apache / apache/datafusion-sqlparser-rs

[EPIC] Improve sqlparser performance

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Dominant language
Rust
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Description

## What problem are you trying to solve?
Normally, in a SQL processing system, parsing SQL is not a major bottleneck compared to actually processing data. That being said, given how many SQL strings are parsed by this crate, I think there is significant benefit to improving the performance of the SQL parser in this crate.

That being said, I also think it is important to minimize the impact on downstream crates as much as possible.

Recently, we started [introducing locations into the parser](https://github.com/apache/datafusion-sqlparser-rs/pull/1435) (thanks again @Nyrox!), which we found slows things down a bit (see https://github.com/apache/datafusion-sqlparser-rs/pull/1435#issuecomment-2500664144).

Thankfully, I think there is significant room for improvement. As as part of the adding location information, I spent some time profiling and I think there are some obvious ways to improve the performance without impacting downstream crates.

Here is the flamegraph for anyone who is interested (you can download it locally to get zoom / etc):

[fixed-flamegraph](https://github.com/user-attachments/assets/7ceae3a0-dec2-462d-9a00-0b49afd9d2bc)

![fixed-flamegraph](https://github.com/user-attachments/assets/7ceae3a0-dec2-462d-9a00-0b49afd9d2bc)

## What would you like to see?
The idea would be
1. Run the benchmarks (instructions in https://github.com/apache/datafusion-sqlparser-rs/pull/1555)
2. Maybe add additional benchmarks so they are more representative
3. Improve the benchmarks

## Ideas to improve performance:
- The most obvious one is to next_token / peek to not clone each `Token` (which involves copying strings)L: https://github.com/apache/datafusion-sqlparser-rs/issues/1558
- https://github.com/apache/datafusion-sqlparser-rs/issues/1381

Contributor guide

No contributing guide indexed for this repository

Research direction

Start with the benchmark instructions in PR #1555 and run the existing benchmarks, then review the linked flamegraph and the performance ideas in issues #1558 and #1381. Done means adding representative benchmarks where needed and improving parser performance without materially affecting downstream crates.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
databases, performance
Issue type
Refactor
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
25/100

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