The test test_scan.py::test_scan_long_partition_tombstone_string
checks that a full-table Scan operation ends a page in the middle of
a very long string of partition tombstones, and does NOT scan the
entire table in one page (if we did that, getting a single page could
take an unbounded amount of time).
The test is currently flaky, having failed in CI runs three times in
the past two months.
The reason for the flakiness is that we don't know exactly how long
we need to make the sequence of partition tombstones in the test before
we can be absolutely sure a single page will not read this entire sequence.
For single-partition scans we have the "query_tombstone_page_limit"
configuration parameter, which tells us exactly how long we need to
make the sequence of row tombstones. But for a full-table scan of
partition tombstones, the situation is more complicated - because the
scan is done in parallel on several vnodes in parallel and each of
them needs to read query_tombstone_page_limit before it stops.
In my experiments, using query_tombstone_limit * 4 consecutive tombstones
was always enough - I ran this test hundreds of times and it didn't fail
once. But since it did fail on Jenkins very rarely (3 times in the last
two months), maybe the multiplier 4 isn't enough. So this patch doubles
it to 8. Hopefully this would be enough for anyone (TM).
This makes this test even bigger and slower than it was. To make it
faster, I changed this test's write isolation mode from the default
always_use_lwt to forbid_rmw (not use LWT). This leaves the test's
total run time to be similar to what it was before this patch - around
0.5 seconds in dev build mode on my laptop.
Fixes#12817
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Closes#12819
In the past we had issue #7933 where very long strings of consecutive
tombstones caused Alternator's paging to take an unbounded amount of
time and/or memory for a single page. This issue was fixed (by commit
e9cbc9ee85) but the two tests we had
reproducing that issue were left with the "xfail" mark.
They were also marked "veryslow" - each taking about 100 seconds - so
they didn't run by default so nobody noticed they started to pass.
In this patch I make these tests much faster (taking less than a second
together), confirm that they pass - and remove the "xfail" mark and
improve their descriptions.
The trick to making these tests faster is to not create a million
tombstones like we used to: We now know that after string of just 10,000
tombstones ('query_tombstone_page_limit') the page should end, so
we can check specifically this number. The story is more complicated for
partition tombstones, but there too it should be a multiple of
query_tombstone_page_limit. To make the tests even faster, we change
run.py to lower the query_tombstone_page_limit from the default 10,000
to 1000. The tests work correctly even without this change, but they are
ten times faster with it.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Closes#12350
This patch fixes the test test_scan.py::test_scan_paging_missing_limit
which failed in a Jenkins run once (that we know of).
That test verifies that an Alternator Scan operation *without* an explicit
"Limit" is nevertheless paged: DynamoDB (and also Scylla) wanted this page
size to be 1 MB, but it turns out (see #10327) that because of the details
of how Scylla's scan works, the page size can be larger than 1 MB. How much
larger? I ran this test hundreds of times and never saw it exceed a 3 MB
page - so the test asserted the page must be smaller than 4 MB. But now
in one run - we got to this 4 MB and failed the test.
So in this patch we increase the table to be scanned from 4 MB to 6 MB,
and assert the page size isn't the full 6 MB. The chance that this size will
eventually fail as well should be (famous last words...) very small for
two reasons: First because 6 MB is even higher than I the maximum I saw
in practice, and second because empirically I noticed that adding more
data to the table reduces the variance of the page size, so it should
become closer to 1 MB and reduce the chance of it reaching 6 MB.
Refs #10327
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Closes#11280
This reverts commit 8e892426e2 and fixes
the code in a different way:
That commit moved the scylla_inject_error function from
test/alternator/util.py to test/cql-pytest/util.py and renamed
test/alternator/util.py. I found the rename confusing and unnecessary.
Moreover, the moved function isn't even usable today by the test suite
that includes it, cql-pytest, because it lacks the "rest_api" fixture :-)
so test/cql-pytest/util.py wasn't the right place for it anyway.
test/rest_api/rest_util.py could have been a good place for this function,
but there is another complication: Although the Alternator and rest_api
tests both had a "rest_api" fixture, it has a different type, which led
to the code in rest_api which used the moved function to have to jump
through hoops to call it instead of just passing "rest_api".
I think the best solution is to revert the above commit, and duplicate
the short scylla_inject_error() function. The duplication isn't an
exact copy - the test/rest_api/rest_util.py version now accepts the
"rest_api" fixture instead of the URL that the Alternator version used.
In the future we can remove some of this duplication by having some
shared "library" code but we should do it carefully and starting with
agreeing on the basic fixtures like "rest_api" and "cql", without that
it's not useful to share small functions that operate on them.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Closes#11275
Move scylla_inject_error from alternator/ to cql-pytest/ so it
can be reached from various tests dirs. alternator/util.py is
renamed to alternator/alternator_util.py to avoid name shadowing.
This patch implements the previously-unimplemented Select option of the
Query and Scan operators.
The most interesting use case of this option is Select=COUNT which means
we should only count the items, without returning their actual content.
But there are actually four different Select settings: COUNT,
ALL_ATTRIBUTES, SPECIFIC_ATTRIBUTES, and ALL_PROJECTED_ATTRIBUTES.
Five previously-failing tests now pass, and their xfail mark is removed:
* test_query.py::test_query_select
* test_scan.py::test_scan_select
* test_query_filter.py::test_query_filter_and_select_count
* test_filter_expression.py::test_filter_expression_and_select_count
* test_gsi.py::test_gsi_query_select_1
These tests cover many different cases of successes and errors, including
combination of Select and other options. E.g., combining Select=COUNT
with filtering requires us to get the parts of the items needed for the
filtering function - even if we don't need to return them to the user
at the end.
Because we do not yet support GSI/LSI projection (issue #5036), the
support for ALL_PROJECTED_ATTRIBUTES is a bit simpler than it will need
to be in the future, but we can only finish that after #5036 is done.
Fixes#5058.
The most intrusive part of this patch is a change from attrs_to_get -
a map of top-level attributes that a read needs to fetch - to an
optional<attrs_to_get>. This change is needed because we also need
to support the case that we want to read no attributes (Select=COUNT),
and attrs_to_get.empty() used to mean that we want to read *all*
attributes, not no attributes. After this patch, an unset
optional<attrs_to_get> means read *all* attributes, a set but empty
attrs_to_get means read *no* attributes, and a set and non-empty
attrs_to_get means read those specific attributes.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20220405113700.9768-2-nyh@scylladb.com>
We had an old TODO in the Alternator "Scan" operation code which
suggested that we may need to do something to limit the size of pages
when a row limit ("Limit") isn't given.
But we do already have a built-in limit on page sizes (1 MB),
so this TODO isn't needed and can be removed.
But I also wanted to make sure we have a test that this limit works:
We already had a test that this 1 MB limit works for a single-partition
Query (test_query.py::test_query_reverse_longish - tested both forward
and reversed queries). In this patch I add a similar test for a whole-
table Scan. It turns out that although page size is limited in this case
as well, it's not exactly 1 MB... For small tables can even reach 3 MB.
I consider this "good enough" and that we can drop the TODO, but also
opened issue #10327 to document this surprising (for me) finding.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20220404145240.354198-1-nyh@scylladb.com>
This patch adds two xfailing tests for issue #7933. That issue is about
what Scan or Query paging does when encountering a very long string of
consecutive tombstones (partition or row tombstones). Ideally, in that
case the scan could stop on one of these tombstones after already
processing too many. But as these two tests demonstrate, the scan can't
stop in the middle of a long string of tombstones - and as a result
retrieving a single page can take an unbounded amount of time, which is
wrong.
Currently the tests are marked `@veryslow` (they each take more than a
minute) because they each create a huge number of tombstones to
demonstrate a huge amount of work for a single page. When we fix
issue #7933 and have a much smaller limit on the number of tombstones
processed in a single page, we can hopefully make these tests much
shorter and remove the `@veryslow` tag. The `@veryslow` tags means
that although these tests can be used manually (with `--runveryslow`)
they will not yet be run as part of the usual regression tests.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20220403070706.250147-1-nyh@scylladb.com>
Instead of lengthy blurbs, switch to single-line, machine-readable
standardized (https://spdx.dev) license identifiers. The Linux kernel
switched long ago, so there is strong precedent.
Three cases are handled: AGPL-only, Apache-only, and dual licensed.
For the latter case, I chose (AGPL-3.0-or-later and Apache-2.0),
reasoning that our changes are extensive enough to apply our license.
The changes we applied mechanically with a script, except to
licenses/README.md.
Closes#9937
Add to the existing tests for the Select parameter of the Query and Scan
operations another check: That when Select is ALL_ATTRIBUTES or COUNT,
specifying AttributesToGet or ProjectionExpression is forbidden -
because the combination doesn't make sense.
The expanded test continues to xfail on Alternator (because the Select
parameter isn't yet implemented), and passes on DynamoDB. Strengthening
the tests for this feature will be helpful when we decide to implement it.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20211125074128.741677-1-nyh@scylladb.com>
...when using Segment/TotalSegment option.
The requirement is not specified in DynamoDB documents, but found
in DynamoDB Local:
{"__type":"com.amazon.coral.validate#ValidationException",
"message":"Exclusive start key must lie within the segment"}
Fixes#9272
Signed-off-by: Liu Lan <liulan_yewu@cmss.chinamobile.com>
Closes#9270
When an Alternator table has partition keys or sort keys of type "bytes"
(blobs), a Scan or Query which required paging used to fail - we used
an incorrect function to output LastEvaluatedKey (which tells the user
where to continue at the next page), and this incorrect function was
correct for strings and numbers - but NOT for bytes (for bytes, we
need to encode them as base-64).
This patch also includes two tests - for bytes partition key and
for bytes sort key - that failed before this patch and now pass.
The test test_fetch_from_system_tables also used to fail after a
Limit was added to it, because one of the tables it scans had a bytes
key. That test is also fixed by this patch.
Fixes#7768
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20201207175957.2585456-1-nyh@scylladb.com>
All tests that write some data and then read it back need to use
ConsistentRead=True, otherwise the test may sporadically fail on a multi-
node cluster.
In the previous patch we fixed the full_query()/full_scan() convenience
functions. In this patch, I audited the calls to the boto3 read methods -
get_item(), batch_get_item(), query(), scan(), and although most of them
did use ConsistentRead=True as needed, I found some missing and this patch
fixes them.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20200616080334.825893-1-nyh@scylladb.com>
This patch provides a complete implementation for the FilterExpression
parameter - the newer syntax for filtering the results of the Query or
Scan operations.
The implementation is pretty straightforward - we already added earlier
a result-filtering framework to Alternator, and used it for the older
filtering syntax - QuryFilter and ScanFilter. All we had to do now was
to run the FilterExpression (which has the same syntax as a
ConditionExpression) on each individual items. The previous cleanup
patches were important to reduce the friction of running these expressions
on the items.
After the previous patches fixing small esoteric bugs in a few expression
functions, with this patch *all* the tests in test_filter_expression.py
now pass, and so do the two FilterExpression tests in test_query.py and
test_scan.py. As far as I know (and of course minus any bugs we'll discover
later), this marks the FilterExpression feature complete.
Fixes#5038.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Parallel scans can be performed by providing Segment and TotalSegments
attributes to Scan request, which can be used to split the work among
many workers.
This test makes the parallel scan test succeed, so the xfail is removed.
Fixes#5059
To make the tests in alternator-test runnable by test.py, we need to
move the directory alternator-test/ to test/alternator, because test.py
only looks for tests in subdirectories of test/. Then, we need to create
a test/alternator/suite.yaml saying that this test directory is of type
"Run", i.e., it has a single run script "run" which runs all its tests.
The "run" script had to be slightly modified to be aware of its new
location relative to the source directory.
To run the Alternator tests from test.py, do:
./test.py --mode dev alternator
Note that in this version, the "--mode" has no effect - test/alternator/run
always runs the latest compiled Scylla, regardless of the chosen mode.
The Alternator tests can still be run manually and individually against
a running Scylla or DynamoDB as before - just go to the test/alternator
directory (instead of alternator-test previously) and run "pytest" with
the desired parameters.
Fixes#6046
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
