Function buildUniqueKeyMinMaxValuesPreparedQuery

go/sql/builder.go:759–789

(databaseName, tableName string, uniqueKey *UniqueKey, order string)

}

func buildUniqueKeyMinMaxValuesPreparedQuery(databaseName, tableName string, uniqueKey *UniqueKey, order string) (string, error) {
	if uniqueKey.Columns.Len() == 0 {
		return "", fmt.Errorf("got 0 columns in BuildUniqueKeyMinMaxValuesPreparedQuery")
	}
	databaseName = EscapeName(databaseName)
	tableName = EscapeName(tableName)

	uniqueKeyColumnNames := duplicateNames(uniqueKey.Columns.Names())
	uniqueKeyColumnOrder := make([]string, len(uniqueKeyColumnNames))
	for i, column := range uniqueKey.Columns.Columns() {
		uniqueKeyColumnNames[i] = EscapeName(uniqueKeyColumnNames[i])
		if column.Type == EnumColumnType {
			uniqueKeyColumnOrder[i] = fmt.Sprintf("concat(%s) %s", uniqueKeyColumnNames[i], order)
		} else {
			uniqueKeyColumnOrder[i] = fmt.Sprintf("%s %s", uniqueKeyColumnNames[i], order)
		}
	}
	query := fmt.Sprintf(`
		select /* gh-ost %s.%s */ %s
		from
			%s.%s
		force index (%s)
		order by
			%s
		limit 1`,
		databaseName, tableName, strings.Join(uniqueKeyColumnNames, ", "),
		databaseName, tableName, uniqueKey.Name,
		strings.Join(uniqueKeyColumnOrder, ", "),
	)
	return query, nil
}

// DMLDeleteQueryBuilder can build DELETE queries for DML events.
// It holds the prepared query statement so it doesn't need to be recreated every time.