Feb. 2006   The chief software engineer of Parity Software, Schwieberdingen near Stuttgart named in an interview Qt, Perl und db++ as his preferred development environment with wich one can develop application software with the highest level of flexibility and efficieny. He ist still thankfull today to Concept asa who eight years ago suggested Qt when he was facing a decision between Java and Nutcracker.

 

Jan. 2006    The Exact Software in Munich distrubuted, as usual at the beginning of the year, the update for their Windows payroll system LohnXL/XXL, which is based on the database kernel of db++, to more than 10,000 installations.

 

Sept. 2005    After extensive tests with their application simulation programme dbstresser the Parity Software, Schwieberdingen near Stuttgart delivered Version 8.11.29 to their customer base.

 

Sept. 2005    Distribution of an update to the specific requirements of  dsoftware, Neuss maintaining compatibility with the ASS development environment and the db++ Version which they deploy. The most important change was the need to access tables with a size of more than 2 GB on Linux/Windows platforms with a 32bit architecture. 

 

2004/2005   David Concept asa brings Goliath DB AG (German Railways) to its knees in a long drawn out trademark dispute. Since 1997, Concept asa has attempted to protect the use of db++ not only as an image-mark this has been the case in both Germany and abroad since 1990 but also as a word-mark. After initial resistance, this status was achieved in Febuary 2001. But the enjoyment of this success by Concept asa did not last very long. In October 2002, the DB AG was successful in revoking the grant of the word-mark to Concept asa. But in a final hearing before the 27th Senate of the Federal Patent court in August 2004, Concept asa won hands down and the  word-mark db++ is now the exclusive property of Concept asa. But we are not vindictive and continue to travel by train when we are not using our modest business car, a 3Litre-Lupo, in keeping with our motto “db++ is the 3litre consumption car under the data base systems slim, fast and efficient”.

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2003/2005   Development of db++ Versionen 8.11.19 to 8.11.31. Below we detail some of the extensions and optimisations:

 

The  following reports on performance improvements should not awaken doubts that db++ was previously slow: on the contrary, db++ always enjoyed the reputation of being extremely fast. Our ambition is to extend our reputation as one of the fastest data base systems available also in the future and the responsible  programmer has a tireless  passion in tweaking out the last drop of speed.

 

in 2003

 

  1. Begin of the total integration of the Makefile systems for both Windows and Linux/UNIX with the goal has that a simple „make“ is all that is required on all platforms.
     
  2. Transfer and first implementation of largefile code developed for EADS Airbus on Sun Sparc for Linux and Windows to permit tables > 2G.

  3. Replacing of the last non posix calls with standard posix insofar as efficiency is not compromised. So, for instance, for the new 2005 finalised  >2GB version of db++, a set of portable I/O/locking routines have been written for Windows. Externally, these look very much like the standard posix calls. Internally, native Windows calls are used on that platform. This has be done because the given standard posix calls under Windows are either unreliable or not efficient.

  4. The mapping mechanism from virtual relation table names to real directories on different host machines and db-servers specified in the RELFTAB-file has been partially redesigned to increase transparency between Linux/UNIX and Windows.

  5. Extension of the cdbFind()and cdbCount functions in particular:
    (a) Both cdbFind() and cdbCount() can be made to return a “buffer” of tuples. A maximum of 8 Kilobytes of tuples can be buffered in one call but the maximum number of tuples to be placed in the buffer can be specified in the arguments to the extended functions cdbFind() and cdbCount(). Subsequent calls to cdbCount() can be made to return tuple buffers until end-of-scan is reached.
    (b) By setting a corresponding flag, a new search operation can be made which retains the status of the last search (scan). Thus a buffer of the first 10 tuples in a new scan can be returned, but a subsequent cdb_next(), cdb_previous(), etc. applies to the old scan.

  6. On the first handshake between a client program and a db-server, it is determined whether the client and server share the same Endian. If so, data is transferred as an opaque data block rather than a multiple of different data types. The number of XDR calls is thereby significantly reduced.

  7. The old ODBC-driver „dbq“ has been replaced by „dbquery“. The new driver supports not only ODBC but also native SQL and AQL queries. This obsoletes the need for the undocumented, but often used function aqlexec().

  8. One optimisation of the dbserver „browse“ (cdb_next(), et al) routines made in an earlier customer specific version of db++ had been inadvertently mislaid in the latest version. The optimisation  was as follows: a search with an incompletely defined constraint may have to search through the entire relation. But it was not pleasant that an additional operation (say cdb_last()) also searched to the physical end of the table. Now the key positions (first, last) are marked by the first search/next sequence.  These routines have been restored.

  9. A simulation model of a typical commercial application – called dbstresser – has been developed in cooperation with Parity Software GmbH. This has been the basis for profiling with the wonderful „kcachegrind“ tool. Many insights have been gained to improving performance, in particular the avoidance of expensive system and library calls (alone the avoidance of sprintf() brought a 10% improvement of dbserver).

in 2004

 

  1. Additional small optimisations
    (a) Use of assembly for string comparison.
    (b) Previously, on inserting a tuple, a string length recalculation of each char field was performed to calculate the maximum print width. Now, a modified Fibonacci-Function is used so that initially most insertions the maximum print widths are calculated, but as the relation grows in size successively fewer calculations are made. This can occasionally lead to inaccuracy in formatting output of records, but the performance gain is certainly preferable.
    (c) An quick page cache (simple code) of very frequently accessed pages. has been inserted before the actual page cache (quite complex code).
    (d) On searching for a free-page on which to place new or modified data, a the search began at the physical start of the relation file. The new algorithm tries hard to find a free page near to the logical adjacency of the data. The algorithm also tries to keep the data in primary and secondary indices as physically separate as possible.

  2. Optimisation of the routines which match a constraint, cbd_next() et al., to avoid, if possible, when scanning a secondary index, unnecessary calls to obtain the primary tuple. In certain situations, this can lead to a an order of magnitude (10 times) or more in performance.

 

  1. On flushing modified pages from the cache to disc, the pages are now presorted to the physical ordering before writing to disc, rather than the logical order of the cache. For large files, this reduces the disc head movement considerably.

  2. The db-server attempts to use inactive process time (milliseconds) to perform file flushing operations. Flushing is also triggered if a weighted variable of operations per  table exceeds a tunable value. Two parameters are available for fine tuning.

  3. Each of the optimisations of 1 to 4 was tested by a new module „dbstresser“, developed by the Firm Parity Software, which simulates a wholesale warehouse application.

  4. dbodbc has been almost re-written, casual insufficient query operations and unpleasant (clumsy) interface problems with MS tools such as MSAccess, have been resolved as also problems with various versions of Microsoft OSs, in particular XP have been fixed. 

in 2005

 

  1. Final work on the makefile system for both Windows and Linux/UNIX. There is now only one Makefile in each directory so that simple „make“ is sufficient to build on all platforms. Also a revision control/history has been implemented in the makefile system so that programmes and libraries have embedded information of the build date and major, minor, mini and build numbers. These can be later displayed so that, for instance, a program can output this information for itself and for any shared libraries with which it is linked.

  2. Large file support for all platforms is now standard. In doing this, a set of portable file IO routines was written which simulate posix calls on Windows with Windows native IO operations. This also made it possible to clean up the incompatibilities with locking over heterogeneous platforms with native, nfs and samba mounts.

  3. Additional extensions of  cdb_find()
    (a) A new function “cdbFindInScan()”, searches for a specific tuple within an existing scan (potentially thousands of tuples). This function can be usefully combined with the cdbSavePos() and cdbRestorePos(), to switch between various positions within a scan.
    (b) cdbFind() was sometimes too clever by half. The function always tried to select the most optimal index (primary or secondary) to make the search. This has  consequence that resulting scan is sorted according to the optimal index chosen by the program. A new argument permits the user to specify a specific index on which the search will be made to retrieve tuples in his desired sorting sequence and not the sequence chosen by the optimiser.

Current development work

 

  1. Completion of earlier, initial work on blob and memo fields, so that these are not just available through the C-programming interface but fully integrated in all of the db++ tools such as „db“, „dbedit“, „dbfsck“ and „dbodbc“.

  2. After considerable re-writing of the dbodbc client -side driver and many changes to the dbodbc server „dbquery“, these are now  in extensive beta testing. „dbodbc“ now contains a new console utility, „drvsetup“ to install and manage dbodbc DLLs and Data Sources (DSNs). This utility can do almost everything which the Microsoft ODBC-Manager can do, but from a console. This makes it the preferred way to write installation scripts for both new and existing customers of our partners. On conclusion of beta testing, the new “dbodbc” will be distributed to a select group of our customers.

 

  1. A completely new algorithm (not found in the literature) for sorting the entire B-tree has been implemented which is almost linear, even for tables > 2G, while requiring very little main memory (< 64K). But if you are lucky enough  to have several gigabytes of main memory, then setting DB_MAXSORTBUF to a very high value is still faster. This experimental code will be integrated in the release version shortly.