This release is “unstable” because the file format will change again in the next few releases. (A manual upgrade with ham_export/ham_import works.) There are no other known issues/bugs/limitations. If that doesn’t bother you then please download!
I’m copy/pasting the README:
This release comes with a major architectural change – the transformation
towards a key/value engine with modern column-store features: cache-optimized,
compressed data structures, reduced I/O and even basic schema support.
hamsterdb is now able to create an optimized Btree for your key data. These
Btrees require less space on disk and therefore less I/O. Also, their layout is
better optimized for CPU caches, since keys and records are now stored
separately from each other. More keys therefore fit into the CPU cache and
lookup operations are faster. (This layout is similar to the “PAX” layout in
the academic database literature.)
To use this functionality, application developers can now specify the type of
key that they insert into a database (i.e. HAM_TYPE_UINT64, HAM_TYPE_REAL32)
Under the hood, hamsterdb will create a Btree using C++ template policies
and template types specifically for this key.
Existing binary arrays are still supported (HAM_TYPE_BINARY), and can either
have fixed length or variable length. This binary type uses a built-in compare
function. For user-supplied callback functions, use HAM_TYPE_CUSTOM.
See the documentation of ham_env_create_db in hamsterdb.h for more details.
This release is the first of at least 3 unstable releases, in which the file
format will frequently change. If this does not bother you, then feel free
to upgrade. See the section “Migrating files from older versions” below on how
to migrate database files from 2.1.2 and older to 2.1.3.
The next few releases will rewrite the handling of extended keys and
duplicate keys by providing a new Btree node layout for variable-length keys.
Also, in-node compression will be implemented, i.e. for prefix compression
and dictionary compression.
This release also introduces the new tool “ham_bench” to benchmark and test
hamsterdb configurations; see the wiki for documentation:
As usual, files are available for downloading.