From 16606e46a96250ba1340ed076cc4a302f888f738 Mon Sep 17 00:00:00 2001
From: "opensearch-trigger-bot[bot]"
 <98922864+opensearch-trigger-bot[bot]@users.noreply.github.com>
Date: Tue, 3 Jan 2023 09:25:25 -0800
Subject: [PATCH] Fix back quoted alias of FROM subquery (#1189) (#1208)

* Unquote from subquery alias

Signed-off-by: Chen Dai <daichen@amazon.com>

* Add comparison test case

Signed-off-by: Chen Dai <daichen@amazon.com>

* Add more comparison test case

Signed-off-by: Chen Dai <daichen@amazon.com>

* Update doc to remove limitations

Signed-off-by: Chen Dai <daichen@amazon.com>

Signed-off-by: Chen Dai <daichen@amazon.com>
(cherry picked from commit 91ef34d396d400aec0db5cad6cfdd9e665ddb9d9)

Co-authored-by: Chen Dai <daichen@amazon.com>
---
 docs/user/limitations/limitations.rst         | 17 ---------------
 .../resources/correctness/bugfixes/550.txt    |  2 ++
 .../opensearch/sql/sql/parser/AstBuilder.java |  3 ++-
 .../sql/sql/parser/AstBuilderTest.java        | 21 +++++++++++++++++++
 4 files changed, 25 insertions(+), 18 deletions(-)
 create mode 100644 integ-test/src/test/resources/correctness/bugfixes/550.txt

diff --git a/docs/user/limitations/limitations.rst b/docs/user/limitations/limitations.rst
index d6e763a73d..8ce75a0e25 100644
--- a/docs/user/limitations/limitations.rst
+++ b/docs/user/limitations/limitations.rst
@@ -34,23 +34,6 @@ Aggregation over expression is not supported for now. You can only apply aggrega
 Here's a link to the Github issue - [Issue #288](https://github.com/opendistro-for-elasticsearch/sql/issues/288).
 
 
-Limitations on Subqueries
-=========================
-
-Subqueries in the FROM clause
------------------------------
-
-Subquery in the `FROM` clause in this format: `SELECT outer FROM (SELECT inner)` is supported only when the query is merged into one query. For example, the following query is supported::
-
-    SELECT t.f, t.d
-    FROM (
-        SELECT FlightNum as f, DestCountry as d
-        FROM opensearch_dashboards_sample_data_flights
-        WHERE OriginCountry = 'US') t
-
-But, if the outer query has `GROUP BY` or `ORDER BY`, then it's not supported.
-
-
 Limitations on JOINs
 ====================
 
diff --git a/integ-test/src/test/resources/correctness/bugfixes/550.txt b/integ-test/src/test/resources/correctness/bugfixes/550.txt
new file mode 100644
index 0000000000..902e3b0d20
--- /dev/null
+++ b/integ-test/src/test/resources/correctness/bugfixes/550.txt
@@ -0,0 +1,2 @@
+SELECT ABS(`flights`.`AvgTicketPrice`) FROM (SELECT `AvgTicketPrice` FROM `opensearch_dashboards_sample_data_flights`) AS `flights` GROUP BY ABS(`flights`.`AvgTicketPrice`)
+SELECT `b`.`Origin`, `b`.`avgPrice` FROM (SELECT `a`.`Origin` AS `Origin`, AVG(`AvgTicketPrice`) AS `avgPrice` FROM (SELECT `Origin`, `AvgTicketPrice` FROM `opensearch_dashboards_sample_data_flights` WHERE `FlightDelay` = True) AS `a` GROUP BY `a`.`Origin`) AS `b` ORDER BY `b`.`avgPrice` DESC
diff --git a/sql/src/main/java/org/opensearch/sql/sql/parser/AstBuilder.java b/sql/src/main/java/org/opensearch/sql/sql/parser/AstBuilder.java
index 6edce6eb15..02a7f7d1b9 100644
--- a/sql/src/main/java/org/opensearch/sql/sql/parser/AstBuilder.java
+++ b/sql/src/main/java/org/opensearch/sql/sql/parser/AstBuilder.java
@@ -170,7 +170,8 @@ public UnresolvedPlan visitTableAsRelation(TableAsRelationContext ctx) {
 
   @Override
   public UnresolvedPlan visitSubqueryAsRelation(SubqueryAsRelationContext ctx) {
-    return new RelationSubquery(visit(ctx.subquery), ctx.alias().getText());
+    String subqueryAlias = StringUtils.unquoteIdentifier(ctx.alias().getText());
+    return new RelationSubquery(visit(ctx.subquery), subqueryAlias);
   }
 
   @Override
diff --git a/sql/src/test/java/org/opensearch/sql/sql/parser/AstBuilderTest.java b/sql/src/test/java/org/opensearch/sql/sql/parser/AstBuilderTest.java
index 2aed4f2834..fafb143291 100644
--- a/sql/src/test/java/org/opensearch/sql/sql/parser/AstBuilderTest.java
+++ b/sql/src/test/java/org/opensearch/sql/sql/parser/AstBuilderTest.java
@@ -518,6 +518,27 @@ public void can_build_from_subquery() {
     );
   }
 
+  @Test
+  public void can_build_from_subquery_with_backquoted_alias() {
+    assertEquals(
+        project(
+            relationSubquery(
+                project(
+                    relation("test"),
+                    alias("firstname", qualifiedName("firstname"), "firstName")),
+                "a"),
+            alias("a.firstName", qualifiedName("a", "firstName"))
+        ),
+        buildAST(
+            "SELECT a.firstName "
+                + "FROM ( "
+                + " SELECT `firstname` AS `firstName` "
+                + " FROM `test` "
+                + ") AS `a`"
+        )
+    );
+  }
+
   @Test
   public void can_build_show_all_tables() {
     assertEquals(