Introduce a new method mysqlConn.Reset()

[zenovich]

Description

This PR introduces a new method mysqlConn.Reset() sending COM_RESET_CONNECTION to the connection and checking the result.

As discussed in #1273, although there are strong reasons (https://github.com/go-sql-driver/mysql/issues/1273#issuecomment-2227210191, https://github.com/go-sql-driver/mysql/issues/1273#issuecomment-3202690653) to call this new method in mysqlConn.ResetSession() (probably at the end of the method), we are not going to call it for now because it has not been decided yet.

Here, we only add the implementation to allow people not to go through creating dirty hacks like those here: https://github.com/France-ioi/AlgoreaBackend/blob/master/app/database/mysql_conn_reset.go#L95

Checklist

• [x] Code compiles correctly
• [x] Created tests which fail without the change (if possible)
• [x] All tests passing
• [x] Extended the README / documentation, if necessary
• [x] Added myself / the copyright holder to the AUTHORS file

[coderabbitai[bot]]

Walkthrough

Adds three MySQL command opcodes, a reusable no-argument command helper, a public mysqlConn.Reset(ctx) method, refactors Ping to use the helper, consolidates connection tests into table-driven cases for Ping/Reset, expands driver tests for Reset behavior, and appends an AUTHORS entry.

Changes

Cohort / File(s)	Summary
Authorship metadata AUTHORS	Adds "Dmitry Zenovich " under Individual Persons.
Command opcodes const.go	Appends comDaemon, comBinlogDumpGTID, and comResetConnection to the MySQL command opcode list (new byte constants).
No-arg command core & public API connection.go	Adds sendSimpleCommandOK(ctx context.Context, cmd byte) helper; adds func (mc *mysqlConn) Reset(ctx context.Context) error which sends COM_RESET_CONNECTION; refactors Ping to delegate to the new helper.
Connection unit tests connection_test.go	Replaces Ping-specific tests with table-driven TestSimpleCommandOK* tests exercising Ping and Reset for clean cancelation, bad-connection marking, and invalid underlying connection scenarios.
Driver/integration tests driver_test.go	Adds TestSimpleCommandOK and TestReset to exercise Ping/Reset via database/sql.Conn.Raw, verify internal buffers are cleared and session variable reset; minor cleanup to Ping test setup.

Sequence Diagram(s)

sequenceDiagram
  autonumber
  actor Client
  participant MC as mysqlConn
  participant Net as net.Conn
  participant S as MySQL Server

  rect rgb(245,250,255)
    note over Client,MC: No-arg command flow (Ping / Reset)
    Client->>MC: Ping(ctx) / Reset(ctx)
    MC->>MC: sendSimpleCommandOK(ctx, cmd)
    MC->>Net: writeCommandPacket(cmd)
    Net->>S: COM_PING / COM_RESET_CONNECTION
    S-->>Net: OK packet
    Net-->>MC: OK packet
    MC->>MC: readResultOK()
    MC-->>Client: return (nil or error)
  end

sequenceDiagram
  autonumber
  actor Test
  participant DB as database/sql.Conn
  participant MC as mysqlConn
  participant S as MySQL Server

  note over Test,MC: Reset clears server session state
  Test->>S: SET @a := 1
  Test->>S: SELECT @a  (expect 1)
  Test->>DB: Conn.Raw => mc
  Test->>MC: Reset(ctx)
  MC->>S: COM_RESET_CONNECTION
  S-->>MC: OK
  Test->>S: SELECT @a  (expect NULL)

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~30 minutes

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[zenovich]

Probably we could add the new method into the interface introduced in #1454 to allow calling it from outside easier.

[zenovich]

PTAL

[zenovich]

PTAL

[zenovich]

PTAL

[zenovich]

PTAL

[zenovich]

Actionable comments posted: 0

🧹 Nitpick comments (2)

driver_test.go (2)> 2355-2368: Avoid potential flakiness: verify result after rows.Close, not before

For SELECT, the driver may finalize result metadata (affectedRows/insertIds) only after the result set is fully consumed/closed. Checking these fields before q.Close risks a race across server versions/protocols. Move the assertions below q.Close:

-					if got, want := c.result.affectedRows, []int64{0}; !reflect.DeepEqual(got, want) {
-						dbt.Fatalf("bad affectedRows: got %v, want=%v", got, want)
-					}
-					if got, want := c.result.insertIds, []int64{0}; !reflect.DeepEqual(got, want) {
-						dbt.Fatalf("bad insertIds: got %v, want=%v", got, want)
-					}
 					if err := q.Close(); err != nil {
 						dbt.fail("Rows", "Close", err)
 					}
+					if got := c.result.affectedRows; len(got) != 1 || got[0] != 0 {
+						dbt.Fatalf("bad affectedRows: got %v, want [0]", got)
+					}
+					if got := c.result.insertIds; len(got) != 1 || got[0] != 0 {
+						dbt.Fatalf("bad insertIds: got %v, want [0]", got)
+					}

2380-2385: Prefer explicit nil checks over reflect.DeepEqual for slices These assertions are specifically verifying nil (not just “empty”). Use direct nil checks for clarity and to avoid reflect costs.

-						if got, want := c.result.affectedRows, []int64(nil); !reflect.DeepEqual(got, want) {
-							t.Errorf("bad affectedRows: got %v, want=%v", got, want)
-						}
-						if got, want := c.result.insertIds, []int64(nil); !reflect.DeepEqual(got, want) {
-							t.Errorf("bad insertIds: got %v, want=%v", got, want)
-						}
+						if c.result.affectedRows != nil {
+							t.Errorf("bad affectedRows: got %v, want nil", c.result.affectedRows)
+						}
+						if c.result.insertIds != nil {
+							t.Errorf("bad insertIds: got %v, want nil", c.result.insertIds)
+						}

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📥 Commits 📒 Files selected for processing (1) 🧰 Additional context used 🔇 Additional comments (2)

This is something that had been done this way before the PR was created.

[zenovich]

LGTM