fix: handle multiple statements for a single event in projections (#2313)

* fix: handle multiple statements for a single event in projections

* export func type

* fix test

* Update internal/eventstore/handler/crdb/statement.go

Co-authored-by: Silvan <silvan.reusser@gmail.com>

* Update internal/eventstore/handler/crdb/statement.go

Co-authored-by: Silvan <silvan.reusser@gmail.com>

* change to pointers

* add error test case

Co-authored-by: Silvan <silvan.reusser@gmail.com>

internal/eventstore/handler/crdb/failed_stmt.go

@@ -20,7 +20,7 @@ const (
 		") AS failure_count"
 )
 
-func (h *StatementHandler) handleFailedStmt(tx *sql.Tx, stmt handler.Statement, execErr error) (shouldContinue bool) {
+func (h *StatementHandler) handleFailedStmt(tx *sql.Tx, stmt *handler.Statement, execErr error) (shouldContinue bool) {
 	failureCount, err := h.failureCount(tx, stmt.Sequence)
 	if err != nil {
 		logging.LogWithFields("CRDB-WJaFk", "projection", h.ProjectionName, "seq", stmt.Sequence).WithError(err).Warn("unable to get failure count")

internal/eventstore/handler/crdb/handler_stmt.go

@@ -116,7 +116,7 @@ func (h *StatementHandler) SearchQuery() (*eventstore.SearchQueryBuilder, uint64
 }
 
 //Update implements handler.Update
-func (h *StatementHandler) Update(ctx context.Context, stmts []handler.Statement, reduce handler.Reduce) (unexecutedStmts []handler.Statement, err error) {
+func (h *StatementHandler) Update(ctx context.Context, stmts []*handler.Statement, reduce handler.Reduce) (unexecutedStmts []*handler.Statement, err error) {
 	tx, err := h.client.BeginTx(ctx, nil)
 	if err != nil {
 		return stmts, errors.ThrowInternal(err, "CRDB-e89Gq", "begin failed")
@@ -158,7 +158,7 @@ func (h *StatementHandler) Update(ctx context.Context, stmts []handler.Statement
 		return stmts, handler.ErrSomeStmtsFailed
 	}
 
-	unexecutedStmts = make([]handler.Statement, len(stmts)-(lastSuccessfulIdx+1))
+	unexecutedStmts = make([]*handler.Statement, len(stmts)-(lastSuccessfulIdx+1))
 	copy(unexecutedStmts, stmts[lastSuccessfulIdx+1:])
 	stmts = nil
 
@@ -174,7 +174,7 @@ func (h *StatementHandler) fetchPreviousStmts(
 	stmtSeq uint64,
 	sequences currentSequences,
 	reduce handler.Reduce,
-) (previousStmts []handler.Statement, err error) {
+) (previousStmts []*handler.Statement, err error) {
 
 	query := eventstore.NewSearchQueryBuilder(eventstore.ColumnsEvent)
 	queriesAdded := false
@@ -202,18 +202,18 @@ func (h *StatementHandler) fetchPreviousStmts(
 	}
 
 	for _, event := range events {
-		stmts, err := reduce(event)
+		stmt, err := reduce(event)
 		if err != nil {
 			return nil, err
 		}
-		previousStmts = append(previousStmts, stmts...)
+		previousStmts = append(previousStmts, stmt)
 	}
 	return previousStmts, nil
 }
 
 func (h *StatementHandler) executeStmts(
 	tx *sql.Tx,
-	stmts []handler.Statement,
+	stmts []*handler.Statement,
 	sequences currentSequences,
 ) int {
 
@@ -244,7 +244,7 @@ func (h *StatementHandler) executeStmts(
 
 //executeStmt handles sql statements
 //an error is returned if the statement could not be inserted properly
-func (h *StatementHandler) executeStmt(tx *sql.Tx, stmt handler.Statement) error {
+func (h *StatementHandler) executeStmt(tx *sql.Tx, stmt *handler.Statement) error {
 	if stmt.IsNoop() {
 		return nil
 	}

internal/eventstore/handler/crdb/handler_stmt_test.go

@@ -162,7 +162,7 @@ func TestStatementHandler_Update(t *testing.T) {
 	}
 	type args struct {
 		ctx    context.Context
-		stmts  []handler.Statement
+		stmts  []*handler.Statement
 		reduce handler.Reduce
 	}
 	tests := []struct {
@@ -212,7 +212,7 @@ func TestStatementHandler_Update(t *testing.T) {
 			},
 			args: args{
 				ctx: context.Background(),
-				stmts: []handler.Statement{
+				stmts: []*handler.Statement{
 					NewNoOpStatement(&testEvent{
 						aggregateType:    "agg",
 						sequence:         6,
@@ -242,7 +242,7 @@ func TestStatementHandler_Update(t *testing.T) {
 			},
 			args: args{
 				ctx: context.Background(),
-				stmts: []handler.Statement{
+				stmts: []*handler.Statement{
 					NewCreateStatement(
 						&testEvent{
 							aggregateType:    "testAgg",
@@ -279,7 +279,7 @@ func TestStatementHandler_Update(t *testing.T) {
 			},
 			args: args{
 				ctx: context.Background(),
-				stmts: []handler.Statement{
+				stmts: []*handler.Statement{
 					NewCreateStatement(
 						&testEvent{
 							aggregateType:    "agg",
@@ -320,7 +320,7 @@ func TestStatementHandler_Update(t *testing.T) {
 			},
 			args: args{
 				ctx: context.Background(),
-				stmts: []handler.Statement{
+				stmts: []*handler.Statement{
 					NewCreateStatement(
 						&testEvent{
 							aggregateType:    "agg",
@@ -361,7 +361,7 @@ func TestStatementHandler_Update(t *testing.T) {
 			},
 			args: args{
 				ctx: context.Background(),
-				stmts: []handler.Statement{
+				stmts: []*handler.Statement{
 					NewNoOpStatement(&testEvent{
 						aggregateType:    "testAgg",
 						sequence:         7,
@@ -392,7 +392,7 @@ func TestStatementHandler_Update(t *testing.T) {
 			},
 			args: args{
 				ctx: context.Background(),
-				stmts: []handler.Statement{
+				stmts: []*handler.Statement{
 					NewNoOpStatement(&testEvent{
 						aggregateType:    "testAgg",
 						sequence:         7,
@@ -428,7 +428,7 @@ func TestStatementHandler_Update(t *testing.T) {
 			},
 			args: args{
 				ctx: context.Background(),
-				stmts: []handler.Statement{
+				stmts: []*handler.Statement{
 					NewNoOpStatement(&testEvent{
 						aggregateType:    "testAgg",
 						sequence:         7,
@@ -684,7 +684,7 @@ func TestStatementHandler_executeStmts(t *testing.T) {
 		failedEventsTable string
 	}
 	type args struct {
-		stmts     []handler.Statement
+		stmts     []*handler.Statement
 		sequences currentSequences
 	}
 	type want struct {
@@ -703,7 +703,7 @@ func TestStatementHandler_executeStmts(t *testing.T) {
 				projectionName: "my_projection",
 			},
 			args: args{
-				stmts: []handler.Statement{
+				stmts: []*handler.Statement{
 					NewCreateStatement(
 						&testEvent{
 							aggregateType:    "agg",
@@ -732,7 +732,7 @@ func TestStatementHandler_executeStmts(t *testing.T) {
 				projectionName: "my_projection",
 			},
 			args: args{
-				stmts: []handler.Statement{
+				stmts: []*handler.Statement{
 					NewCreateStatement(
 						&testEvent{
 							aggregateType:    "agg",
@@ -780,7 +780,7 @@ func TestStatementHandler_executeStmts(t *testing.T) {
 				failedEventsTable: "failed_events",
 			},
 			args: args{
-				stmts: []handler.Statement{
+				stmts: []*handler.Statement{
 					NewCreateStatement(
 						&testEvent{
 							aggregateType:    "agg",
@@ -844,7 +844,7 @@ func TestStatementHandler_executeStmts(t *testing.T) {
 				failedEventsTable: "failed_events",
 			},
 			args: args{
-				stmts: []handler.Statement{
+				stmts: []*handler.Statement{
 					NewCreateStatement(
 						&testEvent{
 							aggregateType:    "agg",
@@ -909,7 +909,7 @@ func TestStatementHandler_executeStmts(t *testing.T) {
 				projectionName: "my_projection",
 			},
 			args: args{
-				stmts: []handler.Statement{
+				stmts: []*handler.Statement{
 					NewCreateStatement(
 						&testEvent{
 							aggregateType:    "agg",
@@ -946,6 +946,29 @@ func TestStatementHandler_executeStmts(t *testing.T) {
 								Value: "val",
 							},
 						}),
+					NewMultiStatement(
+						&testEvent{
+							aggregateType:    "agg",
+							sequence:         8,
+							previousSequence: 7,
+						},
+						AddCreateStatement(
+							[]handler.Column{
+								{
+									Name:  "col",
+									Value: "val",
+								},
+							},
+						),
+						AddCreateStatement(
+							[]handler.Column{
+								{
+									Name:  "col",
+									Value: "val",
+								},
+							},
+						),
+					),
 				},
 				sequences: currentSequences{
 					"agg": 2,
@@ -962,8 +985,12 @@ func TestStatementHandler_executeStmts(t *testing.T) {
 					expectSavePoint(),
 					expectCreate("my_projection", []string{"col"}, []string{"$1"}),
 					expectSavePointRelease(),
+					expectSavePoint(),
+					expectCreate("my_projection", []string{"col"}, []string{"$1"}),
+					expectCreate("my_projection", []string{"col"}, []string{"$1"}),
+					expectSavePointRelease(),
 				},
-				idx: 2,
+				idx: 3,
 			},
 		},
 	}
@@ -1025,7 +1052,7 @@ func TestStatementHandler_executeStmt(t *testing.T) {
 		projectionName string
 	}
 	type args struct {
-		stmt handler.Statement
+		stmt *handler.Statement
 	}
 	type want struct {
 		expectations []mockExpectation
@@ -1532,16 +1559,14 @@ func TestStatementHandler_updateCurrentSequence(t *testing.T) {
 	}
 }
 
-func testReduce(stmts ...handler.Statement) handler.Reduce {
+func testReduce() handler.Reduce {
-	return func(event eventstore.EventReader) ([]handler.Statement, error) {
+	return func(event eventstore.EventReader) (*handler.Statement, error) {
-		return []handler.Statement{
+		return NewNoOpStatement(event), nil
-			NewNoOpStatement(event),
-		}, nil
 	}
 }
 
 func testReduceErr(err error) handler.Reduce {
-	return func(event eventstore.EventReader) ([]handler.Statement, error) {
+	return func(event eventstore.EventReader) (*handler.Statement, error) {
 		return nil, err
 	}
 }

internal/eventstore/handler/crdb/reduce.go

@@ -6,10 +6,10 @@ import (
 )
 
 //reduce implements handler.Reduce function
-func (h *StatementHandler) reduce(event eventstore.EventReader) ([]handler.Statement, error) {
+func (h *StatementHandler) reduce(event eventstore.EventReader) (*handler.Statement, error) {
 	reduce, ok := h.reduces[event.Type()]
 	if !ok {
-		return []handler.Statement{NewNoOpStatement(event)}, nil
+		return NewNoOpStatement(event), nil
 	}
 
 	return reduce(event)

internal/eventstore/handler/crdb/statement.go

@@ -23,7 +23,7 @@ func WithTableSuffix(name string) func(*execConfig) {
 	}
 }
 
-func NewCreateStatement(event eventstore.EventReader, values []handler.Column, opts ...execOption) handler.Statement {
+func NewCreateStatement(event eventstore.EventReader, values []handler.Column, opts ...execOption) *handler.Statement {
 	cols, params, args := columnsToQuery(values)
 	columnNames := strings.Join(cols, ", ")
 	valuesPlaceholder := strings.Join(params, ", ")
@@ -40,7 +40,7 @@ func NewCreateStatement(event eventstore.EventReader, values []handler.Column, o
 		return "INSERT INTO " + config.tableName + " (" + columnNames + ") VALUES (" + valuesPlaceholder + ")"
 	}
 
-	return handler.Statement{
+	return &handler.Statement{
 		AggregateType:    event.Aggregate().Type,
 		Sequence:         event.Sequence(),
 		PreviousSequence: event.PreviousAggregateTypeSequence(),
@@ -48,7 +48,7 @@ func NewCreateStatement(event eventstore.EventReader, values []handler.Column, o
 	}
 }
 
-func NewUpsertStatement(event eventstore.EventReader, values []handler.Column, opts ...execOption) handler.Statement {
+func NewUpsertStatement(event eventstore.EventReader, values []handler.Column, opts ...execOption) *handler.Statement {
 	cols, params, args := columnsToQuery(values)
 	columnNames := strings.Join(cols, ", ")
 	valuesPlaceholder := strings.Join(params, ", ")
@@ -65,7 +65,7 @@ func NewUpsertStatement(event eventstore.EventReader, values []handler.Column, o
 		return "UPSERT INTO " + config.tableName + " (" + columnNames + ") VALUES (" + valuesPlaceholder + ")"
 	}
 
-	return handler.Statement{
+	return &handler.Statement{
 		AggregateType:    event.Aggregate().Type,
 		Sequence:         event.Sequence(),
 		PreviousSequence: event.PreviousAggregateTypeSequence(),
@@ -73,7 +73,7 @@ func NewUpsertStatement(event eventstore.EventReader, values []handler.Column, o
 	}
 }
 
-func NewUpdateStatement(event eventstore.EventReader, values []handler.Column, conditions []handler.Condition, opts ...execOption) handler.Statement {
+func NewUpdateStatement(event eventstore.EventReader, values []handler.Column, conditions []handler.Condition, opts ...execOption) *handler.Statement {
 	cols, params, args := columnsToQuery(values)
 	wheres, whereArgs := conditionsToWhere(conditions, len(params))
 	args = append(args, whereArgs...)
@@ -98,7 +98,7 @@ func NewUpdateStatement(event eventstore.EventReader, values []handler.Column, c
 		return "UPDATE " + config.tableName + " SET (" + columnNames + ") = (" + valuesPlaceholder + ") WHERE " + wheresPlaceholders
 	}
 
-	return handler.Statement{
+	return &handler.Statement{
 		AggregateType:    event.Aggregate().Type,
 		Sequence:         event.Sequence(),
 		PreviousSequence: event.PreviousAggregateTypeSequence(),
@@ -106,7 +106,7 @@ func NewUpdateStatement(event eventstore.EventReader, values []handler.Column, c
 	}
 }
 
-func NewDeleteStatement(event eventstore.EventReader, conditions []handler.Condition, opts ...execOption) handler.Statement {
+func NewDeleteStatement(event eventstore.EventReader, conditions []handler.Condition, opts ...execOption) *handler.Statement {
 	wheres, args := conditionsToWhere(conditions, 0)
 
 	wheresPlaceholders := strings.Join(wheres, " AND ")
@@ -123,7 +123,7 @@ func NewDeleteStatement(event eventstore.EventReader, conditions []handler.Condi
 		return "DELETE FROM " + config.tableName + " WHERE " + wheresPlaceholders
 	}
 
-	return handler.Statement{
+	return &handler.Statement{
 		AggregateType:    event.Aggregate().Type,
 		Sequence:         event.Sequence(),
 		PreviousSequence: event.PreviousAggregateTypeSequence(),
@@ -131,14 +131,56 @@ func NewDeleteStatement(event eventstore.EventReader, conditions []handler.Condi
 	}
 }
 
-func NewNoOpStatement(event eventstore.EventReader) handler.Statement {
+func NewNoOpStatement(event eventstore.EventReader) *handler.Statement {
-	return handler.Statement{
+	return &handler.Statement{
 		AggregateType:    event.Aggregate().Type,
 		Sequence:         event.Sequence(),
 		PreviousSequence: event.PreviousAggregateTypeSequence(),
 	}
 }
 
+func NewMultiStatement(event eventstore.EventReader, opts ...func(eventstore.EventReader) Exec) *handler.Statement {
+	if len(opts) == 0 {
+		return NewNoOpStatement(event)
+	}
+	execs := make([]Exec, len(opts))
+	for i, opt := range opts {
+		execs[i] = opt(event)
+	}
+	return &handler.Statement{
+		AggregateType:    event.Aggregate().Type,
+		Sequence:         event.Sequence(),
+		PreviousSequence: event.PreviousAggregateTypeSequence(),
+		Execute:          multiExec(execs),
+	}
+}
+
+type Exec func(ex handler.Executer, projectionName string) error
+
+func AddCreateStatement(columns []handler.Column, opts ...execOption) func(eventstore.EventReader) Exec {
+	return func(event eventstore.EventReader) Exec {
+		return NewCreateStatement(event, columns, opts...).Execute
+	}
+}
+
+func AddUpsertStatement(values []handler.Column, opts ...execOption) func(eventstore.EventReader) Exec {
+	return func(event eventstore.EventReader) Exec {
+		return NewUpsertStatement(event, values, opts...).Execute
+	}
+}
+
+func AddUpdateStatement(values []handler.Column, conditions []handler.Condition, opts ...execOption) func(eventstore.EventReader) Exec {
+	return func(event eventstore.EventReader) Exec {
+		return NewUpdateStatement(event, values, conditions, opts...).Execute
+	}
+}
+
+func AddDeleteStatement(conditions []handler.Condition, opts ...execOption) func(eventstore.EventReader) Exec {
+	return func(event eventstore.EventReader) Exec {
+		return NewDeleteStatement(event, conditions, opts...).Execute
+	}
+}
+
 func columnsToQuery(cols []handler.Column) (names []string, parameters []string, values []interface{}) {
 	names = make([]string, len(cols))
 	values = make([]interface{}, len(cols))
@@ -166,7 +208,7 @@ func conditionsToWhere(cols []handler.Condition, paramOffset int) (wheres []stri
 
 type query func(config execConfig) string
 
-func exec(config execConfig, q query, opts []execOption) func(ex handler.Executer, projectionName string) error {
+func exec(config execConfig, q query, opts []execOption) Exec {
 	return func(ex handler.Executer, projectionName string) error {
 		if projectionName == "" {
 			return handler.ErrNoProjection
@@ -188,3 +230,14 @@ func exec(config execConfig, q query, opts []execOption) func(ex handler.Execute
 		return nil
 	}
 }
+
+func multiExec(execList []Exec) Exec {
+	return func(ex handler.Executer, projectionName string) error {
+		for _, exec := range execList {
+			if err := exec(ex, projectionName); err != nil {
+				return err
+			}
+		}
+		return nil
+	}
+}

internal/eventstore/handler/crdb/statement_test.go

@@ -11,13 +11,18 @@ import (
 )
 
 type wantExecuter struct {
-	query         string
+	params        []params
-	args          []interface{}
+	i             int
 	t             *testing.T
 	wasExecuted   bool
 	shouldExecute bool
 }
 
+type params struct {
+	query string
+	args  []interface{}
+}
+
 var errTestErr = errors.New("some error")
 
 func (ex *wantExecuter) check(t *testing.T) {
@@ -34,12 +39,18 @@ func (ex *wantExecuter) check(t *testing.T) {
 func (ex *wantExecuter) Exec(query string, args ...interface{}) (sql.Result, error) {
 	ex.t.Helper()
 	ex.wasExecuted = true
-	if query != ex.query {
+	if ex.i >= len(ex.params) {
-		ex.t.Errorf("wrong query:\n  expected:\n    %q\n  got:\n    %q", ex.query, query)
+		ex.t.Errorf("did not expect more exec, but got:\n    %q with %q", query, args)
+		return nil, nil
 	}
-	if !reflect.DeepEqual(ex.args, args) {
+	p := ex.params[ex.i]
-		ex.t.Errorf("wrong args:\n  expected:\n    %v\n  got:\n    %v", ex.args, args)
+	if query != p.query {
+		ex.t.Errorf("wrong query:\n  expected:\n    %q\n  got:\n    %q", p.query, query)
 	}
+	if !reflect.DeepEqual(p.args, args) {
+		ex.t.Errorf("wrong args:\n  expected:\n    %v\n  got:\n    %v", p.args, args)
+	}
+	ex.i++
 	return nil, nil
 }
 
@@ -137,10 +148,14 @@ func TestNewCreateStatement(t *testing.T) {
 				sequence:         1,
 				previousSequence: 1,
 				executer: &wantExecuter{
+					params: []params{
+						{
 							query: "INSERT INTO my_table (col1) VALUES ($1)",
-					shouldExecute: true,
 							args:  []interface{}{"val"},
 						},
+					},
+					shouldExecute: true,
+				},
 				isErr: func(err error) bool {
 					return err == nil
 				},
@@ -255,10 +270,14 @@ func TestNewUpsertStatement(t *testing.T) {
 				sequence:         1,
 				previousSequence: 1,
 				executer: &wantExecuter{
+					params: []params{
+						{
 							query: "UPSERT INTO my_table (col1) VALUES ($1)",
-					shouldExecute: true,
 							args:  []interface{}{"val"},
 						},
+					},
+					shouldExecute: true,
+				},
 				isErr: func(err error) bool {
 					return err == nil
 				},
@@ -422,10 +441,14 @@ func TestNewUpdateStatement(t *testing.T) {
 				sequence:         1,
 				previousSequence: 1,
 				executer: &wantExecuter{
+					params: []params{
+						{
 							query: "UPDATE my_table SET (col1) = ($1) WHERE (col2 = $2)",
-					shouldExecute: true,
 							args:  []interface{}{"val", 1},
 						},
+					},
+					shouldExecute: true,
+				},
 				isErr: func(err error) bool {
 					return err == nil
 				},
@@ -541,10 +564,14 @@ func TestNewDeleteStatement(t *testing.T) {
 				sequence:         1,
 				previousSequence: 1,
 				executer: &wantExecuter{
+					params: []params{
+						{
 							query: "DELETE FROM my_table WHERE (col1 = $1)",
-					shouldExecute: true,
 							args:  []interface{}{1},
 						},
+					},
+					shouldExecute: true,
+				},
 				isErr: func(err error) bool {
 					return err == nil
 				},
@@ -572,7 +599,7 @@ func TestNewNoOpStatement(t *testing.T) {
 	tests := []struct {
 		name string
 		args args
-		want handler.Statement
+		want *handler.Statement
 	}{
 		{
 			name: "generate correctly",
@@ -583,7 +610,7 @@ func TestNewNoOpStatement(t *testing.T) {
 					previousSequence: 3,
 				},
 			},
-			want: handler.Statement{
+			want: &handler.Statement{
 				AggregateType:    "agg",
 				Execute:          nil,
 				Sequence:         5,
@@ -600,6 +627,174 @@ func TestNewNoOpStatement(t *testing.T) {
 	}
 }
 
+func TestNewMultiStatement(t *testing.T) {
+	type args struct {
+		table string
+		event *testEvent
+		execs []func(eventstore.EventReader) Exec
+	}
+
+	type want struct {
+		table            string
+		aggregateType    eventstore.AggregateType
+		sequence         uint64
+		previousSequence uint64
+		executer         *wantExecuter
+		isErr            func(error) bool
+	}
+	tests := []struct {
+		name string
+		args args
+		want want
+	}{
+		{
+			name: "no op",
+			args: args{
+				table: "my_table",
+				event: &testEvent{
+					aggregateType:    "agg",
+					sequence:         1,
+					previousSequence: 0,
+				},
+				execs: nil,
+			},
+			want: want{
+				executer: nil,
+			},
+		},
+		{
+			name: "no condition",
+			args: args{
+				table: "my_table",
+				event: &testEvent{
+					aggregateType:    "agg",
+					sequence:         1,
+					previousSequence: 0,
+				},
+				execs: []func(eventstore.EventReader) Exec{
+					AddDeleteStatement(
+						[]handler.Condition{},
+					),
+					AddCreateStatement(
+						[]handler.Column{
+							{
+								Name:  "col1",
+								Value: 1,
+							},
+						}),
+				},
+			},
+			want: want{
+				table:            "my_table",
+				aggregateType:    "agg",
+				sequence:         1,
+				previousSequence: 1,
+				executer: &wantExecuter{
+					shouldExecute: false,
+				},
+				isErr: func(err error) bool {
+					return errors.Is(err, handler.ErrNoCondition)
+				},
+			},
+		},
+		{
+			name: "correct",
+			args: args{
+				table: "my_table",
+				event: &testEvent{
+					sequence:         1,
+					previousSequence: 0,
+					aggregateType:    "agg",
+				},
+				execs: []func(eventstore.EventReader) Exec{
+					AddDeleteStatement(
+						[]handler.Condition{
+							{
+								Name:  "col1",
+								Value: 1,
+							},
+						}),
+					AddCreateStatement(
+						[]handler.Column{
+							{
+								Name:  "col1",
+								Value: 1,
+							},
+						}),
+					AddUpsertStatement(
+						[]handler.Column{
+							{
+								Name:  "col1",
+								Value: 1,
+							},
+						}),
+					AddUpdateStatement(
+						[]handler.Column{
+							{
+								Name:  "col1",
+								Value: 1,
+							},
+						},
+						[]handler.Condition{
+							{
+								Name:  "col1",
+								Value: 1,
+							},
+						}),
+				},
+			},
+			want: want{
+				table:            "my_table",
+				aggregateType:    "agg",
+				sequence:         1,
+				previousSequence: 1,
+				executer: &wantExecuter{
+					params: []params{
+						{
+							query: "DELETE FROM my_table WHERE (col1 = $1)",
+							args:  []interface{}{1},
+						},
+						{
+							query: "INSERT INTO my_table (col1) VALUES ($1)",
+							args:  []interface{}{1},
+						},
+						{
+							query: "UPSERT INTO my_table (col1) VALUES ($1)",
+							args:  []interface{}{1},
+						},
+						{
+							query: "UPDATE my_table SET (col1) = ($1) WHERE (col1 = $2)",
+							args:  []interface{}{1, 1},
+						},
+					},
+					shouldExecute: true,
+				},
+				isErr: func(err error) bool {
+					return err == nil
+				},
+			},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			stmt := NewMultiStatement(tt.args.event, tt.args.execs...)
+
+			if tt.want.executer != nil && stmt.Execute == nil {
+				t.Error("expected executer, but was nil")
+			}
+			if stmt.Execute == nil {
+				return
+			}
+			tt.want.executer.t = t
+			err := stmt.Execute(tt.want.executer, tt.args.table)
+			if !tt.want.isErr(err) {
+				t.Errorf("unexpected error: %v", err)
+			}
+			tt.want.executer.check(t)
+		})
+	}
+}
+
 func TestStatement_Execute(t *testing.T) {
 	type fields struct {
 		execute func(ex handler.Executer, projectionName string) error

internal/eventstore/handler/handler_projection.go

@@ -18,11 +18,11 @@ type ProjectionHandlerConfig struct {
 }
 
 //Update updates the projection with the given statements
-type Update func(context.Context, []Statement, Reduce) (unexecutedStmts []Statement, err error)
+type Update func(context.Context, []*Statement, Reduce) (unexecutedStmts []*Statement, err error)
 
 //Reduce reduces the given event to a statement
 //which is used to update the projection
-type Reduce func(eventstore.EventReader) ([]Statement, error)
+type Reduce func(eventstore.EventReader) (*Statement, error)
 
 //Lock is used for mutex handling if needed on the projection
 type Lock func(context.Context, time.Duration) <-chan error
@@ -46,7 +46,7 @@ type ProjectionHandler struct {
 	ProjectionName string
 
 	lockMu sync.Mutex
-	stmts  []Statement
+	stmts  []*Statement
 }
 
 func NewProjectionHandler(config ProjectionHandlerConfig) *ProjectionHandler {
@@ -156,7 +156,7 @@ func (h *ProjectionHandler) processEvent(
 	event eventstore.EventReader,
 	reduce Reduce,
 ) error {
-	stmts, err := reduce(event)
+	stmt, err := reduce(event)
 	if err != nil {
 		logging.Log("EVENT-PTr4j").WithError(err).Warn("unable to process event")
 		return err
@@ -165,7 +165,7 @@ func (h *ProjectionHandler) processEvent(
 	h.lockMu.Lock()
 	defer h.lockMu.Unlock()
 
-	h.stmts = append(h.stmts, stmts...)
+	h.stmts = append(h.stmts, stmt)
 
 	return nil
 }

internal/eventstore/handler/handler_projection_test.go

@@ -24,8 +24,9 @@ var (
 	ErrUpdate = errors.New("update err")
 )
 
-func newTestStatement(seq, previousSeq uint64) Statement {
+func newTestStatement(aggType eventstore.AggregateType, seq, previousSeq uint64) *Statement {
-	return Statement{
+	return &Statement{
+		AggregateType:    aggType,
 		Sequence:         seq,
 		PreviousSequence: previousSeq,
 	}
@@ -39,7 +40,7 @@ func initTimer() *time.Timer {
 
 func TestProjectionHandler_processEvent(t *testing.T) {
 	type fields struct {
-		stmts      []Statement
+		stmts      []*Statement
 		pushSet    bool
 		shouldPush *time.Timer
 	}
@@ -50,7 +51,7 @@ func TestProjectionHandler_processEvent(t *testing.T) {
 	}
 	type want struct {
 		isErr func(err error) bool
-		stmts []Statement
+		stmts []*Statement
 	}
 	tests := []struct {
 		name   string
@@ -76,41 +77,43 @@ func TestProjectionHandler_processEvent(t *testing.T) {
 			},
 		},
 		{
-			name: "no stmts",
+			name: "single new stmt",
 			fields: fields{
 				stmts:      nil,
 				pushSet:    false,
 				shouldPush: initTimer(),
 			},
 			args: args{
-				reduce: testReduce(),
+				reduce: testReduce(newTestStatement("aggregate1", 1, 0)),
 			},
 			want: want{
 				isErr: func(err error) bool {
 					return err == nil
 				},
-				stmts: nil,
+				stmts: []*Statement{
+					newTestStatement("aggregate1", 1, 0),
+				},
 			},
 		},
 		{
 			name: "existing stmts",
 			fields: fields{
-				stmts: []Statement{
+				stmts: []*Statement{
-					newTestStatement(1, 0),
+					newTestStatement("aggregate1", 1, 0),
 				},
 				pushSet:    false,
 				shouldPush: initTimer(),
 			},
 			args: args{
-				reduce: testReduce(newTestStatement(2, 1)),
+				reduce: testReduce(newTestStatement("aggregate1", 2, 1)),
 			},
 			want: want{
 				isErr: func(err error) bool {
 					return err == nil
 				},
-				stmts: []Statement{
+				stmts: []*Statement{
-					newTestStatement(1, 0),
+					newTestStatement("aggregate1", 1, 0),
-					newTestStatement(2, 1),
+					newTestStatement("aggregate1", 2, 1),
 				},
 			},
 		},
@@ -163,7 +166,7 @@ func TestProjectionHandler_fetchBulkStmts(t *testing.T) {
 			args: args{
 				ctx:    context.Background(),
 				query:  testQuery(nil, 0, ErrQuery),
-				reduce: testReduce(),
+				reduce: testReduce(newTestStatement("aggregate1", 1, 0)),
 			},
 			fields: fields{},
 			want: want{
@@ -185,7 +188,7 @@ func TestProjectionHandler_fetchBulkStmts(t *testing.T) {
 					5,
 					nil,
 				),
-				reduce: testReduce(),
+				reduce: testReduce(newTestStatement("test", 1, 0)),
 			},
 			fields: fields{
 				eventstore: eventstore.NewEventstore(
@@ -211,7 +214,7 @@ func TestProjectionHandler_fetchBulkStmts(t *testing.T) {
 					5,
 					nil,
 				),
-				reduce: testReduce(),
+				reduce: testReduce(newTestStatement("test", 1, 0)),
 			},
 			fields: fields{
 				eventstore: eventstore.NewEventstore(
@@ -237,7 +240,7 @@ func TestProjectionHandler_fetchBulkStmts(t *testing.T) {
 					5,
 					nil,
 				),
-				reduce: testReduce(),
+				reduce: testReduce(newTestStatement("test", 1, 0)),
 			},
 			fields: fields{
 				eventstore: eventstore.NewEventstore(
@@ -284,7 +287,7 @@ func TestProjectionHandler_fetchBulkStmts(t *testing.T) {
 					2,
 					nil,
 				),
-				reduce: testReduce(),
+				reduce: testReduce(newTestStatement("test", 1, 0)),
 			},
 			fields: fields{
 				eventstore: eventstore.NewEventstore(
@@ -343,7 +346,7 @@ func TestProjectionHandler_fetchBulkStmts(t *testing.T) {
 
 func TestProjectionHandler_push(t *testing.T) {
 	type fields struct {
-		stmts   []Statement
+		stmts   []*Statement
 		pushSet bool
 	}
 	type args struct {
@@ -365,9 +368,9 @@ func TestProjectionHandler_push(t *testing.T) {
 		{
 			name: "previous lock",
 			fields: fields{
-				stmts: []Statement{
+				stmts: []*Statement{
-					newTestStatement(1, 0),
+					newTestStatement("aggregate1", 1, 0),
-					newTestStatement(2, 1),
+					newTestStatement("aggregate1", 2, 1),
 				},
 				pushSet: true,
 			},
@@ -375,7 +378,7 @@ func TestProjectionHandler_push(t *testing.T) {
 				ctx:          context.Background(),
 				previousLock: 200 * time.Millisecond,
 				update:       testUpdate(t, 2, nil),
-				reduce:       testReduce(),
+				reduce:       testReduce(newTestStatement("aggregate1", 1, 0)),
 			},
 			want: want{
 				isErr:        func(err error) bool { return err == nil },
@@ -385,16 +388,16 @@ func TestProjectionHandler_push(t *testing.T) {
 		{
 			name: "error in update",
 			fields: fields{
-				stmts: []Statement{
+				stmts: []*Statement{
-					newTestStatement(1, 0),
+					newTestStatement("aggregate1", 1, 0),
-					newTestStatement(2, 1),
+					newTestStatement("aggregate1", 2, 1),
 				},
 				pushSet: true,
 			},
 			args: args{
 				ctx:    context.Background(),
 				update: testUpdate(t, 2, errors.New("some error")),
-				reduce: testReduce(),
+				reduce: testReduce(newTestStatement("test", 1, 0)),
 			},
 			want: want{
 				isErr: func(err error) bool { return err.Error() == "some error" },
@@ -668,7 +671,7 @@ func TestProjectionHandler_prepareExecuteBulk(t *testing.T) {
 	type fields struct {
 		Handler       Handler
 		SequenceTable string
-		stmts         []Statement
+		stmts         []*Statement
 		pushSet       bool
 		shouldPush    *time.Timer
 	}
@@ -754,7 +757,7 @@ func TestProjectionHandler_prepareExecuteBulk(t *testing.T) {
 					nil,
 				),
 				reduce: testReduce(
-					newTestStatement(2, 1),
+					newTestStatement("aggregate1", 2, 1),
 				),
 				ctx: context.Background(),
 			},
@@ -797,7 +800,7 @@ func TestProjectionHandler_prepareExecuteBulk(t *testing.T) {
 				shouldPush: initTimer(),
 			},
 			args: args{
-				update: testUpdate(t, 4, nil),
+				update: testUpdate(t, 2, nil),
 				query: testQuery(
 					eventstore.NewSearchQueryBuilder(eventstore.ColumnsEvent).
 						AddQuery().
@@ -807,8 +810,7 @@ func TestProjectionHandler_prepareExecuteBulk(t *testing.T) {
 					nil,
 				),
 				reduce: testReduce(
-					newTestStatement(1, 0),
+					newTestStatement("aggregate1", 0, 1),
-					newTestStatement(2, 1),
 				),
 				ctx: context.Background(),
 			},
@@ -838,22 +840,22 @@ func TestProjectionHandler_prepareExecuteBulk(t *testing.T) {
 }
 
 func testUpdate(t *testing.T, expectedStmtCount int, returnedErr error) Update {
-	return func(ctx context.Context, stmts []Statement, reduce Reduce) ([]Statement, error) {
+	return func(ctx context.Context, stmts []*Statement, reduce Reduce) ([]*Statement, error) {
 		if expectedStmtCount != len(stmts) {
 			t.Errorf("expected %d stmts got %d", expectedStmtCount, len(stmts))
 		}
-		return []Statement{}, returnedErr
+		return []*Statement{}, returnedErr
 	}
 }
 
-func testReduce(stmts ...Statement) Reduce {
+func testReduce(stmts *Statement) Reduce {
-	return func(event eventstore.EventReader) ([]Statement, error) {
+	return func(event eventstore.EventReader) (*Statement, error) {
 		return stmts, nil
 	}
 }
 
 func testReduceErr(err error) Reduce {
-	return func(event eventstore.EventReader) ([]Statement, error) {
+	return func(event eventstore.EventReader) (*Statement, error) {
 		return nil, err
 	}
 }

internal/query/projection/org.go

@@ -65,14 +65,13 @@ const (
 	orgNameCol          = "name"
 )
 
-func (p *OrgProjection) reduceOrgAdded(event eventstore.EventReader) ([]handler.Statement, error) {
+func (p *OrgProjection) reduceOrgAdded(event eventstore.EventReader) (*handler.Statement, error) {
 	e, ok := event.(*org.OrgAddedEvent)
 	if !ok {
 		logging.LogWithFields("HANDL-zWCk3", "seq", event.Sequence, "expectedType", org.OrgAddedEventType).Error("was not an  event")
 		return nil, errors.ThrowInvalidArgument(nil, "HANDL-uYq4r", "reduce.wrong.event.type")
 	}
-	return []handler.Statement{
+	return crdb.NewCreateStatement(
-		crdb.NewCreateStatement(
 		e,
 		[]handler.Column{
 			handler.NewCol(orgIDCol, e.Aggregate().ID),
@@ -83,11 +82,10 @@ func (p *OrgProjection) reduceOrgAdded(event eventstore.EventReader) ([]handler.
 			handler.NewCol(orgNameCol, e.Name),
 			handler.NewCol(orgStateCol, domain.OrgStateActive),
 		},
-		),
+	), nil
-	}, nil
 }
 
-func (p *OrgProjection) reduceOrgChanged(event eventstore.EventReader) ([]handler.Statement, error) {
+func (p *OrgProjection) reduceOrgChanged(event eventstore.EventReader) (*handler.Statement, error) {
 	e, ok := event.(*org.OrgChangedEvent)
 	if !ok {
 		logging.LogWithFields("HANDL-q4oq8", "seq", event.Sequence, "expected", org.OrgChangedEventType).Error("wrong event type")
@@ -100,25 +98,22 @@ func (p *OrgProjection) reduceOrgChanged(event eventstore.EventReader) ([]handle
 	if e.Name != "" {
 		values = append(values, handler.NewCol(orgNameCol, e.Name))
 	}
-	return []handler.Statement{
+	return crdb.NewUpdateStatement(
-		crdb.NewUpdateStatement(
 		e,
 		values,
 		[]handler.Condition{
 			handler.NewCond(orgIDCol, e.Aggregate().ID),
 		},
-		),
+	), nil
-	}, nil
 }
 
-func (p *OrgProjection) reduceOrgDeactivated(event eventstore.EventReader) ([]handler.Statement, error) {
+func (p *OrgProjection) reduceOrgDeactivated(event eventstore.EventReader) (*handler.Statement, error) {
 	e, ok := event.(*org.OrgDeactivatedEvent)
 	if !ok {
 		logging.LogWithFields("HANDL-1gwdc", "seq", event.Sequence, "expectedType", org.OrgDeactivatedEventType).Error("wrong event type")
 		return nil, errors.ThrowInvalidArgument(nil, "HANDL-BApK4", "reduce.wrong.event.type")
 	}
-	return []handler.Statement{
+	return crdb.NewUpdateStatement(
-		crdb.NewUpdateStatement(
 		e,
 		[]handler.Column{
 			handler.NewCol(orgChangeDateCol, e.CreationDate()),
@@ -128,18 +123,16 @@ func (p *OrgProjection) reduceOrgDeactivated(event eventstore.EventReader) ([]ha
 		[]handler.Condition{
 			handler.NewCond(orgIDCol, e.Aggregate().ID),
 		},
-		),
+	), nil
-	}, nil
 }
 
-func (p *OrgProjection) reduceOrgReactivated(event eventstore.EventReader) ([]handler.Statement, error) {
+func (p *OrgProjection) reduceOrgReactivated(event eventstore.EventReader) (*handler.Statement, error) {
 	e, ok := event.(*org.OrgReactivatedEvent)
 	if !ok {
 		logging.LogWithFields("HANDL-Vjwiy", "seq", event.Sequence, "expectedType", org.OrgReactivatedEventType).Error("wrong event type")
 		return nil, errors.ThrowInvalidArgument(nil, "HANDL-o37De", "reduce.wrong.event.type")
 	}
-	return []handler.Statement{
+	return crdb.NewUpdateStatement(
-		crdb.NewUpdateStatement(
 		e,
 		[]handler.Column{
 			handler.NewCol(orgChangeDateCol, e.CreationDate()),
@@ -149,18 +142,16 @@ func (p *OrgProjection) reduceOrgReactivated(event eventstore.EventReader) ([]ha
 		[]handler.Condition{
 			handler.NewCond(orgIDCol, e.Aggregate().ID),
 		},
-		),
+	), nil
-	}, nil
 }
 
-func (p *OrgProjection) reducePrimaryDomainSet(event eventstore.EventReader) ([]handler.Statement, error) {
+func (p *OrgProjection) reducePrimaryDomainSet(event eventstore.EventReader) (*handler.Statement, error) {
 	e, ok := event.(*org.DomainPrimarySetEvent)
 	if !ok {
 		logging.LogWithFields("HANDL-79OhB", "seq", event.Sequence, "expectedType", org.OrgDomainPrimarySetEventType).Error("wrong event type")
 		return nil, errors.ThrowInvalidArgument(nil, "HANDL-4TbKT", "reduce.wrong.event.type")
 	}
-	return []handler.Statement{
+	return crdb.NewUpdateStatement(
-		crdb.NewUpdateStatement(
 		e,
 		[]handler.Column{
 			handler.NewCol(orgChangeDateCol, e.CreationDate()),
@@ -170,6 +161,5 @@ func (p *OrgProjection) reducePrimaryDomainSet(event eventstore.EventReader) ([]
 		[]handler.Condition{
 			handler.NewCond(orgIDCol, e.Aggregate().ID),
 		},
-		),
+	), nil
-	}, nil
 }

internal/query/projection/org/owner/projection.go

@@ -110,7 +110,7 @@ func (p *OrgOwnerProjection) reducers() []handler.AggregateReducer {
 	}
 }
 
-func (p *OrgOwnerProjection) reduceMemberAdded(event eventstore.EventReader) ([]handler.Statement, error) {
+func (p *OrgOwnerProjection) reduceMemberAdded(event eventstore.EventReader) (*handler.Statement, error) {
 	e, ok := event.(*org.MemberAddedEvent)
 	if !ok {
 		logging.LogWithFields("PROJE-kL530", "seq", event.Sequence, "expected", org.MemberAddedEventType).Error("wrong event type")
@@ -118,7 +118,7 @@ func (p *OrgOwnerProjection) reduceMemberAdded(event eventstore.EventReader) ([]
 	}
 
 	if !isOrgOwner(e.Roles) {
-		return []handler.Statement{crdb.NewNoOpStatement(e)}, nil
+		return crdb.NewNoOpStatement(e), nil
 	}
 
 	stmt, err := p.addOwner(e, e.Aggregate().ResourceOwner, e.UserID)
@@ -126,10 +126,10 @@ func (p *OrgOwnerProjection) reduceMemberAdded(event eventstore.EventReader) ([]
 		return nil, err
 	}
 
-	return []handler.Statement{stmt}, nil
+	return stmt, nil
 }
 
-func (p *OrgOwnerProjection) reduceMemberChanged(event eventstore.EventReader) ([]handler.Statement, error) {
+func (p *OrgOwnerProjection) reduceMemberChanged(event eventstore.EventReader) (*handler.Statement, error) {
 	e, ok := event.(*org.MemberChangedEvent)
 	if !ok {
 		logging.LogWithFields("PROJE-kL530", "seq", event.Sequence, "expected", org.MemberAddedEventType).Error("wrong event type")
@@ -137,7 +137,7 @@ func (p *OrgOwnerProjection) reduceMemberChanged(event eventstore.EventReader) (
 	}
 
 	if !isOrgOwner(e.Roles) {
-		return []handler.Statement{p.deleteOwner(e, e.Aggregate().ID, e.UserID)}, nil
+		return p.deleteOwner(e, e.Aggregate().ID, e.UserID), nil
 	}
 
 	stmt, err := p.addOwner(e, e.Aggregate().ResourceOwner, e.UserID)
@@ -145,28 +145,27 @@ func (p *OrgOwnerProjection) reduceMemberChanged(event eventstore.EventReader) (
 		return nil, err
 	}
 
-	return []handler.Statement{stmt}, nil
+	return stmt, nil
 }
 
-func (p *OrgOwnerProjection) reduceMemberRemoved(event eventstore.EventReader) ([]handler.Statement, error) {
+func (p *OrgOwnerProjection) reduceMemberRemoved(event eventstore.EventReader) (*handler.Statement, error) {
 	e, ok := event.(*org.MemberRemovedEvent)
 	if !ok {
 		logging.LogWithFields("PROJE-boIbP", "seq", event.Sequence, "expected", org.MemberRemovedEventType).Error("wrong event type")
 		return nil, errors.ThrowInvalidArgument(nil, "PROJE-pk6TS", "reduce.wrong.event.type")
 	}
 
-	return []handler.Statement{p.deleteOwner(e, e.Aggregate().ID, e.UserID)}, nil
+	return p.deleteOwner(e, e.Aggregate().ID, e.UserID), nil
 }
 
-func (p *OrgOwnerProjection) reduceHumanEmailChanged(event eventstore.EventReader) ([]handler.Statement, error) {
+func (p *OrgOwnerProjection) reduceHumanEmailChanged(event eventstore.EventReader) (*handler.Statement, error) {
 	e, ok := event.(*user.HumanEmailChangedEvent)
 	if !ok {
 		logging.LogWithFields("PROJE-IHFwh", "seq", event.Sequence, "expected", user.HumanEmailChangedType).Error("wrong event type")
 		return nil, errors.ThrowInvalidArgument(nil, "PROJE-jMlwT", "reduce.wrong.event.type")
 	}
 
-	return []handler.Statement{
+	return crdb.NewUpdateStatement(
-		crdb.NewUpdateStatement(
 		e,
 		[]handler.Column{
 			handler.NewCol(userEmailCol, e.EmailAddress),
@@ -175,11 +174,10 @@ func (p *OrgOwnerProjection) reduceHumanEmailChanged(event eventstore.EventReade
 			handler.NewCond(userIDCol, e.Aggregate().ID),
 		},
 		crdb.WithTableSuffix(userTableSuffix),
-		),
+	), nil
-	}, nil
 }
 
-func (p *OrgOwnerProjection) reduceHumanProfileChanged(event eventstore.EventReader) ([]handler.Statement, error) {
+func (p *OrgOwnerProjection) reduceHumanProfileChanged(event eventstore.EventReader) (*handler.Statement, error) {
 	e, ok := event.(*user.HumanProfileChangedEvent)
 	if !ok {
 		logging.LogWithFields("PROJE-WqgUS", "seq", event.Sequence, "expected", user.HumanProfileChangedType).Error("wrong event type")
@@ -201,29 +199,26 @@ func (p *OrgOwnerProjection) reduceHumanProfileChanged(event eventstore.EventRea
 	}
 
 	if len(values) == 0 {
-		return []handler.Statement{crdb.NewNoOpStatement(e)}, nil
+		return crdb.NewNoOpStatement(e), nil
 	}
 
-	return []handler.Statement{
+	return crdb.NewUpdateStatement(
-		crdb.NewUpdateStatement(
 		e,
 		values,
 		[]handler.Condition{
 			handler.NewCond(userIDCol, e.Aggregate().ID),
 		},
 		crdb.WithTableSuffix(userTableSuffix),
-		),
+	), nil
-	}, nil
 }
 
-func (p *OrgOwnerProjection) reduceOrgAdded(event eventstore.EventReader) ([]handler.Statement, error) {
+func (p *OrgOwnerProjection) reduceOrgAdded(event eventstore.EventReader) (*handler.Statement, error) {
 	e, ok := event.(*org.OrgAddedEvent)
 	if !ok {
 		logging.LogWithFields("PROJE-wbOrL", "seq", event.Sequence, "expected", org.OrgAddedEventType).Error("wrong event type")
 		return nil, errors.ThrowInvalidArgument(nil, "PROJE-pk6TS", "reduce.wrong.event.type")
 	}
-	return []handler.Statement{
+	return crdb.NewCreateStatement(
-		crdb.NewCreateStatement(
 		e,
 		[]handler.Column{
 			handler.NewCol(orgIDCol, e.Aggregate().ResourceOwner),
@@ -231,11 +226,10 @@ func (p *OrgOwnerProjection) reduceOrgAdded(event eventstore.EventReader) ([]han
 			handler.NewCol(orgCreationDateCol, e.CreationDate()),
 		},
 		crdb.WithTableSuffix(orgTableSuffix),
-		),
+	), nil
-	}, nil
 }
 
-func (p *OrgOwnerProjection) reduceOrgChanged(event eventstore.EventReader) ([]handler.Statement, error) {
+func (p *OrgOwnerProjection) reduceOrgChanged(event eventstore.EventReader) (*handler.Statement, error) {
 	e, ok := event.(*org.OrgChangedEvent)
 	if !ok {
 		logging.LogWithFields("PROJE-piy2b", "seq", event.Sequence, "expected", org.OrgChangedEventType).Error("wrong event type")
@@ -248,46 +242,42 @@ func (p *OrgOwnerProjection) reduceOrgChanged(event eventstore.EventReader) ([]h
 	}
 
 	if len(values) == 0 {
-		return []handler.Statement{crdb.NewNoOpStatement(e)}, nil
+		return crdb.NewNoOpStatement(e), nil
 	}
 
-	return []handler.Statement{
+	return crdb.NewUpdateStatement(
-		crdb.NewUpdateStatement(
 		e,
 		values,
 		[]handler.Condition{
 			handler.NewCond(orgIDCol, e.Aggregate().ResourceOwner),
 		},
 		crdb.WithTableSuffix(orgTableSuffix),
-		),
+	), nil
-	}, nil
 }
 
-func (p *OrgOwnerProjection) reduceOrgRemoved(event eventstore.EventReader) ([]handler.Statement, error) {
+func (p *OrgOwnerProjection) reduceOrgRemoved(event eventstore.EventReader) (*handler.Statement, error) {
-	e, ok := event.(*org.OrgChangedEvent)
+	e, ok := event.(*org.OrgRemovedEvent)
 	if !ok {
 		logging.LogWithFields("PROJE-F1mHQ", "seq", event.Sequence, "expected", org.OrgRemovedEventType).Error("wrong event type")
 		return nil, errors.ThrowInvalidArgument(nil, "PROJE-9ZR2w", "reduce.wrong.event.type")
 	}
 
-	return []handler.Statement{
+	return crdb.NewMultiStatement(e,
 		//delete org in org table
-		crdb.NewDeleteStatement(
+		crdb.AddDeleteStatement(
-			e,
 			[]handler.Condition{
 				handler.NewCond(orgIDCol, e.Aggregate().ResourceOwner),
 			},
 			crdb.WithTableSuffix(orgTableSuffix),
 		),
 		// delete users of the org
-		crdb.NewDeleteStatement(
+		crdb.AddDeleteStatement(
-			e,
 			[]handler.Condition{
 				handler.NewCond(userOrgIDCol, e.Aggregate().ResourceOwner),
 			},
 			crdb.WithTableSuffix(userTableSuffix),
 		),
-	}, nil
+	), nil
 }
 
 func isOrgOwner(roles []string) bool {
@@ -299,7 +289,7 @@ func isOrgOwner(roles []string) bool {
 	return false
 }
 
-func (p *OrgOwnerProjection) deleteOwner(event eventstore.EventReader, orgID, ownerID string) handler.Statement {
+func (p *OrgOwnerProjection) deleteOwner(event eventstore.EventReader, orgID, ownerID string) *handler.Statement {
 	return crdb.NewDeleteStatement(
 		event,
 		[]handler.Condition{
@@ -310,7 +300,7 @@ func (p *OrgOwnerProjection) deleteOwner(event eventstore.EventReader, orgID, ow
 	)
 }
 
-func (p *OrgOwnerProjection) addOwner(event eventstore.EventReader, orgID, userID string) (handler.Statement, error) {
+func (p *OrgOwnerProjection) addOwner(event eventstore.EventReader, orgID, userID string) (*handler.Statement, error) {
 	events, err := p.Eventstore.FilterEvents(context.Background(),
 		eventstore.NewSearchQueryBuilder(eventstore.ColumnsEvent).
 			AddQuery().
@@ -330,12 +320,12 @@ func (p *OrgOwnerProjection) addOwner(event eventstore.EventReader, orgID, userI
 			SequenceLess(event.Sequence()).
 			Builder())
 	if err != nil {
-		return handler.Statement{}, err
+		return nil, err
 	}
 
 	if len(events) == 0 {
 		logging.LogWithFields("mqd3w", "user", userID, "org", orgID, "seq", event.Sequence()).Warn("no events for user found")
-		return handler.Statement{}, errors.ThrowInternal(nil, "PROJE-Qk7Tv", "unable to find user events")
+		return nil, errors.ThrowInternal(nil, "PROJE-Qk7Tv", "unable to find user events")
 	}
 
 	owner := &OrgOwner{

internal/query/projection/project.go

@@ -66,11 +66,10 @@ const (
 	projectInactive
 )
 
-func (p *ProjectProjection) reduceProjectAdded(event eventstore.EventReader) ([]handler.Statement, error) {
+func (p *ProjectProjection) reduceProjectAdded(event eventstore.EventReader) (*handler.Statement, error) {
 	e := event.(*project.ProjectAddedEvent)
 
-	return []handler.Statement{
+	return crdb.NewCreateStatement(
-		crdb.NewCreateStatement(
 		e,
 		[]handler.Column{
 			handler.NewCol(projectIDCol, e.Aggregate().ID),
@@ -81,19 +80,17 @@ func (p *ProjectProjection) reduceProjectAdded(event eventstore.EventReader) ([]
 			handler.NewCol(projectCreatorCol, e.EditorUser()),
 			handler.NewCol(projectStateCol, projectActive),
 		},
-		),
+	), nil
-	}, nil
 }
 
-func (p *ProjectProjection) reduceProjectChanged(event eventstore.EventReader) ([]handler.Statement, error) {
+func (p *ProjectProjection) reduceProjectChanged(event eventstore.EventReader) (*handler.Statement, error) {
 	e := event.(*project.ProjectChangeEvent)
 
 	if e.Name == nil {
-		return []handler.Statement{crdb.NewNoOpStatement(e)}, nil
+		return crdb.NewNoOpStatement(e), nil
 	}
 
-	return []handler.Statement{
+	return crdb.NewUpdateStatement(
-		crdb.NewUpdateStatement(
 		e,
 		[]handler.Column{
 			handler.NewCol(projectNameCol, e.Name),
@@ -102,15 +99,13 @@ func (p *ProjectProjection) reduceProjectChanged(event eventstore.EventReader) (
 		[]handler.Condition{
 			handler.NewCond(projectIDCol, e.Aggregate().ID),
 		},
-		),
+	), nil
-	}, nil
 }
 
-func (p *ProjectProjection) reduceProjectDeactivated(event eventstore.EventReader) ([]handler.Statement, error) {
+func (p *ProjectProjection) reduceProjectDeactivated(event eventstore.EventReader) (*handler.Statement, error) {
 	e := event.(*project.ProjectDeactivatedEvent)
 
-	return []handler.Statement{
+	return crdb.NewUpdateStatement(
-		crdb.NewUpdateStatement(
 		e,
 		[]handler.Column{
 			handler.NewCol(projectStateCol, projectInactive),
@@ -119,15 +114,13 @@ func (p *ProjectProjection) reduceProjectDeactivated(event eventstore.EventReade
 		[]handler.Condition{
 			handler.NewCond(projectIDCol, e.Aggregate().ID),
 		},
-		),
+	), nil
-	}, nil
 }
 
-func (p *ProjectProjection) reduceProjectReactivated(event eventstore.EventReader) ([]handler.Statement, error) {
+func (p *ProjectProjection) reduceProjectReactivated(event eventstore.EventReader) (*handler.Statement, error) {
 	e := event.(*project.ProjectReactivatedEvent)
 
-	return []handler.Statement{
+	return crdb.NewUpdateStatement(
-		crdb.NewUpdateStatement(
 		e,
 		[]handler.Column{
 			handler.NewCol(projectStateCol, projectActive),
@@ -136,19 +129,16 @@ func (p *ProjectProjection) reduceProjectReactivated(event eventstore.EventReade
 		[]handler.Condition{
 			handler.NewCond(projectIDCol, e.Aggregate().ID),
 		},
-		),
+	), nil
-	}, nil
 }
 
-func (p *ProjectProjection) reduceProjectRemoved(event eventstore.EventReader) ([]handler.Statement, error) {
+func (p *ProjectProjection) reduceProjectRemoved(event eventstore.EventReader) (*handler.Statement, error) {
 	e := event.(*project.ProjectRemovedEvent)
 
-	return []handler.Statement{
+	return crdb.NewDeleteStatement(
-		crdb.NewDeleteStatement(
 		e,
 		[]handler.Condition{
 			handler.NewCond(projectIDCol, e.Aggregate().ID),
 		},
-		),
+	), nil
-	}, nil
 }