What causes "failed to prepare delete statement" in micro/go-micro?

Inspect the wrapped cause for the MySQL error code

failed to prepare delete statement

Error message

failed to prepare delete statement

What it means

initDB prepares the DELETE statement used by sqlStore.Delete; failure aborts store configuration. As with the other prepare steps, this almost always means a dead connection or invalid interpolated SQL identifiers.

Source

Thrown at store/mysql/mysql.go:176

		return errors.Wrap(err, "Couldn't create table")
	}

	// prepare statements
	var prepareErr error

	s.readPrepare, prepareErr = s.db.Prepare(fmt.Sprintf("SELECT `key`, value, expiry FROM %s.%s WHERE `key` = ?;", s.database, s.table))
	if prepareErr != nil {
		return errors.Wrap(prepareErr, "failed to prepare read statement")
	}

	s.writePrepare, prepareErr = s.db.Prepare(fmt.Sprintf("INSERT INTO %s.%s (`key`, value, expiry) VALUES(?, ?, ?) ON DUPLICATE KEY UPDATE `value`= ?, `expiry` = ?", s.database, s.table))
	if prepareErr != nil {
		return errors.Wrap(prepareErr, "failed to prepare write statement")
	}

	s.deletePrepare, prepareErr = s.db.Prepare(fmt.Sprintf("DELETE FROM %s.%s WHERE `key` = ?;", s.database, s.table))
	if prepareErr != nil {
		return errors.Wrap(prepareErr, "failed to prepare delete statement")
	}

	return nil
}

func (s *sqlStore) configure() error {
	nodes := s.options.Nodes
	if len(nodes) == 0 {
		nodes = []string{"localhost:3306"}
	}

	database := s.options.Database
	if len(database) == 0 {
		database = DefaultDatabase
	}

	table := s.options.Table
	if len(table) == 0 {

View on GitHub (pinned to 24529f1404)

Solutions

Inspect the wrapped cause for the MySQL error code
Validate database/table identifiers derived from the namespace
Retry configure/recreate the store after connection recovery
Check max_prepared_stmt_count and proxy restrictions on the server

Defensive patterns

Strategy: retry

Validate before calling

if err := db.Ping(); err != nil {
    return fmt.Errorf("mysql unreachable before store configure: %w", err)
}

Try / catch

if err := st.Init(opts...); err != nil {
    if strings.Contains(err.Error(), "failed to prepare delete statement") {
        time.Sleep(time.Second)
        return st.Init(opts...)
    }
    return err
}

Prevention

Ensure a stable connection for all three prepares (read/write/delete)
Validate namespace-derived table names
Watch prepared statement limits and proxy behavior
Retry Init on transient failures

When it happens

Trigger: configure() -> initDB() prepares `DELETE FROM <db>.<table> WHERE key = ?` and db.Prepare errors, typically as the last of the three prepares after an earlier connection drop.

Common situations: MySQL restart or network blip mid-configure; invalid namespace characters in the table identifier; server-side prepared statement limits or restrictions reached.

Related errors

AI-assisted analysis of micro/go-micro@24529f1404 (2026-09-01). Data as JSON: /api/errors/94fdf6f44c136d8f. Report an issue: GitHub.