TableFunction view.

src/Interpreters/QueryNormalizer.cpp

@@ -20,6 +20,7 @@ namespace ErrorCodes
     extern const int TOO_DEEP_AST;
     extern const int CYCLIC_ALIASES;
     extern const int UNKNOWN_QUERY_PARAMETER;
+    extern const int BAD_ARGUMENTS;
 }
 
 
@@ -151,6 +152,13 @@ void QueryNormalizer::visitChildren(const ASTPtr & node, Data & data)
 {
     if (const auto * func_node = node->as<ASTFunction>())
     {
+        if (func_node->query)
+        {
+            if (func_node->name != "view")
+                throw Exception("Query argument can only be used in the `view` TableFunction", ErrorCodes::BAD_ARGUMENTS);
+            /// Don't go into query argument.
+            return;
+        }
         /// We skip the first argument. We also assume that the lambda function can not have parameters.
         size_t first_pos = 0;
         if (func_node->name == "lambda")

src/Parsers/ASTFunction.cpp

@@ -48,6 +48,7 @@ ASTPtr ASTFunction::clone() const
     auto res = std::make_shared<ASTFunction>(*this);
     res->children.clear();
 
+    if (query) { res->query = query->clone(); res->children.push_back(res->query); }
     if (arguments) { res->arguments = arguments->clone(); res->children.push_back(res->arguments); }
     if (parameters) { res->parameters = parameters->clone(); res->children.push_back(res->parameters); }
 
@@ -118,6 +119,18 @@ void ASTFunction::formatImplWithoutAlias(const FormatSettings & settings, Format
     nested_need_parens.need_parens = true;
     nested_dont_need_parens.need_parens = false;
 
+    if (query)
+    {
+        std::string nl_or_nothing = settings.one_line ? "" : "\n";
+        std::string indent_str = settings.one_line ? "" : std::string(4u * frame.indent, ' ');
+        settings.ostr << (settings.hilite ? hilite_function : "") << name << "(" << nl_or_nothing;
+        FormatStateStacked frame_nested = frame;
+        frame_nested.need_parens = false;
+        ++frame_nested.indent;
+        query->formatImpl(settings, state, frame_nested);
+        settings.ostr << nl_or_nothing << indent_str << ")";
+        return;
+    }
     /// Should this function to be written as operator?
     bool written = false;
     if (arguments && !parameters)

src/Parsers/ASTFunction.h

@@ -13,6 +13,7 @@ class ASTFunction : public ASTWithAlias
 {
 public:
     String name;
+    ASTPtr query; // It's possible for a function to accept a query as its only argument.
     ASTPtr arguments;
     /// parameters - for parametric aggregate function. Example: quantile(0.9)(x) - what in first parens are 'parameters'.
     ASTPtr parameters;

src/Parsers/ExpressionElementParsers.cpp

@@ -18,6 +18,8 @@
 #include <Parsers/ASTQueryParameter.h>
 #include <Parsers/ASTTTLElement.h>
 #include <Parsers/ASTOrderByElement.h>
+#include <Parsers/ASTSelectWithUnionQuery.h>
+#include <Parsers/ASTSelectQuery.h>
 #include <Parsers/ASTSubquery.h>
 #include <Parsers/ASTFunctionWithKeyValueArguments.h>
 
@@ -217,10 +219,12 @@ bool ParserFunction::parseImpl(Pos & pos, ASTPtr & node, Expected & expected)
     ParserIdentifier id_parser;
     ParserKeyword distinct("DISTINCT");
     ParserExpressionList contents(false);
+    ParserSelectWithUnionQuery select;
 
     bool has_distinct_modifier = false;
 
     ASTPtr identifier;
+    ASTPtr query;
     ASTPtr expr_list_args;
     ASTPtr expr_list_params;
 
@@ -231,8 +235,36 @@ bool ParserFunction::parseImpl(Pos & pos, ASTPtr & node, Expected & expected)
         return false;
     ++pos;
 
+
     if (distinct.ignore(pos, expected))
         has_distinct_modifier = true;
+    else
+    {
+        auto old_pos = pos;
+        auto maybe_an_subquery = pos->type == TokenType::OpeningRoundBracket;
+
+        if (select.parse(pos, query, expected))
+        {
+            auto & select_ast = query->as<ASTSelectWithUnionQuery &>();
+            if (select_ast.list_of_selects->children.size() == 1 && maybe_an_subquery)
+            {
+                // It's an subquery. Bail out.
+                pos = old_pos;
+            }
+            else
+            {
+                if (pos->type != TokenType::ClosingRoundBracket)
+                    return false;
+                ++pos;
+                auto function_node = std::make_shared<ASTFunction>();
+                tryGetIdentifierNameInto(identifier, function_node->name);
+                function_node->query = query;
+                function_node->children.push_back(function_node->query);
+                node = function_node;
+                return true;
+            }
+        }
+    }
 
     const char * contents_begin = pos->begin;
     if (!contents.parse(pos, expr_list_args, expected))

src/Storages/StorageView.cpp

@@ -104,7 +104,13 @@ void StorageView::replaceWithSubquery(ASTSelectQuery & outer_query, ASTPtr view_
     ASTTableExpression * table_expression = getFirstTableExpression(outer_query);
 
     if (!table_expression->database_and_table_name)
+    {
+        // If it's a view table function, add a fake db.table name.
+        if (table_expression->table_function && table_expression->table_function->as<ASTFunction>()->name == "view")
+            table_expression->database_and_table_name = std::make_shared<ASTIdentifier>("__view");
+        else
             throw Exception("Logical error: incorrect table expression", ErrorCodes::LOGICAL_ERROR);
+    }
 
     DatabaseAndTableWithAlias db_table(table_expression->database_and_table_name);
     String alias = db_table.alias.empty() ? db_table.table : db_table.alias;

src/TableFunctions/TableFunctionView.cpp

@@ -0,0 +1,45 @@
+#include <Interpreters/InterpreterSelectWithUnionQuery.h>
+#include <Parsers/ASTCreateQuery.h>
+#include <Parsers/ASTFunction.h>
+#include <Parsers/ASTSelectWithUnionQuery.h>
+#include <Storages/StorageView.h>
+#include <TableFunctions/ITableFunction.h>
+#include <TableFunctions/TableFunctionFactory.h>
+#include <TableFunctions/TableFunctionView.h>
+#include "registerTableFunctions.h"
+
+
+namespace DB
+{
+namespace ErrorCodes
+{
+    extern const int BAD_ARGUMENTS;
+}
+
+StoragePtr TableFunctionView::executeImpl(const ASTPtr & ast_function, const Context & context, const std::string & table_name) const
+{
+    if (const auto * function = ast_function->as<ASTFunction>())
+    {
+        if (function->query)
+        {
+            if (auto * select = function->query->as<ASTSelectWithUnionQuery>())
+            {
+                auto sample = InterpreterSelectWithUnionQuery::getSampleBlock(function->query, context);
+                auto columns = ColumnsDescription(sample.getNamesAndTypesList());
+                ASTCreateQuery create;
+                create.select = select;
+                auto res = StorageView::create(StorageID(getDatabaseName(), table_name), create, columns);
+                res->startup();
+                return res;
+            }
+        }
+    }
+    throw Exception("Table function '" + getName() + "' requires a query argument.", ErrorCodes::BAD_ARGUMENTS);
+}
+
+void registerTableFunctionView(TableFunctionFactory & factory)
+{
+    factory.registerFunction<TableFunctionView>();
+}
+
+}

src/TableFunctions/TableFunctionView.h

@@ -0,0 +1,27 @@
+#pragma once
+
+#include <TableFunctions/ITableFunction.h>
+#include <Core/Types.h>
+
+
+namespace DB
+{
+
+/* view(query)
+ * Turning subquery into a table.
+ * Useful for passing subquery around.
+ */
+class TableFunctionView : public ITableFunction
+{
+public:
+    static constexpr auto name = "view";
+    std::string getName() const override { return name; }
+private:
+    StoragePtr executeImpl(const ASTPtr & ast_function, const Context & context, const std::string & table_name) const override;
+    const char * getStorageTypeName() const override { return "View"; }
+
+    UInt64 evaluateArgument(const Context & context, ASTPtr & argument) const;
+};
+
+
+}

src/TableFunctions/registerTableFunctions.cpp

@@ -30,6 +30,8 @@ void registerTableFunctions()
     registerTableFunctionODBC(factory);
     registerTableFunctionJDBC(factory);
 
+    registerTableFunctionView(factory);
+
 #if USE_MYSQL
     registerTableFunctionMySQL(factory);
 #endif

src/TableFunctions/registerTableFunctions.h

@@ -30,6 +30,8 @@ void registerTableFunctionHDFS(TableFunctionFactory & factory);
 void registerTableFunctionODBC(TableFunctionFactory & factory);
 void registerTableFunctionJDBC(TableFunctionFactory & factory);
 
+void registerTableFunctionView(TableFunctionFactory & factory);
+
 #if USE_MYSQL
 void registerTableFunctionMySQL(TableFunctionFactory & factory);
 #endif

src/TableFunctions/ya.make

@@ -21,6 +21,7 @@ SRCS(
     TableFunctionRemote.cpp
     TableFunctionURL.cpp
     TableFunctionValues.cpp
+    TableFunctionView.cpp
     TableFunctionZeros.cpp
 
 )

tests/queries/0_stateless/01415_table_function_view.reference

@@ -0,0 +1,10 @@
+1
+1
+SELECT `1`
+FROM view(
+    SELECT 1
+)
+SELECT `1`
+FROM remote(\'127.0.0.1\', view(
+    SELECT 1
+))

tests/queries/0_stateless/01415_table_function_view.sql

@@ -0,0 +1,5 @@
+SELECT * FROM view(SELECT 1);
+SELECT * FROM remote('127.0.0.1', view(SELECT 1));
+
+EXPLAIN SYNTAX SELECT * FROM view(SELECT 1);
+EXPLAIN SYNTAX SELECT * FROM remote('127.0.0.1', view(SELECT 1));