mongo/jstests/core/query/exhaust.js

// @tags: [
//   requires_getmore,
//   no_selinux,
//   # Exhaust does not use runCommand which is required by the `simulate_atlas_proxy` override.
//   simulate_atlas_proxy_incompatible,
//   # This test relies on query commands returning specific batch-sized responses.
//   assumes_no_implicit_cursor_exhaustion,
//   # Time series collections (as views) have specific limitations on aggregation stages (e.g. $merge, $out) or cursor options (e.g. noCursorTimeout, singleBatch).
//   exclude_from_timeseries_crud_passthrough,
// ]

const coll = db.exhaustColl;
coll.drop();

const docCount = 4;
for (let i = 0; i < docCount; i++) {
    assert.commandWorked(coll.insert({a: i}));
}

// Check that the query works without exhaust set
assert.eq(coll.find().batchSize(1).itcount(), docCount);

// Now try to run the same query with exhaust
assert.eq(coll.find().batchSize(1).addOption(DBQuery.Option.exhaust).itcount(), docCount);

// 'internalQueryFindCommandBatchSize' can have a different value on a mongod and a mongos.
// TestData.setParameters.internalQueryFindCommandBatchSize' takes on the mongod value,
// while findCommandBatchSizeKnob takes on the value from mongos if we are in a sharded
// environment. We take the min of these to values to find the correct batch size.
const findCommandBatchSizeKnob = assert.commandWorked(
    db.adminCommand({getParameter: 1, internalQueryFindCommandBatchSize: 1}),
)["internalQueryFindCommandBatchSize"];

const findCommandBatchSize = TestData.setParameters.internalQueryFindCommandBatchSize
    ? Math.min(TestData.setParameters.internalQueryFindCommandBatchSize, findCommandBatchSizeKnob)
    : findCommandBatchSizeKnob;

// Test a case where the amount of data requires a response to the initial find operation as
// well as three getMore reply batches.
(function () {
    coll.drop();

    // Include a long string in each document so that the documents are a bit bigger than 16KB.
    const strSize = 16 * 1024;

    // The docs are ~16KB and each getMore response is 16MB. Therefore, a full getMore batch
    // will contain about 1000 documents. By inserting 3000 we ensure that three subsequent
    // getMore replies are required. Roughly speaking, the initial reply will contain
    // 'findCommandBatchSize' documents, the first getMore reply 1000 more, then another 1000,
    // and then the remaining 900.
    const numDocs = findCommandBatchSize + 2899;

    const str = "A".repeat(strSize);

    let bulk = coll.initializeUnorderedBulkOp();
    for (let i = 0; i < numDocs; ++i) {
        bulk.insert({key: str});
    }
    assert.commandWorked(bulk.execute());

    assert.eq(numDocs, coll.find().addOption(DBQuery.Option.exhaust).itcount());

    // Test that exhaust query with a limit is allowed.
    assert.eq(
        numDocs,
        coll
            .find()
            .addOption(DBQuery.Option.exhaust)
            .limit(numDocs + 1)
            .itcount(),
    );
    assert.eq(
        numDocs - 1,
        coll
            .find()
            .addOption(DBQuery.Option.exhaust)
            .limit(numDocs - 1)
            .itcount(),
    );

    // Test that exhaust with batchSize and limit is allowed.
    assert.eq(
        numDocs,
        coll
            .find()
            .addOption(DBQuery.Option.exhaust)
            .limit(numDocs + 1)
            .batchSize(100)
            .itcount(),
    );
    assert.eq(
        numDocs - 1,
        coll
            .find()
            .addOption(DBQuery.Option.exhaust)
            .limit(numDocs - 1)
            .batchSize(100)
            .itcount(),
    );

    // Test that exhaust with negative limit is allowed. A negative limit means "single batch":
    // the server will return just a single batch and then close the cursor, even if the limit
    // has not yet been reached. When the batchSize is not specified explicitly, we use the
    // value from the 'internalQueryFindCommandBatchSize' parameter. This may be specified in
    // the TestData or retrieved through an admin command.
    assert.eq(findCommandBatchSize, coll.find().addOption(DBQuery.Option.exhaust).limit(-numDocs).itcount());

    assert.eq(50, coll.find().addOption(DBQuery.Option.exhaust).limit(-numDocs).batchSize(50).itcount());
    assert.eq(1, coll.find().addOption(DBQuery.Option.exhaust).limit(-1).itcount());
})();

// Ensure that hasNext() on the closed exhausted cursor does not crash the shell.
(function () {
    const cursor = coll.find().addOption(DBQuery.Option.exhaust);
    cursor.hasNext();
    cursor.close();

    // Ensure assertions are thrown when operating on the closed cursor.
    assert.throws(() => cursor.hasNext());
    assert.throws(() => cursor._hasMoreToCome());
    assert.throws(() => cursor.objsLeftInBatch());
    assert.throws(() => cursor.next());
})();