one plan step per window

src/Interpreters/AggregateDescription.h

@@ -62,6 +62,11 @@ struct WindowDescription
 
     // No frame info as of yet.
 
+
+    // Reverse map to function descriptions, for convenience of building the
+    // plan. Just copy them because it's more convenient.
+    std::vector<WindowFunctionDescription> window_functions;
+
     std::string dump() const;
 };
 

src/Interpreters/ExpressionAnalyzer.cpp

@@ -475,22 +475,20 @@ bool ExpressionAnalyzer::makeAggregateDescriptions(ActionsDAGPtr & actions)
 bool ExpressionAnalyzer::makeWindowDescriptions(ActionsDAGPtr & actions)
 {
     // Convenient to check here because at least we have the Context.
-    if (!windowFunctions().empty() &&
+    if (!syntax->window_function_asts.empty() &&
         !context.getSettingsRef().allow_experimental_window_functions)
     {
         throw Exception(ErrorCodes::NOT_IMPLEMENTED,
             "Window functions are not implemented (while processing '{}')",
-            windowFunctions()[0]->formatForErrorMessage());
+            syntax->window_function_asts[0]->formatForErrorMessage());
     }
 
-    int next_window_index = 1;
-    for (const ASTFunction * function_node : windowFunctions())
+    for (const ASTFunction * function_node : syntax->window_function_asts)
     {
         assert(function_node->is_window_function);
 
         WindowDescription window_description;
-        window_description.window_name = fmt::format("window_{}",
-            next_window_index++);
+        window_description.window_name = function_node->getWindowDescription();
 
         if (function_node->window_partition_by)
         {
@@ -581,12 +579,28 @@ bool ExpressionAnalyzer::makeWindowDescriptions(ActionsDAGPtr & actions)
                 window_function.argument_types,
                 window_function.function_parameters, properties);
 
+        window_function_descriptions.push_back(window_function);
+
+        if (auto it = window_descriptions.find(window_description.window_name);
+            it != window_descriptions.end())
+        {
+            assert(it->second.full_sort_description
+                == window_description.full_sort_description);
+        }
+        else
+        {
             window_descriptions.insert({window_description.window_name,
                 window_description});
-        window_functions.push_back(window_function);
+        }
     }
 
-    return !windowFunctions().empty();
+    // Populate the reverse map.
+    for (const auto & f : window_function_descriptions)
+    {
+        window_descriptions[f.window_name].window_functions.push_back(f);
+    }
+
+    return !window_function_descriptions.empty();
 }
 
 
@@ -965,7 +979,7 @@ void SelectQueryExpressionAnalyzer::appendWindowFunctionsArguments(
 {
     ExpressionActionsChain::Step & step = chain.lastStep(aggregated_columns);
 
-    for (const auto & f : window_functions)
+    for (const auto & f : window_function_descriptions)
     {
         // Requiring a constant reference to a shared pointer to non-const AST
         // doesn't really look sane, but the visitor does indeed require it.
@@ -982,7 +996,7 @@ void SelectQueryExpressionAnalyzer::appendWindowFunctionsArguments(
     }
 
     // 2) mark the columns that are really required:
-    for (const auto & f : window_functions)
+    for (const auto & f : window_function_descriptions)
     {
         for (const auto & a : f.function_node->arguments->children)
         {

src/Interpreters/ExpressionAnalyzer.h

@@ -62,7 +62,7 @@ struct ExpressionAnalyzerData
 
     bool has_window = false;
     WindowDescriptions window_descriptions;
-    WindowFunctionDescriptions window_functions;
+    WindowFunctionDescriptions window_function_descriptions;
     NamesAndTypesList window_columns;
 
     bool has_global_subqueries = false;
@@ -141,7 +141,6 @@ protected:
     const TableJoin & analyzedJoin() const { return *syntax->analyzed_join; }
     const NamesAndTypesList & sourceColumns() const { return syntax->required_source_columns; }
     const std::vector<const ASTFunction *> & aggregates() const { return syntax->aggregates; }
-    const std::vector<const ASTFunction *> & windowFunctions() const { return syntax->window_functions; }
     /// Find global subqueries in the GLOBAL IN/JOIN sections. Fills in external_tables.
     void initGlobalSubqueriesAndExternalTables(bool do_global);
 

src/Interpreters/InterpreterSelectQuery.cpp

@@ -1754,10 +1754,8 @@ void InterpreterSelectQuery::executeExpression(QueryPlan & query_plan, const Act
 
 void InterpreterSelectQuery::executeWindow(QueryPlan & query_plan)
 {
-    for (const auto & f : query_analyzer->window_functions)
+    for (const auto & [_, w] : query_analyzer->window_descriptions)
     {
-        const auto & w = query_analyzer->window_descriptions[f.window_name];
-
         const Settings & settings = context->getSettingsRef();
 
         auto partial_sorting = std::make_unique<PartialSortingStep>(
@@ -1784,7 +1782,7 @@ void InterpreterSelectQuery::executeWindow(QueryPlan & query_plan)
             + w.window_name + "'");
         query_plan.addStep(std::move(merge_sorting_step));
 
-        // First MergeSorted, now MergingSorted......
+        // First MergeSorted, now MergingSorted.
         auto merging_sorted = std::make_unique<MergingSortedStep>(
             query_plan.getCurrentDataStream(),
             w.full_sort_description,
@@ -1797,9 +1795,9 @@ void InterpreterSelectQuery::executeWindow(QueryPlan & query_plan)
         auto window_step = std::make_unique<WindowStep>(
             query_plan.getCurrentDataStream(),
             w,
-            std::vector<WindowFunctionDescription>(1, f));
-        window_step->setStepDescription("Window step for function '"
-            + f.column_name + "'");
+            w.window_functions);
+        window_step->setStepDescription("Window step for window '"
+            + w.window_name + "'");
 
         query_plan.addStep(std::move(window_step));
     }

src/Interpreters/TreeRewriter.cpp

@@ -751,7 +751,7 @@ TreeRewriterResultPtr TreeRewriter::analyzeSelect(
     collectJoinedColumns(*result.analyzed_join, *select_query, tables_with_columns, result.aliases);
 
     result.aggregates = getAggregates(query, *select_query);
-    result.window_functions = getWindowFunctions(query, *select_query);
+    result.window_function_asts = getWindowFunctions(query, *select_query);
     result.collectUsedColumns(query, true);
     result.ast_join = select_query->join();
 

src/Interpreters/TreeRewriter.h

@@ -35,7 +35,7 @@ struct TreeRewriterResult
     Aliases aliases;
     std::vector<const ASTFunction *> aggregates;
 
-    std::vector<const ASTFunction *> window_functions;
+    std::vector<const ASTFunction *> window_function_asts;
 
     /// Which column is needed to be ARRAY-JOIN'ed to get the specified.
     /// For example, for `SELECT s.v ... ARRAY JOIN a AS s` will get "s.v" -> "a.v".

src/Parsers/ASTFunction.cpp

@@ -475,21 +475,44 @@ void ASTFunction::formatImplWithoutAlias(const FormatSettings & settings, Format
     }
 
     settings.ostr << " OVER (";
+    appendWindowDescription(settings, state, nested_dont_need_parens);
+    settings.ostr << ")";
+}
+
+std::string ASTFunction::getWindowDescription() const
+{
+    WriteBufferFromOwnString ostr;
+    FormatSettings settings{ostr, true /* one_line */};
+    FormatState state;
+    FormatStateStacked frame;
+    appendWindowDescription(settings, state, frame);
+    return ostr.str();
+}
+
+void ASTFunction::appendWindowDescription(const FormatSettings & settings,
+    FormatState & state, FormatStateStacked frame) const
+{
+    if (!is_window_function)
+    {
+        return;
+    }
+
     if (window_partition_by)
     {
         settings.ostr << "PARTITION BY ";
-        window_partition_by->formatImpl(settings, state, nested_dont_need_parens);
+        window_partition_by->formatImpl(settings, state, frame);
     }
+
     if (window_partition_by && window_order_by)
     {
         settings.ostr << " ";
     }
+
     if (window_order_by)
     {
         settings.ostr << "ORDER BY ";
-        window_order_by->formatImpl(settings, state, nested_dont_need_parens);
+        window_order_by->formatImpl(settings, state, frame);
     }
-    settings.ostr << ")";
 }
 
 }

src/Parsers/ASTFunction.h

@@ -39,6 +39,11 @@ public:
 
     ASTPtr toLiteral() const;  // Try to convert functions like Array or Tuple to a literal form.
 
+    void appendWindowDescription(const FormatSettings & settings,
+        FormatState & state, FormatStateStacked frame) const;
+
+    std::string getWindowDescription() const;
+
 protected:
     void formatImplWithoutAlias(const FormatSettings & settings, FormatState & state, FormatStateStacked frame) const override;
     void appendColumnNameImpl(WriteBuffer & ostr) const override;

src/Parsers/IAST.h

@@ -158,6 +158,7 @@ public:
         bool always_quote_identifiers = false;
         IdentifierQuotingStyle identifier_quoting_style = IdentifierQuotingStyle::Backticks;
 
+        // Newline or whitespace.
         char nl_or_ws;
 
         FormatSettings(WriteBuffer & ostr_, bool one_line_)

tests/queries/0_stateless/01591_window_functions.reference

@@ -87,6 +87,10 @@ select number, max(number) over (partition by intDiv(number, 3) order by number
 -- window count() is overwritten with aggregate count()
 -- select number, count(), count() over (partition by intDiv(number, 3)) from numbers(10) group by number order by count() desc;
 
+-- different windows
+-- an explain test would also be helpful, but it's too immature now and I don't
+-- want to change reference all the time
+
 9	9
 6	8
 7	8
@@ -97,3 +101,49 @@ select number, max(number) over (partition by intDiv(number, 3) order by number
 0	2
 1	2
 2	2
+select number, max(number) over (partition by intDiv(number, 3) order by number desc), count(number) over (partition by intDiv(number, 5) order by number) as m from numbers(31) order by number settings max_block_size = 2;
+
+-- two functions over the same window
+-- an explain test would also be helpful, but it's too immature now and I don't
+-- want to change reference all the time
+
+0	2	1
+1	2	2
+2	2	3
+3	5	4
+4	5	5
+5	5	1
+6	8	2
+7	8	3
+8	8	4
+9	11	5
+10	11	1
+11	11	2
+12	14	3
+13	14	4
+14	14	5
+15	17	1
+16	17	2
+17	17	3
+18	20	4
+19	20	5
+20	20	1
+21	23	2
+22	23	3
+23	23	4
+24	26	5
+25	26	1
+26	26	2
+27	29	3
+28	29	4
+29	29	5
+30	30	1
+select number, max(number) over (partition by intDiv(number, 3) order by number desc), count(number) over (partition by intDiv(number, 3) order by number desc) as m from numbers(7) order by number settings max_block_size = 2;
+
+0	2	3
+1	2	2
+2	2	1
+3	5	3
+4	5	2
+5	5	1
+6	6	1

tests/queries/0_stateless/01591_window_functions.sql

@@ -30,3 +30,13 @@ select number, max(number) over (partition by intDiv(number, 3) order by number
 -- this one doesn't work yet -- looks like the column names clash, and the
 -- window count() is overwritten with aggregate count()
 -- select number, count(), count() over (partition by intDiv(number, 3)) from numbers(10) group by number order by count() desc;
+
+-- different windows
+-- an explain test would also be helpful, but it's too immature now and I don't
+-- want to change reference all the time
+select number, max(number) over (partition by intDiv(number, 3) order by number desc), count(number) over (partition by intDiv(number, 5) order by number) as m from numbers(31) order by number settings max_block_size = 2;
+
+-- two functions over the same window
+-- an explain test would also be helpful, but it's too immature now and I don't
+-- want to change reference all the time
+select number, max(number) over (partition by intDiv(number, 3) order by number desc), count(number) over (partition by intDiv(number, 3) order by number desc) as m from numbers(7) order by number settings max_block_size = 2;