Convert store iterators to variants rather than using polymorphism. #4759
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Test Results for Commit 37f4f5cPull Request 4759: Results Test Case Results
Last updated: 2024-10-27 03:00:50 UTC |
pwojcikdev
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Oct 21, 2024
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…transaction->GetHandle() Returning either Transaction * or ReadOptions * seems dubious, the intent of this commit is to retain 1-to-1 compatibility while adding strong typing.
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I checked on using std::reverse_iterator rather than implementing our own though it looks like it only supports copyable iterators. https://en.cppreference.com/w/cpp/iterator/reverse_iterator/reverse_iterator |
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pwojcikdev
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Oct 26, 2024
| { | ||
| if (dynamic_cast<nano::store::read_transaction const *> (&transaction_a) != nullptr) | ||
| { | ||
| return static_cast<::rocksdb::ReadOptions *> (transaction_a.get_handle ()); |
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Is it possible for the handle to store the pointer as std::any and use type safe cast std::any_cast? Or is that not necessary here
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Yes, I think applying a similar change to transactions would be another good improvement. I'll leave that to another PR though.
| { | ||
| // FIXME Don't convert via lmdb::db_val, this is just a placeholder | ||
| auto const & data = *iter; | ||
| lmdb::db_val key_val{ MDB_val{ data.first.size (), const_cast<void *> (reinterpret_cast<void const *> (data.first.data ())) } }; |
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Well, if it works it works 😆
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This converts the store iterators from version that use polymorphism to using std::variant.
The primary drivers for this change is to simplify and allow more complex iterators to be created where this was previously fairly difficult to do.
The iterators are separated in the 3 parts:
The iterators are bi-directional with a sentinel value to signify end of iteration. The iterators are also circular so after reaching the end-sentinel value, further incrementing will wrap around to the beginning, or decrementing will position the iterator at the last key/value.
Using std::variant also eliminates heap allocations when constructing iterators which can improve performance in some circumstances.