jhorstmann opened a new pull request, #5909:
URL: https://github.com/apache/arrow-rs/pull/5909
# Which issue does this PR close?
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An alternative implementation of a custom thrift decoder, this time based on
rust declarative macros instead of a separate code generator.
Fixes #5854, Alternative to #5869
# Rationale for this change
The current thrift definitions are not easy to customize and also leave some
performance on the table. The macro-based approach here allows renaming fields
and replacing types with custom implementations, while still being relatively
easy to update.
The downsides of the macro is that error messages in case of typos are not
that easy to deciper. Once there are more customizations, updates would need to
be done via diff with the official definitions.
Even without customizations like borrowing data, the performance improvement
is significant. On my machine, with `native` target and still the default
allocator:
```
open(default) time: [9.9190 µs 9.9540 µs 9.9881 µs]
change: [-33.053% -32.672% -32.380%] (p = 0.00 <
0.05)
Performance has improved.
open(page index) time: [437.81 µs 439.01 µs 440.28 µs]
change: [-26.632% -26.481% -26.313%] (p = 0.00 <
0.05)
Performance has improved.
```
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# What changes are included in this PR?
Replaces the thrift structures and custom protocol with a macro that wraps
the nearly unmodified `parquet.thrift` definitions.
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# Are there any user-facing changes?
This should mostly be a drop-in replacement, customizations and
optimizations could be done in future PRs, for example borrowing data or
replacing a `Vec<Encoding>` with a small bitset.
One api change is that structs and enum no longer derive the `Eq` trait,
only `PartialEq`.
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