Specialize Median Accumulator #7376
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tustvold
commented
Aug 22, 2023
| "AggregateStream", | ||
| ]) | ||
| .with_memory_limit(20_000) | ||
| .with_memory_limit(2_000) |
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We need to lower this memory limit, as it is significantly more space-efficient now
tustvold
commented
Aug 22, 2023
| async fn group_by_none() { | ||
| TestCase::new() | ||
| .with_query("select median(image) from t") | ||
| .with_query("select median(request_bytes) from t") |
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Changed to request_bytes as median isn't well defined for string types, this would only "work" if there happened to be an odd number of values, or the query errored (as in this case)
❯ create table test(c varchar) as values ('foo'), ('world'), ('hello');
0 rows in set. Query took 0.005 seconds.
❯ select median(c) from test;
+----------------+
| MEDIAN(test.c) |
+----------------+
| hello |
+----------------+
1 row in set. Query took 0.005 seconds.
❯ insert into test values ('bar');
+-------+
| count |
+-------+
| 1 |
+-------+
1 row in set. Query took 0.002 seconds.
❯ select median(c) from test;
Internal error: Operator + is not implemented for types Utf8("foo") and Utf8("hello"). This was likely caused by a bug in DataFusion's code and we would welcome that you file an bug report in our issue tracker
Dandandan
reviewed
Aug 22, 2023
| data_type: DataType, | ||
| arrays: Vec<ArrayRef>, | ||
| all_values: Vec<ScalarValue>, | ||
| all_values: Vec<T::Native>, |
Dandandan
reviewed
Aug 22, 2023
| None | ||
| } else if len % 2 == 0 { | ||
| let (low, high, _) = d.select_nth_unstable_by(len / 2, cmp); | ||
| let (_, low, _) = low.select_nth_unstable_by(low.len() - 1, cmp); |
Dandandan
approved these changes
Aug 23, 2023
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Which issue does this PR close?
Part of #6842
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What changes are included in this PR?
Are these changes tested?
Are there any user-facing changes?