Merge pull request #24576 from ClickHouse/aku/inherit-window

allow inheriting from a named window in window definition

src/Interpreters/ExpressionAnalyzer.cpp

@@ -474,10 +474,58 @@ bool ExpressionAnalyzer::makeAggregateDescriptions(ActionsDAGPtr & actions)
     return !aggregates().empty();
 }
 
-void makeWindowDescriptionFromAST(WindowDescription & desc, const IAST * ast)
+void makeWindowDescriptionFromAST(const WindowDescriptions & existing_descriptions,
+    WindowDescription & desc, const IAST * ast)
 {
     const auto & definition = ast->as<const ASTWindowDefinition &>();
 
+    if (!definition.parent_window_name.empty())
+    {
+        auto it = existing_descriptions.find(definition.parent_window_name);
+        if (it == existing_descriptions.end())
+        {
+            throw Exception(ErrorCodes::BAD_ARGUMENTS,
+                "Window definition '{}' references an unknown window '{}'",
+                definition.formatForErrorMessage(),
+                definition.parent_window_name);
+        }
+
+        const auto & parent = it->second;
+        desc.partition_by = parent.partition_by;
+        desc.order_by = parent.order_by;
+        desc.frame = parent.frame;
+
+        // If an existing_window_name is specified it must refer to an earlier
+        // entry in the WINDOW list; the new window copies its partitioning clause
+        // from that entry, as well as its ordering clause if any. In this case
+        // the new window cannot specify its own PARTITION BY clause, and it can
+        // specify ORDER BY only if the copied window does not have one. The new
+        // window always uses its own frame clause; the copied window must not
+        // specify a frame clause.
+        // -- https://www.postgresql.org/docs/current/sql-select.html
+        if (definition.partition_by)
+        {
+            throw Exception(ErrorCodes::BAD_ARGUMENTS,
+                "Derived window definition '{}' is not allowed to override PARTITION BY",
+                definition.formatForErrorMessage());
+        }
+
+        if (definition.order_by && !parent.order_by.empty())
+        {
+            throw Exception(ErrorCodes::BAD_ARGUMENTS,
+                "Derived window definition '{}' is not allowed to override a non-empty ORDER BY",
+                definition.formatForErrorMessage());
+        }
+
+        if (!parent.frame.is_default)
+        {
+            throw Exception(ErrorCodes::BAD_ARGUMENTS,
+                "Parent window '{}' is not allowed to define a frame: while processing derived window definition '{}'",
+                definition.parent_window_name,
+                definition.formatForErrorMessage());
+        }
+    }
+
     if (definition.partition_by)
     {
         for (const auto & column_ast : definition.partition_by->children)
@@ -557,7 +605,7 @@ void ExpressionAnalyzer::makeWindowDescriptions(ActionsDAGPtr actions)
             const auto & elem = ptr->as<const ASTWindowListElement &>();
             WindowDescription desc;
             desc.window_name = elem.name;
-            makeWindowDescriptionFromAST(desc, elem.definition.get());
+            makeWindowDescriptionFromAST(window_descriptions, desc, elem.definition.get());
 
             auto [it, inserted] = window_descriptions.insert(
                 {desc.window_name, desc});
@@ -642,7 +690,7 @@ void ExpressionAnalyzer::makeWindowDescriptions(ActionsDAGPtr actions)
                 const ASTWindowDefinition &>();
             WindowDescription desc;
             desc.window_name = definition.getDefaultWindowName();
-            makeWindowDescriptionFromAST(desc, &definition);
+            makeWindowDescriptionFromAST(window_descriptions, desc, &definition);
 
             auto [it, inserted] = window_descriptions.insert(
                 {desc.window_name, desc});

src/Parsers/ASTWindowDefinition.cpp

@@ -12,6 +12,8 @@ ASTPtr ASTWindowDefinition::clone() const
 {
     auto result = std::make_shared<ASTWindowDefinition>();
 
+    result->parent_window_name = parent_window_name;
+
     if (partition_by)
     {
         result->partition_by = partition_by->clone();
@@ -38,31 +40,48 @@ void ASTWindowDefinition::formatImpl(const FormatSettings & settings,
     FormatState & state, FormatStateStacked format_frame) const
 {
     format_frame.expression_list_prepend_whitespace = false;
+    bool need_space = false;
+
+    if (!parent_window_name.empty())
+    {
+        settings.ostr << backQuoteIfNeed(parent_window_name);
+
+        need_space = true;
+    }
 
     if (partition_by)
     {
+        if (need_space)
+        {
+            settings.ostr << " ";
+        }
+
         settings.ostr << "PARTITION BY ";
         partition_by->formatImpl(settings, state, format_frame);
-    }
 
-    if (partition_by && order_by)
-    {
-        settings.ostr << " ";
+        need_space = true;
     }
 
     if (order_by)
     {
+        if (need_space)
+        {
+            settings.ostr << " ";
+        }
+
         settings.ostr << "ORDER BY ";
         order_by->formatImpl(settings, state, format_frame);
-    }
 
-    if ((partition_by || order_by) && !frame.is_default)
-    {
-        settings.ostr << " ";
+        need_space = true;
     }
 
     if (!frame.is_default)
     {
+        if (need_space)
+        {
+            settings.ostr << " ";
+        }
+
         settings.ostr << WindowFrame::toString(frame.type) << " BETWEEN ";
         if (frame.begin_type == WindowFrame::BoundaryType::Current)
         {

src/Parsers/ASTWindowDefinition.h

@@ -10,6 +10,8 @@ namespace DB
 
 struct ASTWindowDefinition : public IAST
 {
+    std::string parent_window_name;
+
     ASTPtr partition_by;
 
     ASTPtr order_by;

src/Parsers/ExpressionElementParsers.cpp

@@ -502,9 +502,6 @@ bool ParserWindowReference::parseImpl(Pos & pos, ASTPtr & node, Expected & expec
 
     // Variant 1:
     // function_name ( * ) OVER window_name
-    // FIXME doesn't work anyway for now -- never used anywhere, window names
-    // can't be defined, and TreeRewriter thinks the window name is a column so
-    // the query fails.
     if (pos->type != TokenType::OpeningRoundBracket)
     {
         ASTPtr window_name_ast;
@@ -662,16 +659,10 @@ static bool tryParseFrameDefinition(ASTWindowDefinition * node, IParser::Pos & p
     return true;
 }
 
-bool ParserWindowDefinition::parseImpl(Pos & pos, ASTPtr & node, Expected & expected)
+// All except parent window name.
+static bool parseWindowDefinitionParts(IParser::Pos & pos,
+    ASTWindowDefinition & node, Expected & expected)
 {
-    auto result = std::make_shared<ASTWindowDefinition>();
-
-    ParserToken parser_openging_bracket(TokenType::OpeningRoundBracket);
-    if (!parser_openging_bracket.ignore(pos, expected))
-    {
-        return false;
-    }
-
     ParserKeyword keyword_partition_by("PARTITION BY");
     ParserNotEmptyExpressionList columns_partition_by(
         false /* we don't allow declaring aliases here*/);
@@ -683,8 +674,8 @@ bool ParserWindowDefinition::parseImpl(Pos & pos, ASTPtr & node, Expected & expe
         ASTPtr partition_by_ast;
         if (columns_partition_by.parse(pos, partition_by_ast, expected))
         {
-            result->children.push_back(partition_by_ast);
-            result->partition_by = partition_by_ast;
+            node.children.push_back(partition_by_ast);
+            node.partition_by = partition_by_ast;
         }
         else
         {
@@ -697,8 +688,8 @@ bool ParserWindowDefinition::parseImpl(Pos & pos, ASTPtr & node, Expected & expe
         ASTPtr order_by_ast;
         if (columns_order_by.parse(pos, order_by_ast, expected))
         {
-            result->children.push_back(order_by_ast);
-            result->order_by = order_by_ast;
+            node.children.push_back(order_by_ast);
+            node.order_by = order_by_ast;
         }
         else
         {
@@ -706,9 +697,45 @@ bool ParserWindowDefinition::parseImpl(Pos & pos, ASTPtr & node, Expected & expe
         }
     }
 
-    if (!tryParseFrameDefinition(result.get(), pos, expected))
+    return tryParseFrameDefinition(&node, pos, expected);
+}
+
+bool ParserWindowDefinition::parseImpl(Pos & pos, ASTPtr & node, Expected & expected)
+{
+    auto result = std::make_shared<ASTWindowDefinition>();
+
+    ParserToken parser_openging_bracket(TokenType::OpeningRoundBracket);
+    if (!parser_openging_bracket.ignore(pos, expected))
+    {
+        return false;
+    }
+
+    // We can have a parent window name specified before all other things. No
+    // easy way to distinguish identifier from keywords, so just try to parse it
+    // both ways.
+    if (parseWindowDefinitionParts(pos, *result, expected))
+    {
+        // Successfully parsed without parent window specifier. It can be empty,
+        // so check that it is followed by the closing bracket.
+        ParserToken parser_closing_bracket(TokenType::ClosingRoundBracket);
+        if (parser_closing_bracket.ignore(pos, expected))
+        {
+            node = result;
+            return true;
+        }
+    }
+
+    // Try to parse with parent window specifier.
+    ParserIdentifier parser_parent_window;
+    ASTPtr window_name_identifier;
+    if (!parser_parent_window.parse(pos, window_name_identifier, expected))
+    {
+        return false;
+    }
+    result->parent_window_name = window_name_identifier->as<const ASTIdentifier &>().name();
+
+    if (!parseWindowDefinitionParts(pos, *result, expected))
     {
-        /* Broken frame definition. */
         return false;
     }
 

tests/queries/0_stateless/01591_window_functions.reference

@@ -1120,3 +1120,31 @@ select count() over (rows between 2147483648 preceding and 2147493648 following)
 select count() over () from (select 1 a) l inner join (select 2 a) r using a;
 -- This case works as expected, one empty input chunk marked as input end.
 select count() over () where null;
+-- Inheriting another window.
+select number, count() over (w1 rows unbounded preceding) from numbers(10)
+window
+    w0 as (partition by intDiv(number, 5) as p),
+    w1 as (w0 order by mod(number, 3) as o)
+order by p, o, number
+;
+0	1
+3	2
+1	3
+4	4
+2	5
+6	1
+9	2
+7	3
+5	4
+8	5
+-- can't redefine PARTITION BY
+select count() over (w partition by number) from numbers(1) window w as (partition by intDiv(number, 5)); -- { serverError 36 }
+-- can't redefine existing ORDER BY
+select count() over (w order by number) from numbers(1) window w as (partition by intDiv(number, 5) order by mod(number, 3)); -- { serverError 36 }
+-- parent window can't have frame
+select count() over (w range unbounded preceding) from numbers(1) window w as (partition by intDiv(number, 5) order by mod(number, 3) rows unbounded preceding); -- { serverError 36 }
+-- looks weird but probably should work -- this is a window that inherits and changes nothing
+select count() over (w) from numbers(1) window w as ();
+1
+-- nonexistent parent window
+select count() over (w2 rows unbounded preceding); -- { serverError 36 }

tests/queries/0_stateless/01591_window_functions.sql

@@ -427,3 +427,26 @@ select count() over (rows between 2147483648 preceding and 2147493648 following)
 select count() over () from (select 1 a) l inner join (select 2 a) r using a;
 -- This case works as expected, one empty input chunk marked as input end.
 select count() over () where null;
+
+-- Inheriting another window.
+select number, count() over (w1 rows unbounded preceding) from numbers(10)
+window
+    w0 as (partition by intDiv(number, 5) as p),
+    w1 as (w0 order by mod(number, 3) as o)
+order by p, o, number
+;
+
+-- can't redefine PARTITION BY
+select count() over (w partition by number) from numbers(1) window w as (partition by intDiv(number, 5)); -- { serverError 36 }
+
+-- can't redefine existing ORDER BY
+select count() over (w order by number) from numbers(1) window w as (partition by intDiv(number, 5) order by mod(number, 3)); -- { serverError 36 }
+
+-- parent window can't have frame
+select count() over (w range unbounded preceding) from numbers(1) window w as (partition by intDiv(number, 5) order by mod(number, 3) rows unbounded preceding); -- { serverError 36 }
+
+-- looks weird but probably should work -- this is a window that inherits and changes nothing
+select count() over (w) from numbers(1) window w as ();
+
+-- nonexistent parent window
+select count() over (w2 rows unbounded preceding); -- { serverError 36 }