Save join_use_nulls in SETTINGS section for storage View

src/Storages/StorageView.cpp

@@ -29,6 +29,57 @@ namespace ErrorCodes
     extern const int LOGICAL_ERROR;
 }
 
+namespace
+{
+
+void addSettingsChanges(ASTPtr ast, const Settings & settings)
+{
+    auto * settings_ast = ast->as<ASTSetQuery>();
+    if (!settings_ast)
+        throw DB::Exception(DB::ErrorCodes::LOGICAL_ERROR, "ASTSetQuery expected");
+
+    settings_ast->is_standalone = false;
+    if (settings_ast->changes.tryGet("join_use_nulls") == nullptr)
+        settings_ast->changes.emplace_back("join_use_nulls", Field(settings.join_use_nulls));
+}
+
+/// Save to AST settings from context that affects view behaviour.
+void saveSettingsToAst(ASTSelectWithUnionQuery * select, const Settings & settings)
+{
+    /// Check SETTINGS section on the top level
+    if (select->settings_ast)
+    {
+        addSettingsChanges(select->settings_ast, settings);
+        return;
+    }
+
+    /// We cannot add SETTINGS on the top level because it will clash with section from inner SELECT
+    /// and will got query: SELECT ... SETTINGS ... SETTINGS ...
+
+    /// Process every select in ast and add SETTINGS section to each
+    for (const auto & child : select->list_of_selects->children)
+    {
+        auto * child_select = child->as<ASTSelectQuery>();
+        if (!child_select)
+            continue;
+
+        ASTPtr ast_set_query = child_select->settings();
+        if (ast_set_query)
+        {
+            /// Modify existing SETTINGS section
+            addSettingsChanges(ast_set_query, settings);
+        }
+        else
+        {
+            /// Add SETTINGS section to query
+            ast_set_query = std::make_shared<ASTSetQuery>();
+            addSettingsChanges(ast_set_query, settings);
+            child_select->setExpression(ASTSelectQuery::Expression::SETTINGS, std::move(ast_set_query));
+        }
+    }
+}
+
+}
 
 StorageView::StorageView(
     const StorageID & table_id_,
@@ -37,7 +88,6 @@ StorageView::StorageView(
     const String & comment,
     const Settings & settings)
     : IStorage(table_id_)
-    , settings_changes(settings.changes())
 {
     StorageInMemoryMetadata storage_metadata;
     storage_metadata.setColumns(columns_);
@@ -46,6 +96,7 @@ StorageView::StorageView(
     if (!query.select)
         throw Exception("SELECT query is not specified for " + getName(), ErrorCodes::INCORRECT_QUERY);
 
+    saveSettingsToAst(query.select, settings);
     SelectQueryDescription description;
 
     description.inner_query = query.select->ptr();
@@ -89,10 +140,7 @@ void StorageView::read(
         current_inner_query = query_info.view_query->clone();
     }
 
-    auto modified_context = Context::createCopy(context);
-    modified_context->applySettingsChanges(settings_changes);
-
-    InterpreterSelectWithUnionQuery interpreter(current_inner_query, modified_context, {}, column_names);
+    InterpreterSelectWithUnionQuery interpreter(current_inner_query, context, {}, column_names);
     interpreter.buildQueryPlan(query_plan);
 
     /// It's expected that the columns read from storage are not constant.

src/Storages/StorageView.h

@@ -55,8 +55,6 @@ protected:
         const ColumnsDescription & columns_,
         const String & comment,
         const Settings & settings);
-
-    SettingsChanges settings_changes;
 };
 
 }

tests/queries/0_stateless/01866_view_persist_settings.reference

@@ -1,3 +1,27 @@
+SELECT
+    a,
+    b,
+    c
+FROM 
+(
+    SELECT *
+    FROM 
+    (
+        SELECT
+            number + 1 AS a,
+            number + 11 AS b
+        FROM numbers(2)
+    ) AS t1
+    FULL OUTER JOIN 
+    (
+        SELECT
+            number + 2 AS a,
+            number + 22 AS c
+        FROM numbers(2)
+    ) AS t2 USING (a)
+    ORDER BY a ASC
+    SETTINGS max_block_size = 666, join_use_nulls = 0
+) AS view_no_nulls
 1	11	0
 2	12	22
 3	0	23

tests/queries/0_stateless/01866_view_persist_settings.sql

@@ -8,13 +8,17 @@ SET join_use_nulls = 0;
 CREATE OR REPLACE VIEW view_no_nulls AS
 SELECT * FROM ( SELECT number + 1 AS a, number + 11 AS b FROM numbers(2) ) AS t1
 FULL JOIN ( SELECT number + 2 AS a, number + 22 AS c FROM numbers(2) ) AS t2
-USING a ORDER BY a;
+USING a ORDER BY a
+SETTINGS max_block_size = 666;
+
+-- check that max_block_size not rewriten
+EXPLAIN SYNTAX SELECT * FROM view_no_nulls;
 
 CREATE OR REPLACE VIEW view_nulls_set AS
 SELECT * FROM ( SELECT number + 1 AS a, number + 11 AS b FROM numbers(2) ) AS t1
 FULL JOIN ( SELECT number + 2 AS a, number + 22 AS c FROM numbers(2) ) AS t2
 USING a ORDER BY a
-SETTINGS join_use_nulls = 1;
+SETTINGS join_use_nulls = 1, max_block_size = 666;
 
 SET join_use_nulls = 1;