More info...
The following is from the HSQLDB FAQ site at SourceForge:
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1) If only memory tables (CREATE TABLE or CREATE MEMORY TABLE) are used then the database is limited by the memory. A minimum of bout 100 bytes plus the actual data size are required for each row. If you use CREATE CACHED TABLE, then the size of the table is not limited by the memory beyond a certain minimum size. The data and indexes of cached tables are saved to disk. With text tables, indexes are memory resident but the data is cached to disk.
2) If data has been added to CACHED tables then the database was not shut down properly. When you restart the database, the *.log file will be processed and an automatic checkpoint will be performed. No commited data will be lost.
The statements that make up the database are saved in the *.script file (mostly CREATE statements and INSERT statements for memory tables). Only data of cached tables (CREATE CACHED TABLE) are stored in the *.data file. Also all data manipulation operations are stored in the *.log file (mostly DELETE/INSERT) for crash recovery. When the SHUTDOWN or CHECKPOINT command is issued to a database, then the *.script file is re-created and becomes up-to-date. The .log file is deleted. The *.data file is also closed and backed up as the *.backup file. When the database is restarted, all statements of the *.script file are executed first and new statements are appended to the .log file as the database is used.
-------------------------------------------------------------- In short:
The default 'CREATE TABLE' is by default a memory table and _only the DDL/DML_ gets written to a '.script' file !!
It is the 'CREATE CACHED TABLE' that will create the .dat files to store the data for such tables in the database.
Hope the above info helps in your comparision.
Regards, Rajesh
Daniel John Debrunner wrote:
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zhangjinsheng wrote:
Both hsqldb and derby are embedded, I haven't do any settings (all are in
default).
With your test Derby and hsqlb are not performing the same functionality, thus you have to consider if this is a reasonable performance test.
Each INSERT statement is a seprate transaction due to auto commit mode, auto commit is on by default as defined by the JDBC spec.
Derby is guaranteeing that if the system crashes in any way that any committed transactions will remain committed, in this case each insert statement has an implicit commit. This guarantee requires a forced write to the disk for every commit, this is where Derby is spending most of its time, waiting for the data to be flushed to disk.
I do not belive hsqldb is providing this guarantee, thus it goes faster because it is not waiting for the disk after each statement.
This thread has some info on the differences between Derby and hsqldb.
http://nagoya.apache.org/eyebrowse/[EMAIL PROTECTED]&from=630545&to=630545&count=10&by=subject&paged=false
Dan.
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