@jahed/sparql-engine/dist/operators/expressions/sparql-aggregates.js

SPARQL query engine for servers and web browsers.

// SPDX-License-Identifier: MIT
import { maxBy, meanBy, minBy, sample } from "lodash-es";
import { asJS, createInteger, literalIsNumeric, RDF, termIsLiteral, } from "../../utils/rdf.js";
/**
 * SPARQL Aggregation operations.
 * Each operation takes an arguments a SPARQL variable and a row of bindings, i.e., a list of
 * solutions bindings on which the aggregation must be applied.
 * Each operations is expected to return a term, as with classic SPARQL operations
 * @see https://www.w3.org/TR/sparql11-query/#aggregateAlgebra
 */
export default {
    count: function (variable, rows) {
        let count = 0;
        if (variable.value in rows) {
            count = rows[variable.value].map((v) => v !== null).length;
        }
        return createInteger(count);
    },
    sum: function (variable, rows) {
        let sum = 0;
        if (variable.value in rows) {
            sum = rows[variable.value].reduce((acc, b) => {
                if (termIsLiteral(b) && literalIsNumeric(b)) {
                    return acc + asJS(b.value, b.datatype.value);
                }
                return acc;
            }, 0);
        }
        return createInteger(sum);
    },
    avg: function (variable, rows) {
        let avg = 0;
        if (variable.value in rows) {
            avg = meanBy(rows[variable.value], (term) => {
                if (termIsLiteral(term) && literalIsNumeric(term)) {
                    return asJS(term.value, term.datatype.value);
                }
            });
        }
        return createInteger(avg);
    },
    min: function (variable, rows) {
        return (minBy(rows[variable.value], (v) => {
            if (termIsLiteral(v)) {
                return asJS(v.value, v.datatype.value);
            }
            return v.value;
        }) || createInteger(-1));
    },
    max: function (variable, rows) {
        return (maxBy(rows[variable.value], (v) => {
            if (termIsLiteral(v)) {
                return asJS(v.value, v.datatype.value);
            }
            return v.value;
        }) || createInteger(-1));
    },
    group_concat: function (variable, rows, sep = "") {
        const value = rows[variable.value].map((v) => v.value).join(sep);
        return RDF.literal(value);
    },
    sample: function (variable, rows) {
        return sample(rows[variable.value]);
    },
};
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