Platform and Client Compatibility
Many platforms use the database system. External compatibility of the database system provides a lot of convenience for platforms.
transform_null_equals
Parameter description: Specifies whether expressions of the form expr = NULL (or NULL = expr) are treated as expr IS NULL. They return true if expr evaluates to the null value, and false otherwise.
- The correct SQL-standard-compliant behavior of expr = NULL is to always return null (unknown).
- Filtered forms in Microsoft Access generate queries that appear to use expr = NULL to test for null values. If you turn this option on, you can use this interface to access the database.
This is a USERSET parameter. Set it based on instructions provided in Table 2.
Value range: Boolean
- on indicates that expressions of the form expr = NULL (or NULL = expr) are treated as expr IS NULL.
- off indicates that expr = NULL always returns null (unknown).
Default value: off

New users are always confused about the semantics of expressions involving NULL values. Therefore, off is used as the default value.
support_extended_features
Parameter description: Specifies whether extended database features are supported.
This is a POSTMASTER parameter. Set it based on instructions in Table 2.
Value range: Boolean
- on indicates that extended database features are supported.
- off indicates that extended database features are not supported.
Default value: off
lastval_supported
Parameter description: Specifies whether the lastval function can be used.
This is a POSTMASTER parameter. Set it based on instructions in Table 2.
Value range: Boolean
- on indicates that the lastval function can be used and the nextval function cannot be pushed down.
- off indicates that the lastval function cannot be used and the nextval function can be pushed down.
Default value: off
sql_compatibility
Parameter description: Specifies the type of mainstream database with which the SQL syntax and statement behavior of the database is compatible. This parameter is an INTERNAL parameter. It can be viewed but cannot be modified.
Value range: enumerated values
- ORA indicates that the SQL syntax and statement behavior of the database is compatible with the Oracle database.
- TD indicates that the SQL syntax and statement behavior of the database is compatible with the Teradata database.
- MYSQL indicates that the SQL syntax and statement behavior of the database is compatible with the MySQL database.
- PG indicates that the database is compatible with the PostgreSQL database.
Default value: MYSQL

- This parameter can be set only when you run the CREATE DATABASE command to create a database.
- In the database, this parameter must be set to a specific value. It can be set to ORA or TD and cannot be changed randomly. Otherwise, the setting is not consistent with the database behavior.
behavior_compat_options
Parameter description: Specifies database compatibility behavior. Multiple items are separated by commas (,).
This is a USERSET parameter. Set it based on instructions in Table 1.
Value range: a string
Default value: ""

- Currently, only Table 1 is supported.
- Multiple items are separated by commas (,), for example, set behavior_compat_options='end_month_calculate,display_leading_zero';.
Compatibility Configuration Item |
Compatibility Behavior Control |
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display_leading_zero |
Specifies how floating point numbers are displayed. It controls the display of zeros before the decimal point of all character string types (such as char, character, nchar, varchar, character varying, varchar2, nvarchar2, text, and clob) and any precision types (such as float4, float8, and numeric) in the numeric type. In addition, the length of the calculated number is displayed synchronously.
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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 month of param1 and param2 is result.
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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. |
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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. |
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bind_procedure_searchpath |
Specifies the search path of the database object in a stored procedure 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:
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correct_to_number |
Controls the compatibility of the to_number() result. If this item is not set, the result of the to_number() function is the same as that in the ORA database by default.
If this item is set, the result of the to_number() function is the same as that of pg11.
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unbind_divide_bound |
Controls the range check on the result of integer division. If this item is not set, the range of the division result is verified. For example, an out-of-bounds error is reported because the output result of INT_MIN/(-1) is greater than INT_MAX.
If this item is specified, the range of the division result does not need to be verified. For example, the output result of INT_MIN/(–1) is INT_MAX+1.
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convert_string_digit_to_numeric |
Determines whether to convert numeric constants of the character string type to those of the numeric type before these two types are compared.
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return_null_string |
Specifies how to display the empty result (empty string '') of the lpad() and rpad() functions.
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compat_concat_variadic |
Specifies the compatibility of variadic results of the concat() and concat_ws() functions. The MY database does not have the variadic type. Therefore, this option has no impact on the MY database. If this item is not set and the concat function parameter is of the variadic type, the results of the ORA and TD databases in compatibility mode are the same by default.
If this item is set and the concat function parameter is of the variadic type, different result formats of the ORA and TD databases in compatibility mode are retained.
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merge_update_multi |
When MERGE INTO... When WHEN MATCHED THEN UPDATE (see "SQL Reference" > "SQL Syntax" > "MERGE INTO" in Developer Guide) and INSERT ... ON DUPLICATE KEY UPDATE (see "SQL Reference" > "SQL Syntax" > INSERT" in Developer Guide) are used, it controls the UPDATE behavior if a piece of target data in the target table conflicts with multiple pieces of source data. If this item is specified and the preceding scenario exists, the system performs multiple UPDATE operations on the conflicting row. If this item is not specified and the preceding scenario exists, an error is reported, that is, the MERGE or INSERT operation fails. |
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plstmt_implicit_savepoint |
Determines whether the execution of an UPDATE statement in a stored procedure has an independent subtransaction. If this parameter is set, the implicit savepoint is enabled before executing each UPDATE statement in the stored procedure, and the subtransaction is rolled backed to the latest savepoint in the EXCEPTION block by default, ensuring that only the modification of failed statements is rolled back. This option is used to be compatible with the EXCEPTION behavior of the O database. |
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hide_tailing_zero |
Configuration item for numeric display. If this parameter is not set, numeric values are displayed based on the specified precision. If this parameter is set, all numeric values are output with trailing zeros (after a decimal point) hidden, including the to_char(numeric, format) scenario. For example: openGauss=# set behavior_compat_options='hide_tailing_zero'; openGauss=# select cast(123.123 as numeric(15,10)) as a, to_char(cast(123.123 as numeric(15,10)), '999D999999'); a | to_char ---------+---------- 123.123 | 123.123 (1 row) openGauss=# set behavior_compat_options=''; openGauss=# select cast(123.123 as numeric(15,10)) as a, to_char(cast(123.123 as numeric(15,10)), '999D999999'); a | to_char ----------------+------------- 123.1230000000 | 123.123000 (1 row) |
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plsql_security_definer |
After this parameter is enabled, the definer permission is used by default when a stored procedure is created. |
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char_coerce_compat |
Specifies the behavior when the char(n) type is converted to other variable-length string types. If this parameter is not set, spaces at the end are omitted when the char(n) type is converted to other variable-length string types. After this parameter is set, spaces at the end are not omitted during conversion. In addition, if the length of the char(n) type exceeds the length of other variable-length string types, an error is reported. This parameter is valid only when the sql_compatibility parameter is set to ORA. After this parameter is enabled, spaces at the end are not omitted in implicit conversion, explicit conversion, or conversion by calling the text(bpchar) function. openGauss=# set behavior_compat_options=''; openGauss=# create table tab_1(col1 varchar(3)); openGauss=# create table tab_2(col2 char(3)); openGauss=# insert into tab_2 values(' '); openGauss=# insert into tab_1 select col2 from tab_2; openGauss=# select * from tab_1 where col1 is null; col1 ------ (1 row) openGauss=# select * from tab_1 where col1=' '; col1 ------ (0 rows) openGauss=# delete from tab_1; openGauss=# set behavior_compat_options = 'char_coerce_compat'; openGauss=# insert into tab_1 select col2 from tab_2; openGauss=# select * from tab_1 where col1 is null; col1 ------ (0 rows) openGauss=# select * from tab_1 where col1=' '; col1 ------ (1 row) |
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truncate_numeric_tail_zero |
Configuration item for numeric display. If this parameter is not specified, numeric values are displayed based on the default precision. If this parameter is specified, the last 0 after the decimal point is hidden in all numeric output scenarios except to_char(numeric, format). For example: openGauss=#set behavior_compat_options='truncate_numeric_tail_zero'; openGauss=#select cast(123.123 as numeric(15,10)) as a, to_char(cast(123.123 as numeric(15,10)), '999D999999'); a | to_char ---------+------------- 123.123 | 123.123000 (1 row) openGauss=#set behavior_compat_options=''; openGauss=#select cast(123.123 as numeric(15,10)) as a, to_char(cast(123.123 as numeric(15,10)), '999D999999'); a | to_char ----------------+------------- 123.1230000000 | 123.123000 (1 row) |
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array_count_compat |
Controls the array.count function. If the parameter is enabled, the function returns 0. Otherwise, the function returns null. |
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aformat_regexp_match |
Determines the matching behavior of regular expression functions.
When this parameter is set and sql_compatibility is set to ORA or MYSQL, the options supported by the flags parameter of the regular expression are changed as follows:
Otherwise, the meanings of the options supported by the flags parameter of the regular expression are as follows:
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disable_emptystr2null |
If this parameter is enabled, the function of converting empty strings to null by default is disabled for the following character types: text, clob, blob, raw, bytea, varchar, nvarchar2, bpchar, char, name, byteawithoutorderwithqualcol, and byteawithoutordercol. This parameter is reserved for emergency. Do not set it unless necessary. |
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proc_uncheck_default_param |
When a function is called, the system does not check whether the default parameter is omitted.
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plsql_rollback_keep_user |
Determines whether ROLLBACK and ROLLBACK TO SAVEPOINT in PL/SQL rolls back the current user. If this parameter is enabled, ROLLBACK in the PL/SQL does not change the current user.
Example:
openGauss=# CREATE USER plsql_rollback1 password 'huawei@123'; openGauss=# CREATE USER plsql_rollback2 password 'huawei@123'; openGauss=# GRANT plsql_rollback1 to plsql_rollback2; openGauss=# CREATE OR REPLACE procedure plsql_rollback1.p1 () authid definer openGauss-# as openGauss$# va int; openGauss$# begin openGauss$# raise info 'current usr:%', current_user; openGauss$# rollback; openGauss$# raise info 'current usr:%', current_user; openGauss$# end; openGauss$# / CREATE PROCEDURE openGauss=# SET session AUTHORIZATION plsql_rollback2 PASSWORD 'huawei@123'; SET openGauss=> SET behavior_compat_options = 'plsql_rollback_keep_user'; SET openGauss=> CALL plsql_rollback1.p1 (); INFO: current usr:plsql_rollback1 INFO: current usr:plsql_rollback1 p1 ---- (1 row)
CAUTION:
This parameter is valid only in the ORA compatibility mode. |
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dynamic_sql_check |
After the parameter is enabled, the number of template parameters in the template SQL statement is compared with the number of variables in the USING clause. If they are inconsistent, an error is reported. openGauss=# create table tb_t1(col1 varchar2,col2 varchar2,col3 varchar2); CREATE TABLE gaussdb=# insert into tb_t1 select '1','1','2'; INSERT 0 1 openGauss=# create or replace procedure proc_test()as openGauss$# v_a varchar2; openGauss$# v_b varchar2; openGauss$# v_cnt int; openGauss$# v_sql varchar2; openGauss$# begin openGauss$# v_a = '1'; openGauss$# v_b = '2'; openGauss$# v_sql = 'select count(1) from tb_t1 where col1 = :va and col2 = :va and col3 = :vb;'; openGauss$# execute immediate v_sql into v_cnt using v_a,v_a,v_b; openGauss$# raise info 'v_cnt:%',v_cnt; openGauss$# end; openGauss$# / CREATE PROCEDURE openGauss=# call proc_test(); INFO: v_cnt:0 proc_test ----------- (1 row) openGauss=# set behavior_compat_options='dynamic_sql_check'; SET openGauss=# call proc_test(); ERROR: argnum not match in Dynamic SQL, using args num : 3 , actual sql args num : 2 CONTEXT: SQL statement "select count(1) from tb_t1 where col1 = :va and col2 = :va and col3 = :vb;" PL/SQL function proc_test() line 10 at EXECUTE statemen
CAUTION:
If the dynamic_sql_compat option is enabled, the dynamic_sql_check option does not take effect. |
a_format_version
Parameter description: Specifies the database platform compatibility configuration item. The value of this parameter is an enumerated string.
This is a USERSET parameter. Set it based on instructions provided in Table 2.
Value range: a string
Default value: ""

Set a character string for the compatibility configuration item, for example, set a_format_version='10c'.
Compatibility Configuration Item |
Compatibility Behavior Control |
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10c |
Compatible version of platform A |
a_format_dev_version
Parameter description: Specifies the database platform minor version compatibility configuration item. The value of this parameter is an enumerated string.
This is a USERSET parameter. Set it based on instructions provided in Table 2.
Value range: a string
Default value: ""

Set a character string for the compatibility configuration item, for example, set a_format_dev_version='s1'.
Compatibility Configuration Item |
Compatibility Behavior Control |
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s1 |
After this parameter is enabled, the int casted from text can be rounded off. |
plpgsql.variable_conflict
Parameter description: Sets the priority of using stored procedure variables and table columns with the same name.
This is a USERSET parameter. Set it based on instructions provided in Table 2.
Value range: a string
- error indicates that a compilation error is reported when the name of a stored procedure variable is the same as that of a table column.
- use_variable indicates that if the name of a stored procedure variable is the same as that of a table column, the variable is used preferentially.
- use_column indicates that if the name of a stored procedure variable is the same as that of a table column, the column name is used preferentially.
Default value: error
td_compatible_truncation
Parameter description: Specifies whether to enable features compatible with a Teradata database. You can set this parameter to on when connecting to a database compatible with the Teradata database, so that when you perform the INSERT operation, overlong strings are truncated based on the allowed maximum length before being inserted into char- and varchar-type columns in the target table. This ensures all data is inserted into the target table without errors reported.

If inserting multi-byte character data (such as Chinese characters) to database with the character set byte encoding (such as SQL_ASCII or LATIN1), and the character data crosses the truncation position, the string is truncated based on its bytes instead of characters. Unexpected result will occur in tail after the truncation. If you want correct truncation result, you are advised to adopt encoding set such as UTF8, which has no character data crossing the truncation position.
This is a USERSET parameter. Set it based on instructions provided in Table 2.
Value range: Boolean
- on indicates that overlong strings are truncated.
- off indicates that overlong strings are not truncated.
Default value: off
nls_timestamp_format
Parameter description: Specifies the default timestamp format.
This is a USERSET parameter. Set it based on instructions in Table 1.
Value range: a string
Default value: DD-Mon-YYYY HH:MI:SS.FF AM
max_function_args
Parameter description: Specifies the maximum number of parameters allowed for a function.
This is a fixed INTERNAL parameter. It can be viewed but cannot be modified.
Value range: an integer.
Default value: 8192
convert_string_to_digit
Parameter description: Specifies the implicit conversion priority, which determines whether to preferentially convert strings into numbers.
This is a USERSET parameter. Set it based on instructions in Table 1.
Value range: Boolean
- on indicates that strings are preferentially converted into numbers.
- off indicates that strings are not preferentially converted into numbers.
Default value: on

Adjusting this parameter will change the internal data type conversion rule and cause unexpected behavior. Exercise caution when performing this operation.
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