ClickHouse/src/TableFunctions/TableFunctionView.cpp

#include <Interpreters/InterpreterSelectWithUnionQuery.h>
#include <Interpreters/InterpreterSelectQueryAnalyzer.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;
}


const ASTSelectWithUnionQuery & TableFunctionView::getSelectQuery() const
{
    return *create.select;
}

std::vector<size_t> TableFunctionView::skipAnalysisForArguments(const QueryTreeNodePtr &, ContextPtr) const
{
    return {0};
}

void TableFunctionView::parseArguments(const ASTPtr & ast_function, ContextPtr /*context*/)
{
    const auto * function = ast_function->as<ASTFunction>();
    if (function)
    {
        if (auto * select = function->tryGetQueryArgument())
        {
            create.set(create.select, select->clone());
            return;
        }
    }
    throw Exception(ErrorCodes::BAD_ARGUMENTS, "Table function '{}' requires a query argument.", getName());
}

ColumnsDescription TableFunctionView::getActualTableStructure(ContextPtr context, bool /*is_insert_query*/) const
{
    assert(create.select);
    assert(create.children.size() == 1);
    assert(create.children[0]->as<ASTSelectWithUnionQuery>());

    Block sample_block;

    if (context->getSettingsRef().allow_experimental_analyzer)
        sample_block = InterpreterSelectQueryAnalyzer::getSampleBlock(create.children[0], context);
    else
        sample_block = InterpreterSelectWithUnionQuery::getSampleBlock(create.children[0], context);

    return ColumnsDescription(sample_block.getNamesAndTypesList());
}

StoragePtr TableFunctionView::executeImpl(
    const ASTPtr & /*ast_function*/, ContextPtr context, const std::string & table_name, ColumnsDescription /*cached_columns*/, bool is_insert_query) const
{
    auto columns = getActualTableStructure(context, is_insert_query);
    auto res = std::make_shared<StorageView>(StorageID(getDatabaseName(), table_name), create, columns, "");
    res->startup();
    return res;
}

void registerTableFunctionView(TableFunctionFactory & factory)
{
    factory.registerFunction<TableFunctionView>({.documentation = {}, .allow_readonly = true});
}

}