[SPARK-52588][SQL] Approx_top_k: accumulate and estimate #51308
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yhuang-db
changed the title
yhuang-db
changed the title
| defaultCheck | ||
| } else if (!k.foldable) { | ||
| TypeCheckFailure("K must be a constant literal") | ||
| } else { |
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shall we also check the StructType of state?
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Also, let's add test for this.
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| def getSketchStateDataType(itemDataType: DataType): StructType = | ||
| StructType( | ||
| StructField("Sketch", BinaryType, nullable = false) :: |
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Sketch => sketch. let's use camelCase
| * and the maximum number of items tracked by the sketch. | ||
| * | ||
| * @param expr the child expression to accumulate items from | ||
| * @param maxItemsTracked the maximum number of items to track in the sketch |
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Let's also add doc for mutableAggBufferOffset and inputAggBufferOffset
| k = Literal(10), | ||
| maxItemsTracked = Literal(10000) | ||
| ) | ||
| assert(agg.checkInputDataTypes().isFailure) |
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let's also check the failure message
| k = Sum(BoundReference(1, IntegerType, nullable = true)), | ||
| maxItemsTracked = Literal(10) | ||
| ) | ||
| assert(badAgg.checkInputDataTypes().isFailure) |
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let's also check the failure message
| @@ -2931,6 +2904,112 @@ class DataFrameAggregateSuite extends QueryTest | |||
| res, | |||
| Row(LocalTime.of(22, 1, 0), LocalTime.of(3, 0, 0))) | |||
| } | |||
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| test("SPARK-52588: accumulate and estimate of Integer with default parameters") { | |||
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shall we move the new tests related to approx_top_k_* to a new test suite?
| @@ -2931,6 +2904,112 @@ class DataFrameAggregateSuite extends QueryTest | |||
| res, | |||
| Row(LocalTime.of(22, 1, 0), LocalTime.of(3, 0, 0))) | |||
| } | |||
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| test("SPARK-52588: accumulate and estimate of Integer with default parameters") { | |||
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Let's also test inputs with different data types, similar to the approx_top_k function.
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What changes were proposed in this pull request?
This PR adds two SQL functions;
approx_top_k_accumulate, an aggregation function that accumulates input data into a sketch, andapprox_top_k_estimate, an expression function that estimates the top k frequent items from a sketch.1. approx_top_k_accumulate
Syntax
Arguments
expr: An expression of BOOLEAN, BINARY, STRING, DATE, TIMESTAMP or numeric type.maxItemsTracked: An optional INTEGER literal. If maxItemsTracked is not specified, it defaults to 10000. This is the maximum number of distinct values that can be tracked by the sketch.Returns
The return of this function is a STRUCT with three fields: (1) Sketch field, which is the BINARY form of the sketch status; (2) ItemTypeNull field, which is a null value indicating the original type of
expr. And (3) MaxItemsTracked, which is themaxItemsTrackedargument.2. approx_top_k_estimate
Syntax
Arguments
state: An expression for the sketch STRUCT that is generated by approx_top_k_accumulate or approx_top_k_combinek: An optional INTEGER literal greater than 0. If k is not specified, it defaults to 5.Returns
Results are returned as an ARRAY of type STRUCT, where each STRUCT contains an item field for the value (with its original input type) and a count field (of type LONG) with the approximate number of occurrences. The array is sorted by count descending.
Summary of changes:
Tests:
approx_top_k_estimate(approx_top_k_accumulate(expr, maxItemsTracked), k)together.Implementation:
approx_top_k_accumulateapprox_top_k_estimationWhy are the changes needed?
They are useful sibling functions for approx_top_k queries.
Does this PR introduce any user-facing change?
Yes, this PR introduces a new user-facing SQL function. See user examples as below.
How was this patch tested?
Unit tests for end-to-end SQL queries and invalid input for expressions.
Was this patch authored or co-authored using generative AI tooling?
N/A