Don't use more than 999 variables in SQLite querys. (#1425)

* Don't use more than 999 variables in SQLite querys.

Solve this problem in a more general and reusable way.
Also fix #1369
Add some unit tests.

Signed-off-by: Henrik Sölver <henrik.solver@gmail.com>

* Don't rely on testify for basic assertions

* Readability improvements and linting

Co-authored-by: Henrik Sölver <henrik.solver@gmail.com>

internal/sqlutil/sqlutil_test.go

@@ -0,0 +1,173 @@
+package sqlutil
+
+import (
+	"context"
+	"database/sql"
+	"reflect"
+	"testing"
+
+	sqlmock "github.com/DATA-DOG/go-sqlmock"
+)
+
+func TestShouldReturnCorrectAmountOfResulstIfFewerVariablesThanLimit(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	assertNoError(t, err, "Failed to make DB")
+	limit := uint(4)
+
+	r := mock.NewRows([]string{"id"}).
+		AddRow(1).
+		AddRow(2).
+		AddRow(3)
+
+	mock.ExpectQuery(`SELECT id WHERE id IN \(\$1, \$2, \$3\)`).WillReturnRows(r)
+	// nolint:goconst
+	q := "SELECT id WHERE id IN ($1)"
+	v := []int{1, 2, 3}
+	iKeyIDs := make([]interface{}, len(v))
+	for i, d := range v {
+		iKeyIDs[i] = d
+	}
+
+	ctx := context.Background()
+	var result = make([]int, 0)
+	err = RunLimitedVariablesQuery(ctx, q, db, iKeyIDs, limit, func(rows *sql.Rows) error {
+		for rows.Next() {
+			var id int
+			err = rows.Scan(&id)
+			assertNoError(t, err, "rows.Scan returned an error")
+			result = append(result, id)
+		}
+		return nil
+	})
+	assertNoError(t, err, "Call returned an error")
+	if len(result) != len(v) {
+		t.Fatalf("Result should be 3 long")
+	}
+}
+
+func TestShouldReturnCorrectAmountOfResulstIfEqualVariablesAsLimit(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	assertNoError(t, err, "Failed to make DB")
+	limit := uint(4)
+
+	r := mock.NewRows([]string{"id"}).
+		AddRow(1).
+		AddRow(2).
+		AddRow(3).
+		AddRow(4)
+
+	mock.ExpectQuery(`SELECT id WHERE id IN \(\$1, \$2, \$3, \$4\)`).WillReturnRows(r)
+	// nolint:goconst
+	q := "SELECT id WHERE id IN ($1)"
+	v := []int{1, 2, 3, 4}
+	iKeyIDs := make([]interface{}, len(v))
+	for i, d := range v {
+		iKeyIDs[i] = d
+	}
+
+	ctx := context.Background()
+	var result = make([]int, 0)
+	err = RunLimitedVariablesQuery(ctx, q, db, iKeyIDs, limit, func(rows *sql.Rows) error {
+		for rows.Next() {
+			var id int
+			err = rows.Scan(&id)
+			assertNoError(t, err, "rows.Scan returned an error")
+			result = append(result, id)
+		}
+		return nil
+	})
+	assertNoError(t, err, "Call returned an error")
+	if len(result) != len(v) {
+		t.Fatalf("Result should be 4 long")
+	}
+}
+
+func TestShouldReturnCorrectAmountOfResultsIfMoreVariablesThanLimit(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	assertNoError(t, err, "Failed to make DB")
+	limit := uint(4)
+
+	r1 := mock.NewRows([]string{"id"}).
+		AddRow(1).
+		AddRow(2).
+		AddRow(3).
+		AddRow(4)
+
+	r2 := mock.NewRows([]string{"id"}).
+		AddRow(5)
+
+	mock.ExpectQuery(`SELECT id WHERE id IN \(\$1, \$2, \$3, \$4\)`).WillReturnRows(r1)
+	mock.ExpectQuery(`SELECT id WHERE id IN \(\$1\)`).WillReturnRows(r2)
+	// nolint:goconst
+	q := "SELECT id WHERE id IN ($1)"
+	v := []int{1, 2, 3, 4, 5}
+	iKeyIDs := make([]interface{}, len(v))
+	for i, d := range v {
+		iKeyIDs[i] = d
+	}
+
+	ctx := context.Background()
+	var result = make([]int, 0)
+	err = RunLimitedVariablesQuery(ctx, q, db, iKeyIDs, limit, func(rows *sql.Rows) error {
+		for rows.Next() {
+			var id int
+			err = rows.Scan(&id)
+			assertNoError(t, err, "rows.Scan returned an error")
+			result = append(result, id)
+		}
+		return nil
+	})
+	assertNoError(t, err, "Call returned an error")
+	if len(result) != len(v) {
+		t.Fatalf("Result should be 5 long")
+	}
+	if !reflect.DeepEqual(v, result) {
+		t.Fatalf("Result is not as expected: got %v want %v", v, result)
+	}
+}
+
+func TestShouldReturnErrorIfRowsScanReturnsError(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	assertNoError(t, err, "Failed to make DB")
+	limit := uint(4)
+
+	// adding a string ID should result in rows.Scan returning an error
+	r := mock.NewRows([]string{"id"}).
+		AddRow("hej").
+		AddRow(2).
+		AddRow(3)
+
+	mock.ExpectQuery(`SELECT id WHERE id IN \(\$1, \$2, \$3\)`).WillReturnRows(r)
+	// nolint:goconst
+	q := "SELECT id WHERE id IN ($1)"
+	v := []int{-1, -2, 3}
+	iKeyIDs := make([]interface{}, len(v))
+	for i, d := range v {
+		iKeyIDs[i] = d
+	}
+
+	ctx := context.Background()
+	var result = make([]uint, 0)
+	err = RunLimitedVariablesQuery(ctx, q, db, iKeyIDs, limit, func(rows *sql.Rows) error {
+		for rows.Next() {
+			var id uint
+			err = rows.Scan(&id)
+			if err != nil {
+				return err
+			}
+			result = append(result, id)
+		}
+		return nil
+	})
+	if err == nil {
+		t.Fatalf("Call did not return an error")
+	}
+}
+
+func assertNoError(t *testing.T, err error, msg string) {
+	t.Helper()
+	if err == nil {
+		return
+	}
+	t.Fatalf(msg)
+}