Unfortunately the datetime picker does not support seconds. But it is
one of the few that support date and time and are flexible enough to
be used with VueJS.
Ingestion speed dropped drastically with the old implementation.
In some situations to 7 entries per second over a 10 second period
(sic!). When using the already opened RandomAccessFile the speed
is back to previous values of 40k-50k entries per second on my 10 year
old machine on an encrypted spinning disk.
The old implementation opened a new buffered reader everytime
getPathByOffset was called. This took 1/20th of a second or
longer. For queries that visited thousands of files this could
take a long time.
We are now using a RandomAccessFile, that is opened once. The
average time spend in getPathByOffset is now down to 0.11ms.
The path in Doc is not optional. This reduces memory consumption,
because we only have to store a long (the offset in the listing file).
This assumes, that only a small percentage of Docs is requested.
Sometimes it is useful to specify the certain y-axis range. For example
when you are only interested in the values that take longer than a
threshold. Or when you want to exclude some outliers. When you want to
compare plots in a gallery, it is very handy when all plots have the
same data-area.
Counting the available values is quite expensive and there are only a
few corner cases where this makes sense. One of them is when the query
is for a method that is not project specific and therefore no project
values can be found.
Now we can find writer much faster, because we don't have to execute
a query for documents that match the tags. We can just look up the
documents in the map.
Speedup: 2-4ms -> 0.002-0.01ms
I checked if computing the proposals with a parallel stream would be
beneficial. Turns out the stream uses several threads, but the overall
computation is not faster, because each individual computation is
slower.
The IntLists were no longer sorted since we made the initialization run
in parallel. Therefore a much slower implementation for
intersection/union was used.
When we parallelized the initialization we forgot to
synchronize the docIdToDoc list.
Luckily there is a high probability, that queries return
results, that are obviously wrong.
This reduces memory usage by 1 or 2 MB.
33% of an ArrayList can be free. If the list is 1 million entries long,
then the list wastes 2.6 MB.
The Doc objects in the list are much bigger.
This reduces the size of the old generation by 100MB (300MB down to
200MB). Unfortunately the total JVM size didn't change and is still
512MB.
Doc stores the path as byte array instead of Path.
We are using ANTLR listeners to find out where in the
query the cursor is. Then we generate a list of keys/values
that might fit at that position. With that information we
can generate new queries and sort them by the number
of results they yield.
This is done in preparation for the proposal API.
In order to compute proposals we need to consume the
API of the DataStore, but the code does not need to
be in the DataStore.
Extracting the API allows us to separate these concerns.
LuDB has a few disadvantages.
1. Most notably disk space. H2 wastes a lot of valuable disk space.
For my test data set with 44 million entries it is 14 MB
(sometimes a lot more; depends on H2 internal cleanup). With
data-store it is 15 KB.
Overall I could reduce the disk space from 231 MB to 200 MB (13.4 %
in this example). That is an average of 4.6 bytes per entry.
2. Speed:
a) Liquibase is slow. The first time it takes approx. three seconds
b) Query and insertion. with data-store we can insert entries
up to 1.6 times faster.
Data-store uses a few tricks to save disk space:
1. We encode the tags into the file names.
2. To keep them short we translate the key/value of the tag into
shorter numbers. For example "foo" -> 12 and "bar" to 47. So the
tag "foo"/"bar" would be 12/47.
We then translate this number into a numeral system of base 62
(a-zA-Z0-9), so it can be used for file names and it is shorter.
That way we only have to store the mapping of string to int.
3. We do that in a simple tab separated file.
