GUC Parameters of GaussDB (MySQL-Compatible Mode)

For a MySQL-compatible GaussDB database, you can set GUC parameters listed in Table 1 to enhance compatibility.

GaussDB provides many parameters, which determine how the database system works. Before modifying these parameters, you need to understand the impact on databases. Otherwise, unexpected results may occur.

Set the b_format_dev_version parameter as follows:

• For GaussDB V2.0-8.0 Enterprise Edition, set the value to s1.
• For GaussDB V2.0-8.100 Enterprise Edition and GaussDB V2.0-8.200 Enterprise Edition, set the value to s2.

• Setting b_format_dev_version to s1 will affect:
  • NEW() function, last_day() function, date_sub(date, INTERVAL expr unit), datediff(expr1, expr2), day()/dayofmonth(), and dayname()
  • dayofweek(), dayofyear(), extract(unit FROM date), from_days(days), from_unixtime(unix_timestamp[,format]), get_format({DATE | TIME | DATETIME | TIMESTAMP}, {'EUR' | 'USA' | 'JIS' | 'ISO' | 'INTERNAL'}), hour(), makedate(year,dayofyear), microsecond(), minute(), month(), monthname(), period_add(period, month_number)
  • TIMESTAMPDIFF, yearweek(date[, mode]), year(), weekofyear(date), weekday(), week(date[, mode]), utc_timestamp(), utc_time(), period_diff(p1,p2), second().
  • quarter(), str_to_date(str, format), subdate(expr, days), time_format(time, format), ifnull(expr1, expr2), database(), current_date, current_time, current_timestamp
  • round(arg1, arg2), localtime([precision]), localtimestamp, dbtimezone, timenow(), numtodsinterval(num, interval_unit), numtoyminterval(num, interval_unit)
  • new_time(date, timezone1,timezone2), sysdate([precision]), add_months(d,n), months_between(d1, d2), convert_tz(dt, from_tz, to_tz)
  • adddate(date, INTERVAL expr unit), date_format(date, format)

• Setting b_format_dev_version to s2 will affect:
  • Compatibility behaviors of s1
  • The following functions:
    • When data is imported to the AUTO_INCREMENT column or the BATCH INSERT execution plan is inserted, if 0, NULL, and determined values are used together, the auto-increment count is updated immediately when the determined value is inserted, the subsequent 0 or NULL increases automatically based on the determined value.
    • The like operator does not report an error when an escape character is at the end of the matching string.
    • The priorities of the sorting rules for character sets and character orders are changed.
  • The following syntax is affected:
    • The CREATE TABLE table_name LIKE source_table syntax is supported.
    • The INCLUDING and EXCLUDING options cannot be specified for the CREATE TABLE table_name LIKE source_table and CREATE TABLE table_name (LIKE source_table) syntax. By default, INCLUDING ALL is specified.
    • The LOAD DATA syntax is supported. Some syntax functions in gs_loader that are consistent with the LOAD DATA syntax will change.
    • The COLLATE clause can be specified in SET NAMES.
    • The syntax for changing table names, such as ALTER TABLE and RENAME TABLE, is involved. For example, if the character string corresponding to the new table name starts with #MySQL50# and is followed by other characters, #MySQL50# will be ignored.