开启双引号开关时把别名转化为小写

src/common/backend/parser/gram.y

@@ -28622,7 +28622,15 @@ target_el:	a_expr AS ColLabel
 			| a_expr IDENT
 				{
 					$$ = makeNode(ResTarget);
-					$$->name = $2;
+					if (u_sess->attr.attr_sql.enable_ignore_case_in_dquotes 
+					    && (pg_yyget_extra(yyscanner))->core_yy_extra.ident_quoted)
+					{
+						$$->name = pg_strtolower(pstrdup($2));
+					}
+					else
+					{
+						$$->name = $2;
+					}
 					$$->indirection = NIL;
 					$$->val = (Node *)$1;
 					$$->location = @1;

src/test/regress/expected/ignore_double_quotes.out

@@ -79,6 +79,13 @@ select * from "啊啊";
 insert into ￥("￥","$") values(1,2);
 insert into ￥(￥,"$") values(4,3);
 insert into "啊啊"("，",",") values(1,2);
+-- alias
+create table t_ignore_case_in_dquotes_use_case0001(col1 int,col2 varchar(10));
+insert into t_ignore_case_in_dquotes_use_case0001 values(1,'one'),(2,'two'),(3,'three');
+select col1 as "AS_COL1",col2 "AS_COL2" from "t_ignore_case_in_dquotes_use_case0001" where "COL2"='two';
+ERROR:  column "COL2" does not exist
+LINE 1: ...rom "t_ignore_case_in_dquotes_use_case0001" where "COL2"='tw...
+                                                             ^
 -- function
 create function f1(b int) returns int
 as $$
@@ -264,6 +271,12 @@ call "P1"();
  
 (1 row)
 
+select col1 as "AS_COL1",col2 "AS_COL2" from "t_ignore_case_in_dquotes_use_case0001" where "COL2"='two';
+ as_col1 | as_col2 
+---------+---------
+       2 | two
+(1 row)
+
 select * from "TeSt";
  A | a 
 ---+---
@@ -336,6 +349,7 @@ drop index i1;
 drop view test_view;
 drop view "TeSt_view";
 drop table test;
+drop table t_ignore_case_in_dquotes_use_case0001;
 drop table "TeSt";
 drop table "￥￥";
 drop table "$";

src/test/regress/sql/ignore_double_quotes.sql

@@ -39,6 +39,11 @@ insert into ￥("￥","$") values(1,2);
 insert into ￥(￥,"$") values(4,3);
 insert into "啊啊"("，",",") values(1,2);
 
+-- alias
+create table t_ignore_case_in_dquotes_use_case0001(col1 int,col2 varchar(10));
+insert into t_ignore_case_in_dquotes_use_case0001 values(1,'one'),(2,'two'),(3,'three');
+select col1 as "AS_COL1",col2 "AS_COL2" from "t_ignore_case_in_dquotes_use_case0001" where "COL2"='two';
+
 -- function
 create function f1(b int) returns int
 as $$
@@ -114,6 +119,7 @@ CREATE SEQUENCE "S1" START 801 CACHE 90;-- error
 call p1();
 select * from test;
 call "P1"();
+select col1 as "AS_COL1",col2 "AS_COL2" from "t_ignore_case_in_dquotes_use_case0001" where "COL2"='two';
 select * from "TeSt";
 create table "SCH_ignore_quote_01"."TAB_quote"("A" int);
 insert into tab_quote (a) values (4);
@@ -140,6 +146,7 @@ drop index i1;
 drop view test_view;
 drop view "TeSt_view";
 drop table test;
+drop table t_ignore_case_in_dquotes_use_case0001;
 drop table "TeSt";
 drop table "￥￥";
 drop table "$";