database/sql: close driver.Connector if it implements io.Closer

This change allows driver implementations to manage resources in
driver.Connector, e.g. to share the same underlying database handle
between multiple connections. That is, it allows embedded databases
with in-memory backends like SQLite and Genji to safely release the
resources once the sql.DB is closed.

This makes it possible to address oddities with in-memory stores in
SQLite and Genji drivers without introducing too much complexity in
the driver implementations.

See also:
- https://github.com/mattn/go-sqlite3/issues/204
- https://github.com/mattn/go-sqlite3/issues/511
- https://github.com/genjidb/genji/issues/210

Fixes #41790

Change-Id: Idbd19763134438ed38288b9d44f16608e4e97fd7
GitHub-Last-Rev: 962c785dfb3bb6ad98b2216bcedd84ba383fe872
GitHub-Pull-Request: golang/go#41710
Reviewed-on: https://go-review.googlesource.com/c/go/+/258360
Reviewed-by: Emmanuel Odeke <emmanuel@orijtech.com>
Reviewed-by: Daniel Theophanes <kardianos@gmail.com>
Trust: Emmanuel Odeke <emmanuel@orijtech.com>
Run-TryBot: Emmanuel Odeke <emmanuel@orijtech.com>
TryBot-Result: Go Bot <gobot@golang.org>

diff --git a/src/database/sql/driver/driver.go b/src/database/sql/driver/driver.go
index 5bbcf20db2f07d90f91d1d3d2f82786b55b7d948..f09396175acf86099e5d902fb944d1f8131210e2 100644 (file)
--- a/src/database/sql/driver/driver.go
+++ b/src/database/sql/driver/driver.go
@@ -115,6 +115,9 @@ type DriverContext interface {
 // DriverContext's OpenConnector method, to allow drivers
 // access to context and to avoid repeated parsing of driver
 // configuration.
+//
+// If a Connector implements io.Closer, the sql package's DB.Close
+// method will call Close and return error (if any).
 type Connector interface {
        // Connect returns a connection to the database.
        // Connect may return a cached connection (one previously

diff --git a/src/database/sql/fakedb_test.go b/src/database/sql/fakedb_test.go
index 7605a2a6d23e0327bcccaf1d8a8cd9d616a26a23..1bfd1118aad68b1ae24f207b0b8dcfe49f972631 100644 (file)
--- a/src/database/sql/fakedb_test.go
+++ b/src/database/sql/fakedb_test.go
@@ -56,6 +56,7 @@ type fakeConnector struct {
        name string
 
        waiter func(context.Context)
+       closed bool
 }
 
 func (c *fakeConnector) Connect(context.Context) (driver.Conn, error) {
@@ -68,6 +69,14 @@ func (c *fakeConnector) Driver() driver.Driver {
        return fdriver
 }
 
+func (c *fakeConnector) Close() error {
+       if c.closed {
+               return errors.New("fakedb: connector is closed")
+       }
+       c.closed = true
+       return nil
+}
+
 type fakeDriverCtx struct {
        fakeDriver
 }

diff --git a/src/database/sql/sql.go b/src/database/sql/sql.go
index 726aadb8990e6871fdb1253e4f422e60b39f229f..37bcb0d09186457f3cea265fd2827fa7968f5e42 100644 (file)
--- a/src/database/sql/sql.go
+++ b/src/database/sql/sql.go
@@ -850,6 +850,12 @@ func (db *DB) Close() error {
                }
        }
        db.stop()
+       if c, ok := db.connector.(io.Closer); ok {
+               err1 := c.Close()
+               if err1 != nil {
+                       err = err1
+               }
+       }
        return err
 }
 

diff --git a/src/database/sql/sql_test.go b/src/database/sql/sql_test.go
index 99bfd62491fa3beb3d4721b024ba93dc5b5181df..c06e565ea9c7a57d54b8dce533086391eb46ea63 100644 (file)
--- a/src/database/sql/sql_test.go
+++ b/src/database/sql/sql_test.go
@@ -4059,9 +4059,18 @@ func TestOpenConnector(t *testing.T) {
        }
        defer db.Close()
 
-       if _, is := db.connector.(*fakeConnector); !is {
+       c, ok := db.connector.(*fakeConnector)
+       if !ok {
                t.Fatal("not using *fakeConnector")
        }
+
+       if err := db.Close(); err != nil {
+               t.Fatal(err)
+       }
+
+       if !c.closed {
+               t.Fatal("connector is not closed")
+       }
 }
 
 type ctxOnlyDriver struct {