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// Test to guarantee read repeatability, meaning that while in a transaction, we should repeatedly
// read the same data even if it was modified outside of the transaction.
// @tags: [uses_transactions, uses_snapshot_read_concern]
(function() {
"use strict";
const dbName = "test";
const collName = "repeatable_reads_in_transaction";
const testDB = db.getSiblingDB(dbName);
const testColl = testDB[collName];
testDB.runCommand({drop: collName, writeConcern: {w: "majority"}});
assert.commandWorked(testDB.createCollection(collName, {writeConcern: {w: "majority"}}));
const sessionOptions = {
causalConsistency: false
};
const session = db.getMongo().startSession(sessionOptions);
const sessionDb = session.getDatabase(dbName);
const sessionColl = sessionDb.getCollection(collName);
// Initialize second session variables.
const session2 = testDB.getMongo().startSession(sessionOptions);
const session2Db = session2.getDatabase(dbName);
const session2Coll = session2Db.getCollection(collName);
jsTest.log("Prepopulate the collection.");
assert.writeOK(testColl.insert([{_id: 0}, {_id: 1}, {_id: 2}], {writeConcern: {w: "majority"}}));
// Create a constant array of documents we expect to be returned during a read-only transaction.
// The value should not change since external changes should not be visible within this
// transaction.
const expectedDocs = [{_id: 0}, {_id: 1}, {_id: 2}];
jsTestLog("Start a read-only transaction on the first session.");
session.startTransaction({writeConcern: {w: "majority"}});
assert.sameMembers(expectedDocs, sessionColl.find().toArray());
jsTestLog("Start a transaction on the second session that modifies the same collection.");
session2.startTransaction({readConcern: {level: "snapshot"}, writeConcern: {w: "majority"}});
assert.commandWorked(session2Coll.insert({_id: 3}));
assert.commandWorked(session2Coll.update({_id: 1}, {$set: {a: 1}}));
assert.commandWorked(session2Coll.deleteOne({_id: 2}));
jsTestLog(
"Continue reading in the first transaction. Changes from the second transaction should not be visible.");
assert.sameMembers(expectedDocs, sessionColl.find().toArray());
jsTestLog("Committing the second transaction.");
assert.commandWorked(session2.commitTransaction_forTesting());
jsTestLog(
"Committed changes from the second transaction should still not be visible to the first.");
assert.sameMembers(expectedDocs, sessionColl.find().toArray());
jsTestLog(
"Writes that occur outside of a transaction should not be visible to a read only transaction.");
assert.writeOK(testColl.insert({_id: 4}, {writeConcern: {w: "majority"}}));
assert.sameMembers(expectedDocs, sessionColl.find().toArray());
jsTestLog("Committing first transaction.");
assert.commandWorked(session.commitTransaction_forTesting());
// Make sure the correct documents exist after committing the second transaction.
assert.sameMembers([{_id: 0}, {_id: 1, a: 1}, {_id: 3}, {_id: 4}], sessionColl.find().toArray());
session.endSession();
session2.endSession();
}());
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