LightDB23.4 GBK和UTF8转码失败的字符替换成空格

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LightDB23.4 GBK和UTF8转码失败的字符替换成空格

背景介绍

用户使用迁移工具从Oracle数据库迁移数据到LightDB的过程中发现，某些GBK编码转成UTF8编码后，在插入到LightDB中会报错。以GBK编码AAA1为例，LightDB的GBK和UTF8映射表中不支持AAA1这个GBK编码的转换。不支持的GBK编码都是处于GBK编码的自定义区间。

在上图中，UTF8编码EE8080对应于GBK编码AAA1，插入到LightDB时报错。
所以，在LightDB23.4中，将GBK和UTF8转码失败的字符替换成空格。只有在客户端和服务端编码不一致，且需要GBK和UTF8之间转码的时候，这个功能才生效。

功能示例

客户端编码GBK，服务端编码UTF8

1. 建表，插入数据

lightdb@postgres=# \c lt_test
You are now connected to database "lt_test" as user "lightdb".
compatible type: postgresql
lightdb@lt_test=# 
lightdb@lt_test=# 
lightdb@lt_test=# create table t1(cont text);
CREATE TABLE
lightdb@lt_test=# 
lightdb@lt_test=# 
lightdb@lt_test=# show server_encoding ;server_encoding 
-----------------UTF8
(1 row)lightdb@lt_test=# 
lightdb@lt_test=# \encoding gbk
lightdb@lt_test=# 
lightdb@lt_test=# \i gbk.test 
INSERT 0 1
lightdb@lt_test=# 
lightdb@lt_test=# select * from t1;cont  
-------我 们
(1 row)lightdb@lt_test=# select oid,datname from pg_database where datname = 'lt_test';oid  | datname 
-------+---------25485 | lt_test
(1 row)lightdb@lt_test=# 
lightdb@lt_test=# select oid,relfilenode from pg_class where relname = 't1';oid  | relfilenode 
-------+-------------25486 |       25486
(1 row)lightdb@lt_test=# checkpoint ;
CHECKPOINT
lightdb@lt_test=# 
lightdb@lt_test=# select oid,relfilenode from pg_class where relname = 't1';oid  | relfilenode 
-------+-------------25486 |       25486
(1 row)lightdb@lt_test=# 

2. 查看实际表文件中的数据， e6 88 91 20 e4 bb ac，e6 88 91表示我，e4 bb ac表示们，中间的20就是转换后的空格

[lightdb@localhost 25485]$ hexdump -C 25486
00000000  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00002000
[lightdb@localhost 25485]$ hexdump -C 25486
00000000  00 00 00 00 f0 a9 0c 22  00 00 00 00 1c 00 e0 1f  |......."........|
00000010  00 20 04 20 00 00 00 00  e0 9f 40 00 00 00 00 00  |. . ......@.....|
00000020  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00001fe0  07 05 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00001ff0  01 00 01 00 02 09 18 00  11 e6 88 91 20 e4 bb ac  |............ ...|
00002000
[lightdb@localhost 25485]$