branch-4.1: [improvement](be) Optimize count on nullable column #64166#64202
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Count aggregation without GROUP BY reaches
AggFnEvaluator::execute_single_add(), which calls
add_batch_single_place(). AggregateFunctionCount and
AggregateFunctionCountNotNullUnary previously inherited the row-by-row
helper there, so count(*) and count(nullable_expr) paid per-row
add/is_null_at costs even when all rows were aggregated into one state.
This patch adds batch implementations: count(*) increments the state
once by batch_size, while unary count(nullable_expr) checks the nullable
null map once and fast-paths the no-NULL case to count += batch_size.
When NULLs exist it uses simd::count_zero_num() over the null map to
count non-NULL rows. The nullable class name is kept because SQL
count(expr) counts non-NULL values, not NULL values.
Performance:
test with sql
```sql
select count(nullable(number)) from numbers("number"="1000000000");
select count(nullable(if(number >= 0, null, number))) from numbers("number"="1000000000");
select count(nullable(if(number % 2 = 0, number, null))) from numbers("number"="1000000000");
```
get result
```
Scenario before median / mean after median / mean median diff
━━━━━━━━━━━ ━━━━━━━━━━━━━━━━━━━━━━ ━━━━━━━━━━━━━━━━━━━━━ ━━━━━━━━━━━━━
non NULL 645 / 648.6 ms 555 / 556.4 ms -14.0%
─────────── ────────────────────── ───────────────────── ─────────────
all NULL 1541 / 1539.6 ms 1448 / 1450.6 ms -6.0%
─────────── ────────────────────── ───────────────────── ─────────────
half NULL 4256 / 4261.2 ms 4192 / 4232.2 ms -1.5%
```
Contributor
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Thank you for your contribution to Apache Doris. Please clearly describe your PR:
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Contributor
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run buildall |
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Cherry-picked from #64166