jstests/noPassthroughWithMongod/captrunc_cursor_invalidation.js


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// Test that when a capped collection is truncated, tailable cursors die on getMore with the error
// code 'CappedPositionLost'.
//
// @tags: [requires_capped]
(function() {
    "use strict";

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

    // Create a capped collection with four documents.
    assert.commandWorked(db.createCollection(coll.getName(), {capped: true, size: 1024}));
    const numDocs = 4;
    const bulk = coll.initializeUnorderedBulkOp();
    for (let i = 0; i < numDocs; ++i) {
        bulk.insert({_id: i});
    }
    assert.commandWorked(bulk.execute());

    // Open a tailable cursor against the capped collection.
    const findRes = assert.commandWorked(db.runCommand({find: coll.getName(), tailable: true}));
    assert.neq(findRes.cursor.id, 0);
    assert.eq(findRes.cursor.ns, coll.getFullName());
    assert.eq(findRes.cursor.firstBatch.length, 4);
    const cursorId = findRes.cursor.id;

    // Truncate the capped collection so that the cursor's position no longer exists.
    assert.commandWorked(db.runCommand({captrunc: coll.getName(), n: 2}));

    // A subsequent getMore should fail with 'CappedPositionLost'.
    assert.commandFailedWithCode(db.runCommand({getMore: cursorId, collection: coll.getName()}),
                                 ErrorCodes.CappedPositionLost);

    // The cursor has now been destroyed, so another getMore should fail with 'CursorNotFound'.
    assert.commandFailedWithCode(db.runCommand({getMore: cursorId, collection: coll.getName()}),
                                 ErrorCodes.CursorNotFound);
}());