Function generateFilterActions

src/Interpreters/InterpreterSelectQuery.cpp:246–322

Assumes `storage` is set and the table filter (row-level security) is not empty.

/// Assumes `storage` is set and the table filter (row-level security) is not empty.
static FilterDAGInfoPtr generateFilterActions(
    const StorageID & table_id,
    const ASTPtr & row_policy_filter_expression,
    const ContextPtr & context,
    const StoragePtr & storage,
    const StorageSnapshotPtr & storage_snapshot,
    const StorageMetadataPtr & metadata_snapshot,
    Names & prerequisite_columns,
    PreparedSetsPtr prepared_sets)
try
{
    auto filter_info = std::make_shared<FilterDAGInfo>();

    const auto & db_name = table_id.getDatabaseName();
    const auto & table_name = table_id.getTableName();

    /// TODO: implement some AST builders for this kind of stuff
    ASTPtr query_ast = make_intrusive<ASTSelectQuery>();
    auto * select_ast = query_ast->as<ASTSelectQuery>();

    select_ast->setExpression(ASTSelectQuery::Expression::SELECT, make_intrusive<ASTExpressionList>());
    auto expr_list = select_ast->select();

    /// The first column is our filter expression.
    /// the row_policy_filter_expression should be cloned, because it may be changed by TreeRewriter.
    /// which make it possible an invalid expression, although it may be valid in whole select.
    expr_list->children.push_back(row_policy_filter_expression->clone());

    /// Keep columns that are required after the filter actions.
    for (const auto & column_str : prerequisite_columns)
    {
        ParserExpression expr_parser;
        /// We should add back quotes around column name as it can contain dots.
        expr_list->children.push_back(parseQuery(
            expr_parser,
            backQuoteIfNeed(column_str),
            0,
            context->getSettingsRef()[Setting::max_parser_depth],
            context->getSettingsRef()[Setting::max_parser_backtracks]));
    }

    select_ast->setExpression(ASTSelectQuery::Expression::TABLES, make_intrusive<ASTTablesInSelectQuery>());
    auto tables = select_ast->tables();
    auto tables_elem = make_intrusive<ASTTablesInSelectQueryElement>();
    auto table_expr = make_intrusive<ASTTableExpression>();
    tables->children.push_back(tables_elem);
    tables_elem->table_expression = table_expr;
    tables_elem->children.push_back(table_expr);
    table_expr->database_and_table_name = make_intrusive<ASTTableIdentifier>(db_name, table_name);
    table_expr->children.push_back(table_expr->database_and_table_name);

    /// Using separate expression analyzer to prevent any possible alias injection
    auto syntax_result = TreeRewriter(context).analyzeSelect(query_ast, TreeRewriterResult({}, storage, storage_snapshot));
    SelectQueryExpressionAnalyzer analyzer(query_ast, syntax_result, context, metadata_snapshot, {}, false, {}, prepared_sets);
    filter_info->actions = std::move(analyzer.simpleSelectActions()->dag);

    filter_info->column_name = expr_list->children.at(0)->getColumnName();
    filter_info->actions.removeUnusedActions(NameSet{filter_info->column_name});