Merge pull request #39850 from kitaisreal/select-query-has-join-method

Add hasJoin method into ASTSelectQuery

src/Parsers/ASTSelectQuery.cpp

@@ -344,6 +344,25 @@ const ASTTablesInSelectQueryElement * ASTSelectQuery::join() const
     return getFirstTableJoin(*this);
 }
 
+bool ASTSelectQuery::hasJoin() const
+{
+    if (!tables())
+        return false;
+
+    const auto & tables_in_select_query = tables()->as<ASTTablesInSelectQuery &>();
+    if (tables_in_select_query.children.empty())
+        return false;
+
+    for (const auto & child : tables_in_select_query.children)
+    {
+        const auto & tables_element = child->as<ASTTablesInSelectQueryElement &>();
+        if (tables_element.table_join)
+            return true;
+    }
+
+    return false;
+}
+
 static String getTableExpressionAlias(const ASTTableExpression * table_expression)
 {
     if (table_expression->subquery)

src/Parsers/ASTSelectQuery.h

@@ -131,6 +131,7 @@ public:
     std::pair<ASTPtr, bool> arrayJoinExpressionList() const;
 
     const ASTTablesInSelectQueryElement * join() const;
+    bool hasJoin() const;
     bool final() const;
     bool withFill() const;
     void replaceDatabaseAndTable(const String & database_name, const String & table_name);

src/Storages/MergeTree/MergeTreeData.cpp

@@ -5489,7 +5489,7 @@ std::optional<ProjectionCandidate> MergeTreeData::getQueryProcessingStageWithAgg
     // In order to properly analyze joins, aliases should be recognized. However, aliases get lost during projection analysis.
     // Let's disable projection if there are any JOIN clauses.
     // TODO: We need a better identifier resolution mechanism for projection analysis.
-    if (select_query->join())
+    if (select_query->hasJoin())
         return std::nullopt;
 
     // INTERPOLATE expressions may include aliases, so aliases should be preserved