Add cascade deletes for host software (#1739)

* Add cascade deletes for host software

* Add changes file

* The drop doesn't work on certain mysql

* Fix error message

changes/host-removal-with-software

@@ -0,0 +1 @@
+* MariaDB compatibility fixes: add explicit foreign key constraint and on cascade delete for host_software to allow for hosts with software to be deleted.

server/datastore/mysql/hosts_test.go

@@ -96,6 +96,42 @@ func TestSaveHosts(t *testing.T) {
 	assert.Nil(t, host)
 }
 
+func TestDeleteHostWithSoftware(t *testing.T) {
+	ds := CreateMySQLDS(t)
+	defer ds.Close()
+
+	host, err := ds.NewHost(&fleet.Host{
+		DetailUpdatedAt: time.Now(),
+		LabelUpdatedAt:  time.Now(),
+		SeenTime:        time.Now(),
+		NodeKey:         "1",
+		UUID:            "1",
+		Hostname:        "foo.local",
+		PrimaryIP:       "192.168.1.1",
+		PrimaryMac:      "30-65-EC-6F-C4-58",
+	})
+	require.NoError(t, err)
+	require.NotNil(t, host)
+
+	soft := fleet.HostSoftware{
+		Modified: true,
+		Software: []fleet.Software{
+			{Name: "foo", Version: "0.0.1", Source: "chrome_extensions"},
+			{Name: "foo", Version: "0.0.3", Source: "chrome_extensions"},
+		},
+	}
+	host.HostSoftware = soft
+	err = ds.SaveHostSoftware(host)
+	require.NoError(t, err)
+
+	err = ds.DeleteHost(host.ID)
+	require.NoError(t, err)
+
+	host, err = ds.Host(host.ID)
+	assert.NotNil(t, err)
+	assert.Nil(t, host)
+}
+
 func TestSaveHostPackStats(t *testing.T) {
 	ds := CreateMySQLDS(t)
 	defer ds.Close()

server/datastore/mysql/migrations/tables/20210818151827_RemoveForeignKeysSchedQStats.go

@@ -12,22 +12,14 @@ func init() {
 }
 
 func Up_20210818151827(tx *sql.Tx) error {
-	rows, err := tx.Query(`SELECT DISTINCT CONSTRAINT_NAME, REFERENCED_TABLE_NAME FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE WHERE TABLE_NAME = 'scheduled_query_stats' AND CONSTRAINT_NAME <> 'PRIMARY'`)
+	referencedTables := map[string]struct{}{"hosts": {}, "scheduled_queries": {}}
+	table := "scheduled_query_stats"
+
+	constraints, err := constraintsForTable(tx, table, referencedTables)
 	if err != nil {
-		return errors.Wrap(err, "getting fk for scheduled_query_stats")
-	}
-	var constraints []string
-	for rows.Next() {
-		var constraintName string
-		var referencedTable string
-		err := rows.Scan(&constraintName, &referencedTable)
-		if err != nil {
-			return errors.Wrap(err, "scanning fk for scheduled_query_stats")
-		}
-		if referencedTable == "hosts" || referencedTable == "scheduled_queries" {
-			constraints = append(constraints, constraintName)
-		}
+		return err
 	}
+
 	if len(constraints) == 0 {
 		return errors.New("Found no constraints in scheduled_query_stats")
 	}
@@ -41,6 +33,27 @@ func Up_20210818151827(tx *sql.Tx) error {
 	return nil
 }
 
+func constraintsForTable(tx *sql.Tx, table string, referencedTables map[string]struct{}) ([]string, error) {
+	var constraints []string
+	query := `SELECT DISTINCT CONSTRAINT_NAME, REFERENCED_TABLE_NAME FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE WHERE TABLE_NAME = ? AND CONSTRAINT_NAME <> 'PRIMARY'`
+	rows, err := tx.Query(query, table)
+	if err != nil {
+		return nil, errors.Wrap(err, "getting fk for scheduled_query_stats")
+	}
+	for rows.Next() {
+		var constraintName string
+		var referencedTable string
+		err := rows.Scan(&constraintName, &referencedTable)
+		if err != nil {
+			return nil, errors.Wrap(err, "scanning fk for scheduled_query_stats")
+		}
+		if _, ok := referencedTables[referencedTable]; ok {
+			constraints = append(constraints, constraintName)
+		}
+	}
+	return constraints, nil
+}
+
 func Down_20210818151827(tx *sql.Tx) error {
 	return nil
 }

server/datastore/mysql/migrations/tables/20210819131107_AddCascadeToHostSoftware.go

@@ -0,0 +1,46 @@
+package tables
+
+import (
+	"database/sql"
+	"fmt"
+	"strings"
+
+	"github.com/pkg/errors"
+)
+
+func init() {
+	MigrationClient.AddMigration(Up_20210819131107, Down_20210819131107)
+}
+
+func Up_20210819131107(tx *sql.Tx) error {
+	referencedTables := map[string]struct{}{"hosts": {}, "software": {}}
+	table := "host_software"
+
+	constraints, err := constraintsForTable(tx, table, referencedTables)
+	if err != nil {
+		return err
+	}
+
+	for _, constraint := range constraints {
+		_, err = tx.Exec(fmt.Sprintf(`ALTER TABLE host_software DROP FOREIGN KEY %s;`, constraint))
+		if err != nil {
+			if !strings.Contains(err.Error(), "check that column/key exists") {
+				return errors.Wrapf(err, "dropping fk %s", constraint)
+			}
+		}
+	}
+
+	if _, err := tx.Exec(`
+		ALTER TABLE host_software
+		ADD FOREIGN KEY host_software_hosts_fk(host_id) REFERENCES hosts (id) ON DELETE CASCADE,
+		ADD FOREIGN KEY host_software_software_fk(software_id) REFERENCES software (id) ON DELETE CASCADE
+	`); err != nil {
+		return errors.Wrap(err, "add fk on host_software hosts & software")
+	}
+
+	return nil
+}
+
+func Down_20210819131107(tx *sql.Tx) error {
+	return nil
+}