nil {
 			return nil, status.Errorf(codes.Internal, err.Error())
 		}
 		return &authz.Grant{
 			Authorization: authorizationAny,
-			Expiration:    value.Expiration,
+			Expiration:    auth.Expiration,
 		}, nil
 	})
 	if err != nil {
@@ -102,34 +101,27 @@ func (k Keeper) GranterGrants(c context.Context, req *authz.QueryGranterGrantsRe
 	store := ctx.KVStore(k.storeKey)
 	authzStore := prefix.NewStore(store, grantStoreKey(nil, granter, ""))
 
-	var grants []*authz.GrantAuthorization
-	pageRes, err := query.FilteredPaginate(authzStore, req.Pagination, func(key []byte, value []byte, accumulate bool) (bool, error) {
-		auth, err := unmarshalAuthorization(k.cdc, value)
+	grants, pageRes, err := query.GenericFilteredPaginate(k.cdc, authzStore, req.Pagination, func(key []byte, auth authz.Grant) (*authz.GrantAuthorization, error) {
+		auth1, err := auth.GetAuthorization()
 		if err != nil {
-			return false, err
+			return nil, err
 		}
 
-		auth1, err := auth.GetAuthorization()
+		any, err := codectypes.NewAnyWithValue(auth1)
 		if err != nil {
-			return false, err
+			return nil, status.Errorf(codes.Internal, err.Error())
 		}
 
-		if accumulate {
-			any, err := codectypes.NewAnyWithValue(auth1)
-			if err != nil {
-				return false, status.Errorf(codes.Internal, err.Error())
-			}
-
-			grantee := firstAddressFromGrantStoreKey(key)
-			grants = append(grants, &authz.GrantAuthorization{
-				Granter:       granter.String(),
-				Grantee:       grantee.String(),
-				Authorization: any,
-				Expiration:    auth.Expiration,
-			})
-		}
-		return true, nil
+		grantee := firstAddressFromGrantStoreKey(key)
+		return &authz.GrantAuthorization{
+			Granter:       granter.String(),
+			Grantee:       grantee.String(),
+			Authorization: any,
+			Expiration:    auth.Expiration,
+		}, nil
+
 	})
+
 	if err != nil {
 		return nil, err
 	}
@@ -154,36 +146,28 @@ func (k Keeper) GranteeGrants(c context.Context, req *authz.QueryGranteeGrantsRe
 	ctx := sdk.UnwrapSDKContext(c)
 	store := prefix.NewStore(ctx.KVStore(k.storeKey), GrantKey)
 
-	var authorizations []*authz.GrantAuthorization
-	pageRes, err := query.FilteredPaginate(store, req.Pagination, func(key []byte, value []byte, accumulate bool) (bool, error) {
-		auth, err := unmarshalAuthorization(k.cdc, value)
+	authorizations, pageRes, err := query.GenericFilteredPaginate(k.cdc, store, req.Pagination, func(key []byte, auth authz.Grant) (*authz.GrantAuthorization, error) {
+		auth1, err := auth.GetAuthorization()
 		if err != nil {
-			return false, err
+			return nil, err
 		}
 
 		granter, g, _ := parseGrantStoreKey(append(GrantKey, key...))
 		if !g.Equals(grantee) {
-			return false, nil
+			return nil, nil
 		}
 
-		auth1, err := auth.GetAuthorization()
+		authorizationAny, err := codectypes.NewAnyWithValue(auth1)
 		if err != nil {
-			return false, err
-		}
-		if accumulate {
-			any, err := codectypes.NewAnyWithValue(auth1)
-			if err != nil {
-				return false, status.Errorf(codes.Internal, err.Error())
-			}
-
-			authorizations = append(authorizations, &authz.GrantAuthorization{
-				Authorization: any,
-				Expiration:    auth.Expiration,
-				Granter:       granter.String(),
-				Grantee:       grantee.String(),
-			})
+			return nil, status.Errorf(codes.Internal, err.Error())
 		}
-		return true, nil
+
+		return &authz.GrantAuthorization{
+			Authorization: authorizationAny,
+			Expiration:    auth.Expiration,
+			Granter:       granter.String(),
+			Grantee:       grantee.String(),
+		}, nil
 	})
 	if err != nil {
 		return nil, err
@@ -194,9 +178,3 @@ func (k Keeper) GranteeGrants(c context.Context, req *authz.QueryGranteeGrantsRe
 		Pagination: pageRes,
 	}, nil
 }
-
-// unmarshal an authorization from a store value
-func unmarshalAuthorization(cdc codec.BinaryCodec, value []byte) (v authz.Grant, err error) {
-	err = cdc.Unmarshal(value, &v)
-	return v, err
-}
diff --git a/x/authz/keeper/grpc_query_test.go b/x/authz/keeper/grpc_query_test.go
index d2f0b09e8b19..9b717e9d40d7 100644
--- a/x/authz/keeper/grpc_query_test.go
+++ b/x/authz/keeper/grpc_query_test.go
@@ -198,7 +198,8 @@ func (suite *TestSuite) TestGRPCQueryGranterGrants() {
 		},
 		{
 			"valid case, pagination",
-			func() {},
+			func() {
+			},
 			false,
 			authz.QueryGranterGrantsRequest{
 				Granter: addrs[0].String(),

From 4ebaaaa784e637ec9382b10ceb1025ddcd61173b Mon Sep 17 00:00:00 2001
From: Facundo Medica <facundomedica@gmail.com>
Date: Tue, 14 Jun 2022 19:42:53 -0300
Subject: [PATCH 03/12] fix when returned object is nil

---
 types/query/filtered_pagination.go | 8 ++++----
 x/authz/keeper/grpc_query_test.go  | 9 +++++++++
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/types/query/filtered_pagination.go b/types/query/filtered_pagination.go
index ca4668c20060..53886b83e705 100644
--- a/types/query/filtered_pagination.go
+++ b/types/query/filtered_pagination.go
@@ -135,7 +135,7 @@ func GenericFilteredPaginate[V any, F codec.ProtoMarshaler](
 	results := []F{}
 
 	if offset > 0 && key != nil {
-		return nil, nil, fmt.Errorf("invalid request, either offset or key is expected, got both")
+		return results, nil, fmt.Errorf("invalid request, either offset or key is expected, got both")
 	}
 
 	if limit == 0 {
@@ -173,13 +173,13 @@ func GenericFilteredPaginate[V any, F codec.ProtoMarshaler](
 				return nil, nil, err
 			}
 
-			if any(val) != nil {
+			if val.Size() != 0 {
 				results = append(results, val)
 				numHits++
 			}
 		}
 
-		return nil, &PageResponse{
+		return results, &PageResponse{
 			NextKey: nextKey,
 		}, nil
 	}
@@ -208,7 +208,7 @@ func GenericFilteredPaginate[V any, F codec.ProtoMarshaler](
 			return nil, nil, err
 		}
 
-		if any(val) != nil {
+		if val.Size() != 0 {
 			// Previously this was the "accumulate" flag
 			if numHits >= offset && numHits < end {
 				results = append(results, val)
diff --git a/x/authz/keeper/grpc_query_test.go b/x/authz/keeper/grpc_query_test.go
index 9b717e9d40d7..440859ee24b1 100644
--- a/x/authz/keeper/grpc_query_test.go
+++ b/x/authz/keeper/grpc_query_test.go
@@ -254,6 +254,15 @@ func (suite *TestSuite) TestGRPCQueryGranteeGrants() {
 			},
 			1,
 		},
+		{
+			"valid case, no authorization found",
+			func() {},
+			false,
+			authz.QueryGranteeGrantsRequest{
+				Grantee: addrs[2].String(),
+			},
+			0,
+		},
 		{
 			"valid case, multiple authorization",
 			func() {

From 6db3de3d85fae502b7334f14869185564e7b1031 Mon Sep 17 00:00:00 2001
From: Facundo Medica <facundomedica@gmail.com>
Date: Wed, 15 Jun 2022 14:19:18 -0300
Subject: [PATCH 04/12] use reflect to accept codec.ProtoMarshaler

---
 types/query/filtered_pagination.go | 27 +++++++++++++++++++--------
 x/authz/keeper/grpc_query.go       |  6 +++---
 2 files changed, 22 insertions(+), 11 deletions(-)

diff --git a/types/query/filtered_pagination.go b/types/query/filtered_pagination.go
index 53886b83e705..68f9f56a88a2 100644
--- a/types/query/filtered_pagination.go
+++ b/types/query/filtered_pagination.go
@@ -2,6 +2,7 @@ package query
 
 import (
 	"fmt"
+	"reflect"
 
 	"github.com/cosmos/cosmos-sdk/codec"
 	"github.com/cosmos/cosmos-sdk/store/types"
@@ -116,11 +117,11 @@ func FilteredPaginate(
 	return res, nil
 }
 
-func GenericFilteredPaginate[V any, F codec.ProtoMarshaler](
+func GenericFilteredPaginate[T codec.ProtoMarshaler, F codec.ProtoMarshaler](
 	cdc codec.BinaryCodec,
 	prefixStore types.KVStore,
 	pageRequest *PageRequest,
-	onResult func(key []byte, value V) (F, error),
+	onResult func(key []byte, value T) (F, error),
 ) ([]F, *PageResponse, error) {
 	// if the PageRequest is nil, use default PageRequest
 	if pageRequest == nil {
@@ -162,13 +163,18 @@ func GenericFilteredPaginate[V any, F codec.ProtoMarshaler](
 				return nil, nil, iterator.Error()
 			}
 
-			protoMsg := any(new(V))
-			err := cdc.Unmarshal(iterator.Value(), protoMsg.(codec.ProtoMarshaler))
+			// initialize the proto message
+			va := reflect.ValueOf(new(T)).Elem()
+			v := reflect.New(va.Type().Elem())
+			va.Set(v)
+			protoMsg := va.Interface().(codec.ProtoMarshaler)
+
+			err := cdc.Unmarshal(iterator.Value(), protoMsg)
 			if err != nil {
 				return nil, nil, err
 			}
 
-			val, err := onResult(iterator.Key(), *(protoMsg.(*V)))
+			val, err := onResult(iterator.Key(), protoMsg.(T))
 			if err != nil {
 				return nil, nil, err
 			}
@@ -197,13 +203,18 @@ func GenericFilteredPaginate[V any, F codec.ProtoMarshaler](
 			return nil, nil, iterator.Error()
 		}
 
-		protoMsg := any(new(V))
-		err := cdc.Unmarshal(iterator.Value(), protoMsg.(codec.ProtoMarshaler))
+		// initialize the proto message
+		va := reflect.ValueOf(new(T)).Elem()
+		v := reflect.New(va.Type().Elem())
+		va.Set(v)
+		protoMsg := va.Interface().(codec.ProtoMarshaler)
+
+		err := cdc.Unmarshal(iterator.Value(), protoMsg)
 		if err != nil {
 			return nil, nil, err
 		}
 
-		val, err := onResult(iterator.Key(), *(protoMsg.(*V)))
+		val, err := onResult(iterator.Key(), (protoMsg).(T))
 		if err != nil {
 			return nil, nil, err
 		}
diff --git a/x/authz/keeper/grpc_query.go b/x/authz/keeper/grpc_query.go
index e1a54d6dd619..88e057e44aa6 100644
--- a/x/authz/keeper/grpc_query.go
+++ b/x/authz/keeper/grpc_query.go
@@ -61,7 +61,7 @@ func (k Keeper) Grants(c context.Context, req *authz.QueryGrantsRequest) (*authz
 	key := grantStoreKey(grantee, granter, "")
 	grantsStore := prefix.NewStore(store, key)
 
-	authorizations, pageRes, err := query.GenericFilteredPaginate(k.cdc, grantsStore, req.Pagination, func(key []byte, auth authz.Grant) (*authz.Grant, error) {
+	authorizations, pageRes, err := query.GenericFilteredPaginate(k.cdc, grantsStore, req.Pagination, func(key []byte, auth *authz.Grant) (*authz.Grant, error) {
 		auth1, err := auth.GetAuthorization()
 		if err != nil {
 			return nil, err
@@ -101,7 +101,7 @@ func (k Keeper) GranterGrants(c context.Context, req *authz.QueryGranterGrantsRe
 	store := ctx.KVStore(k.storeKey)
 	authzStore := prefix.NewStore(store, grantStoreKey(nil, granter, ""))
 
-	grants, pageRes, err := query.GenericFilteredPaginate(k.cdc, authzStore, req.Pagination, func(key []byte, auth authz.Grant) (*authz.GrantAuthorization, error) {
+	grants, pageRes, err := query.GenericFilteredPaginate(k.cdc, authzStore, req.Pagination, func(key []byte, auth *authz.Grant) (*authz.GrantAuthorization, error) {
 		auth1, err := auth.GetAuthorization()
 		if err != nil {
 			return nil, err
@@ -146,7 +146,7 @@ func (k Keeper) GranteeGrants(c context.Context, req *authz.QueryGranteeGrantsRe
 	ctx := sdk.UnwrapSDKContext(c)
 	store := prefix.NewStore(ctx.KVStore(k.storeKey), GrantKey)
 
-	authorizations, pageRes, err := query.GenericFilteredPaginate(k.cdc, store, req.Pagination, func(key []byte, auth authz.Grant) (*authz.GrantAuthorization, error) {
+	authorizations, pageRes, err := query.GenericFilteredPaginate(k.cdc, store, req.Pagination, func(key []byte, auth *authz.Grant) (*authz.GrantAuthorization, error) {
 		auth1, err := auth.GetAuthorization()
 		if err != nil {
 			return nil, err

From 85fc29bc3e504467ab76231241b63bd90bb85ffc Mon Sep 17 00:00:00 2001
From: Facundo Medica <facundomedica@gmail.com>
Date: Wed, 15 Jun 2022 14:35:17 -0300
Subject: [PATCH 05/12] suggestion

---
 types/query/filtered_pagination.go | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/types/query/filtered_pagination.go b/types/query/filtered_pagination.go
index 68f9f56a88a2..f71bd0988b65 100644
--- a/types/query/filtered_pagination.go
+++ b/types/query/filtered_pagination.go
@@ -47,8 +47,10 @@ func FilteredPaginate(
 		iterator := getIterator(prefixStore, key, reverse)
 		defer iterator.Close()
 
-		var numHits uint64
-		var nextKey []byte
+		var (
+			numHits uint64
+			nextKey []byte
+		)
 
 		for ; iterator.Valid(); iterator.Next() {
 			if numHits == limit {
@@ -80,8 +82,10 @@ func FilteredPaginate(
 
 	end := offset + limit
 
-	var numHits uint64
-	var nextKey []byte
+	var (
+		numHits uint64
+		nextKey []byte
+	)
 
 	for ; iterator.Valid(); iterator.Next() {
 		if iterator.Error() != nil {
@@ -195,8 +199,10 @@ func GenericFilteredPaginate[T codec.ProtoMarshaler, F codec.ProtoMarshaler](
 
 	end := offset + limit
 
-	var numHits uint64
-	var nextKey []byte
+	var (
+		numHits uint64
+		nextKey []byte
+	)
 
 	for ; iterator.Valid(); iterator.Next() {
 		if iterator.Error() != nil {

From 6353df02fe5673eebbf37c7c075e59ae50bfb92f Mon Sep 17 00:00:00 2001
From: Facundo Medica <facundomedica@gmail.com>
Date: Wed, 15 Jun 2022 15:43:18 -0300
Subject: [PATCH 06/12] try out constructor

---
 types/query/filtered_pagination.go | 18 +++++-------------
 x/authz/keeper/grpc_query.go       |  6 ++++++
 2 files changed, 11 insertions(+), 13 deletions(-)

diff --git a/types/query/filtered_pagination.go b/types/query/filtered_pagination.go
index f71bd0988b65..9d1614e34b6d 100644
--- a/types/query/filtered_pagination.go
+++ b/types/query/filtered_pagination.go
@@ -2,7 +2,6 @@ package query
 
 import (
 	"fmt"
-	"reflect"
 
 	"github.com/cosmos/cosmos-sdk/codec"
 	"github.com/cosmos/cosmos-sdk/store/types"
@@ -126,6 +125,7 @@ func GenericFilteredPaginate[T codec.ProtoMarshaler, F codec.ProtoMarshaler](
 	prefixStore types.KVStore,
 	pageRequest *PageRequest,
 	onResult func(key []byte, value T) (F, error),
+	constructor func() T,
 ) ([]F, *PageResponse, error) {
 	// if the PageRequest is nil, use default PageRequest
 	if pageRequest == nil {
@@ -167,18 +167,14 @@ func GenericFilteredPaginate[T codec.ProtoMarshaler, F codec.ProtoMarshaler](
 				return nil, nil, iterator.Error()
 			}
 
-			// initialize the proto message
-			va := reflect.ValueOf(new(T)).Elem()
-			v := reflect.New(va.Type().Elem())
-			va.Set(v)
-			protoMsg := va.Interface().(codec.ProtoMarshaler)
+			protoMsg := constructor()
 
 			err := cdc.Unmarshal(iterator.Value(), protoMsg)
 			if err != nil {
 				return nil, nil, err
 			}
 
-			val, err := onResult(iterator.Key(), protoMsg.(T))
+			val, err := onResult(iterator.Key(), protoMsg)
 			if err != nil {
 				return nil, nil, err
 			}
@@ -209,18 +205,14 @@ func GenericFilteredPaginate[T codec.ProtoMarshaler, F codec.ProtoMarshaler](
 			return nil, nil, iterator.Error()
 		}
 
-		// initialize the proto message
-		va := reflect.ValueOf(new(T)).Elem()
-		v := reflect.New(va.Type().Elem())
-		va.Set(v)
-		protoMsg := va.Interface().(codec.ProtoMarshaler)
+		protoMsg := constructor()
 
 		err := cdc.Unmarshal(iterator.Value(), protoMsg)
 		if err != nil {
 			return nil, nil, err
 		}
 
-		val, err := onResult(iterator.Key(), (protoMsg).(T))
+		val, err := onResult(iterator.Key(), protoMsg)
 		if err != nil {
 			return nil, nil, err
 		}
diff --git a/x/authz/keeper/grpc_query.go b/x/authz/keeper/grpc_query.go
index 88e057e44aa6..3273ee282533 100644
--- a/x/authz/keeper/grpc_query.go
+++ b/x/authz/keeper/grpc_query.go
@@ -75,6 +75,8 @@ func (k Keeper) Grants(c context.Context, req *authz.QueryGrantsRequest) (*authz
 			Authorization: authorizationAny,
 			Expiration:    auth.Expiration,
 		}, nil
+	}, func() *authz.Grant {
+		return &authz.Grant{}
 	})
 	if err != nil {
 		return nil, err
@@ -120,6 +122,8 @@ func (k Keeper) GranterGrants(c context.Context, req *authz.QueryGranterGrantsRe
 			Expiration:    auth.Expiration,
 		}, nil
 
+	}, func() *authz.Grant {
+		return &authz.Grant{}
 	})
 
 	if err != nil {
@@ -168,6 +172,8 @@ func (k Keeper) GranteeGrants(c context.Context, req *authz.QueryGranteeGrantsRe
 			Granter:       granter.String(),
 			Grantee:       grantee.String(),
 		}, nil
+	}, func() *authz.Grant {
+		return &authz.Grant{}
 	})
 	if err != nil {
 		return nil, err

From 23b5fdc1162144e5708f50020da69ec88435f8af Mon Sep 17 00:00:00 2001
From: Facundo Medica <facundomedica@gmail.com>
Date: Wed, 15 Jun 2022 17:45:20 -0300
Subject: [PATCH 07/12] rename

---
 types/query/filtered_pagination.go | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/types/query/filtered_pagination.go b/types/query/filtered_pagination.go
index 9d1614e34b6d..0fcf8c183cbc 100644
--- a/types/query/filtered_pagination.go
+++ b/types/query/filtered_pagination.go
@@ -125,7 +125,7 @@ func GenericFilteredPaginate[T codec.ProtoMarshaler, F codec.ProtoMarshaler](
 	prefixStore types.KVStore,
 	pageRequest *PageRequest,
 	onResult func(key []byte, value T) (F, error),
-	constructor func() T,
+	c func() T,
 ) ([]F, *PageResponse, error) {
 	// if the PageRequest is nil, use default PageRequest
 	if pageRequest == nil {
@@ -167,7 +167,7 @@ func GenericFilteredPaginate[T codec.ProtoMarshaler, F codec.ProtoMarshaler](
 				return nil, nil, iterator.Error()
 			}
 
-			protoMsg := constructor()
+			protoMsg := c()
 
 			err := cdc.Unmarshal(iterator.Value(), protoMsg)
 			if err != nil {
@@ -205,7 +205,7 @@ func GenericFilteredPaginate[T codec.ProtoMarshaler, F codec.ProtoMarshaler](
 			return nil, nil, iterator.Error()
 		}
 
-		protoMsg := constructor()
+		protoMsg := c()
 
 		err := cdc.Unmarshal(iterator.Value(), protoMsg)
 		if err != nil {

From bf01daababb2d16d42d4e2af5f1f4cf87408cf82 Mon Sep 17 00:00:00 2001
From: Facundo Medica <facundomedica@gmail.com>
Date: Thu, 16 Jun 2022 10:36:10 -0300
Subject: [PATCH 08/12] docs

---
 types/query/filtered_pagination.go | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/types/query/filtered_pagination.go b/types/query/filtered_pagination.go
index 0fcf8c183cbc..d6bd74913834 100644
--- a/types/query/filtered_pagination.go
+++ b/types/query/filtered_pagination.go
@@ -120,6 +120,13 @@ func FilteredPaginate(
 	return res, nil
 }
 
+// GenericFilteredPaginate does pagination of all the results in the PrefixStore based on the
+// provided PageRequest. `onResult` should be used to filter or transform the results.
+// `c` is a constructor function that needs to return a new instance of the type T.
+// If key is provided, the pagination uses the optimized querying.
+// If offset is used, the pagination uses lazy filtering i.e., searches through all the records.
+// The resulting slice (of type F) can be of a different type than the one being iterated through
+// (type T), so it's possible to do any necessary transformation inside the onResult function.
 func GenericFilteredPaginate[T codec.ProtoMarshaler, F codec.ProtoMarshaler](
 	cdc codec.BinaryCodec,
 	prefixStore types.KVStore,
@@ -154,8 +161,10 @@ func GenericFilteredPaginate[T codec.ProtoMarshaler, F codec.ProtoMarshaler](
 		iterator := getIterator(prefixStore, key, reverse)
 		defer iterator.Close()
 
-		var numHits uint64
-		var nextKey []byte
+		var (
+			numHits uint64
+			nextKey []byte
+		)
 
 		for ; iterator.Valid(); iterator.Next() {
 			if numHits == limit {

From 2c59802057c53226b4de30bb176d95d74b585e0e Mon Sep 17 00:00:00 2001
From: Facundo Medica <facundomedica@gmail.com>
Date: Thu, 16 Jun 2022 10:39:13 -0300
Subject: [PATCH 09/12] docs

---
 types/query/filtered_pagination.go | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/types/query/filtered_pagination.go b/types/query/filtered_pagination.go
index d6bd74913834..4f15f05553f6 100644
--- a/types/query/filtered_pagination.go
+++ b/types/query/filtered_pagination.go
@@ -122,7 +122,8 @@ func FilteredPaginate(
 
 // GenericFilteredPaginate does pagination of all the results in the PrefixStore based on the
 // provided PageRequest. `onResult` should be used to filter or transform the results.
-// `c` is a constructor function that needs to return a new instance of the type T.
+// `c` is a constructor function that needs to return a new instance of the type T (this is to
+// workaround some generic pitfalls in which we can't instantiate a T struct inside the function).
 // If key is provided, the pagination uses the optimized querying.
 // If offset is used, the pagination uses lazy filtering i.e., searches through all the records.
 // The resulting slice (of type F) can be of a different type than the one being iterated through

From 40cd7b62b1167f7963a982a8017487207d6fe696 Mon Sep 17 00:00:00 2001
From: Facundo Medica <14063057+facundomedica@users.noreply.github.com>
Date: Mon, 27 Jun 2022 07:53:09 -0300
Subject: [PATCH 10/12] Apply suggestions from code review

Co-authored-by: Aleksandr Bezobchuk <alexanderbez@users.noreply.github.com>
---
 types/query/filtered_pagination.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/types/query/filtered_pagination.go b/types/query/filtered_pagination.go
index 4f15f05553f6..81fa265438d3 100644
--- a/types/query/filtered_pagination.go
+++ b/types/query/filtered_pagination.go
@@ -133,7 +133,7 @@ func GenericFilteredPaginate[T codec.ProtoMarshaler, F codec.ProtoMarshaler](
 	prefixStore types.KVStore,
 	pageRequest *PageRequest,
 	onResult func(key []byte, value T) (F, error),
-	c func() T,
+	constructor func() T,
 ) ([]F, *PageResponse, error) {
 	// if the PageRequest is nil, use default PageRequest
 	if pageRequest == nil {

From baf7f7f91f3dd83782419fca84fb38967b438cdf Mon Sep 17 00:00:00 2001
From: Facundo Medica <facundomedica@gmail.com>
Date: Mon, 27 Jun 2022 08:03:52 -0300
Subject: [PATCH 11/12] cl++, small fix

---
 CHANGELOG.md                       | 1 +
 types/query/filtered_pagination.go | 4 ++--
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8cd1265333ba..9bb091cb231b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -40,6 +40,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 ### Features
 
 * (cli) [#12028](https://github.com/cosmos/cosmos-sdk/pull/12028) Add the `tendermint key-migrate` to perform Tendermint v0.35 DB key migration.
+* (orm) [#12253](https://github.com/cosmos/cosmos-sdk/pull/12253) Add `GenericFilteredPaginate` to the ORM to improve UX.
 
 ### Improvements
 
diff --git a/types/query/filtered_pagination.go b/types/query/filtered_pagination.go
index 81fa265438d3..50c85ac49a51 100644
--- a/types/query/filtered_pagination.go
+++ b/types/query/filtered_pagination.go
@@ -177,7 +177,7 @@ func GenericFilteredPaginate[T codec.ProtoMarshaler, F codec.ProtoMarshaler](
 				return nil, nil, iterator.Error()
 			}
 
-			protoMsg := c()
+			protoMsg := constructor()
 
 			err := cdc.Unmarshal(iterator.Value(), protoMsg)
 			if err != nil {
@@ -215,7 +215,7 @@ func GenericFilteredPaginate[T codec.ProtoMarshaler, F codec.ProtoMarshaler](
 			return nil, nil, iterator.Error()
 		}
 
-		protoMsg := c()
+		protoMsg := constructor()
 
 		err := cdc.Unmarshal(iterator.Value(), protoMsg)
 		if err != nil {

From b0070c226b86d883d32797bf8b6f9eacba8c3fd1 Mon Sep 17 00:00:00 2001
From: Facundo Medica <facundomedica@gmail.com>
Date: Mon, 27 Jun 2022 08:20:30 -0300
Subject: [PATCH 12/12] cl++

---
 CHANGELOG.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9bb091cb231b..301c6e4deb53 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -40,7 +40,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 ### Features
 
 * (cli) [#12028](https://github.com/cosmos/cosmos-sdk/pull/12028) Add the `tendermint key-migrate` to perform Tendermint v0.35 DB key migration.
-* (orm) [#12253](https://github.com/cosmos/cosmos-sdk/pull/12253) Add `GenericFilteredPaginate` to the ORM to improve UX.
+* (query) [#12253](https://github.com/cosmos/cosmos-sdk/pull/12253) Add `GenericFilteredPaginate` to the `query` package to improve UX.
 
 ### Improvements