median_approx.js

/**
 * Tests that the approximate median accumulator semantics matches the percentile semantics with the
 * field 'p':[0.5].
 * @tags: [
 *   requires_fcv_70,
 * ]
 */
import {
    testWithMultipleGroupsMedian,
    testWithSingleGroupMedian
} from "jstests/aggregation/libs/percentiles_util.js";

const coll = db[jsTestName()];

/**
 * Tests for correctness without grouping. Confirms that $median computes the expected value and
 * also checks that $percentile for p=0.5 computes the same value, because $median is supposed to be
 * completely equivalent to the latter (e.g. we should not optimize $median independently of
 * $percentile).
 */
testWithSingleGroupMedian({
    coll: coll,
    docs: [{x: 0}, {x: "non-numeric"}, {x: 1}, {no_x: 0}, {x: 2}],
    medianSpec: {$median: {input: "$x", method: "approximate"}},
    expectedResult: 1,
    msg: "Non-numeric data should be ignored"
});

testWithSingleGroupMedian({
    coll: coll,
    docs: [{x: "non-numeric"}, {non_x: 1}],
    medianSpec: {$median: {input: "$x", method: "approximate"}},
    expectedResult: null,
    msg: "Median of completely non-numeric data."
});

/**
 * Tests for correctness with grouping on $k and computing the percentile on $x.
 */
testWithMultipleGroupsMedian({
    coll: coll,
    docs: [{k: 0, x: 2}, {k: 0, x: 1}, {k: 1, x: 2}, {k: 2}, {k: 0, x: "str"}, {k: 1, x: 0}],
    medianSpec: {$median: {input: "$x", method: "approximate"}},
    expectedResult: [/* k:0 */ 1, /* k:1 */ 0, /* k:2 */ null],
    msg: "Median of multiple groups"
});