mongo/jstests/change_streams/lookup_pre_image.js

/**
 * Tests the behaviour of the 'fullDocumentBeforeChange' argument to the $changeStream stage.
 *
 * @tags: [
 *   assumes_unsharded_collection,
 *   do_not_wrap_aggregations_in_facets,
 *   uses_multiple_connections,
 * ]
 */
import {assertDropAndRecreateCollection, assertDropCollection} from "jstests/libs/collection_drop_recreate.js";
import {assertChangeStreamEventEq, ChangeStreamTest} from "jstests/libs/query/change_stream_util.js";

const coll = assertDropAndRecreateCollection(db, "change_stream_pre_images");
const cst = new ChangeStreamTest(db);

// Enable pre-image recording on the test collection.
assert.commandWorked(db.runCommand({collMod: coll.getName(), changeStreamPreAndPostImages: {enabled: true}}));

// Open three streams on the collection, one for each "fullDocumentBeforeChange" mode.
const csNoPreImages = cst.startWatchingChanges({
    collection: coll,
    pipeline: [{$changeStream: {"fullDocumentBeforeChange": "off", fullDocument: "updateLookup"}}],
});
const csPreImageWhenAvailableCursor = cst.startWatchingChanges({
    collection: coll,
    pipeline: [{$changeStream: {"fullDocumentBeforeChange": "whenAvailable", fullDocument: "updateLookup"}}],
});
const csPreImageRequiredCursor = cst.startWatchingChanges({
    collection: coll,
    pipeline: [{$changeStream: {fullDocumentBeforeChange: "required", fullDocument: "updateLookup"}}],
});

// Test pre-image lookup for an insertion. No pre-image exists on any cursor.
assert.commandWorked(coll.insert({_id: "x"}));
let latestChange = cst.getOneChange(csNoPreImages);
assert.eq(latestChange.operationType, "insert");
assert(!latestChange.hasOwnProperty("fullDocumentBeforeChange"));
assert.docEq({_id: "x"}, latestChange.fullDocument);
assert.docEq(latestChange, cst.getOneChange(csPreImageWhenAvailableCursor));
assert.docEq(latestChange, cst.getOneChange(csPreImageRequiredCursor));

// Test pre-image lookup for a replacement operation.
assert.commandWorked(coll.update({_id: "x"}, {foo: "bar"}));
latestChange = cst.getOneChange(csNoPreImages);
assert.eq(latestChange.operationType, "replace");
assert(!latestChange.hasOwnProperty("fullDocumentBeforeChange"));
assert.docEq({_id: "x", foo: "bar"}, latestChange.fullDocument);
// Add the expected "fullDocumentBeforeChange" and confirm that both pre-image cursors see it.
latestChange.fullDocumentBeforeChange = {
    _id: "x",
};
assert.docEq(latestChange, cst.getOneChange(csPreImageWhenAvailableCursor));
assert.docEq(latestChange, cst.getOneChange(csPreImageRequiredCursor));

// Test pre-image lookup for an op-style update operation.
assert.commandWorked(coll.update({_id: "x"}, {$set: {foo: "baz"}}));
latestChange = cst.assertNextChangesEqual({
    cursor: csNoPreImages,
    expectedChanges: [
        {
            documentKey: {_id: "x"},
            fullDocument: {_id: "x", foo: "baz"},
            ns: {db: coll.getDB().getName(), coll: coll.getName()},
            operationType: "update",
            updateDescription: {updatedFields: {foo: "baz"}, removedFields: [], truncatedArrays: []},
        },
    ],
})[0];

// Add the expected "fullDocumentBeforeChange" and confirm that both pre-image cursors see it.
latestChange.fullDocumentBeforeChange = {
    _id: "x",
    foo: "bar",
};
assertChangeStreamEventEq(cst.getOneChange(csPreImageWhenAvailableCursor), latestChange);
assertChangeStreamEventEq(cst.getOneChange(csPreImageRequiredCursor), latestChange);

// Test pre-image lookup for a delete operation.
assert.commandWorked(coll.remove({_id: "x"}));
latestChange = cst.getOneChange(csNoPreImages);
assert.eq(latestChange.operationType, "delete");
assert(!latestChange.hasOwnProperty("fullDocument"));
assert(!latestChange.hasOwnProperty("fullDocumentBeforeChange"));
// Add the expected "fullDocumentBeforeChange" and confirm that both pre-image cursors see it.
latestChange.fullDocumentBeforeChange = {
    _id: "x",
    foo: "baz",
};
assert.docEq(latestChange, cst.getOneChange(csPreImageWhenAvailableCursor));
assert.docEq(latestChange, cst.getOneChange(csPreImageRequiredCursor));

// Now disable pre-image generation on the test collection and re-test.
assert.commandWorked(db.runCommand({collMod: coll.getName(), changeStreamPreAndPostImages: {enabled: false}}));

// Test pre-image lookup for an insertion. No pre-image exists on any cursor.
assert.commandWorked(coll.insert({_id: "y"}));
latestChange = cst.getOneChange(csNoPreImages);
assert.eq(latestChange.operationType, "insert");
assert(!latestChange.hasOwnProperty("fullDocumentBeforeChange"));
assert.docEq({_id: "y"}, latestChange.fullDocument);
assert.docEq(latestChange, cst.getOneChange(csPreImageWhenAvailableCursor));
assert.docEq(latestChange, cst.getOneChange(csPreImageRequiredCursor));

// Test pre-image lookup for a replacement operation.
assert.commandWorked(coll.update({_id: "y"}, {foo: "bar"}));
latestChange = cst.getOneChange(csNoPreImages);
assert.eq(latestChange.operationType, "replace");
assert(!latestChange.hasOwnProperty("fullDocumentBeforeChange"));
assert.docEq({_id: "y", foo: "bar"}, latestChange.fullDocument);

// Add the expected "fullDocumentBeforeChange" and confirm that pre-image is not present.
latestChange.fullDocumentBeforeChange = null;

// The "whenAvailable" cursor retrieves a document without the pre-image...
assert.docEq(latestChange, cst.getOneChange(csPreImageWhenAvailableCursor));
// ... but the "required" cursor throws an exception.
assert.throwsWithCode(() => cst.getOneChange(csPreImageRequiredCursor), ErrorCodes.NoMatchingDocument);

// Test pre-image lookup for an op-style update operation.
assert.commandWorked(coll.update({_id: "y"}, {$set: {foo: "baz"}}));

latestChange = cst.assertNextChangesEqual({
    cursor: csNoPreImages,
    expectedChanges: [
        {
            documentKey: {_id: "y"},
            fullDocument: {_id: "y", foo: "baz"},
            ns: {db: coll.getDB().getName(), coll: coll.getName()},
            operationType: "update",
            updateDescription: {updatedFields: {foo: "baz"}, removedFields: [], truncatedArrays: []},
        },
    ],
})[0];

// Add the expected "fullDocumentBeforeChange" and confirm that pre-image is not present.
latestChange.fullDocumentBeforeChange = null;

// The "whenAvailable" cursor returns an event without the pre-image.
assertChangeStreamEventEq(cst.getOneChange(csPreImageWhenAvailableCursor), latestChange);

// Test pre-image lookup for a delete operation.
assert.commandWorked(coll.remove({_id: "y"}));
latestChange = cst.getOneChange(csNoPreImages);
assert.eq(latestChange.operationType, "delete");
assert(!latestChange.hasOwnProperty("fullDocument"));
assert(!latestChange.hasOwnProperty("fullDocumentBeforeChange"));

// Add the expected "fullDocumentBeforeChange" and confirm that pre-image is not present.
latestChange.fullDocumentBeforeChange = null;

// The "whenAvailable" cursor returns an event without the pre-image.
assert.docEq(latestChange, cst.getOneChange(csPreImageWhenAvailableCursor));

assertDropCollection(db, coll.getName());