GUC参数说明

d_format_behavior_compat_options

取值范围：字符串

默认值：''

参数说明：参数值为逗号间隔的字符串，仅允许合法字符串设定，不合法情况下，启动后报error。同样，设置时候，如果新值非法，则报error并且不修改老值。目前可选参数有：

enable_sbr_identifier：是否允许使用 [] 包裹标识符。开启以后内核原有的数组相关语法会被禁用。

openGauss=# set d_format_behavior_compat_options = 'enable_sbr_identifier';
SET
openGauss=# create table[array](a1 int);
CREATE TABLE
openGauss=# select ARRAY[1,2,3];
ERROR:  syntax error at or near "[1,2,3]"

enable_table_hint_identifier：是否允许table_hint当做标识符，用于列名、变量名等。开启后允许下述hint用作标识符。涉及的hint有：NOLOCK、READUNCOMMITTED、UPDLOCK、REPEATABLEREAD、SERIALIZABLE、READCOMMITTED、TABLOCK、TABLOCKX、PAGLOCK、ROWLOCK、NOWAIT、READPAST、XLOCK、SNAPSHOT、NOEXPAND。

openGauss=# set d_format_behavior_compat_options = 'enable_table_hint_identifier';
SET
openGauss=# create table testhint(nowait int);
CREATE TABLE
openGauss=# insert into testhint (nowait) values(1);
INSERT 0 1
openGauss=# select max(nowait) from testhint;
 max
-----
   1
(1 row)

openGauss=# set d_format_behavior_compat_options = '';
SET
openGauss=# create table testhint(nowait int);
ERROR:  syntax error at or near "("
LINE 1: create table testhint(nowait int);
                             ^

ANSI_NULLS

取值范围：on/off

默认值：on

参数说明：用于控制NULL值与非NULL值比较时的表现。如果设置为on，那么NULL值与NULL或者非NULL值做等于或者不等于比较结果都是NULL。如果设置成off，NULL值与NULL值做等于比较结果为true，NULL值与非NULL值做等于比较时结果为false。

openGauss=# set ANSI_NULLS on;
SET
openGauss=# select NULL = NULL;
 ?column?
----------

(1 row)

openGauss=# select 1 = NULL;
 ?column?
----------

(1 row)

openGauss=# select NULL <> NULL;
 ?column?
----------

(1 row)

openGauss=# select 1 <> NULL;
 ?column?
----------

(1 row)

openGauss=# set ANSI_NULLS off;
SET
openGauss=# select NULL = NULL;
 ?column?
----------
 t
(1 row)

openGauss=# select 1 = NULL;
 ?column?
----------
 f
(1 row)

openGauss=# select NULL <> NULL;
 ?column?
----------
 f
(1 row)

openGauss=# select 1 <> NULL;
 ?column?
----------
 t
(1 row)