impl

src/Parsers/ExpressionElementParsers.cpp

@@ -3,10 +3,10 @@
 
 #include <Poco/String.h>
 
-#include <IO/ReadHelpers.h>
 #include <IO/ReadBufferFromMemory.h>
-#include <Common/typeid_cast.h>
+#include <IO/ReadHelpers.h>
 #include <Parsers/DumpASTNode.h>
+#include <Common/typeid_cast.h>
 
 #include <Parsers/ASTAsterisk.h>
 #include <Parsers/ASTColumnsTransformers.h>
@@ -49,6 +49,7 @@ namespace ErrorCodes
     extern const int BAD_ARGUMENTS;
     extern const int SYNTAX_ERROR;
     extern const int LOGICAL_ERROR;
+    extern const int ILLEGAL_AGGREGATION;
 }
 
 
@@ -268,7 +269,6 @@ bool ParserCompoundIdentifier::parseImpl(Pos & pos, ASTPtr & node, Expected & ex
     return true;
 }
 
-
 bool ParserFunction::parseImpl(Pos & pos, ASTPtr & node, Expected & expected)
 {
     ParserIdentifier id_parser;
@@ -276,6 +276,7 @@ bool ParserFunction::parseImpl(Pos & pos, ASTPtr & node, Expected & expected)
     ParserKeyword all("ALL");
     ParserExpressionList contents(false, is_table_function);
     ParserSelectWithUnionQuery select;
+    ParserKeyword filter("FILTER");
     ParserKeyword over("OVER");
 
     bool has_all = false;
@@ -440,16 +441,27 @@ bool ParserFunction::parseImpl(Pos & pos, ASTPtr & node, Expected & expected)
         function_node->children.push_back(function_node->parameters);
     }
 
-    if (over.ignore(pos, expected))
+    if (filter.ignore(pos, expected))
     {
-        function_node->is_window_function = true;
-
         // We are slightly breaking the parser interface by parsing the window
         // definition into an existing ASTFunction. Normally it would take a
         // reference to ASTPtr and assign it the new node. We only have a pointer
         // of a different type, hence this workaround with a temporary pointer.
         ASTPtr function_node_as_iast = function_node;
 
+        ParserFilterClause filter_parser;
+        if (!filter_parser.parse(pos, function_node_as_iast, expected))
+        {
+            return false;
+        }
+    }
+
+    if (over.ignore(pos, expected))
+    {
+        function_node->is_window_function = true;
+
+        ASTPtr function_node_as_iast = function_node;
+
         ParserWindowReference window_reference;
         if (!window_reference.parse(pos, function_node_as_iast, expected))
         {
@@ -504,6 +516,51 @@ bool ParserTableFunctionView::parseImpl(Pos & pos, ASTPtr & node, Expected & exp
     return true;
 }
 
+bool ParserFilterClause::parseImpl(Pos & pos, ASTPtr & node, Expected & expected)
+{
+    assert(node);
+    ASTFunction & function = dynamic_cast<ASTFunction &>(*node);
+
+    ParserToken parser_openging_bracket(TokenType::OpeningRoundBracket);
+    if (!parser_openging_bracket.ignore(pos, expected))
+    {
+        return false;
+    }
+
+    ParserKeyword parser_where("WHERE");
+    if (!parser_where.ignore(pos, expected))
+    {
+        return false;
+    }
+    ParserExpressionList parser_condition(false);
+    ASTPtr condition;
+    if (!parser_condition.parse(pos, condition, expected))
+    {
+        return false;
+    }
+
+    ParserToken parser_closing_bracket(TokenType::ClosingRoundBracket);
+    if (!parser_closing_bracket.ignore(pos, expected))
+    {
+        return false;
+    }
+
+    if (function.name.find("If") != String::npos)
+    {
+        throw Exception(
+            ErrorCodes::ILLEGAL_AGGREGATION,
+            "Filter clause provided for an aggregating function (" + function.name + ") already containing If suffix");
+    }
+    if (condition->children.empty())
+    {
+        throw Exception(ErrorCodes::SYNTAX_ERROR, "Empty condition for WHERE");
+    }
+
+    function.name += "If";
+    function.arguments->children.push_back(condition->children[0]);
+    return true;
+}
+
 bool ParserWindowReference::parseImpl(Pos & pos, ASTPtr & node, Expected & expected)
 {
     assert(node);

src/Parsers/ExpressionElementParsers.h

@@ -171,6 +171,13 @@ protected:
     bool parseImpl(Pos & pos, ASTPtr & node, Expected & expected) override;
 };
 
+// Allows to make queries like SELECT SUM(<expr>) FILTER(WHERE <cond>) FROM ...
+class ParserFilterClause : public IParserBase
+{
+    const char * getName() const override { return "filter"; }
+    bool parseImpl(Pos & pos, ASTPtr & node, Expected & expected) override;
+};
+
 // Window reference (the thing that goes after OVER) for window function.
 // Can be either window name or window definition.
 class ParserWindowReference : public IParserBase

tests/queries/0_stateless/02000_select_with_filter.reference

@@ -0,0 +1,2 @@
+98
+2450

tests/queries/0_stateless/02000_select_with_filter.sql

@@ -0,0 +1,4 @@
+SELECT argMax(number, number + 1) FILTER(WHERE number != 99) FROM numbers(100) ;
+SELECT sum(number) FILTER(WHERE number % 2 == 0) FROM numbers(100);
+SELECT sumIfOrNull(number, number % 2 == 1) FILTER(WHERE number % 2 == 0) FROM numbers(100); -- { clientError 184 }
+SELECT sum(number) FILTER(WHERE) FROM numbers(100); -- { clientError 62 }