try to remove redundant alias in expression rewriter and select

[buraksenn]

Which issue does this PR close?

Not closes

Rationale for this change

In #20780 (comment) @alamb mentioned whether we can remove redundant alias of count(*) AS count(*) to count(*) and I tried to give this a go.

I'm not sure about the implications at the moment it would be great to have input on this PR

What changes are included in this PR?

Main changes are in:

• order_by.rs: match only top level expressions instead of recursively searching sub expressions (otherwise we may match wrong expressions)
• select.rs: strip alias before comparing otherwise we dont use existing alias at all

Are these changes tested?

I've added some tests for alias. Existing tests and plan outputs changed as well you can see in the PR.

Are there any user-facing changes?

Plans will change but not sure if it has impact

[buraksenn]

run benchmarks

[alamb-ghbot]

🤖 Hi @buraksenn, thanks for the request (#20867 (comment)). scrape_comments.py only responds to whitelisted users. Allowed users: Dandandan, Jefffrey, Omega359, adriangb, alamb, comphead, etseidl, gabotechs, geoffreyclaude, klion26, rluvaton, xudong963, zhuqi-lucas.

[buraksenn]

I think clickbench plan changes are ok but tried to run benchmark to make sure regressions

[alamb]

run benchmarks

[alamb-ghbot]

🤖 ./gh_compare_branch.sh gh_compare_branch.sh Running
Linux aal-dev 6.14.0-1018-gcp #19~24.04.1-Ubuntu SMP Wed Sep 24 23:23:09 UTC 2025 x86_64 x86_64 x86_64 GNU/Linux
Comparing try-to-remove-redundant-alias (66ad5c2) to da05287 diff using: tpch_mem clickbench_partitioned clickbench_extended
Results will be posted here when complete

[alamb-ghbot]

🤖: Benchmark completed

Details

Comparing HEAD and try-to-remove-redundant-alias
--------------------
Benchmark clickbench_extended.json
--------------------
┏━━━━━━━━━━┳━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┳━━━━━━━━━━━┓
┃ Query    ┃        HEAD ┃ try-to-remove-redundant-alias ┃    Change ┃
┡━━━━━━━━━━╇━━━━━━━━━━━━━╇━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━╇━━━━━━━━━━━┩
│ QQuery 0 │  2179.24 ms │                    2140.75 ms │ no change │
│ QQuery 1 │   846.97 ms │                     871.77 ms │ no change │
│ QQuery 2 │  1679.04 ms │                    1669.15 ms │ no change │
│ QQuery 3 │  1020.87 ms │                    1011.77 ms │ no change │
│ QQuery 4 │  2119.86 ms │                    2097.23 ms │ no change │
│ QQuery 5 │ 26363.21 ms │                   25969.03 ms │ no change │
│ QQuery 6 │  3441.45 ms │                    3457.07 ms │ no change │
│ QQuery 7 │  2420.65 ms │                    2451.58 ms │ no change │
└──────────┴─────────────┴───────────────────────────────┴───────────┘
┏━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┳━━━━━━━━━━━━┓
┃ Benchmark Summary                            ┃            ┃
┡━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━╇━━━━━━━━━━━━┩
│ Total Time (HEAD)                            │ 40071.29ms │
│ Total Time (try-to-remove-redundant-alias)   │ 39668.35ms │
│ Average Time (HEAD)                          │  5008.91ms │
│ Average Time (try-to-remove-redundant-alias) │  4958.54ms │
│ Queries Faster                               │          0 │
│ Queries Slower                               │          0 │
│ Queries with No Change                       │          8 │
│ Queries with Failure                         │          0 │
└──────────────────────────────────────────────┴────────────┘
--------------------
Benchmark clickbench_partitioned.json
--------------------
┏━━━━━━━━━━━┳━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━┓
┃ Query     ┃        HEAD ┃ try-to-remove-redundant-alias ┃        Change ┃
┡━━━━━━━━━━━╇━━━━━━━━━━━━━╇━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━╇━━━━━━━━━━━━━━━┩
│ QQuery 0  │     2.56 ms │                       2.57 ms │     no change │
│ QQuery 1  │    47.98 ms │                      47.58 ms │     no change │
│ QQuery 2  │   150.55 ms │                     148.94 ms │     no change │
│ QQuery 3  │   156.51 ms │                     158.98 ms │     no change │
│ QQuery 4  │   946.44 ms │                     973.82 ms │     no change │
│ QQuery 5  │  1159.11 ms │                    1197.97 ms │     no change │
│ QQuery 6  │     6.43 ms │                       6.35 ms │     no change │
│ QQuery 7  │    52.32 ms │                      52.68 ms │     no change │
│ QQuery 8  │  1329.11 ms │                    1346.30 ms │     no change │
│ QQuery 9  │  1730.86 ms │                    1721.32 ms │     no change │
│ QQuery 10 │   318.36 ms │                     326.18 ms │     no change │
│ QQuery 11 │   363.51 ms │                     370.73 ms │     no change │
│ QQuery 12 │  1104.11 ms │                    1134.70 ms │     no change │
│ QQuery 13 │  1807.41 ms │                    1767.04 ms │     no change │
│ QQuery 14 │  1113.93 ms │                    1133.79 ms │     no change │
│ QQuery 15 │  1098.39 ms │                    1133.95 ms │     no change │
│ QQuery 16 │  2273.85 ms │                    2329.89 ms │     no change │
│ QQuery 17 │  2280.48 ms │                    2338.03 ms │     no change │
│ QQuery 18 │  4590.51 ms │                    4421.44 ms │     no change │
│ QQuery 19 │   119.18 ms │                     121.07 ms │     no change │
│ QQuery 20 │  1688.04 ms │                    1701.67 ms │     no change │
│ QQuery 21 │  1972.20 ms │                    1952.55 ms │     no change │
│ QQuery 22 │  3352.14 ms │                    3347.70 ms │     no change │
│ QQuery 23 │ 11524.76 ms │                   10838.23 ms │ +1.06x faster │
│ QQuery 24 │   183.11 ms │                     186.97 ms │     no change │
│ QQuery 25 │   409.10 ms │                     404.15 ms │     no change │
│ QQuery 26 │   181.48 ms │                     187.80 ms │     no change │
│ QQuery 27 │  2513.69 ms │                    2541.51 ms │     no change │
│ QQuery 28 │ 24147.62 ms │                   24056.03 ms │     no change │
│ QQuery 29 │   995.60 ms │                     977.38 ms │     no change │
│ QQuery 30 │  1169.44 ms │                    1156.68 ms │     no change │
│ QQuery 31 │  1223.32 ms │                    1245.04 ms │     no change │
│ QQuery 32 │  4327.14 ms │                    4561.65 ms │  1.05x slower │
│ QQuery 33 │  5283.15 ms │                    5121.73 ms │     no change │
│ QQuery 34 │  5877.27 ms │                    5497.92 ms │ +1.07x faster │
│ QQuery 35 │  1092.49 ms │                    1087.38 ms │     no change │
│ QQuery 36 │   180.21 ms │                     179.45 ms │     no change │
│ QQuery 37 │    71.11 ms │                      68.65 ms │     no change │
│ QQuery 38 │   105.98 ms │                     107.02 ms │     no change │
│ QQuery 39 │   327.60 ms │                     318.78 ms │     no change │
│ QQuery 40 │    39.53 ms │                      36.94 ms │ +1.07x faster │
│ QQuery 41 │    33.18 ms │                      33.33 ms │     no change │
│ QQuery 42 │    28.78 ms │                      30.20 ms │     no change │
└───────────┴─────────────┴───────────────────────────────┴───────────────┘
┏━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┳━━━━━━━━━━━━┓
┃ Benchmark Summary                            ┃            ┃
┡━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━╇━━━━━━━━━━━━┩
│ Total Time (HEAD)                            │ 87378.51ms │
│ Total Time (try-to-remove-redundant-alias)   │ 86372.10ms │
│ Average Time (HEAD)                          │  2032.06ms │
│ Average Time (try-to-remove-redundant-alias) │  2008.65ms │
│ Queries Faster                               │          3 │
│ Queries Slower                               │          1 │
│ Queries with No Change                       │         39 │
│ Queries with Failure                         │          0 │
└──────────────────────────────────────────────┴────────────┘
--------------------
Benchmark tpch_mem_sf1.json
--------------------
┏━━━━━━━━━━━┳━━━━━━━━━━━┳━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┳━━━━━━━━━━━┓
┃ Query     ┃      HEAD ┃ try-to-remove-redundant-alias ┃    Change ┃
┡━━━━━━━━━━━╇━━━━━━━━━━━╇━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━╇━━━━━━━━━━━┩
│ QQuery 1  │ 103.99 ms │                     103.51 ms │ no change │
│ QQuery 2  │  30.83 ms │                      30.11 ms │ no change │
│ QQuery 3  │  34.51 ms │                      35.31 ms │ no change │
│ QQuery 4  │  29.14 ms │                      29.51 ms │ no change │
│ QQuery 5  │  79.12 ms │                      78.53 ms │ no change │
│ QQuery 6  │  20.29 ms │                      20.23 ms │ no change │
│ QQuery 7  │ 144.43 ms │                     141.25 ms │ no change │
│ QQuery 8  │  38.09 ms │                      36.52 ms │ no change │
│ QQuery 9  │  92.29 ms │                      95.35 ms │ no change │
│ QQuery 10 │  62.05 ms │                      62.92 ms │ no change │
│ QQuery 11 │  18.05 ms │                      18.50 ms │ no change │
│ QQuery 12 │  54.52 ms │                      54.46 ms │ no change │
│ QQuery 13 │  45.10 ms │                      46.90 ms │ no change │
│ QQuery 14 │  14.11 ms │                      13.96 ms │ no change │
│ QQuery 15 │  29.06 ms │                      28.87 ms │ no change │
│ QQuery 16 │  26.89 ms │                      26.61 ms │ no change │
│ QQuery 17 │ 136.81 ms │                     139.67 ms │ no change │
│ QQuery 18 │ 262.74 ms │                     263.52 ms │ no change │
│ QQuery 19 │  43.04 ms │                      43.14 ms │ no change │
│ QQuery 20 │  53.96 ms │                      53.91 ms │ no change │
│ QQuery 21 │ 185.83 ms │                     185.09 ms │ no change │
│ QQuery 22 │  21.75 ms │                      21.89 ms │ no change │
└───────────┴───────────┴───────────────────────────────┴───────────┘
┏━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┳━━━━━━━━━━━┓
┃ Benchmark Summary                            ┃           ┃
┡━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━╇━━━━━━━━━━━┩
│ Total Time (HEAD)                            │ 1526.58ms │
│ Total Time (try-to-remove-redundant-alias)   │ 1529.75ms │
│ Average Time (HEAD)                          │   69.39ms │
│ Average Time (try-to-remove-redundant-alias) │   69.53ms │
│ Queries Faster                               │         0 │
│ Queries Slower                               │         0 │
│ Queries with No Change                       │        22 │
│ Queries with Failure                         │         0 │
└──────────────────────────────────────────────┴───────────┘

[buraksenn]

There is no notable change then can we say this only removes redundant alias and has no bad side effects?

[alamb]

There is no notable change then can we say this only removes redundant alias and has no bad side effects?

Yes that is my conclusion as well

[alamb]

Looks good to me -- thank you @buraksenn