ac9062644f
When describing a table, we need to do it carefully: if some
columns were dropped, we must specify that explicitly by
```
ALTER TABLE {table} DROP {column} USING TIMESTAMP ...
```
in the result of the DESCRIBE statement. Failing to do so
could lead to data resurrection.
However, if a table has been altered many, many times,
we might end up with a huge create statement. Constructing
it could, in turn, trigger an oversized allocation.
Some tests ran into that very problem in fact.
In this commit, we want to mitigate the problem: instead of
allocating a contiguous chunk of memory for the create
statement, we use `fragmented_ostringstream` and `managed_string`
to possibly keep data scattered in memory. It makes handling
`cql3::description` less convenient in the code, but since
the struct is pretty much immediately serialized after
creating it, it's a very good trade-off.
We provide a reproducer. It consistently passes with this commit,
while having about 50% chance of failure before it (based on my
own experiments). Playing with the parameters of the test
doesn't seem to improve that chance, so let's keep it as-is.
Fixes scylladb/scylladb#24018
112 lines
3.9 KiB
C++
112 lines
3.9 KiB
C++
/*
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* Copyright (C) 2019-present ScyllaDB
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*/
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/*
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* SPDX-License-Identifier: LicenseRef-ScyllaDB-Source-Available-1.0
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*/
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#include "user_function.hh"
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#include "cql3/description.hh"
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#include "cql3/util.hh"
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#include "utils/log.hh"
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#include "lang/wasm.hh"
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#include "utils/managed_string.hh"
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#include <seastar/core/thread.hh>
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#include <ranges>
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namespace cql3 {
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namespace functions {
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extern logging::logger log;
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user_function::user_function(function_name name, std::vector<data_type> arg_types, std::vector<sstring> arg_names,
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sstring body, sstring language, data_type return_type, bool called_on_null_input, context ctx)
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: abstract_function(std::move(name), std::move(arg_types), std::move(return_type)),
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_arg_names(std::move(arg_names)), _body(std::move(body)), _language(std::move(language)),
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_called_on_null_input(called_on_null_input), _ctx(std::move(ctx)) {}
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bool user_function::is_pure() const { return true; }
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bool user_function::is_native() const { return false; }
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bool user_function::is_aggregate() const { return false; }
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bool user_function::requires_thread() const { return true; }
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bytes_opt user_function::execute(std::span<const bytes_opt> parameters) {
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const auto& types = arg_types();
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if (parameters.size() != types.size()) {
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throw std::logic_error("Wrong number of parameters");
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}
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if (!seastar::thread::running_in_thread()) {
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on_internal_error(log, "User function cannot be executed in this context");
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}
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for (auto& param : parameters) {
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if (!param && !_called_on_null_input) {
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return std::nullopt;
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}
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}
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return seastar::visit(_ctx,
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[&] (lua_context& ctx) -> bytes_opt {
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std::vector<data_value> values;
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values.reserve(parameters.size());
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for (int i = 0, n = types.size(); i != n; ++i) {
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const data_type& type = types[i];
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const bytes_opt& bytes = parameters[i];
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values.push_back(bytes ? type->deserialize(*bytes) : data_value::make_null(type));
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}
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return lua::run_script(lua::bitcode_view{ctx.bitcode}, values, return_type(), ctx.cfg).get();
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},
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[&] (wasm::context& ctx) -> bytes_opt {
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try {
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return wasm::run_script(name(), ctx, arg_types(), parameters, return_type(), _called_on_null_input).get();
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} catch (const wasm::exception& e) {
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throw exceptions::invalid_request_exception(format("UDF error: {}", e.what()));
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}
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});
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}
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description user_function::describe(with_create_statement with_stmt) const {
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auto maybe_create_statement = std::invoke([&] -> std::optional<managed_string> {
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if (!with_stmt) {
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return std::nullopt;
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}
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fragmented_ostringstream stream;
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auto arg_type_range = _arg_types | std::views::transform(std::mem_fn(&abstract_type::cql3_type_name_without_frozen));
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auto arg_range = std::views::zip(_arg_names, arg_type_range)
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| std::views::transform([] (std::tuple<std::string_view, std::string_view> arg) {
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const auto [name, type] = arg;
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return seastar::format("{} {}", name, type);
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});
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fmt::format_to(stream.to_iter(), "CREATE FUNCTION {}.{}({})\n"
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"{} ON NULL INPUT\n"
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"RETURNS {}\n"
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"LANGUAGE {}\n"
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"AS $${}$$;",
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cql3::util::maybe_quote(name().keyspace), cql3::util::maybe_quote(name().name), fmt::join(arg_range, ", "),
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_called_on_null_input ? "CALLED" : "RETURNS NULL",
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_return_type->cql3_type_name_without_frozen(),
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_language,
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_body);
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return std::move(stream).to_managed_string();
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});
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return description {
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.keyspace = name().keyspace,
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.type = "function",
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.name = name().name,
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.create_statement = std::move(maybe_create_statement)
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};
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}
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}
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}
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