Miscellaneous Parameters

display_leading_zero

Specifies how floating point numbers are displayed.

• If this item is not specified, for a decimal number between -1 and 1, the 0 before the decimal point is not displayed. For example, 0.25 is displayed as .25.
• If this item is specified, for a decimal number between -1 and 1, the 0 before the decimal point is displayed. For example, 0.25 is displayed as 0.25.

ORA

TD

end_month_calculate

Specifies the calculation logic of the add_months function.

Assume that the two parameters of the add_months function are param1 and param2, and that the sum of param1 and param2 is result.

• If this item is not specified, and the Day of param1 indicates the last day of a month shorter than result, the Day in the calculation result will equal that in param1. For example:

• If this item is specified, and the Day of param1 indicates the last day of a month shorter than result, the Day in the calculation result will equal that in result. For example:

ORA

TD

compat_analyze_sample

Specifies the sampling behavior of the ANALYZE operation.

If this item is specified, the sample collected by the ANALYZE operation will be limited to around 30,000 records, controlling CN memory consumption and maintaining the stability of ANALYZE.

ORA

TD

MySQL

bind_schema_tablespace

Binds a schema with the tablespace with the same name.

If a tablespace name is the same as sche_name, default_tablespace will also be set to sche_name if search_path is set to sche_name.

ORA

TD

MySQL

bind_procedure_searchpath

Specifies the search path of the database object for which no schema name is specified.

If no schema name is specified for a stored procedure, the search is performed in the schema to which the stored procedure belongs.

If the stored procedure is not found, the following operations are performed:

• If this item is not specified, the system reports an error and exits.
• If this item is specified, the search continues based on the settings of search_path. If the issue persists, the system reports an error and exits.

ORA

TD

MySQL

correct_to_number

Controls the compatibility of the to_number() result.

If this item is specified, the result of the to_number() function is the same as that of PG11. Otherwise, the result is the same as that of Oracle.

ORA

unbind_divide_bound

Controls the range check on the result of integer division.

• If this item is not specified, the division result is checked. If the result is out of the range, an error is reported. In the following example, an out-of-range error is reported because the value of INT_MIN/(-1) is greater than the value of INT_MAX.

SELECT (-2147483648)::int / (-1)::int;
ERROR:  integer out of range

• If this item is specified, the range of the division result does not need to be checked. In the following example, INT_MIN/(-1) can be used to obtain the output result INT_MAX+1.

SELECT (-2147483648)::int / (-1)::int;
  ?column?
------------
 2147483648
(1 row)

ORA

TD

merge_update_multi

Specifies whether to perform an update when MERGE INTO is executed to match multiple rows.

If this item is specified, no error is reported when multiple rows are matched. Otherwise, an error is reported (same as Oracle).

ORA

TD

disable_row_update_multi

Specifies whether to perform an update when multiple rows of a row-store table are matched.

If this item is specified, an error is reported when multiple rows are matched. Otherwise, multiple rows can be matched and updated by default.

ORA

TD

return_null_string

Specifies how to display the empty result (empty string '') of the lpad(), rpad(), repeat(), regexp_split_to_table(), and split_part() functions.

• If this item is not specified, the empty string is displayed as NULL.

• If this item is specified, the empty string is displayed as single quotation marks ('').

ORA

compat_concat_variadic

Specifies the compatibility of variadic results of the concat() and concat_ws() functions.

If this item is specified and a concat function has a parameter of the variadic type, different result formats in Oracle and Teradata are retained. If this item is not specified and a concat function has a parameter of the variadic type, the result format of Oracle is retained for both Oracle and Teradata.

ORA

TD

convert_string_digit_to_numeric

Specifies the type casting priority for binary BOOL operations on the CHAR type and INT type.

• If this item is not specified, the type casting priority is the same as that of PG9.6.
• After this item is configured, all binary BOOL operations of the CHAR type and INT type are forcibly converted to the NUMERIC type for computation.

  After this configuration item is set, the CHAR types that are affected include BPCHAR, VARCHAR, NVARCHAR2, and TEXT, and the INT types that are affected include INT1, INT2, INT4, and INT8.

ORA

TD

MySQL

check_function_conflicts

Controls the check of the custom plpgsql/SQL function attributes.

• If this parameter is not specified, the IMMUTABLE/STABLE/VOLATILE attributes of a custom function are not checked.
• If this parameter is specified, the IMMUTABLE attribute of a custom function is checked. If the function contains a table or the STABLE/VOLATILE function, an error is reported during the function execution. In a custom function, a table or the STABLE/VOLATILE function conflicts with the IMMUTABLE attribute, thus function behaviors are not IMMUTABLE in this case.

For example, when this parameter is specified, an error is reported in the following scenarios:

CREATE OR replace FUNCTION sql_immutable (INTEGER)
RETURNS INTEGER AS 'SELECT a+$1 from shipping_schema.t4 where a=1;'
LANGUAGE SQL IMMUTABLE
RETURNS NULL
ON NULL INPUT;
select sql_immutable(1);
ERROR:  IMMUTABLE function cannot contain SQL statements with relation or Non-IMMUTABLE function.
CONTEXT:  SQL function "sql_immutable" during startup
referenced column: sql_immutable

ORA

TD

MySQL

varray_verification

Indicates whether to verify the array length and array type length. Compatible with GaussDB(DWS) versions earlier than 8.1.0.

If this parameter is specified, the array length and array type length are not verified.

Scenario 1
CREATE OR REPLACE PROCEDURE varray_verification 
AS 
    TYPE org_varray_type IS varray(5) OF VARCHAR2(2); 
    v_org_varray org_varray_type; 
BEGIN 
    v_org_varray(1) := '111'; --If the value exceeds the limit of VARCHAR2(2), the setting will be consistent with that in the historical version and no verification is performed after configuring this option.
END; 
/ 
Scenario 2
CREATE OR REPLACE PROCEDURE varray_verification_i3_1 
AS 
    TYPE org_varray_type IS varray(2) OF NUMBER(2); 
    v_org_varray org_varray_type; 
BEGIN 
    v_org_varray(3) := 1; --If the value exceeds the limit of varray(2) specified for array length, the setting will be consistent with that in the historical version and no verification is performed after configuring this option.
END; 
/ 

ORA

TD

strict_concat_functions

Indicates whether the textanycat() and anytextcat() functions are compatible with the return value if there are null parameters. This parameter and strict_text_concat_td are mutually exclusive.

In MySQL-compatible mode, this parameter has no impact.

• If this configuration item is not specified, the returned values of the textanycat() and anytextcat() functions are the same as those in the Oracle database.
• When this configuration item is specified, if there are null parameters in the textanycat() and anytextcat() functions, the returned value is also null. Different result formats in Oracle and Teradata are retained.

If this configuration item is not specified, the returned values of the textanycat() and anytextcat() functions are the same as those in the Oracle database.

SELECT textanycat('gauss', cast(NULL as BOOLEAN));
 textanycat
------------
 gauss
(1 row)

SELECT 'gauss' || cast(NULL as BOOLEAN); -- In this case, the || operator is converted to the textanycat function.
 ?column?
----------
 gauss
(1 row)

When setting this configuration item, retain the results that are different from those in Oracle and Teradata:

SELECT textanycat('gauss', cast(NULL as BOOLEAN));
 textanycat
------------

(1 row)

SELECT 'gauss' || cast(NULL as BOOLEAN); -- In this case, the || operator is converted to the textanycat function.
 ?column?
----------

(1 row)

ORA

TD

strict_text_concat_td

In Teradata compatible mode, whether the textcat(), textanycat() and anytextcat() functions are compatible with the return value if there are null parameters. This parameter and strict_concat_functions are mutually exclusive.

• If this parameter is not specified, the return values of the textcat(), textanycat(), and anytextcat() functions in Teradata-compatible mode are the same as those in GaussDB(DWS).
• When this parameter is specified, if the textcat(), textanycat(), and anytextcat() functions contain any null parameter values, the return value is null in the Teradata-compatible mode.

If this parameter is not specified, the returned values of the textcat(), textanycat(), and anytextcat() functions are the same as those in the GaussDB(DWS).

td_compatibility_db=# SELECT textcat('abc', NULL);
textcat
---------
abc
(1 row)

td_compatibility_db=# SELECT 'abc' || NULL; -- In this case, the operator || is converted to the textcat() function.
?column?
----------
abc
(1 row)

When this parameter is specified, NULL is returned if any of the textcat(), textanycat(), and anytextcat() functions returns a null value.

td_compatibility_db=# SELECT textcat('abc', NULL);
textcat
---------

(1 row)

td_compatibility_db=# SELECT 'abc' || NULL;
?column?
----------

(1 row)

TD

compat_display_ref_table

Sets the column display format in the view.

• If this parameter is not specified, the prefix is used by default, in the tab.col format.
• Specify this parameter to the same original definition. It is displayed only when the original definition contains a prefix.

SET behavior_compat_options='compat_display_ref_table';
CREATE OR REPLACE VIEW viewtest2 AS SELECT a.c1, c2, a.c3, 0 AS c4 FROM viewtest_tbl a;
SELECT pg_get_viewdef('viewtest2');
pg_get_viewdef
-----------------------------------------------------
SELECT a.c1, c2, a.c3, 0 AS c4 FROM viewtest_tbl a;
(1 row)

ORA

TD

para_support_set_func

Whether the input parameters of the COALESCE(), NVL(), GREATEST(), and LEAST() functions in a column-store table support multiple result set expressions.

• If this item is not specified and the input parameter contains multiple result set expressions, an error is reported, indicating that the function is not supported.

• When this configuration item is specified, the function input parameter can contain multiple result set expressions.

ORA

TD

disable_select_truncate_parallel

Controls the DDL lock level such as TRUNCATE in a partitioned table.

• If this item is specified, the concurrent execution of TRUNCATE and DML operations (such as SELECT) on different partitions is forbidden, and the fast query shipping (FQS) of the SELECT operation on the partitioned table is allowed. You can set this parameter in the OLTP database, where there are many simple queries on partitioned tables, and there is no requirement for concurrent TRUNCATE and DML operations on different partitions.
• If this item is not specified, SELECT and TRUNCATE operations can be concurrently performed on different partitions in a partitioned table, and the FQS of the partitioned table is disabled to avoid possible inconsistency.

ORA

TD

MySQL

bpchar_text_without_rtrim

In Teradata-compatible mode, controls the space to be retained on the right during the character conversion from bpchar to text. If the actual length is less than the length specified by bpchar, spaces are added to the value to be compatible with the Teradata style of the bpchar character string.

Currently, ignoring spaces at the end of a string for comparison is not supported. If the concatenated string contains spaces at the end, the comparison is space-sensitive.

The following is an example:

td_compatibility_db=# select length('a'::char(10)::text);
length
--------
10
(1 row)

td_compatibility_db=# select length('a'||'a'::char(10));
length
--------
11
(1 row)

TD

convert_empty_str_to_null_td

In Teradata-compatible mode, controls the to_date, to_timestamp, and to_number type conversion functions to return null when they encounter empty strings, and controls the format of the return value when the to_char function encounters an input parameter of the date type.

Example:

If this parameter is not specified:

td_compatibility_db=# select to_number('');
 to_number 
-----------
         0
(1 row)

td_compatibility_db=# select to_date('');
ERROR:  the format is not correct
DETAIL:  invalid date length "0", must between 8 and 10.
CONTEXT:  referenced column: to_date

td_compatibility_db=# select to_timestamp('');
      to_timestamp
------------------------
 0001-01-01 00:00:00 BC
(1 row)

td_compatibility_db=# select to_char(date '2020-11-16');
        to_char         
------------------------
 2020-11-16 00:00:00+08
(1 row)

If this parameter is specified, and parameters of to_number, to_date, and to_timestamp functions contain empty strings:

td_compatibility_db=# select to_number('');
 to_number 
-----------

(1 row)

td_compatibility_db=# select to_date('');
 to_date 
---------

(1 row)

td_compatibility_db=# select to_timestamp('');
 to_timestamp
--------------

(1 row)

td_compatibility_db=# select to_char(date '2020-11-16');
  to_char   
------------
 2020/11/16
(1 row)

TD

disable_case_specific

Determines whether to ignore case sensitivity during character type match. This parameter is valid only in Teradata-compatible mode.

• If this item is not specified, characters are case sensitive during character type match.
• If this item is specified, characters are case insensitive during character type match.

After being specified, this item will affect five character types (CHAR, TEXT, BPCHAR, VARCHAR, and NVARCHAR), 12 operators (<, >, =, >=, <=, !=, <>, !=, like, not like, in, and not in), and expressions case when and decode.

TD

enable_interval_to_text

Controls the implicit conversion from the interval type to the text type.

• When this option is enabled, the implicit conversion from the interval type to the text type is supported.

  SELECT TO_DATE('20200923', 'yyyymmdd') - TO_DATE('20200920', 'yyyymmdd') = '3'::text;
  ?column?
  ----------
  f
  (1 row)

• When this option is disabled, the implicit conversion from the interval type to the text type is not supported.

  SELECT TO_DATE('20200923', 'yyyymmdd') - TO_DATE('20200920', 'yyyymmdd') = '3'::text;
  ?column?
  ----------
  t
  (1 row)

ORA

TD

MySQL

case_insensitive

In MySQL-compatible mode, configure this parameter to specify the case-insensitive input parameters of the locate, strpos, and instr string functions.

Currently, this parameter is not configured by default. That is, the input parameter is case-sensitive.

The following shows an example:

• If this parameter is not configured, the input parameter is case-sensitive.

  mysql_compatibility_db=# SELECT LOCATE('sub', 'Substr');
   locate
  --------
        0
  (1 row)

• If this parameter is configured, the input parameter is case-insensitive.

  mysql_compatibility_db=# SELECT LOCATE('sub', 'Substr');
   locate
  --------
        1
  (1 row)

MySQL

inherit_not_null_strict_func

Controls the original strict attribute of a function. A function with one parameter can transfer the NOT NULL attribute. func(x) is used an example. If func() is the strict attribute and x contains the NOT NULL constraint, func(x) also contains the NOT NULL constraint.

The compatible configuration item is effective in some optimization scenarios, for example, NOT IN and COUNT(DISTINCT) optimization. However, the optimization results may be incorrect in specific scenarios.

Currently, this parameter is not configured by default to ensure that the result is correct. However, the performance may be rolled back. If an error occurs, you can set this parameter to roll back to the historical version.

ORA

TD

MySQL

disable_compat_minmax_expr_mysql

Specifies the method for processing the input parameter null in the greatest/least expression in MySQL-compatible mode.

You can configure this parameter to roll back to a historical version.

• If this parameter is not configured and the input parameter is null, null is returned.

  mysql_compatibility_db=# SELECT greatest(1, 2, null), least(1, 2, null);
   greatest | least
  ----------+-------
            |
  (1 row)

• If this parameter is configured, the maximum or minimum value of non-null parameters is returned.

  mysql_compatibility_db=# SELECT greatest(1, 2, null), least(1, 2, null);
   greatest | least
  ----------+-------
          2 |     1
  (1 row)

MySQL

disable_compat_substr_mysql

Specifies the behavior of the substr/substring function when the start position pos is ≤ 0 in MySQL-compatible mode.

You can configure this parameter to roll back to a historical version.

• If this parameter is not configured, that is, an empty string is returned when pos = 0. When pos < 0, TRUNCATE starts from the last |pos| character on.

  mysql_compatibility_db=# SELECT substr('helloworld',0);
   substr
  --------
  
  (1 row)
  mysql_compatibility_db=# SELECT substring('helloworld',0),substring('helloworld',-2,4);
   substring | substring
  -----------+-----------
             | ld
  (1 row)

• If this parameter is configured and pos is ≤ 0, characters are truncated from the left.

  mysql_compatibility_db=# SELECT substr('helloworld',0);
     substr
  ------------
   helloworld
  (1 row)
  mysql_compatibility_db=# SELECT substring('helloworld',0),substring('helloworld',-2,4);
   substring  | substring
  ------------+-----------
   helloworld | h
  (1 row)

MySQL

disable_compat_trim_mysql

Specifies the method for processing the input parameter in the trim/ltrim/rtrim function in MySQL-compatible mode.

You can configure this parameter to roll back to a historical version.

• If this parameter is not configured, the entire substring is matched.

  mysql_compatibility_db=# SELECT trim('{}{name}{}','{}'),trim('xyznamezyx','xyz');
   btrim  |  btrim
  --------+---------
   {name} | namezyx
  (1 row)

• If this parameter is configured, a single character in the character set is matched.

  mysql_compatibility_db=# SELECT trim('{}{name}{}','{}'),trim('xyznamezyx','xyz');
   btrim | btrim
  -------+-------
   name  | name
  (1 row)

MySQL

light_object_mtime

Specifies whether the mtime column in the pg_object system catalog records object operations.

• If this parameter is configured, the GRANT, REVOKE, and TRUNCATE operations are not recorded by mtime, that is, the mtime column is not updated.
• If this parameter is not configured (by default), the ALTER, COMMENT, GRANT, REVOKE, and TRUNCATE operations are recorded by mtime, that is, the mtime column is updated.

ORA

TD

MySQL

disable_including_all_mysql

In MySQL-compatible mode, this parameter controls whether the CREATE TABLE...LIKE syntax is INCLUDING_ALL.

By default, this parameter is not set. That is, in MySQL compatibility mode, CREATE TABLE... LIKE syntax is INCLUDING_ALL.

Set this parameter to roll back to a historical version.

• If this parameter is not set, in MySQL-compatible mode, the CREATE TABLE... LIKE syntax is in INCLUDING_ALL.

  mysql_compatibility_db=# create table mysql_like(id int, name varchar(10), score int) distribute by hash(id) COMMENT 'mysql_like';
  CREATE TABLE
  mysql_compatibility_db=# create index index_like on mysql_like(name);
  CREATE INDEX
  mysql_compatibility_db=# \d+ mysql_like;
                               Table "public.mysql_like"
   Column |         Type          | Modifiers | Storage  | Stats target | Description
  --------+-----------------------+-----------+----------+--------------+-------------
   id     | integer               |           | plain    |              |
   name   | character varying(10) |           | extended |              |
   score  | integer               |           | plain    |              |
  Indexes:
      "index_like" btree (name) TABLESPACE pg_default
  Has OIDs: no
  Distribute By: HASH(id)
  Location Nodes: ALL DATANODES
  Options: orientation=row, compression=no
  
  mysql_compatibility_db=# create table copy_like like mysql_like;
  CREATE TABLE
  mysql_compatibility_db=# \d+ copy_like;
                                Table "public.copy_like"
   Column |         Type          | Modifiers | Storage  | Stats target | Description
  --------+-----------------------+-----------+----------+--------------+-------------
   id     | integer               |           | plain    |              |
   name   | character varying(10) |           | extended |              |
   score  | integer               |           | plain    |              |
  Indexes:
      "copy_like_name_idx" btree (name) TABLESPACE pg_default
  Has OIDs: no
  Distribute By: HASH(id)
  Location Nodes: ALL DATANODES
  Options: orientation=row, compression=no

• If this parameter is set, in MySQL-compatible mode, the CREATE TABLE... LIKE syntax is empty.

  mysql_compatibility_db=# set behavior_compat_options = 'disable_including_all_mysql';
  SET
  mysql_compatibility_db=# create table mysql_copy like mysql_like;
  NOTICE:  The 'DISTRIBUTE BY' clause is not specified. Using round-robin as the distribution mode by default.
  HINT:  Please use 'DISTRIBUTE BY' clause to specify suitable data distribution column.
  CREATE TABLE
  mysql_db=# \d+ mysql_copy;
                               Table "public.mysql_copy"
   Column |         Type          | Modifiers | Storage  | Stats target | Description
  --------+-----------------------+-----------+----------+--------------+-------------
   id     | integer               |           | plain    |              |
   name   | character varying(10) |           | extended |              |
   score  | integer               |           | plain    |              |
  Has OIDs: no
  Distribute By: ROUND ROBIN
  Location Nodes: ALL DATANODES
  Options: orientation=row, compression=no

MySQL

cte_onetime_inline

Indicates whether to execute inline for non-stream plans.

• When this parameter is set, the CTE that is not in a stream plan and is referenced only once executes inline.
• If this parameter is not set, the CTE that is not in a stream plan and is referenced only once does not execute inline.

ORA

TD

MySQL

skip_first_after_mysql

Determines whether to ignore the FIRST/AFTER colname syntax in ALTER TABLE ADD/MODIFY/CHANGE COLUMN in MySQL compatibility mode.

• If this parameter is set, the FIRST/AFTER colname syntax is ignored and executing this syntax does not cause errors

  mysql_compatibility_db=# set behavior_compat_options = 'skip_first_after_mysql';
  mysql_compatibility_db=# alter table t1 add column b text after a;
  ALTER TABLE

• If this parameter is not set, the FIRST/AFTER colname syntax is not supported, and executing this syntax causes error.

  mysql_compatibility_db=# set behavior_compat_options = '';
  mysql_compatibility_db=# alter table t1 add column b text after a;
  ERROR:  FIRST/AFTER is not yet supported.

MySQL

enable_division_by_zero_mysql

Specifies whether to report an error when the divisor is 0 in MySQL compatibility mode. (This configuration item is supported only by clusters of 8.1.3.110 and later versions.)

• If this parameter is set, NULL is returned if the divisor is 0 in a division or modulo operation.

  compatible_mysql_db=# SET behavior_compat_options = 'enable_division_by_zero_mysql';
  SET
  compatible_mysql_db=# select 1/0 as test;
   test 
  ----------
           
  (1 row)

• If this parameter is not set, an error is returned if the divisor is 0 in a division or modulo operation.

  compatible_mysql_db=# select 1/0;
  ERROR:  division by zero

MySQL

merge_into_with_trigger

Controls whether the MERGE INTO operation can be performed on tables with triggers. (This parameter is supported only in 8.1.3.200 and later cluster versions.)

• When this option is set, the MERGE INTO operation can be performed on tables with triggers. When the MERGE INTO operation is performed, the trigger on the table is not activated.
• If this option is not set, an error is reported when the MERGE INTO operation is performed on a table with triggers.

ORA

TD

MySQL

add_column_default_v_func

Controls whether expression in alter table add column default expression supports volatile functions. (This parameter is supported only in 8.1.3.200 and later cluster versions.)

• If this option is selected, expression in alter table add column default expression supports volatile functions.
• If this option is not selected, expression in alter table add column default expression does not support volatile functions. If expression contains volatile functions, an error will be reported during statement execution.

ORA

TD

MySQL

disable_gc_fdw_filter_partial_pushdown

Controls whether filter criteria are pushed down when filter criteria are used to query data in a collaborative analysis foreign table (type: gc_fdw). (This parameter is supported only in 8.1.3.310 and later cluster versions.)

• When this option is selected, if the filter criteria contain elements (such as non-immutable functions) that do not meet the pushdown conditions, all filter criteria are not pushed down to ensure the normal generation of the result set document. This behavior is compatible with the behavior in versions earlier than 8.1.3.310.
• If this parameter is not set, the filter criteria that can be pushed down are executed in the source cluster, and the filter criteria that cannot be pushed down are executed in the local cluster. This improves the query efficiency of foreign tables.

ORA

TD

MySQL