Platform and Client Compatibility

enable_set_variables

Indicates whether to enable the enhancement of the SET syntax.

• If this parameter is not set, user-defined variables and the SET [GLOBAL | SESSION] syntax are not supported.
• If this parameter is set, the preceding syntax is supported in the B-compatible mode, for example, set @v1 = 1;.

set_session_transaction

Indicates whether to enable the SET SESSION TRANSACTION syntax.

• If this parameter is not set, SET SESSION TRANSACTION is equivalent to SET LOCAL TRANSACTION.
• If this parameter is set, the preceding syntax can be used in the B-compatible mode to modify the transaction features in the current session.

enable_modify_column

Indicates whether to enable the ALTER TABLE MODIFY syntax.

• If this parameter is not set, running ALTER TABLE table_name MODIFY column_name data_type; can change only the data type of the column.
• If this parameter is set, running ALTER TABLE table_name MODIFY column_name data_type; can change the entire column definition.

default_collation

Indicates whether to enable forward compatibility of the default collation.

• If this parameter is not set, the character set or collation of a column of the character type is not explicitly specified, and the collation of a table is empty, the column uses the default collation.
• If this parameter is set, the character collation of a column of the character type inherits the character collation of a table (if it is not empty). If the character collation of a table is empty, the default character collation corresponding to the database is used.

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.

• 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:

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  gaussdb=# select 0.1231243 as a, 0.1231243::numeric as b,0.1231243::integer(10,3) as c, length(0.1242343) as d; a | b | c | d ----------+----------+------+--- .1231243 | .1231243 | .123 | 8 (1 row)

• If this item is specified, for a decimal number between –1 and 1, the 0 before the decimal point is displayed. For example:

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  gaussdb=# select 0.1231243 as a, 0.1231243::numeric as b,0.1231243::integer(10,3) as c, length(0.1242343) as d; a | b | c | d -----------+-----------+-------+--- 0.1231243 | 0.1231243 | 0.123 | 9 (1 row)

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.

• 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:

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gaussdb=# select add_months('2018-02-28',3) from sys_dummy;
add_months
---------------------
2018-05-28 00:00:00
(1 row)

• 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:

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gaussdb=# select add_months('2018-02-28',3) from sys_dummy;
add_months
---------------------
2018-05-31 00:00:00
(1 row)

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 database node memory consumption and maintaining the stability of ANALYZE.

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.

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:

• 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.

correct_to_number

Specifies 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 A database by default.

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gaussdb=# select '' AS to_number_14, to_number('34,50','999,99');
ERROR:  invalid data.
CONTEXT:  referenced column: to_number

If this item is set, the result of the to_number() function is the same as that of pg11.

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gaussdb=# select '' AS to_number_14, to_number('34,50','999,99');
 to_number_14 | to_number
--------------+-----------
              |      3450
(1 row)

unbind_divide_bound

Specifies 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.

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gaussdb=# select (-2147483648)::int4 / (-1)::int4;
ERROR:  integer out of range

If this item is set, 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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gaussdb=# select (-2147483648)::int4 / (-1)::int4;
  ?column?  
------------
 2147483648
(1 row)

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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gaussdb=# create table test1 (c1 int, c2 varchar);
gaussdb=# insert into test1 values (2, '1.1');
gaussdb=# set behavior_compat_options='';
gaussdb=# select * from test1 where c2 > 1;
ERROR:  invalid input syntax for type bigint: "1.1"

gaussdb=# set behavior_compat_options='convert_string_digit_to_numeric';
gaussdb=# select * from test1 where c2 > 1;
 c1 | c2  
----+-----
  2 | 1.1 
(1 row)

return_null_string

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

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

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gaussdb=# select length(lpad('123',0,'*')) from sys_dummy;
length
--------

(1 row)

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

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gaussdb=# select length(lpad('123',0,'*')) from sys_dummy;
length
--------
0
(1 row)

compat_concat_variadic

Specifies the compatibility of variadic results of the concat() and concat_ws() functions. The B database does not have the variadic type. Therefore, this option has no impact on the B database.

If this item is not set and the concat function parameter is of the variadic type, the results of the A and C databases in compatibility mode are the same by default.

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gaussdb=# select concat(variadic NULL::int[]) is NULL;
 ?column? 
----------
 t
(1 row)

If this item is set and the concat function parameter is of the variadic type, different result formats of the A and C databases in compatibility mode are retained.

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--In the A database:
gaussdb=# select concat(variadic NULL::int[]) is NULL;
 ?column? 
----------
 t
(1 row)
--In the C database:
gaussdb=# select concat(variadic NULL::int[]) is NULL;
 ?column? 
----------
 f
(1 row)

merge_update_multi

When MERGE INTO ... 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. Otherwise, an error is reported by default, that is, the MERGE or INSERT operation fails.

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.

hide_tailing_zero

Configuration item for numeric display. If this parameter is not set, numeric data is displayed in the specified precision. If this parameter is set, the trailing zeros after the decimal point are hidden in all scenarios where numeric values are output, even if the precision format is specified.

gaussdb=# set behavior_compat_options='hide_tailing_zero';
gaussdb=# 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)
gaussdb=# set behavior_compat_options='';
gaussdb=# 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)

rownum_type_compat

Specifies the ROWNUM type. The default value is BIGINT. After this parameter is specified, the value is changed to NUMERIC.

gaussdb=# set behavior_compat_options='';
gaussdb=# create table tb_test(c1 int,c2 varchar2,c3 varchar2);
gaussdb=# insert into tb_test values(1,'a','b');
gaussdb=# create or replace view v_test as select rownum from tb_test;
gaussdb=# \d+ v_test
                View "public.v_test"
 Column |  Type  | Modifiers | Storage | Description 
--------+--------+-----------+---------+-------------
 rownum | bigint |           | plain   | 
View definition:
 SELECT ROWNUM AS "rownum"
   FROM tb_test;

gaussdb=# set behavior_compat_options = 'rownum_type_compat';
gaussdb=# create or replace view v_test1 as select rownum from tb_test;
gaussdb=# \d+ v_test1
                View "public.v_test1"
 Column |  Type   | Modifiers | Storage | Description 
--------+---------+-----------+---------+-------------
 rownum | numeric |           | main    | 
View definition:
 SELECT ROWNUM AS "rownum"
   FROM tb_test;

aformat_null_test

Specifies the logic for checking whether rowtype is not null.

When this parameter is set, if one column in a row is not empty, true is returned for checking whether rowtype is not null. When this parameter is not set, if all columns in a row are not empty, true is returned for checking whether rowtype is not null. This parameter has no influence on checking whether rowtype is not null.

gaussdb=# set behavior_compat_options='aformat_null_test';
gaussdb=# select r, r is null as isnull, r is not null as isnotnull from (values (1,row(1,2)), (1,row(null,null)), (1,null), (null,row(1,2)), (null,row(null,null)), (null,null) ) r(a,b);
      r      | isnull | isnotnull 
-------------+--------+-----------
 (1,"(1,2)") | f      | t
 (1,"(,)")   | f      | t
 (1,)        | f      | t
 (,"(1,2)")  | f      | t
 (,"(,)")    | f      | t
 (,)         | t      | f
(6 rows)
gaussdb=# set behavior_compat_options='';
gaussdb=# select r, r is null as isnull, r is not null as isnotnull from (values (1,row(1,2)), (1,row(null,null)), (1,null), (null,row(1,2)), (null,row(null,null)), (null,null) ) r(a,b);
      r      | isnull | isnotnull 
-------------+--------+-----------
 (1,"(1,2)") | f      | t
 (1,"(,)")   | f      | t
 (1,)        | f      | f
 (,"(1,2)")  | f      | f
 (,"(,)")    | f      | f
 (,)         | t      | f
(6 rows)

aformat_regexp_match

Determines the matching behavior of regular expression functions.

Otherwise, the meanings of the options supported by the flags parameter of the regular expression are as follows:

1. By default, the character '\n' can be matched.
2. The n option in flags indicates that the multi-line matching mode is used.
3. The regexp_replace(source, pattern replacement) function replaces only the first matched substring.
4. If the value of flags is '' or null, the return value of regexp_replace(source, pattern, replacement, flags) is the character string after replacement.

compat_cursor

Determines the compatibility behavior of implicit cursor states. If this parameter is set and the O compatibility mode is used, the effective scope of implicit cursor states (SQL%FOUND, SQL%NOTFOUND, SQL%ISOPNE, and SQL%ROWCOUNT) is extended from only the currently executed function to all subfunctions invoked by this function.

proc_outparam_override

Determines the overloading of output parameters of a stored procedure. After this parameter is enabled, the stored procedure can be properly created and invoked even if only the output parameters of the stored procedure are different. Currently, this parameter can be used only when gsql and JDBC are used to connect to the database. If this parameter is enabled for other tools to connect to the database, stored procedures with the out parameter cannot be invoked.

It supports the functions that contain the out output parameter and returns data of the record type. Besides, a value is assigned to the out parameter.

proc_implicit_for_loop_variable

Controls the behavior of the FOR_LOOP query statement in a stored procedure. When this parameter is set, if rec has been defined in the FOR rec IN query LOOP statement, the defined rec variable is not reused and a new variable is created. Otherwise, the defined rec variable is reused and no variable is created.

allow_procedure_compile_check

Controls the compilation check of the SELECT and OPEN CURSOR statements in a stored procedure. If this parameter is set, when the SELECT, OPEN CURSOR FOR, CURSOR%rowtype, or FOR rec IN statement is executed in a stored procedure, the stored procedure cannot be created if the queried table does not exist, and the compilation check of the trigger function is not supported. If the queried table exists, the stored procedure is successfully created.

Note: When creating an encrypted function, you need to disable allow_procedure_compile_check.

char_coerce_compat

Controls the behavior when char(n) types are 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. If 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 A. 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.

gaussdb=# set behavior_compat_options='';
gaussdb=# create table tab_1(col1 varchar(3)); 
gaussdb=# create table tab_2(col2 char(3));
gaussdb=# insert into tab_2 values('   ');
gaussdb=# insert into tab_1 select col2 from tab_2;
gaussdb=# select * from tab_1 where col1 is null;
 col1 
------
 
(1 row)
gaussdb=# select * from tab_1 where col1='   ';
 col1 
------
(0 rows)
gaussdb=# delete from tab_1;
gaussdb=# set behavior_compat_options = 'char_coerce_compat';
gaussdb=# insert into tab_1 select col2 from tab_2;
gaussdb=# select * from tab_1 where col1 is null;
 col1 
------
(0 rows)
gaussdb=# select * from tab_1 where col1='   ';
 col1 
------
    
(1 row)

truncate_numeric_tail_zero

Configuration item for numeric display. If this parameter is not set, numeric data is displayed in the default precision. When this parameter is set, the trailing zeros after the decimal point are hidden in all numeric output scenarios except to_char(numeric, format). For example:

gaussdb=# set behavior_compat_options='truncate_numeric_tail_zero';
gaussdb=# 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)
gaussdb=# set behavior_compat_options='';
gaussdb=# 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)

plsql_security_definer

After this parameter is enabled, the definer permission is used by default when a stored procedure is created.

plpgsql_dependency

If this parameter is set, a function, stored procedure, or package containing undefined objects can be created. You can query the dependency in GS_DEPENDENCIES and GS_DEPENDENCIES_OBJ.

If this parameter is enabled, when creating a PL/SQL object, the OID that depends on the PL/SQL object is automatically updated.

disable_rewrite_nesttable

If this parameter is enabled, rewriting of columns related to the tableof type in the pg_type table will be disabled. That is, when reading the pg_type table, the actual stored value of the tableof type is displayed.

skip_insert_gs_source

If this parameter is enabled, data is not inserted into the dbe_pldeveloper.gs_source table when the PL/SQL objects are created.

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.

select_into_return_null

This parameter takes effect only in PG-compatible mode. If this parameter is enabled, a NULL value can be assigned to the variables in the stored procedure statement SELECT select_expressions INTO [STRICT] target FROM... without specifying STRICT when the query result is empty.

proc_uncheck_default_param

When a function is called, the system does not check whether the default parameter is omitted.

• If this item is not set and a function with default parameters is invoked, input parameters are added to the function from left to right. If inputs of non-default parameters are missing, an error is reported. For example:

  gaussdb=# create or replace function test(f1 int, f2 int default 20, f3 int, f4 int default 40, f5 int default 50) return int
  gaussdb-# as
  gaussdb$# begin
  gaussdb$# raise info 'f1:%',f1;
  gaussdb$# raise info 'f2:%',f2;
  gaussdb$# raise info 'f3:%',f3;
  gaussdb$# raise info 'f4:%',f4;
  gaussdb$# raise info 'f5:%',f5;
  gaussdb$# return 1;
  gaussdb$# end;
  gaussdb$# /
  CREATE FUNCTION
  gaussdb=# select test(1,2);
  ERROR:  function test(integer, integer) does not exist
  LINE 1: select test(1,2);
                 ^
  HINT:  No function matches the given name and argument types. You might need to add explicit type casts.
  CONTEXT:  referenced column: test

• If this item is set and a function with default parameters is invoked, input parameters are added to the function from left to right. The number of defaulted inputs depends on the number of default parameters. If an input of a non-default parameter is missing, the previous default value is used to fill this parameter. For example:

  gaussdb=# create or replace function test(f1 int, f2 int default 20, f3 int, f4 int default 40, f5 int default 50) return int
  gaussdb-# as
  gaussdb$# begin
  gaussdb$# raise info 'f1:%',f1;
  gaussdb$# raise info 'f2:%',f2;
  gaussdb$# raise info 'f3:%',f3;
  gaussdb$# raise info 'f4:%',f4;
  gaussdb$# raise info 'f5:%',f5;
  gaussdb$# return 1;
  gaussdb$# end;
  gaussdb$# /
  CREATE FUNCTION
  gaussdb=# select test(1,2);
  INFO:  f1:1
  CONTEXT:  referenced column: test
  INFO:  f2:2
  CONTEXT:  referenced column: test
  INFO:  f3:20
  CONTEXT:  referenced column: test
  INFO:  f4:40
  CONTEXT:  referenced column: test
  INFO:  f5:50
  CONTEXT:  referenced column: test
   test 
  ------
      1
  (1 row)

  As shown above, f3 is filled with an incorrect default value.

  WARNING:

  In this scenario, a non-default parameter is filled with the previous default value.

dynamic_sql_compat

After this parameter is enabled, the dynamic statement does not consider the template parameters with the same name in the template SQL statement as the same variable. Instead, the variables in the USING clause are matched in sequence.

dynamic_sql_check

If this parameter is enabled, an error is reported during dynamic statement execution if the number of different template parameters in the dynamic statement template SQL is different from the number of variables in the USING clause.

enable_funcname_with_argsname

If the parameter is enabled, the projection alias displays the complete function when the SELECT function is invoked.

• If this item is not set, the projection alias displays the function name when the SELECT function is invoked. For example:

  gaussdb=# SELECT power(2,3);
   power 
  -------
       8
  (1 row)
  
  gaussdb=# SELECT count(*) FROM db_ind_columns;
   count 
  -------
     611
  (1 row)
  
  gaussdb=# SELECT count(index_name) FROM db_ind_columns;
   count 
  -------
     611
  (1 row)
  
  gaussdb=# SELECT left('abcde', 2);
   left 
  ------
   ab
  (1 row)
  
  gaussdb=# SELECT pg_client_encoding();
   pg_client_encoding 
  --------------------
   UTF8
  (1 row)

• If the item is set, the projection alias displays the complete function when the SELECT function is invoked. For example:

  gaussdb=# SET behavior_compat_options = 'enable_funcname_with_argsname';
  SET
  gaussdb=# SELECT power(2,3);
   power(2,3) 
  ------------
            8
  (1 row)
  
  gaussdb=# SELECT count(*) FROM db_ind_columns;
   count(*) 
  ----------
        611
  (1 row)
  
  gaussdb=# SELECT count(index_name) FROM db_ind_columns;
   count(index_name) 
  -------------------
                 611
  (1 row)
  
  gaussdb=# SELECT left('abcde', 2);
   left('abcde',2) 
  -----------------
   ab
  (1 row)
  
  gaussdb=# SELECT pg_client_encoding();
   pg_client_encoding() 
  ----------------------
   UTF8
  (1 row)

  CAUTION:

  • Currently, only func_name(args_list), func_name(), and func_name(*) are supported to display complete functions. The args parameter only supports character type, value type, column name, and function. A function name can contain a schema or package name. The parameter cannot contain other clauses (such as the ORDER BY clause) or be an expression. The parameter can contain only the DISTINCT keyword. If the parameter contains other keywords, the complete function cannot be displayed.
  • Some special functions do not support displaying projection alias, including COLLATION FOR, CURRENT_DATE, CURRENT_TIME, CURRENT_TIMESTAMP, DBTIMEZONE, LOCALTIME, LOCALTIMESTAMP, SYSDATE, SESSIONTIMEZONE, ROWNUM, CURRENT_ROLE, CURRENT_USER, SESSION_USER, USER, CURRENT_CATALOG, CURRENT_SCHEMA, CAST, EXTRACT, TIMESTAMPDIFF, OVERLAY, POSITION, SUBSTRING, TREAT, TRIM, NULLIF, NVL, NVL2, COALESCE, GREATEST, LEAST, LNNVL, REGEXP_LIKE, and XML functions.
  • Some security encryption and decryption functions, anonymization functions, and projection aliases display functions may have security problems. Therefore, only function names are displayed here, including gs_encrypt_aes128, gs_decrypt_aes128, gs_encrypt, gs_decrypt, aes_encrypt, aes_decrypt, pg_create_physical_replication_slot_extern, dblink_connect,creditcardmasking, "basicemailmasking", fullemailmasking, alldigitsmasking, shufflemasking, randommasking, regexpmasking, and gs_digest.
  • The parameter transfer mode using => is not supported for the projection alias to display the complete function. The projection alias cannot contain double quotation marks (""), for example, select "power" (2,3).
  • To enable the projection alias to display the complete function, this function is not affected by parameters such as removing 0 at the end.

allow_rownum_alias

After this parameter is enabled, ROWNUM can be used as a column alias in SQL statements using the AS syntax. ROWNUM is used as a common identifier and cannot be used as a pseudocolumn.

current_sysdate

If this parameter is enabled, the current OS time is returned when the sysdate command is executed.

gaussdb=# set behavior_compat_options='current_sysdate';

SET

gaussdb=# select sysdate;

current_sysdate

---------------------

2023-06-20 20:15:27

(1 row)

10c

Compatible version of platform A

s1

• Compatible minor version of platform A, which affects functions TRUNC(date, fmt), ROUND(date, fmt), NVL2, LPAD, RPAD, ADD_MONTHS, MONTHS_BETWEEN, REGEXP_REPLACE, REGEXP_COUNT, TREAT, EMPTY_CLOB, INSTRB, trunc(number), greatest, least, mod, round(number), cast, to_date, to_timestamp, chr, rtrim, translate, to_char, to_number, and to_timestamp_tz.
• Data type conversion: A decimal character string is rounded off when it is converted to an integer (int1/int2/int4/int8/int16).
• Data type conversion: Implicit conversion from timestamp with time zone to timestamp without time zone is supported.

s2

• Compatible minor version of platform A, which affects functions dump, to_single_byte, to_multi_byte, nls_upper, nls_lower, initcap, ascii2, asciistr, unistr, vsize, cosh, remainder, sinh, tanh, nanvl, current_date, current_timestamp, dbtimezone, numtodsinterval, numtoyminterval, new_time, sessiontimezone, sys_extract_utc, tz_offset, to_binary_double, to_binary_float, to_dsinterval, to_yminterval, lnnvl, ora_hash, rawtohex2, bit2coding, and bit4coding.
• Supports all behaviors when the compatibility configuration item is set to s1.

s1

• Supports gs_loader specifying data type (CHAR[(length)]/INTEGER external[(length)]/FLOAT external[(length)]/DECIMAL external[(length)]/TIMESTAMP/DATE/DATE EXTERNAL/INTEGER/SMALLINT/RAW[(length)]) to import data.
• Supports gs_loader converting expressions and extending scenarios for columns.