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@tanstack/db-ivm

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Incremental View Maintenance for TanStack DB based on Differential Dataflow

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{"version":3,"file":"groupBy.cjs","sources":["../../../src/operators/groupBy.ts"],"sourcesContent":["import { map } from \"./map.js\"\nimport { reduce } from \"./reduce.js\"\nimport type { IStreamBuilder, KeyValue } from \"../types.js\"\n\ntype GroupKey = Record<string, unknown>\n\ntype BasicAggregateFunction<T, R, V = unknown> = {\n preMap: (data: T) => V\n reduce: (values: Array<[V, number]>) => V\n postMap?: (result: V) => R\n}\n\ntype PipedAggregateFunction<T, R> = {\n pipe: (stream: IStreamBuilder<T>) => IStreamBuilder<KeyValue<string, R>>\n}\n\ntype AggregateFunction<T, R, V = unknown> =\n | BasicAggregateFunction<T, R, V>\n | PipedAggregateFunction<T, R>\n\ntype ExtractAggregateReturnType<T, A> =\n A extends AggregateFunction<T, infer R, any> ? R : never\n\ntype AggregatesReturnType<T, A> = {\n [K in keyof A]: ExtractAggregateReturnType<T, A[K]>\n}\n\nfunction isPipedAggregateFunction<T, R>(\n aggregate: AggregateFunction<T, R>\n): aggregate is PipedAggregateFunction<T, R> {\n return `pipe` in aggregate\n}\n\n/**\n * Groups data by key and applies multiple aggregate operations\n * @param keyExtractor Function to extract grouping key from data\n * @param aggregates Object mapping aggregate names to aggregate functions\n */\nexport function groupBy<\n T,\n K extends GroupKey,\n A extends Record<string, AggregateFunction<T, any, any>>,\n>(keyExtractor: (data: T) => K, aggregates: A = {} as A) {\n type ResultType = K & AggregatesReturnType<T, A>\n\n const basicAggregates = Object.fromEntries(\n Object.entries(aggregates).filter(\n ([_, aggregate]) => !isPipedAggregateFunction(aggregate)\n )\n ) as Record<string, BasicAggregateFunction<T, any, any>>\n\n // @ts-expect-error - TODO: we don't use this yet, but we will\n // eslint-disable-next-line @typescript-eslint/no-unused-vars\n const pipedAggregates = Object.fromEntries(\n Object.entries(aggregates).filter(([_, aggregate]) =>\n isPipedAggregateFunction(aggregate)\n )\n ) as Record<string, PipedAggregateFunction<T, any>>\n\n return (\n stream: IStreamBuilder<T>\n ): IStreamBuilder<KeyValue<string, ResultType>> => {\n // Special key to store the original key object\n const KEY_SENTINEL = `__original_key__`\n\n // First map to extract keys and pre-aggregate values\n const withKeysAndValues = stream.pipe(\n map((data) => {\n const key = keyExtractor(data)\n const keyString = JSON.stringify(key)\n\n // Create values object with pre-aggregated values\n const values: Record<string, unknown> = {}\n\n // Store the original key object\n values[KEY_SENTINEL] = key\n\n // Add pre-aggregated values\n for (const [name, aggregate] of Object.entries(basicAggregates)) {\n values[name] = aggregate.preMap(data)\n }\n\n return [keyString, values] as KeyValue<string, Record<string, unknown>>\n })\n )\n\n // Then reduce to compute aggregates\n const reduced = withKeysAndValues.pipe(\n reduce((values) => {\n // Calculate total multiplicity to check if the group should exist\n let totalMultiplicity = 0\n for (const [_, multiplicity] of values) {\n totalMultiplicity += multiplicity\n }\n\n // If total multiplicity is 0 or negative, the group should be removed completely\n if (totalMultiplicity <= 0) {\n return []\n }\n\n const result: Record<string, unknown> = {}\n\n // Get the original key from first value in group\n const originalKey = values[0]?.[0]?.[KEY_SENTINEL]\n result[KEY_SENTINEL] = originalKey\n\n // Apply each aggregate function\n for (const [name, aggregate] of Object.entries(basicAggregates)) {\n const preValues = values.map(\n ([v, m]) => [v[name], m] as [any, number]\n )\n result[name] = aggregate.reduce(preValues)\n }\n\n return [[result, 1]]\n })\n )\n\n // Finally map to extract the key and include all values\n return reduced.pipe(\n map(([keyString, values]) => {\n // Extract the original key\n const key = values[KEY_SENTINEL] as K\n\n // Create intermediate result with key values and aggregate results\n const result: Record<string, unknown> = {}\n\n // Add key properties to result\n Object.assign(result, key)\n\n // Apply postMap if provided\n for (const [name, aggregate] of Object.entries(basicAggregates)) {\n if (aggregate.postMap) {\n result[name] = aggregate.postMap(values[name])\n } else {\n result[name] = values[name]\n }\n }\n\n // Return with the string key instead of the object\n return [keyString, result] as KeyValue<string, ResultType>\n })\n )\n }\n}\n\n/**\n * Creates a sum aggregate function\n */\nexport function sum<T>(\n valueExtractor: (value: T) => number = (v) => v as unknown as number\n): AggregateFunction<T, number, number> {\n return {\n preMap: (data: T) => valueExtractor(data),\n reduce: (values: Array<[number, number]>) => {\n let total = 0\n for (const [value, multiplicity] of values) {\n total += value * multiplicity\n }\n return total\n },\n }\n}\n\n/**\n * Creates a count aggregate function\n */\nexport function count<T>(): AggregateFunction<T, number, number> {\n return {\n preMap: () => 1,\n reduce: (values: Array<[number, number]>) => {\n let totalCount = 0\n for (const [_, multiplicity] of values) {\n totalCount += multiplicity\n }\n return totalCount\n },\n }\n}\n\n/**\n * Creates an average aggregate function\n */\nexport function avg<T>(\n valueExtractor: (value: T) => number = (v) => v as unknown as number\n): AggregateFunction<T, number, { sum: number; count: number }> {\n return {\n preMap: (data: T) => ({\n sum: valueExtractor(data),\n count: 0,\n }),\n reduce: (values: Array<[{ sum: number; count: number }, number]>) => {\n let totalSum = 0\n let totalCount = 0\n for (const [value, multiplicity] of values) {\n totalSum += value.sum * multiplicity\n totalCount += multiplicity\n }\n return {\n sum: totalSum,\n count: totalCount,\n }\n },\n postMap: (result: { sum: number; count: number }) => {\n return result.sum / result.count\n },\n }\n}\n\n/**\n * Creates a min aggregate function that computes the minimum value in a group\n * @param valueExtractor Function to extract a numeric value from each data entry\n */\nexport function min<T>(\n valueExtractor: (value: T) => number = (v) => v as unknown as number\n): AggregateFunction<T, number, number> {\n return {\n preMap: (data: T) => valueExtractor(data),\n reduce: (values: Array<[number, number]>) => {\n let minValue = Number.POSITIVE_INFINITY\n for (const [value, _multiplicity] of values) {\n if (value < minValue) {\n minValue = value\n }\n }\n return minValue === Number.POSITIVE_INFINITY ? 0 : minValue\n },\n }\n}\n\n/**\n * Creates a max aggregate function that computes the maximum value in a group\n * @param valueExtractor Function to extract a numeric value from each data entry\n */\nexport function max<T>(\n valueExtractor: (value: T) => number = (v) => v as unknown as number\n): AggregateFunction<T, number, number> {\n return {\n preMap: (data: T) => valueExtractor(data),\n reduce: (values: Array<[number, number]>) => {\n let maxValue = Number.NEGATIVE_INFINITY\n for (const [value, _multiplicity] of values) {\n if (value > maxValue) {\n maxValue = value\n }\n }\n return maxValue === Number.NEGATIVE_INFINITY ? 0 : maxValue\n },\n }\n}\n\n/**\n * Creates a median aggregate function that computes the middle value in a sorted group\n * If there's an even number of values, returns the average of the two middle values\n * @param valueExtractor Function to extract a numeric value from each data entry\n */\nexport function median<T>(\n valueExtractor: (value: T) => number = (v) => v as unknown as number\n): AggregateFunction<T, number, Array<number>> {\n return {\n preMap: (data: T) => [valueExtractor(data)],\n reduce: (values: Array<[Array<number>, number]>) => {\n // Flatten all values, taking multiplicity into account\n const allValues: Array<number> = []\n for (const [valueArray, multiplicity] of values) {\n for (const value of valueArray) {\n // Add each value multiple times based on multiplicity\n for (let i = 0; i < multiplicity; i++) {\n allValues.push(value)\n }\n }\n }\n\n // Return empty array if no values\n if (allValues.length === 0) {\n return []\n }\n\n // Sort values\n allValues.sort((a, b) => a - b)\n\n return allValues\n },\n postMap: (result: Array<number>) => {\n if (result.length === 0) return 0\n\n const mid = Math.floor(result.length / 2)\n\n // If even number of values, average the two middle values\n if (result.length % 2 === 0) {\n return (result[mid - 1]! + result[mid]!) / 2\n }\n\n // If odd number of values, return the middle value\n return result[mid]!\n },\n }\n}\n\n/**\n * Creates a mode aggregate function that computes the most frequent value in a group\n * If multiple values have the same highest frequency, returns the first one encountered\n * @param valueExtractor Function to extract a value from each data entry\n */\nexport function mode<T>(\n valueExtractor: (value: T) => number = (v) => v as unknown as number\n): AggregateFunction<T, number, Map<number, number>> {\n return {\n preMap: (data: T) => {\n const value = valueExtractor(data)\n const frequencyMap = new Map<number, number>()\n frequencyMap.set(value, 1)\n return frequencyMap\n },\n reduce: (values: Array<[Map<number, number>, number]>) => {\n // Combine all frequency maps\n const combinedMap = new Map<number, number>()\n\n for (const [frequencyMap, multiplicity] of values) {\n for (const [value, frequencyCount] of frequencyMap.entries()) {\n const currentCount = combinedMap.get(value) || 0\n combinedMap.set(value, currentCount + frequencyCount * multiplicity)\n }\n }\n\n return combinedMap\n },\n postMap: (result: Map<number, number>) => {\n if (result.size === 0) return 0\n\n let modeValue = 0\n let maxFrequency = 0\n\n for (const [value, frequency] of result.entries()) {\n if (frequency > maxFrequency) {\n maxFrequency 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