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<title>IDBObjectStore.delete() and IDBCursor.continue() - object store - remove a record from the object store while iterating cursor</title>
<link rel="author" title="Mozilla" href="https://www.mozilla.org">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="resources/support.js"></script>
<script>
/* The goal here is to test that any prefetching of cursor values performs
* correct invalidation of prefetched data. This test is motivated by the
* particularities of the Firefox implementation of preloading, and is
* specifically motivated by an edge case when prefetching prefetches at
* least 2 extra records and at most determines whether a mutation is
* potentially relevant based on current cursor position and direction and
* does not test for key equivalence. Future implementations may want to
* help refine this test if their cursors are more clever.
*
* Step-wise we:
* - Open a cursor, returning key 0.
* - When the cursor request completes, without yielding control:
* - Issue a delete() call that won't actually delete anything but looks
* relevant. This should purge prefetched records 1 and 2.
* - Issue a continue() which should result in record 1 being fetched
* again and record 2 being prefetched again.
* - Delete record 2. Unless there's a synchronously available source
* of truth, the data from continue() above will not be present and
* we'll expect the implementation to need to set a flag to invalidate
* the prefetched data when it arrives.
* - When the cursor request completes, validate we got record 1 and issue
* a continue.
* - When the request completes, we should have a null cursor result value
* because 2 was deleted.
*/
var db,
count = 0,
t = async_test(),
records = [ { pKey: "primaryKey_0" },
{ pKey: "primaryKey_1" },
{ pKey: "primaryKey_2" } ];
// This is a key that is not present in the database, but that is known to
// be relevant to a forward iteration of the above keys by comparing to be
// greater than all of them.
var plausibleFutureKey = "primaryKey_9";
var open_rq = createdb(t);
open_rq.onupgradeneeded = function(e) {
db = e.target.result;
var objStore = db.createObjectStore("test", { keyPath: "pKey" });
for (var i = 0; i < records.length; i++)
objStore.add(records[i]);
};
open_rq.onsuccess = t.step_func(CursorDeleteRecord);
function CursorDeleteRecord(e) {
var txn = db.transaction("test", "readwrite", {durability: 'relaxed'}),
object_store = txn.objectStore("test"),
cursor_rq = object_store.openCursor();
var iteration = 0;
cursor_rq.onsuccess = t.step_func(function(e) {
var cursor = e.target.result;
switch (iteration) {
case 0:
object_store.delete(plausibleFutureKey);
assert_true(cursor != null, "cursor valid");
assert_equals(cursor.value.pKey, records[iteration].pKey);
cursor.continue();
object_store.delete(records[2].pKey);
break;
case 1:
assert_true(cursor != null, "cursor valid");
assert_equals(cursor.value.pKey, records[iteration].pKey);
cursor.continue();
break;
case 2:
assert_equals(cursor, null, "cursor no longer valid");
break;
};
iteration++;
});
txn.oncomplete = t.step_func(VerifyRecordWasDeleted);
}
function VerifyRecordWasDeleted(e) {
var cursor_rq = db.transaction("test", "readonly", {durability: 'relaxed'})
.objectStore("test")
.openCursor();
cursor_rq.onsuccess = t.step_func(function(e) {
var cursor = e.target.result;
if (!cursor) {
assert_equals(count, 2, 'count');
t.done();
}
assert_equals(cursor.value.pKey, records[count].pKey);
count++;
cursor.continue();
});
}
</script>
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