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Vectorized aggregation with grouping by one fixed-size column #7341

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@akuzm akuzm commented Oct 14, 2024

The implementation uses the Postgres simplehash hash table for by-value fixed-size compressed columns.

The biggest improvement on a "sensible" query is about 90%, and a couple of queries show bigger improvements but these are very synthetic cases that don't make much sense:
https://grafana.ops.savannah-dev.timescale.com/d/fasYic_4z/compare-akuzm?orgId=1&var-branch=All&var-run1=3815&var-run2=3816&var-threshold=0.02&var-use_historical_thresholds=true&var-threshold_expression=2%20%2A%20percentile_cont%280.90%29&var-exact_suite_version=false&from=now-2d&to=now

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codecov bot commented Oct 14, 2024

Codecov Report

Attention: Patch coverage is 92.30769% with 28 lines in your changes missing coverage. Please review.

Project coverage is 82.27%. Comparing base (59f50f2) to head (10e66ad).
Report is 660 commits behind head on main.

Files with missing lines Patch % Lines
tsl/src/nodes/vector_agg/grouping_policy_hash.c 91.13% 3 Missing and 11 partials ⚠️
tsl/src/nodes/vector_agg/plan.c 80.00% 4 Missing and 5 partials ⚠️
...nodes/vector_agg/function/agg_many_vector_helper.c 95.00% 0 Missing and 1 partial ⚠️
...rc/nodes/vector_agg/hashing/batch_hashing_params.h 85.71% 0 Missing and 1 partial ⚠️
...rc/nodes/vector_agg/hashing/hash_strategy_common.c 94.44% 0 Missing and 1 partial ⚠️
.../src/nodes/vector_agg/hashing/hash_strategy_impl.c 98.18% 0 Missing and 1 partial ⚠️
..._agg/hashing/hash_strategy_impl_single_fixed_key.c 95.65% 1 Missing ⚠️
Additional details and impacted files
@@            Coverage Diff             @@
##             main    #7341      +/-   ##
==========================================
+ Coverage   80.06%   82.27%   +2.21%     
==========================================
  Files         190      237      +47     
  Lines       37181    43668    +6487     
  Branches     9450    10957    +1507     
==========================================
+ Hits        29770    35930    +6160     
- Misses       2997     3403     +406     
+ Partials     4414     4335      -79     

☔ View full report in Codecov by Sentry.
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}
}

/*
* Currently the only grouping policy we use is per-batch grouping.
* Determine which grouping policy we are going to use.
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Out of curiosity: Why is the grouping policy decided at execution time and not plan time? Should it not affect the plan and cost calc?

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I moved it all to plan time, although as we discussed today on call, it doesn't affect the costs yet.

tsl/src/nodes/vector_agg/grouping_policy_hash.c Outdated Show resolved Hide resolved
tsl/src/nodes/vector_agg/grouping_policy_hash.h Outdated Show resolved Hide resolved
tsl/src/nodes/vector_agg/grouping_policy_hash.h Outdated Show resolved Hide resolved
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3 participants