diff --git a/src/TableFunctions/TableFunctionNull.cpp b/src/TableFunctions/TableFunctionNull.cpp new file mode 100644 index 00000000000..fe9c2d36d92 --- /dev/null +++ b/src/TableFunctions/TableFunctionNull.cpp @@ -0,0 +1,42 @@ +#include +#include +#include +#include +#include +#include +#include +#include +#include "registerTableFunctions.h" + + +namespace DB +{ +namespace ErrorCodes +{ + extern const int NUMBER_OF_ARGUMENTS_DOESNT_MATCH; +} + +StoragePtr TableFunctionNull::executeImpl(const ASTPtr & ast_function, const Context & context, const std::string & table_name) const +{ + if (const auto * function = ast_function->as()) + { + auto arguments = function->arguments->children; + + if (arguments.size() != 1) + throw Exception("Table function '" + getName() + "' requires 'structure'.", ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH); + + auto structure = arguments[0]->as().value.safeGet(); + ColumnsDescription columns = parseColumnsListFromString(structure, context); + + auto res = StorageNull::create(StorageID(getDatabaseName(), table_name), columns, ConstraintsDescription()); + res->startup(); + return res; + } + throw Exception("Table function '" + getName() + "' requires 'structure'.", ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH); +} + +void registerTableFunctionNull(TableFunctionFactory & factory) +{ + factory.registerFunction(); +} +} diff --git a/src/TableFunctions/TableFunctionNull.h b/src/TableFunctions/TableFunctionNull.h new file mode 100644 index 00000000000..48617352b25 --- /dev/null +++ b/src/TableFunctions/TableFunctionNull.h @@ -0,0 +1,24 @@ +#pragma once + +#include +#include + + +namespace DB +{ + +/* null(structure) - creates a temporary null storage + * + * Used for testing purposes, for convenience writing tests and demos. + */ +class TableFunctionNull : public ITableFunction +{ +public: + static constexpr auto name = "null"; + 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 "Null"; } +}; + +} diff --git a/src/TableFunctions/registerTableFunctions.cpp b/src/TableFunctions/registerTableFunctions.cpp index 25a495a9185..09255c2bd74 100644 --- a/src/TableFunctions/registerTableFunctions.cpp +++ b/src/TableFunctions/registerTableFunctions.cpp @@ -11,6 +11,7 @@ void registerTableFunctions() registerTableFunctionMerge(factory); registerTableFunctionRemote(factory); registerTableFunctionNumbers(factory); + registerTableFunctionNull(factory); registerTableFunctionZeros(factory); registerTableFunctionFile(factory); registerTableFunctionURL(factory); diff --git a/src/TableFunctions/registerTableFunctions.h b/src/TableFunctions/registerTableFunctions.h index 8ff64a22fea..ab05187eeab 100644 --- a/src/TableFunctions/registerTableFunctions.h +++ b/src/TableFunctions/registerTableFunctions.h @@ -11,6 +11,7 @@ class TableFunctionFactory; void registerTableFunctionMerge(TableFunctionFactory & factory); void registerTableFunctionRemote(TableFunctionFactory & factory); void registerTableFunctionNumbers(TableFunctionFactory & factory); +void registerTableFunctionNull(TableFunctionFactory & factory); void registerTableFunctionZeros(TableFunctionFactory & factory); void registerTableFunctionFile(TableFunctionFactory & factory); void registerTableFunctionURL(TableFunctionFactory & factory);