GBK字符集下，使用chr函数将ASCII 码转换为字符，报错的问题

src/common/backend/utils/adt/a_compat.cpp

@@ -932,10 +932,29 @@ Datum chr(PG_FUNCTION_ARGS)
             wch[2] = 0x80 | ((cvalue >> 6) & 0x3F);
             wch[3] = 0x80 | (cvalue & 0x3F);
         }
+    } else if (encoding == PG_GBK && u_sess->attr.attr_sql.sql_compatibility == A_FORMAT) {
+        unsigned char bytes[2];
+        char* wch = NULL;
+        if (cvalue > 0xfefe)
+            ereport(ERROR,
+                (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+                    errmsg("requested character too large for encoding: %u", cvalue)));
 
-    }
+        for (int i = 0; i < 2; i++) {
+            bytes[i] = (cvalue >> ((1 - i) * 8)) & 0xFF;
+        }
 
-    else {
+        if (!pg_gbk_islegal(bytes, 2))
+            ereport(ERROR,
+                (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+                    errmsg("invalid character length for encoding: %u", cvalue)));
+
+        result = (text*)palloc(VARHDRSZ + 2);
+        SET_VARSIZE(result, VARHDRSZ + 2);
+        wch = VARDATA(result);
+        wch[0] = (char)bytes[0];
+        wch[1] = (char)bytes[1];
+    } else {
         bool is_mb = false;
 
         /*

src/test/regress/expected/chr_gbk.out

@@ -0,0 +1,41 @@
+--test chr function in GBK encoded database
+CREATE DATABASE db1 ENCODING 'GBK' TEMPLATE template0 lc_collate = 'zh_CN.gbk' lc_ctype = 'zh_CN.gbk' ;
+\c db1
+set client_encoding = 'UTF8';
+select chr(52144);
+ chr 
+-----
+ 税
+(1 row)
+
+select chr(33088); --0x8140
+ chr 
+-----
+ 丂
+(1 row)
+
+select chr(65278); --0xfefe
+ chr 
+-----
+ 
+(1 row)
+
+--error
+select chr(32146);
+ERROR:  invalid character length for encoding: 32146
+CONTEXT:  referenced column: chr
+select chr(33087);
+ERROR:  invalid character length for encoding: 33087
+CONTEXT:  referenced column: chr
+select chr(65279);
+ERROR:  requested character too large for encoding: 65279
+CONTEXT:  referenced column: chr
+select chr(33151); --0x817f
+ERROR:  invalid character length for encoding: 33151
+CONTEXT:  referenced column: chr
+select chr(65151); --0xfe7f
+ERROR:  invalid character length for encoding: 65151
+CONTEXT:  referenced column: chr
+\c regression
+clean connection to all force for database db1;
+drop database db1;

src/test/regress/parallel_schedule0

@@ -45,7 +45,7 @@ test: spm_adaptive_gplan
 test: smp
 test: alter_hw_package
 test: hw_grant_package gsc_func gsc_db
-test: uppercase_attribute_name decode_compatible_with_o outerjoin_bugfix
+test: uppercase_attribute_name decode_compatible_with_o outerjoin_bugfix chr_gbk
 test: replace_func_with_two_args trunc_func_for_date nlssort_pinyin updatable_views test_cursor_arg_defexpr
 
 # test multiple statistics

src/test/regress/sql/chr_gbk.sql

@@ -0,0 +1,17 @@
+--test chr function in GBK encoded database
+CREATE DATABASE db1 ENCODING 'GBK' TEMPLATE template0 lc_collate = 'zh_CN.gbk' lc_ctype = 'zh_CN.gbk' ;
+\c db1
+set client_encoding = 'UTF8';
+select chr(52144);
+select chr(33088); --0x8140
+select chr(65278); --0xfefe
+
+--error
+select chr(32146);
+select chr(33087);
+select chr(65279);
+select chr(33151); --0x817f
+select chr(65151); --0xfe7f
+\c regression
+clean connection to all force for database db1;
+drop database db1;