Function explainQueryTree

src/Interpreters/InterpreterExplainQuery.cpp:556–622

}

bool explainQueryTree(
    ASTPtr explained_query,
    ContextPtr query_context,
    const QueryTreeSettings & settings,
    WriteBuffer & buf,
    bool format_ast_as_syntax)
{
    if (explained_query->as<ASTSelectWithUnionQuery>() == nullptr)
        return false;

    auto query_tree = buildQueryTree(explained_query, query_context);
    bool need_newline = false;

    if (!query_context->getSettingsRef()[Setting::format_display_secrets_in_show_and_select])
    {
        TableFunctionSecretsVisitor visitor;
        visitor.visit(query_tree);
    }

    if (settings.run_passes)
    {
        auto query_tree_pass_manager = QueryTreePassManager(query_context);
        addQueryTreePasses(query_tree_pass_manager);

        size_t pass_index = settings.passes < 0 ? query_tree_pass_manager.getPasses().size() : static_cast<size_t>(settings.passes);

        if (settings.dump_passes)
        {
            query_tree_pass_manager.dump(buf, pass_index);
            need_newline = true;
        }

        query_tree_pass_manager.run(query_tree, pass_index);
    }

    if (settings.dump_tree)
    {
        if (need_newline)
            buf << "\n\n";

        query_tree->dumpTree(buf);
        need_newline = true;
    }

    if (settings.dump_ast)
    {
        if (need_newline)
            buf << "\n\n";

        IAST::FormatSettings format_settings(settings.ast_one_line);
        format_settings.show_secrets = query_context->getSettingsRef()[Setting::format_display_secrets_in_show_and_select];

        ConvertToASTOptions ast_options;
        /// `EXPLAIN SYNTAX` shows the query in a canonical, close-to-syntax form, so constants are
        /// rendered as their source expressions and function calls are preferred over operator syntax.
        /// `EXPLAIN QUERY TREE` (dump_ast) must show the query as it actually is after the query tree passes,
        /// so neither source-expression rendering nor operator-to-function conversion is applied there.
        ast_options.use_source_expression_for_constants = format_ast_as_syntax;