58 lines
2.4 KiB
C++
58 lines
2.4 KiB
C++
/*
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* Copyright 2015 Cloudius Systems
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*/
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#pragma once
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#include <vector>
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#include "mutation.hh"
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#include "core/future.hh"
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#include "core/future-util.hh"
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#include "core/do_with.hh"
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// A mutation_reader is an object which allows iterating on mutations: invoke
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// the function to get a future for the next mutation, with an unset optional
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// marking the end of iteration. After calling mutation_reader's operator(),
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// caller must keep the object alive until the returned future is fulfilled.
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//
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// The mutations returned have strictly monotonically increasing keys. Two
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// consecutive mutations never have equal keys.
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//
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// TODO: When iterating over mutations, we don't need a schema_ptr for every
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// single one as it is normally the same for all of them. So "mutation" might
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// not be the optimal object to use here.
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using mutation_reader = std::function<future<mutation_opt>()>;
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mutation_reader make_combined_reader(std::vector<mutation_reader>);
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mutation_reader make_reader_returning(mutation);
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mutation_reader make_reader_returning_many(std::initializer_list<mutation>);
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mutation_reader make_empty_reader();
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// Calls the consumer for each element of the reader's stream until end of stream
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// is reached or the consumer requests iteration to stop by returning stop_iteration::yes.
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// The consumer should accept mutation as the argument and return stop_iteration.
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// The returned future<> resolves when consumption ends.
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template <typename Consumer>
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inline
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future<> consume(mutation_reader& reader, Consumer consumer) {
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static_assert(std::is_same<future<stop_iteration>, futurize_t<std::result_of_t<Consumer(mutation&&)>>>::value, "bad Consumer signature");
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using futurator = futurize<std::result_of_t<Consumer(mutation&&)>>;
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return do_with(std::move(consumer), [&reader] (Consumer& c) -> future<> {
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return repeat([&reader, &c] () {
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return reader().then([&c] (mutation_opt&& mo) -> future<stop_iteration> {
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if (!mo) {
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return make_ready_future<stop_iteration>(stop_iteration::yes);
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}
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return futurator::apply(c, std::move(*mo));
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});
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});
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});
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}
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// mutation_source represents source of data in mutation form. The data source
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// can be queried multiple times and in parallel. For each query it returns
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// independent mutation_reader.
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using mutation_source = std::function<mutation_reader(const query::partition_range& range)>;
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