Method writeExecutePacket

packets.go:1045–1241

Execute Prepared Statement https://dev.mysql.com/doc/dev/mysql-server/latest/page_protocol_com_stmt_execute.html

(args []driver.Value)

// Execute Prepared Statement
// https://dev.mysql.com/doc/dev/mysql-server/latest/page_protocol_com_stmt_execute.html
func (stmt *mysqlStmt) writeExecutePacket(args []driver.Value) error {
	if len(args) != stmt.paramCount {
		return fmt.Errorf(
			"argument count mismatch (got: %d; has: %d)",
			len(args),
			stmt.paramCount,
		)
	}

	const minPktLen = 4 + 1 + 4 + 1 + 4
	mc := stmt.mc

	// Determine threshold dynamically to avoid packet size shortage.
	longDataSize := max(mc.maxAllowedPacket/(stmt.paramCount+1), 64)

	// Reset packet-sequence
	mc.resetSequence()

	var data []byte
	var err error

	if len(args) == 0 {
		data, err = mc.buf.takeBuffer(minPktLen)
	} else {
		data, err = mc.buf.takeCompleteBuffer()
		// In this case the len(data) == cap(data) which is used to optimise the flow below.
	}
	if err != nil {
		return err
	}

	// command [1 byte]
	data[4] = comStmtExecute

	// statement_id [4 bytes]
	binary.LittleEndian.PutUint32(data[5:], stmt.id)

	// flags (0: CURSOR_TYPE_NO_CURSOR) [1 byte]
	data[9] = 0x00

	// iteration_count (uint32(1)) [4 bytes]
	binary.LittleEndian.PutUint32(data[10:], 1)

	if len(args) > 0 {
		pos := minPktLen

		var nullMask []byte
		if maskLen, typesLen := (len(args)+7)/8, 1+2*len(args); pos+maskLen+typesLen >= cap(data) {
			// buffer has to be extended but we don't know by how much so
			// we depend on append after all data with known sizes fit.
			// We stop at that because we deal with a lot of columns here
			// which makes the required allocation size hard to guess.
			tmp := make([]byte, pos+maskLen+typesLen)
			copy(tmp[:pos], data[:pos])
			data = tmp
			nullMask = data[pos : pos+maskLen]
			// No need to clean nullMask as make ensures that.
			pos += maskLen