Add support for array_least_frequent UDF#20752
Add support for array_least_frequent UDF#20752NikhilCollooru merged 1 commit intoprestodb:masterfrom
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LGTM (docs), with a very small suggestion for consideration.
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presto-main/src/main/java/com/facebook/presto/operator/scalar/sql/ArraySqlFunctions.java
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Did you try transposing and sorting?
array_sort(TRANSFORM(MAP_ENTRIES(m),(k,v)->(v,k)))
Then you don't need the lambda for the comparison
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Yeah what I'm doing is pretty much same. If we're to remove the lambda then it requires additional transform. This is how its gonna look which is not much different from what we have.
TRANSFORM(SLICE(ARRAY_SORT(TRANSFORM(MAP_ENTRIES(ARRAY_FREQUENCY(REMOVE_NULLS(input))), x -> ROW(x[2], x[1]))), 1, n), x -> x[2])
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yeah it will be good to do a sqlbenchmark to see which is best.
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Ran the banchmark test. Turned out the non lambda version is 0.7 secs faster than compared to the one with lambda.
Here is the result without lambda
Here is the result with lambda
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UDF to return the least frequent eleement of an array
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Subject: Re: [prestodb/presto] Add support for array_least_frequent UDF (PR #20752)
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Description
UDF to return the least frequent element of an array
Motivation and Context
Currently there is no easy way to get least frequent element of an array. This change add that support natively.
Test Plan
./mvnw clean install -Dtest=TestArraySqlFunctions -Dmaven.javadoc.skip=true -T1C -fn -pl presto-main== RELEASE NOTES ==
General Changes
Add function :func:
array_least_frequentSELECT ARRAY_LEAST_FREQUENT(ARRAY[1, 2, 2, 3, 3, 3]); -- 1