Method createStreamForQuery

src/Dictionaries/ClickHouseDictionarySource.cpp:165–202

}

BlockIO ClickHouseDictionarySource::createStreamForQuery(const String & query)
{
    BlockIO io;

    /// Sample block should not contain first row default values
    auto empty_sample_block = std::make_shared<const Block>(sample_block.cloneEmpty());

    /// Copy context because results of scalar subqueries potentially could be cached
    auto context_copy = Context::createCopy(context);
    context_copy->makeQueryContext();

    const char * query_begin = query.data();
    const char * query_end = query.data() + query.size();
    ParserQuery parser(query_end);
    ASTPtr ast = parseQuery(parser, query_begin, query_end, "Query for ClickHouse dictionary", 0, DBMS_DEFAULT_MAX_PARSER_DEPTH, DBMS_DEFAULT_MAX_PARSER_BACKTRACKS);

    if (!ast || ast->getQueryKind() != IAST::QueryKind::Select)
        throw Exception(ErrorCodes::INCORRECT_QUERY, "Only SELECT query can be used as a dictionary source");

    if (configuration.is_local)
    {
        context_copy->setCurrentQueryId({});

        if (!CurrentThread::getGroup())
            io.query_scope = QueryScope::create(context_copy);

        io = executeQuery(query, context_copy, QueryFlags{ .internal = true }).second;

        io.pipeline.convertStructureTo(empty_sample_block->getColumnsWithTypeAndName(), context_copy);
    }
    else
    {
        io.pipeline = QueryPipeline(std::make_shared<RemoteSource>(
            std::make_shared<RemoteQueryExecutor>(pool, query, empty_sample_block, std::move(context_copy)), false, false, false));
    }

    return io;
}

std::string ClickHouseDictionarySource::doInvalidateQuery(const std::string & request) const
{