Queries like "firstname=John and lastname=???" were slightly
inefficient.
They fetched all firstnames, filtered to those that matched the prefix
(e.g. John or Jonathan is this example) and then iterated over all those
values and return the lastnames.
Fixed by having two implementations. One for the case that only a few
of the values in fieldA match and one for the case that many match.
When using autocomplete to return field values I
missed, that autocomplete had the feature that cut
values at dots. So instead of returning full field
values only the prefix up to the first dot was
returned.
Fixed by making the cut-at-dot feature optional.
We had a method that returned the values of a field
with respect to a query. That method was inefficient,
because it executed the query, fetched all Docs
and collected the values.
The autocomplete method we introduced a while back
can answer the same question but much more efficiently.
Guava's cache does not evict elements reliably by
time. Configure a cache to have a lifetime of n
seconds, then you cannot expect that an element is
actually evicted after n seconds with Guava.
The MAX_KEY inserted into the tree had a value of one byte. This
triggered an assertion for maps with values of type Empty, because they
expected values to be empty.
Fixed by using an empty array for the value of the MAX_KEY.
The computation of proposals is done by searching for values in a
combined index. If one of the values didn't exist, then the algorithm
returned all values. Fixed by checking that we query only existing
field/values from the combined index.
In order to prevent files from getting too big and
make it easier to implement retention policies, we
are splitting all files into chunks. Each chunk
contains the data for a time interval (1 month per
default).
This first changeset introduces the ClusteredPersistentMap
that implements this for PersistentMap. It is used
for a couple (not all) of indices.
BSFile was used to store two types of data. This makes
the API complex. I split the API into two files with
easier and more clear APIs. Interestingly the API of
BSFile is still rather complex and has to consider both
use cases.
Due to a mistake in Tag which added all strings used
by Tag into the String dictionary, the dictionary
did contain all values that were used in queries.
The old implementation searched for all possible values and then
executed each query to see what matches.
The new implementation uses several indices to find only
the matching values.
The reason seems to be the number of memory allocations. In order
to create the union of 100 lists we have 99 memory allocations.
The first needs the space for the first two lists, the second the
space for the first three lists, and so on.
We can reduce the number of allocations drastically (in many
cases to one) by leveraging the fact that many of the lists
were already sorted, non-overlapping and increasing, so that
we can simply concatenate them.
We are now reading the CSV input without transforming
the data into strings. This reduces the amount of bytes
that have to be converted and copied.
We also made Tag smaller. It no longer stores pointers
to strings, instead it stored integers obtained by
compressing the strings (see StringCompressor). This
reduces memory usage and it speeds up hashcode and
equals, which speeds up access to the writer cache.
Performance gain is almost 100%:
- 330k entries/s -> 670k entries/s, top speed measured over a second
- 62s -> 32s, to ingest 16 million entries
Calling Instant.now() several hundred thousand times per
second can be expensive. In my measurements >10% of the
time spend when loading new data was spend calling
Instant.now().
Fixed this by storing an Instant as static member and
updating it periodically in a separate thread.
Replaced Tags.filenameBytes with a SortedSet<Tag>. Tags are now
stored as longs (variable length encoded) in the PersistenMap.
Tags.filenameBytes was introduced to reduce memory consumption, when
all tags were hold in memory. Tags are now stored in a PersistentMap
and only read when needed.
Moved the VariableByteEncoder into its own project, because it was
needed by pdb-api.
Replaces the use of in-memory data structures with the PersistentMap.
This is the crucial step in reducing memory usage for both persistent
storage and main memory.
